JP2011203234A - Signal acquisition method, signal acquisition apparatus and electronic device - Google Patents

Abstract

A new technique is provided for enabling correlation processing over a correlation integration time longer than the bit length of navigation message data.
In a first multiplier 211, a reception signal is converted into a signal of a specific frequency by multiplying a reception signal by a first carrier removal signal generated from a first carrier removal signal generator 221. The The second multiplier 212 multiplies the received signal by the second carrier removal signal generated by the second carrier removal signal generator 222, thereby converting the received signal into a signal having a frequency of zero. Then, the correlation calculation for the signal of the specific frequency is performed by the first correlator 231 to calculate the first correlation value, and the correlation calculation for the signal of zero frequency is performed by the second correlator 232 to calculate the second correlation value. Is done. Then, the integration result of the first correlation value and the integration result of the second correlation value are added together, and a GPS satellite signal is captured using the added integration correlation value.
[Selection] Figure 6

Description

  The present invention relates to a signal capturing method, a signal capturing apparatus, and an electronic apparatus.

  A GPS (Global Positioning System) is widely known as a positioning system using positioning signals, and is used in a position calculation device built in a mobile phone or a car navigation device. In the GPS, position calculation calculation for obtaining position coordinates and clock error of the position calculation device is performed based on information such as positions of a plurality of GPS satellites and pseudo distances from each GPS satellite to the position calculation device.

  A GPS satellite signal transmitted from a GPS satellite is modulated with a spreading code different for each GPS satellite called a CA (Coarse and Acquisition) code. In order to capture a GPS satellite signal from a weak received signal, the position calculation device performs a correlation operation between the received signal and a replica CA code that is a replica of the CA code, and based on the correlation value, the GPS satellite signal To capture. In this case, in order to facilitate the detection of the peak of the correlation value, a technique of integrating the correlation value acquired by the correlation calculation over a predetermined integration time is used.

  However, since the CA code itself for spreading and modulating the GPS satellite signal is BPSK (Binary Phase Shift Keying) modulated by the navigation message data every 20 milliseconds, the CA code is generated every 20 milliseconds which is the bit length of the navigation message data. The polarity of can be reversed. Therefore, when the correlation values are integrated across the timing at which the bit value of the navigation message data changes, there is a possibility that correlation values having different signs are integrated. As a technique for solving this problem, for example, as disclosed in Patent Document 1, a technique is known in which correlation values are accumulated using assist data regarding timing at which the bit value of navigation message data changes. Yes.

JP 2001-349935 A

  According to the technique of Patent Document 1, the correlation integration time can be set longer than the bit length (20 milliseconds) of the navigation message data. However, in the technique of Patent Document 1, it is necessary to acquire assist data about the timing at which the bit value of the navigation message data changes from the outside. Therefore, there are limitations and problems related to data acquisition such as communication costs and communication time problems. It was. In particular, after the navigation message data transmitted from the GPS satellite signal is switched to new data, it becomes necessary to wait for the assist data to be updated and acquire the new assist data.

  The present invention has been made in view of the above-mentioned problems, and its object is to propose a new technique for enabling correlation processing over a correlation integration time longer than the bit length of navigation message data. There is to do.

  In a first mode for solving the above problems, the frequency of the received signal, which is a satellite signal received from the positioning satellite, is changed to a specific frequency corresponding to the bit length of the navigation message data carried in the satellite signal. Performing a frequency conversion, performing a first correlation operation on the frequency-converted signal of the specific frequency, and obtaining a result of the first correlation operation over a predetermined time longer than the bit length. A signal capturing method including summing and capturing the satellite signal using the summed result.

  Further, as a fifth mode, the receiving unit that receives the satellite signal from the positioning satellite, and the frequency of the received signal received by the receiving unit correspond to the bit length of the navigation message data carried in the satellite signal. Over a predetermined time longer than the bit length, a frequency conversion unit that converts the signal to a specific frequency signal, a correlation calculation unit that performs a correlation operation on the signal of the specific frequency converted by the frequency conversion unit, The signal acquisition device may include an integration unit that integrates the result of the correlation calculation, and a capture unit that captures the satellite signal using the result of the correlation operation accumulated by the integration unit. Good.

  According to the first embodiment, the frequency of the received signal, which is a satellite signal received from the positioning satellite, is frequency-converted to a specific frequency corresponding to the bit length of the navigation message data carried in the satellite signal. Then, the first correlation calculation is performed on the frequency-converted signal of the specific frequency, and the results of the first correlation calculation are integrated over a predetermined time longer than the bit length of the navigation message data. Then, the satellite signal is captured using the integrated result.

  When correlation processing is performed over an arbitrary time longer than the bit length of the navigation message data for the received signal of the satellite signal carrying the navigation message data, even if acquisition is performed according to the correct frequency, This results in time-series data of correlation values with sign changes. However, as a result of experiments, when a signal with a specific frequency corresponding to the bit length of navigation message data is captured, time-series data with a correlation value that has a different code change pattern from that when capturing with the correct frequency is obtained. It became clear that it was obtained. The time-series data of correlation values having different code change patterns is obtained by converting the frequency of the received signal to a specific frequency and performing a correlation operation on the signal of the specific frequency. The correlation calculation results are accumulated based on the time-series data of the correlation values obtained in this way, and the satellite signal is captured using the accumulation results, so that the correlation integration time longer than the bit length of the navigation message data is obtained. Correlation processing is possible.

  Further, as a second form, the signal capturing method according to the first form, wherein the frequency of the received signal is converted to a frequency of zero, and the frequency-converted signal of the frequency zero is first. Performing the second correlation calculation, and accumulating the results of the second correlation calculation over the predetermined time, and capturing the satellite signal includes: You may comprise the signal acquisition method including capturing the said satellite signal using the total value which totaled the result of integrating | accumulating the result and the result of said 2nd correlation calculation.

  According to the second embodiment, the frequency of the received signal is frequency-converted to zero. Then, a second correlation calculation is performed on the frequency-converted frequency zero signal, and the results of the second correlation calculation are integrated over a predetermined time. Then, the result of integrating the results of the first correlation calculation and the result of integrating the results of the second correlation calculation are added together, and the satellite signal is captured using the added value. By taking into account not only the correlation calculation result for the signal of the specific frequency but also the correlation calculation result for the signal of zero frequency, the influence of the bit inversion of the navigation message data can be further reduced, and the correlation over the arbitrary correlation integration time Processing is possible.

  Further, as a third mode, the signal acquisition method according to the first mode, wherein the frequency of the received signal is frequency-converted to a frequency of zero, and the frequency-converted signal of the frequency zero is Performing the second correlation calculation, and accumulating the results of the second correlation calculation over the predetermined time, and capturing the satellite signal includes: You may comprise the signal capture method including capturing the said satellite signal using the result of integrating | accumulating either the result of integrating | accumulating a result and the result of integrating | accumulating the result of said 2nd correlation calculation.

  According to the third embodiment, the frequency of the received signal is frequency-converted to zero. Then, a second correlation calculation is performed on the frequency-converted frequency zero signal, and the results of the second correlation calculation are integrated over a predetermined time. Then, the satellite signal is captured using a result obtained by integrating one of a result obtained by integrating the results of the first correlation calculation and a result obtained by integrating the result of the second correlation calculation. For example, the satellite signal can be appropriately captured by using a result having a larger value of the result of integrating the results of the first correlation calculation and the result of integrating the results of the second correlation calculation. it can.

  Moreover, you may comprise the signal acquisition method whose specific frequency is 25 Hz in the signal acquisition method of any one of the 1st-3rd form as a 4th form. The specific frequency in this case is a frequency corresponding to the case where the bit length of the navigation message data is 20 milliseconds.

  Further, as a sixth mode, it is also possible to configure an electronic device provided with the signal capturing device of the fifth mode.

(A) is an example of a time change of the correlation value. (B) is an example of a frequency analysis result. (A) and (B) are DC components of the correlation value. (C) is a specific frequency component of the correlation value. (A) is explanatory drawing of the frequency zero signal in case there is no bit inversion of navigation message data. (B) is an explanatory diagram of a frequency zero signal when there is bit inversion of navigation message data. (A) is explanatory drawing of the specific frequency signal in case there is no bit inversion of navigation message data. (B) Explanatory drawing of a specific frequency signal in case bit reversal of navigation message data exists. The block diagram which shows an example of a function structure of a portable telephone. The block diagram which shows an example of the circuit structure of a baseband process circuit part. The flowchart which shows the flow of a baseband process. The flowchart which shows the flow of a correlation process. The figure which shows an example of the correlation processing result of the phase direction in the past, and a frequency direction. The figure which shows an example of the correlation processing result of the frequency direction in the past. The figure which shows an example of the correlation processing result of the phase direction in the past. The figure which shows an example of the correlation processing result of the phase direction in the past, and a frequency direction. The figure which shows an example of the correlation processing result of the frequency direction in the past. The figure which shows an example of the correlation processing result of the phase direction in the past. The figure which shows an example of the correlation process result of the phase direction in the Example, and a frequency direction. The figure which shows an example of the correlation process result of the frequency direction in an Example. The figure which shows an example of the correlation process result of the phase direction in an Example. The figure which shows an example of the correlation process result of the phase direction in the Example, and a frequency direction. The figure which shows an example of the correlation process result of the frequency direction in an Example. The figure which shows an example of the correlation process result of the phase direction in an Example. The block diagram which shows the circuit structure of the baseband process circuit part in a modification. The figure which shows the data structure of the memory | storage part of the baseband process circuit part in a modification.

1. Principle First, the principle of satellite signal acquisition in this embodiment will be described.
In a position calculation system using GPS satellites, a GPS satellite, which is a type of positioning satellite, places navigation message data including satellite orbit data such as almanac and ephemeris on a GPS satellite signal, which is a type of positioning satellite signal. Outgoing.

  The GPS satellite signal is a 1.57542 [GHz] communication signal modulated by a CDMA (Code Division Multiple Access) system known as a spread spectrum system by a CA (Coarse and Acquisition) code which is a kind of spreading code. The CA code is a pseudo-random noise code having a repetition period of 1 ms with a code length of 1023 chips as one PN frame, and is different for each satellite.

  The frequency at which a GPS satellite transmits a GPS satellite signal (specified carrier frequency) is specified in advance as 1.57542 [GHz]. However, due to the influence of Doppler caused by the movement of the GPS satellite and the GPS receiver, the GPS The frequency at which the receiving device receives the GPS satellite signal does not necessarily match the specified carrier frequency. Therefore, the conventional GPS receiver captures a GPS satellite signal by performing a frequency search that is a correlation calculation in the frequency direction for capturing a GPS satellite signal from the received signal. In addition, in order to specify the phase of the received GPS satellite signal (CA code), the GPS receiving device performs a phase search that is a correlation calculation in the phase direction to capture the GPS satellite signal.

  However, particularly in a weak electric field environment such as an indoor environment, the level of the correlation value at the true reception frequency and the true code phase is low, so that it is difficult to distinguish it from noise. As a result, it is difficult to detect the true reception frequency and the true code phase, that is, to acquire the signal. Therefore, under such a reception environment, the correlation value obtained by the correlation calculation is accumulated over a predetermined correlation accumulation time, and a peak is detected from the accumulated correlation value, thereby obtaining the GPS satellite signal. A capture technique is used.

  However, the GPS satellite signal is spread and modulated by the CA code, and the CA code itself is BPSK (Binary Phase Shift Keying) modulated according to the bit value of the navigation message data. Since the bit length of the navigation message data is 20 milliseconds, the bit value may change (invert) every 20 milliseconds. The possibility means that the bit value may not change. In the present embodiment, the timing at which the bit value of the navigation message data actually changes is referred to as “bit inversion timing”.

  Changing the bit value of the navigation message data means that the polarity of the CA code is reversed. Therefore, when the correlation calculation between the received CA code and the replica code is performed, correlation values having different codes can be calculated every 20 milliseconds that is the bit length of the navigation message data. Therefore, if the correlation values are accumulated across the bit inversion timing of the navigation message data, the correlation values with different signs cancel each other, resulting in a small correlation value (0 in an extreme case). There's a problem. In order to solve this problem, the inventor of the present application has devised a new method for integrating the correlation values by invalidating the influence of the sign change of the correlation values, focusing on the specific frequency corresponding to the bit length of the navigation message data.

  1 and 2 are diagrams for explaining a specific frequency. FIG. 1A shows an example of time-series changes in correlation values. In order to make the explanation easy to understand, the correlation value is expressed by two positive and negative values of “+1” and “−1”. Here, a case will be described in which the true value of the reception frequency is known and the correlation value is obtained by performing the correlation calculation using the replica code whose phase exactly matches the reception CA code.

  When the polarity of the CA code when the bit value of the navigation message data is “1” is “positive”, the correlation value “+1” is obtained by multiplying the received CA code by the replica code. On the other hand, when the polarity of the CA code when the bit value of the navigation message data is “0” is “negative”, the correlation value “−1” is obtained by multiplying the received CA code by the replica code.

  As can be seen from FIG. 1A, the sign of the correlation value is switched at the bit inversion timing of the navigation message data. Depending on the bit value, when the bit inversion timing comes 20 milliseconds after the previous bit inversion timing, the sign of the correlation value is reversed at the time 20 minutes later. In addition, when the bit inversion timing comes after 40 milliseconds, the sign of the correlation value is reversed at the time after the 40 milliseconds.

  When the time-series correlation values shown in FIG. 1A are accumulated for a predetermined time longer than the bit length and the frequency analysis is performed, for example, a power spectrum as shown in FIG. 1B is obtained. In FIG. 1B, the horizontal axis indicates the frequency and the vertical axis indicates the power value, and the white noise is not shown for easy understanding.

  As shown in FIG. 1B, a power value peak appears at a frequency of zero (0 Hz). This indicates the DC component of the time-series correlation value. That is, as shown in FIGS. 2 (A) and 2 (B), a frequency component (DC component) corresponding to a portion having no sign change in the time-series correlation value appears as a power value peak at 0 Hz. It is.

  However, as shown in FIG. 1B, a peak with a large power value appears at a frequency of 25 Hz. This is due to the fact that the bit length of the navigation message data is 20 milliseconds. That is, as shown in FIG. 2C, when the bit value of the navigation message data changes every 20 milliseconds, for example, the first 20 milliseconds is “1”, the next 20 milliseconds is “−1”, Since the correlation value changes such that the next 20 milliseconds is “1”, the period of the correlation value is 40 milliseconds.

This period of 40 milliseconds is a period corresponding to twice the bit length of the navigation message data. When the period of 40 milliseconds is converted into a frequency, “f = 1 / T = 1 / (40 × 10 ⁻³ ) = 25 Hz”. This 25 Hz frequency component included in the time-series correlation value appears as a peak of the power value. In the present embodiment, the frequency of 25 Hz is defined as “specific frequency”.

  Moreover, when FIG. 1 (B) is seen, although it is not as large a peak as a specific frequency (25 Hz) also in the high-order frequencies, such as 75 Hz, 125 Hz, and 175 Hz, it turns out that the minute peak has appeared. Since the waveform of the correlation value is a symmetric waveform, a peak of the power value appears at a frequency that is an odd multiple of the specific frequency that is the fundamental frequency, that is, an odd-order harmonic frequency.

  The peaks of these power values originate from the fact that the polarity of the CA code is inverted at the bit inversion timing of the navigation message data, and that the sign of the correlation value changes accordingly. For example, when the frequency analysis is performed with the integration time of the correlation value being 20 milliseconds or less of the bit length so as not to cross the bit inversion timing, a peak occurs only at the frequency zero, and the peak at other frequencies Does not occur. That is, if there is no sign change of the correlation value, no power value peak occurs except for the frequency zero.

  When the inventor performs correlation processing over an arbitrary time longer than the bit length of the navigation message data as described above, power value peaks appear at the frequency zero (0 Hz) and the specific frequency (25 Hz). Focused on that. In addition, the frequency of the received signal of the GPS satellite signal corresponds to a frequency of zero (the received signal of this frequency is referred to as a “frequency zero signal”) and the specific frequency (the received signal of this frequency is referred to as a “specific frequency signal”). ") We considered capturing GPS satellite signals using the results of frequency conversion for each signal and correlation calculation for each signal.

  In this embodiment, in order to make the explanation easy to understand, only the positive frequency is considered and the negative frequency is not considered.

  This will be specifically described. The received signal “r (t)” of the GPS satellite signal received by the GPS receiver at time “t” can be expressed as the following equation (1).

  In Expression (1), “I (t)” and “Q (t)” are IQ components of the received signal “r (t)”, respectively. The I component indicates the in-phase component (real part) of the received signal, and the Q component indicates the quadrature component (imaginary part) of the received signal. “CA (t)” is a CA code of the received GPS satellite signal (hereinafter referred to as “reception CA code”), and is a value of “+1” or “−1”. “Exp (iωt)” is a carrier wave that carries a GPS satellite signal.

  In Equation (1), “ω” is a reception frequency at which a GPS satellite signal is received, and is represented by Equation (2) below.

但し、「ω_c」はＧＰＳ衛星信号の搬送波周波数であり、「ω_d」はドップラー周波数である。

However, “ω _c ” is the carrier frequency of the GPS satellite signal, and “ω _d ” is the Doppler frequency.

  When the received signal “r (t)” of the GPS satellite signal is multiplied by a signal whose frequency is different from the frequency “ω” of the carrier wave “exp (iωt)” by “Δω”, the received signal is the signal “r (t, t, Δω) = CA (t) · exp (iΔωt) ”. In the present embodiment, “Δω” is defined as “frequency shift”.

If there is no frequency shift (Δω = 0), the frequency of the received signal is converted to frequency zero “r (t, 0) = CA (t)”. That is, it means that it has been demodulated and becomes the received CA code itself. On the other hand, if the frequency shift is equal to the specific frequency “ω _s ” (Δω = ω _s ), the frequency of the received signal is the specific frequency “r (t, ω _s ) = CA (t) · exp (iω _s t)”. Converted.

  FIG. 3 is an explanatory diagram of a signal “r (t, 0)” having a frequency of zero. In FIG. 3, the horizontal axis represents time. Here, paying attention to the period of two bit lengths (40 milliseconds) of the navigation message data, the term “exp (iΔωt) that represents the carrier wave of zero frequency with the received CA code“ CA (t) ”indicated by a one-dot chain line. "Is indicated by a dotted line, and a signal" r (t, 0) "having a frequency of zero is indicated by a solid line. In FIGS. 3 and 4, since the lines cannot be identified when they are overlapped, the lines are slightly shifted from each other.

  FIG. 3A is an explanatory diagram when the bit value of the navigation message data is not inverted in 20 milliseconds. When the received CA code in the first 20 milliseconds is set to a positive polarity, the polarity of the received CA code remains positive if the bit value of the navigation message data does not change at the timing when 20 milliseconds have elapsed. Further, since the frequency shift is “0 Hz”, the carrier wave is removed and “exp (i · 0 · t) = 1”. Therefore, the polarity of the zero-frequency signal “r (t, 0)” becomes positive through 40 milliseconds. Multiplying the zero polarity signal “r (t, 0)” by a positive polarity replica code yields a positive correlation value over a 40 millisecond period.

  FIG. 3B is an explanatory diagram when the bit value of the navigation message data is inverted in 20 milliseconds. When the bit value of the navigation message data changes at the timing when 20 milliseconds have elapsed, the polarity of the received CA code also changes and becomes a negative polarity. Therefore, the polarity of the zero-frequency signal “r (t, 0)” is positive for the first 20 milliseconds and negative for the next 20 milliseconds. When a positive polarity replica code is multiplied by a zero-frequency signal “r (t, 0)”, a positive correlation value is obtained for the first 20 milliseconds, and a negative correlation value is obtained for the next 20 milliseconds.

FIG. 4 is an explanatory diagram of a signal “r (t, ω _s )” having a specific frequency. 3 is the same as FIG. 3, the received CA code “CA (t)” is indicated by a one-dot chain line, the term “exp (iωt)” representing a carrier having a specific frequency is indicated by a dotted line, and the signal “r (t , Ω _s ) ”are indicated by solid lines.

FIG. 4A is an explanatory diagram when the bit value of the navigation message data is not inverted in 20 milliseconds. Similar to FIG. 3A, the polarity of the received CA code does not change at the timing when 20 milliseconds elapses, and becomes positive polarity over a period of 40 milliseconds. Further, since the frequency shift is “25 Hz” which is a specific frequency, the term representing the carrier wave is expressed by a sine wave (sin wave) having a frequency of 25 Hz. Therefore, the polarity of the signal “r (t, ω _s )” of the specific frequency is positive for the first 20 milliseconds and negative for the next 20 milliseconds. When the positive-polarity replica code is multiplied by the signal “r (t, ω _s )” of the specific frequency, a positive correlation value is obtained for the first 20 milliseconds and a negative correlation value is obtained for the next 20 milliseconds.

FIG. 4B is an explanatory diagram when the bit value of the navigation message data is reversed in 20 milliseconds. Similar to FIG. 3B, the polarity of the received CA code changes from positive to negative at the timing when 20 milliseconds elapse. A term representing a carrier wave is expressed by a sine wave (sin wave) having a frequency of 25 Hz. Therefore, the polarity of the signal “r (t, ω _s )” of the specific frequency is positive for the first 20 milliseconds and positive for the next 20 milliseconds. When a positive polarity replica code is multiplied by a signal “r (t, ω _s )” of a specific frequency, a positive correlation value is obtained over a period of 40 milliseconds.

  From the above, the correlation calculation result (first correlation calculation) result for the signal of the specific frequency and the correlation calculation result (second correlation calculation) result for the signal of zero frequency are in conflict with respect to the influence of bit inversion of the navigation message data. It can be seen that it exhibits properties. In other words, the time-series data of the correlation value for the signal of the specific frequency and the time-series data of the correlation value for the signal of the frequency zero are the way of changing the code (the pattern of the code change depending on the bit inversion of the navigation message data ) Can be said to be reversed data.

  Focusing on this property, in this embodiment, the result of integrating the correlation calculation results for the signal of the specific frequency and the result of integrating the correlation calculation results for the signal of the frequency zero are added together, and the resultant integrated integration correlation is obtained. The GPS satellite signal is captured based on the value. That is, a process of calculating the summed integrated correlation value while changing the phase of the replica code is performed, and the GPS satellite signal is captured by detecting the phase of the replica code having the maximum summed accumulated correlation value.

  In this case, since the time-series data of the correlation value with the reversed sign change pattern is superimposed, the influence of the bit inversion of the navigation message data can be nullified. This is because the time-series data of either one of the correlation values is data with the same code, regardless of whether the bit of the navigation message data is inverted or not, and the value increases when the correlation values are integrated. For this reason, the signs of the time-series data of the other correlation value are not aligned, and even when the correlation value is integrated, the value is increased as a whole even if the value is decreased. Based on the above principle, correlation values can be integrated over a correlation integration time longer than the bit length of navigation message data.

2. Embodiment Next, an embodiment in which the present invention is applied to a mobile phone which is a kind of electronic apparatus including a satellite signal capturing device (signal capturing device) and a position calculating device will be described. Needless to say, the embodiments to which the present invention is applicable are not limited to the embodiments described below.

2-1. Functional Configuration FIG. 5 is a block diagram illustrating an example of a functional configuration of the mobile phone 1 according to the present embodiment. The mobile phone 1 includes a GPS antenna 5, a GPS receiving unit 10, a host CPU (Central Processing Unit) 30, an operation unit 40, a display unit 50, a mobile phone antenna 60, and a mobile phone radio communication circuit. Unit 70 and storage unit 80.

  The GPS antenna 5 is an antenna that receives an RF (Radio Frequency) signal including a GPS satellite signal transmitted from a GPS satellite, and outputs a received signal to the GPS receiver 10.

  The GPS receiving unit 10 is a position calculating circuit or a position calculating device that measures the position of the mobile phone 1 based on a signal output from the GPS antenna 5, and is a functional block corresponding to a so-called GPS receiving device. The GPS receiving unit 10 includes an RF receiving circuit unit 11 and a baseband processing circuit unit 20. The RF receiving circuit unit 11 and the baseband processing circuit unit 20 can be manufactured as separate LSIs (Large Scale Integration) or can be manufactured as one chip.

  The RF receiving circuit unit 11 is an RF signal receiving circuit. As a circuit configuration, for example, a receiving circuit that converts an RF signal output from the GPS antenna 5 into a digital signal by an A / D converter and processes the digital signal may be configured. Alternatively, the RF signal output from the GPS antenna 5 may be processed as an analog signal and finally A / D converted to output a digital signal to the baseband processing circuit unit 20.

  In the latter case, for example, the RF receiving circuit unit 11 can be configured as follows. That is, an oscillation signal for RF signal multiplication is generated by dividing or multiplying a predetermined oscillation signal. Then, by multiplying the generated oscillation signal by the RF signal output from the GPS antenna 5, the RF signal is down-converted to an intermediate frequency signal (hereinafter referred to as an "IF (Intermediate Frequency) signal"), After the IF signal is amplified, it is converted into a digital signal by an A / D converter and output to the baseband processing circuit unit 20.

  The baseband processing circuit unit 20 performs correlation processing or the like on the reception signal output from the RF reception circuit unit 11 to capture a GPS satellite signal, and based on satellite orbit data, time data, and the like extracted from the GPS satellite signal. The processing circuit block calculates the position (position coordinates) of the mobile phone 1 by performing a predetermined position calculation calculation. The baseband processing circuit unit 20 functions as a satellite signal capturing device that captures GPS satellite signals from received signals.

  FIG. 6 is a diagram illustrating an example of a circuit configuration of the baseband processing circuit unit 20, and is a diagram mainly illustrating circuit blocks according to the present embodiment. The baseband processing circuit unit 20 includes, for example, a multiplication unit 21 having a first multiplier 211 and a second multiplier 212, and a carrier having a first carrier removal signal generation unit 221 and a second carrier removal signal generation unit 222. The signal generator 22 for removal, the correlation unit 23 having the first correlator 231 and the second correlator 232, the replica code generation unit 24, the processing unit 25, and the storage unit 27 are configured.

  The first multiplier 211 multiplies the received signal by the first carrier removal signal generated and generated by the first carrier removal signal generator 221 to thereby make the received signal a first received signal that is a signal of a specific frequency. Downconverted to (specific frequency signal) and outputs to the first correlator 231. It can be said that the first multiplier 211 is a frequency converter (first converter) that converts the frequency of the received signal to a specific frequency corresponding to the bit length of the navigation message data.

  The first carrier removal signal generator 221 is a circuit that generates a first carrier removal signal whose frequency is shifted by a specific frequency from the frequency of the carrier signal of the GPS satellite signal, such as a carrier NCO (Numerical Controlled Oscillator). It is configured with an oscillator. When the signal output from the RF receiving circuit unit 11 is an IF signal, a signal shifted by a specific frequency from the IF frequency may be generated. As described above, even when the RF reception circuit unit 11 down-converts the reception signal into the IF signal, the present embodiment can be applied substantially in the same manner.

  The second multiplier 212 multiplies the reception signal by the second carrier removal signal generated and generated by the second carrier removal signal generation unit 222, whereby the second reception signal is a signal having a frequency of zero. Down-converted to (frequency zero signal) and output to the second correlator 232. It can be said that the second multiplier 212 is a frequency conversion unit (second conversion unit) that converts the frequency of the received signal to frequency zero.

  The second carrier removal signal generator 222 is a circuit that generates a second carrier removal signal having the same frequency as that of the carrier signal of the GPS satellite signal, and includes an oscillator such as a carrier NCO, for example. . In addition, what is necessary is just to produce | generate the signal of IF frequency, when the signal output from RF receiving circuit part 11 is an IF signal.

  The first correlator 231 performs a correlation operation between the first received signal output from the first multiplier 211 and the replica code generated by the replica code generator 24, and performs a first correlation that is a correlation value of a specific frequency. A correlation calculation unit (first correlation calculation unit) that outputs a value (specific frequency correlation value) to the processing unit 25.

  The second correlator 232 performs a correlation operation between the second reception signal output from the second multiplier 212 and the replica code generated by the replica code generation unit 24, and performs a second correlation that is a correlation value of frequency zero. It is a correlation calculation unit (second correlation calculation unit) that outputs a value (frequency zero correlation value) to the processing unit 25.

  The replica code generation unit 24 is a circuit unit that generates a replica code (replica CA code) that simulates a CA code that is a spreading code of a GPS satellite signal, and includes an oscillator such as a code NCO. The replica code generation unit 24 generates a replica code corresponding to the PRN number (satellite number) instructed from the processing unit 25 by adjusting the output phase (time) in accordance with the instructed phase. Output.

  Correlator 23 (first correlator 231 and second correlator 232) performs a correlation operation with the replica code input from replica code generator 24 for each IQ component of the received signal. In addition, although illustration is abbreviate | omitted about the circuit block which isolate | separates IQ component (IQ isolation | separation) of a received signal, you may comprise a circuit block how. For example, when the received signal is down-converted to an IF signal in the RF receiving circuit unit 11, IQ separation may be performed by multiplying the received signal by a local oscillation signal having a phase difference of 90 degrees.

  The processing unit 25 is a control device that comprehensively controls each functional unit of the baseband processing circuit unit 20, and includes a processor such as a CPU, for example. The processing unit 25 functions as an integration unit that integrates the correlation calculation results output from the correlation unit 23 and a capturing unit that acquires GPS satellite signals using the integrated correlation calculation results. The processing unit 25 includes a satellite signal acquisition unit 251 and a position calculation unit 253 as main functional units.

  The satellite signal acquisition unit 251 integrates the first correlation value output from the first correlator 231 and the second correlation value output from the second correlator 232 for each predetermined correlation integration time, and sums them. A GPS satellite signal is captured based on the total accumulated correlation value.

  The position calculation unit 253 is a calculation unit that performs a known position calculation calculation using the GPS satellite signal captured by the satellite signal capturing unit 251 to calculate the position of the mobile phone 1. It outputs to CPU30.

  The storage unit 27 is configured by a storage device (memory) such as a ROM (Read Only Memory), a flash ROM, or a RAM (Random Access Memory), and the system program of the baseband processing circuit unit 20, the satellite signal capturing function, and the position calculation. Various programs, data, and the like for realizing various functions such as functions are stored. In addition, it has a work area for temporarily storing data being processed and results of various processes.

  For example, as illustrated in FIG. 6, the storage unit 27 stores a baseband processing program 271 that is read as a program by the processing unit 25 and executed as baseband processing (see FIG. 7). The baseband processing program 271 has a correlation processing program 2711 executed as correlation processing (see FIG. 8) as a subroutine.

  As temporary storage data, for example, satellite orbit data 272, correlation integration time 273, accumulation time 274, correlation value data 275, integration correlation value data 276, and total integration correlation value data 277 are stored. Stored in the unit 27.

  In the baseband processing, the processing unit 25 performs correlation processing on each GPS satellite to be captured (hereinafter referred to as “capture target satellite”) to capture a GPS satellite signal, and captures GPS. This is a process for calculating the position of the mobile phone 1 by performing position calculation using satellite signals. The baseband process will be described later in detail using a flowchart.

  The satellite orbit data 272 is data such as an almanac that stores approximate satellite orbit information of all GPS satellites, and an ephemeris that stores detailed satellite orbit information for each GPS satellite. The satellite orbit data 272 is obtained by decoding GPS satellite signals received from GPS satellites, and is obtained as assist data from, for example, the base station of the mobile phone 1 or an assist server.

  The correlation integration time 273 is a time for integrating the correlation value in order to obtain an integration correlation value used for capturing the GPS satellite signal, and is variably set based on information such as the signal strength of the reception signal and the reception environment, for example. . Although the details of the method of setting the correlation integration time 273 will be described later, the feature of this embodiment is that the correlation integration time longer than the bit length (20 milliseconds) of the navigation message data can be set.

  The accumulation time 274 is a unit time for temporarily integrating the first correlation value and the second correlation value output from the correlation unit 23. The accumulation time 274 may be a time shorter than the correlation integration time 273, and is set to 1 / m times (m> 1) the correlation integration time 273, for example.

  The correlation value data 275 is data in which the first correlation value output from the first correlator 231 and the second correlation value output from the second correlator 232 are accumulated for the accumulation time 274, respectively. Of course, correlation value data is stored for each phase of the replica code.

  The accumulated correlation value data 276 includes a first accumulated correlation value obtained by integrating the first correlation value accumulated for the accumulation time 274, and a second accumulated correlation value obtained by integrating the second correlation value accumulated for the accumulation time 274. Are the stored data. As a matter of course, accumulated correlation value data is stored for each phase of the replica code.

  The total integrated correlation value data 277 is data of a total integrated correlation value used for capturing a GPS satellite signal. In the following description, the total integrated correlation value calculated by adding the first integrated correlation value and the second integrated correlation value in units of the accumulation time 274 is defined as a “short-time total integrated correlation value”. On the other hand, the sum total integrated correlation value obtained by collecting and accumulating the short-time total accumulated correlation values calculated for each accumulation time 274 for the correlation integral time 273 is defined as a “long-time total accumulated correlation value”. As a matter of course, the data of the accumulated integrated correlation value is stored for each phase of the replica code.

  Returning to the functional blocks in FIG. 5, the host CPU 30 is a processor that comprehensively controls each unit of the mobile phone 1 according to various programs such as a system program stored in the storage unit 80. Based on the position coordinates output from the baseband processing circuit unit 20, the host CPU 30 displays a map indicating the current position on the display unit 50, or uses the position coordinates for various application processes.

  The operation unit 40 is an input device configured by, for example, a touch panel, a button switch, or the like, and outputs a pressed key or button signal to the host CPU 30. By operating the operation unit 40, various instructions such as a call request, a mail transmission / reception request, and a position calculation request are input.

  The display unit 50 is configured by an LCD (Liquid Crystal Display) or the like, and is a display device that performs various displays based on display signals input from the host CPU 30. The display unit 50 displays a position display screen, time information, and the like.

  The cellular phone antenna 60 is an antenna that transmits and receives cellular phone radio signals to and from a radio base station installed by a communication service provider of the cellular phone 1.

  The cellular phone wireless communication circuit unit 70 is a cellular phone communication circuit unit configured by an RF conversion circuit, a baseband processing circuit, and the like, and performs modulation and demodulation of the cellular phone radio signal, thereby enabling communication and mailing. Realize transmission / reception and so on.

  The storage unit 80 is a storage device that stores a system program for the host CPU 30 to control the mobile phone 1 and various programs and data for executing various application processes.

2-2. Processing Flow FIG. 7 is a flowchart showing a flow of baseband processing executed in the baseband processing circuit unit 20 when the baseband processing program 271 stored in the storage unit 27 is read by the processing unit 25. .

  First, the satellite signal acquisition unit 251 performs acquisition target satellite determination processing (step A1). Specifically, a GPS satellite located in the sky at a given reference position at a current time measured by a clock unit (not shown) is used as a satellite orbit data 272 such as an almanac or an ephemeris stored in the storage unit 27. To determine the satellite to be captured. For example, in the case of the first position calculation after power-on, the reference position is a position acquired from the assist server by so-called server assist, and in the second and subsequent position calculation, the reference position is the latest calculated position. Can be set.

  Next, the satellite signal acquisition unit 251 executes the process of loop A for each acquisition target satellite determined in step A1 (steps A3 to A17). In the process of loop A, the satellite signal acquisition unit 251 sets the correlation integration time 273 and the accumulation time 274 for the acquisition target satellite (step A5).

  The setting of the correlation integration time can be realized by various methods. For example, the correlation integration time may be set based on the signal strength of the GPS satellite signal received from the capture target satellite. In general, the weaker the signal strength, the more difficult it is to detect the correlation value peak unless the correlation values are accumulated over a longer period of time. Therefore, it is appropriate to set the correlation integration time so that the correlation integration time becomes longer as the signal strength becomes weaker.

  Further, the reception environment of the GPS satellite signal may be determined, and the correlation integration time may be set based on the determined reception environment. For example, when the reception environment is “indoor environment (indoor environment)”, the correlation integration time is set to a longer “1000 milliseconds”, and when the reception environment is “outdoor environment (outdoor environment)”, the correlation It is conceivable to set the accumulated time to “200 milliseconds”, which is a little shorter. Note that these correlation integration time setting methods are merely examples, and the settings can be changed as appropriate.

  Further, the accumulation time is set so that a time shorter than the correlation integration time is set. For example, the correlation integration time is set to be an integral multiple of the accumulation time, and a time that is 1 / m times the correlation integration time (m> 1) is set as the accumulation time. The value of “m” can be determined as appropriate. For example, when the correlation integration time is set to “1000 milliseconds” and “m = 25”, “40 milliseconds” is set as the accumulation time.

  Next, the satellite signal acquisition unit 251 sets the initial phase of the replica code (step A7). Then, an instruction signal indicating the PRN number of the acquisition target satellite and the phase of the replica code is output to the replica code generation unit 24 (step A9). Then, the satellite signal acquisition unit 251 performs the correlation process by reading and executing the correlation processing program 2711 stored in the storage unit 27 (step A11).

FIG. 8 is a flowchart showing the flow of correlation processing.
First, the satellite signal acquisition unit 251 accumulates and stores the correlation value output from the first correlator 231 for the accumulation time 274 set in Step A5, integrates them, and calculates the first accumulated correlation value (step) B1). Further, the correlation value output from the second correlator 232 is accumulated and stored for an accumulation time of 274, and these are accumulated to calculate a second accumulated correlation value (step B3).

  Next, the satellite signal acquisition unit 251 adds the first accumulated correlation value calculated in Step B1 and the second accumulated correlation value calculated in Step B3, thereby obtaining the short-time accumulated correlation value in the accumulation time 274. Calculate (step B5). Then, the calculated short-time total integration correlation value is added to the latest long-term total integration correlation value to update the total integration correlation value data 277 (step B7).

  The satellite signal acquisition unit 251 repeatedly executes the processes of Steps B1 to B7 until the correlation integration time 273 set in Step A5 elapses (Step B9; No → Step B1). Then, when the correlation integration time 273 has elapsed (step B9; Yes), the correlation process is terminated.

  Returning to the baseband processing of FIG. 7, after performing the correlation processing, the satellite signal acquisition unit 251 performs peak detection for the long-time summed correlation value stored in the summed summed correlation value data 277 (step A13). If it is determined that no peak is detected (step A13; No), the phase of the replica code is changed (step A15), and the process returns to step A9.

  If it is determined that a peak has been detected (step A13; Yes), the satellite signal acquisition unit 251 shifts the processing to the next acquisition target satellite. Then, after performing the processing of steps A5 to A15 for all the capture target satellites, the processing of loop A is terminated (step A17).

  Thereafter, the position calculation unit 253 performs position calculation calculation using the GPS satellite signals captured for each capture target satellite (step A19). The position calculation calculation can be realized by performing a known convergence calculation using, for example, a least square method or a Kalman filter using a pseudo distance between the mobile phone 1 and each captured satellite.

  The pseudo distance can be calculated as follows. That is, the integer part of the pseudorange is calculated using the satellite position of the captured satellite obtained from the satellite orbit data 272 and the latest calculated position of the mobile phone 1. Further, the fractional portion of the pseudo distance is calculated using the phase (code phase) of the replica code corresponding to the peak of the total integrated correlation value detected in step A13. The pseudo distance can be calculated by adding the integer part and the fractional part thus obtained.

  Next, the position calculation unit 253 outputs the calculated position (position coordinates) to the host CPU 30 (step A21). Then, the processing unit 25 determines whether or not to end the processing (step A23). If it is determined that the processing is not yet ended (step A23; No), the processing unit 25 returns to step A1. If it is determined that the process is to be terminated (step A23; Yes), the baseband process is terminated.

2-3. Experimental Results With reference to FIG. 9 to FIG. 20, experimental results of experiments for capturing GPS satellite signals will be described. The present inventor conducted experiments under various conditions. Here, the GPS satellite signal is acquired by performing correlation processing with the accumulation time being “40 milliseconds” and the correlation integration time being “1 second (1000 milliseconds)”. An example of the results of the experiment will be described.

  9 to 14 are diagrams showing examples of experimental results obtained by capturing a GPS satellite signal according to a conventional correlation processing method. FIG. 9 to FIG. 11 show experimental results for obtaining integrated correlation values (hereinafter referred to as “short-time integrated correlation values”) obtained by integrating the correlation values for the accumulation time in each of the frequency direction and the phase direction. FIG. 12 to 14 are experiments in which integrated correlation values (hereinafter, referred to as “long-time integrated correlation values”) obtained by integrating the short-time integrated correlation values calculated for the respective accumulation times by the correlation integrated time are described. It is a figure which shows a result.

  FIG. 9 is a graph in which short-time integrated correlation values in the phase direction and the frequency direction are three-dimensionally plotted. In FIG. 9, the right depth direction indicates the phase difference between the phase of the received CA code and the phase of the replica code, and the left depth direction indicates the frequency difference (frequency) between the frequency of the received signal and the frequency of the carrier removal signal. Deviation). The vertical axis represents the short time integrated correlation value. Among the graphs in FIG. 9, FIG. 10 is a graph obtained by extracting the correlation processing result in the frequency direction, and FIG. 11 is a graph obtained by extracting the correlation processing result in the phase direction.

  From the correlation processing result in the phase direction in FIG. 11, it can be seen that the peak of the short-time integrated correlation value appears in the portion of the phase difference “0”. However, looking at the correlation processing result in the frequency direction of FIG. 10, the peak of the short-term integrated correlation value does not appear in the portion of the frequency difference “0 Hz”, and in the frequency difference slightly apart in the left and right directions from “0 Hz”. It can be seen that a peak appears. When the frequency difference at which this peak appeared was examined, it was a frequency difference corresponding to a specific frequency of “± 25 Hz”. This is because the frequency component of the specific frequency is included in the correlation value due to the bit inversion of the navigation message data during the accumulation time of “40 milliseconds”.

  FIG. 12 is a graph in which the long-term accumulated correlation values in the phase direction and the frequency direction are three-dimensionally plotted. Among the graphs of FIG. 12, a graph obtained by extracting the correlation processing result in the frequency direction is shown in FIG. 13, and a graph obtained by extracting the correlation processing result in the phase direction is shown in FIG.

  From the correlation processing result in the phase direction of FIG. 14, it can be seen that the peak of the long-time integrated correlation value appears in the portion of the phase difference “0”, as in the case of FIG. 11. On the other hand, when the correlation processing result in the frequency direction of FIG. 13 is seen, a peak does not appear in the portion corresponding to “± 25 Hz” as shown in FIG. 10, but “0 Hz” instead of the frequency difference “0 Hz” portion. A peak appears in the part of the frequency difference that is slightly shifted to the right. Since no peak appears in the frequency difference “0 Hz” portion, it can be said that the conventional method has failed to acquire the GPS satellite signal.

  15-20 is a figure which shows an example of the experimental result which acquired the GPS satellite signal according to the correlation calculation method of a present Example. FIG. 15 to FIG. 17 are diagrams showing experimental results obtained by obtaining short-time summed correlation values for each of the frequency direction and the phase direction. 18 to 20 are diagrams illustrating experimental results obtained by obtaining long-time summed correlation values for each of the frequency direction and the phase direction.

  FIG. 15 is a graph obtained by three-dimensionally plotting the short-time summed correlation value in the phase direction and the frequency direction, and FIG. 16 is a graph obtained by extracting the correlation processing result in the frequency direction from the graph in FIG. FIG. 17 is a graph obtained by extracting the correlation processing result in the phase direction. The way of viewing the graph is the same as in FIGS.

  From the correlation processing result in the phase direction in FIG. 17, it can be seen that the peak of the short-time summed correlation value appears in the portion of the phase difference “0”. Further, when looking at the correlation processing result in the frequency direction of FIG. 16, the short-time summation integrated correlation value is obtained at three locations of the frequency difference “0 Hz” portion and the frequency difference portion corresponding to the specific frequency “± 25 Hz”. It can be seen that the peak appears. This is because the integrated correlation value corresponding to the specific frequency (first integrated correlation value) and the integrated correlation value corresponding to frequency zero (second integrated correlation value) are added. That is, as a result of extracting two types of frequency components, that is, the frequency zero component (DC component) and the specific frequency component included in the temporal change of the correlation value, a peak appears in the frequency difference corresponding to this.

  FIG. 18 is a graph obtained by three-dimensionally plotting the long-time total accumulated correlation value in the phase direction and the frequency direction, and FIG. 19 is a graph obtained by extracting the correlation processing result in the frequency direction from the graph in FIG. FIG. 20 is a graph obtained by extracting the correlation processing result in the phase direction. The way of viewing the graph is the same as in FIGS.

  From the correlation processing result in the phase direction of FIG. 20, it can be seen that the peak of the long-time summed correlation value appears in the portion of the phase difference “0” as in the case of FIG. Also, from the correlation processing result in the frequency direction of FIG. 19, it can be seen that the peak of the long-time summed correlation value appears in the portion of the frequency difference “0 Hz”. The phase and the frequency are exactly the same, and it can be said that the GPS satellite signal has been successfully captured by the method of this embodiment. In particular, with respect to the correlation processing result in the frequency direction, since a sharp peak appears in the portion of the frequency difference “0 Hz”, the effectiveness of the GPS satellite signal capturing method of the present embodiment can be confirmed.

2-4. In the baseband processing circuit unit 20, the first multiplier 211 multiplies the reception signal by the first carrier removal signal generated and generated by the first carrier removal signal generation unit 221. Are converted into specific frequencies. Also, in the second multiplier 212, the frequency of the received signal is converted to zero by multiplying the received signal by the second carrier removing signal generated and generated by the second carrier removing signal generator 222. The Then, the first correlation value is calculated by the first correlator 231 with respect to the specific frequency signal, and the second correlation value is calculated with the second correlator 232 with respect to the zero frequency signal. Is calculated. Then, the integration result of the first correlation value and the integration result of the second correlation value are added together, and a GPS satellite signal is captured using the added integration correlation value.

  When correlation processing is performed over an arbitrary time of 20 ms or more, which is the bit length of navigation message data, with respect to the received signal of the GPS satellite signal, even if the acquisition is performed at the correct frequency, the sign change It becomes time series data of a certain correlation value. However, when the frequency is shifted by a specific frequency (25 Hz) corresponding to the bit length of the navigation message data, as described in the principle, the sign change of the correlation value due to the presence or absence of the bit inversion of the navigation message data. Time-series data of correlation values with different ways (sign change patterns) is obtained.

  Therefore, the frequency of the received signal is converted to a specific frequency and converted to zero. Then, if a correlation operation is performed on each of the converted signals and the correlation values are added together, the correlation values having different sign change patterns are superimposed on each other. You can disable the impact. In other words, whether or not there is bit inversion in the navigation message data, but because one correlation value supplements the other correlation value, the correlation values with different signs cancel each other when the correlation values are integrated. Can be suppressed. Accordingly, the correlation values can be integrated over an arbitrary correlation integration time.

3. Modification 3-1. Electronic Device In the above-described embodiments, the case where the present invention is applied to a mobile phone which is a kind of electronic device has been described as an example. However, an electronic device to which the present invention can be applied is not limited thereto. For example, the present invention can be similarly applied to other electronic devices such as a car navigation device, a portable navigation device, a personal computer, a PDA (Personal Digital Assistant), and a wristwatch.

3-2. In the above-described embodiment, the GPS has been described as an example of the position calculation system. However, WAAS (Wide Area Augmentation System), QZSS (Quasi Zenith Satellite System), GLONASS (GLObal NAvigation Satellite System), GALILEO It may be a position calculation system using other satellite positioning systems.

3-3. Specific frequency In the above-described embodiment, the specific frequency is described as being 25 Hz corresponding to the bit length of the navigation message data. However, the processing may be performed using another frequency as the specific frequency.

  When the frequency analysis is performed on the time series data of the correlation value, although not shown in FIG. 1B, a peak of the power value may appear at a frequency lower than the specific frequency of 25 Hz. This is because the bit inversion timing of the navigation message data is not necessarily the timing every 20 milliseconds. That is, when the bit inversion timing of the navigation message data arrives in a period longer than 20 milliseconds, the period of the correlation value corresponding to that period is not 40 milliseconds, but is longer. If the period is longer than 40 milliseconds, the frequency is lower than 25 Hz.

  For example, when the bit inversion timing of the navigation message data arrives at an interval of 40 milliseconds, the cycle of the correlation value corresponding to the interval (period) is 80 milliseconds and the frequency is 12.5 Hz. Therefore, if the processing is performed by adding a frequency lower than 25 Hz (for example, a frequency 1 / n times 25 Hz (n> 1)) to the specific frequency, the GPS satellite signal can be captured more accurately. .

  FIG. 21 is a block diagram showing an example of the circuit configuration of the baseband processing circuit unit 20 in this case. In addition, about the structure same as FIG. 6, the same code | symbol is attached | subjected and description is abbreviate | omitted. In the baseband processing circuit unit 20 of FIG. 21, a first signal path that performs correlation calculation by converting the frequency of the reception signal to the first specific frequency, and a first signal path that performs correlation calculation by converting the frequency of the reception signal to frequency zero. Three signal paths are provided: a two-signal path and a third signal path that performs correlation calculation by converting the frequency of the received signal to the second specific frequency. As the specific frequency in this case, for example, the first specific frequency can be set to 25 Hz, and the second specific frequency can be set to 12.5 Hz which is a half thereof.

  That is, the first multiplier 211 multiplies the reception signal by the first carrier removal signal generated and generated by the first carrier removal signal generation unit 221, so that the reception signal is a signal of the first specific frequency. Down-converted to a first received signal (first specific frequency signal) and outputs to the first correlator 231. The second multiplier 212 multiplies the reception signal by the second carrier removal signal generated and generated by the second carrier removal signal generation unit 222, whereby the second reception signal is a signal having a frequency of zero. Down-converted to (frequency zero signal) and output to the second correlator 232. Then, the third multiplier 213 multiplies the received signal by the third carrier removal signal generated and generated by the third carrier removal signal generator 223, so that the received signal is a signal of the second specific frequency. Downconverted to a third received signal (second specific frequency signal) and outputs to the third correlator 233.

  In the case of such a circuit configuration, the processing unit 25 calculates the integration result (first correlation calculation result) of the correlation value (first correlation value) of the first specific frequency output from the first correlator 231. The correlation between the zero-frequency correlation value (second correlation value) output from the second correlator 232 (second correlation calculation result) and the second specific frequency correlation output from the third correlator 233. The integration result of the value (third correlation value) (the result of the third correlation calculation) is summed, and the GPS satellite signal is captured using the summed correlation value.

  In addition, a k-th multiplier, a k-th carrier removal signal generator, and a k-th correlator (k ≧ 4) are provided, and for example, a frequency 1 / n times (n> 2) of 25 Hz is similarly added to the specific frequency. Processing may be performed.

  Further, in the above-described embodiment, the processing is performed while paying attention to the positive frequency. However, it is also possible to perform the processing focusing on the negative frequency. In this case, for example, the process may be performed by setting the specific frequency described with reference to FIG. 6 to “−25 Hz”.

  It is also possible to perform processing in consideration of both positive and negative frequencies. In this case, for example, the first specific frequency described with reference to FIG. 21 may be set to “+25 Hz”, and the second specific frequency may be set to “−25 Hz”. By considering both positive and negative, GPS satellite signals can be captured more accurately. Of course, even when a frequency other than 25 Hz, such as 12.5 Hz, is used, a negative frequency may be similarly considered.

3-4. Capture of GPS satellite signal In the embodiment described above, the result of integrating the correlation calculation results for the signal of the specific frequency and the result of integrating the correlation calculation results for the signal of frequency zero are added together, and the total integrated correlation value is used. It has been described as capturing GPS satellite signals. However, the summation is merely an example. For example, the sum of the results obtained by integrating the correlation calculation results for the specific frequency signal and the results obtained by integrating the correlation calculation results for the frequency zero signal is used. The GPS satellite signal may be captured.

  FIG. 22 is a diagram illustrating an example of data stored in the storage unit 27 of the baseband processing circuit unit 20 in this case. Note that the same reference numerals are assigned to the same data as the storage unit 27 in FIG. In the storage unit 27 of FIG. 22, a first long-time integrated correlation value obtained by collecting and integrating the first correlation values calculated for each accumulation time 274 for the correlation integration time 273 and a second calculated for each accumulation time 274. The long-time integrated correlation value data 278 is stored as data storing the second long-time integrated correlation value obtained by collecting and integrating the correlation values for the correlation integrated time 273 minutes.

  In this case, the satellite signal acquisition unit 251 performs peak detection for each long-time integrated correlation value stored in the long-time integrated correlation value data 278 of the storage unit 27. And when a peak is detected about any one long time integration correlation value, a GPS satellite signal is captured by detecting a code phase based on the detected peak. When peaks are detected for both long-time integrated correlation values, the GPS satellite signal is captured by detecting the code phase using the peak with the larger value.

3-5. Accumulation time In the above-described embodiment, it has been described that the short-time total integration correlation value is calculated for each accumulation time, and the long-time total integration correlation value corresponding to the correlation integration time is calculated by adding them. The long-time total integrated correlation value may be calculated directly from the correlation value for the time. That is, the first correlation value and the second correlation value accumulated for the correlation integration time are respectively integrated to calculate the first integration correlation value and the second integration correlation value, and these are added together to obtain the long-time total integration correlation value. May be calculated.

3-6. Conversion of received signal and correlation calculation In the above-described embodiment, a circuit configuration (hardware) that performs conversion of the frequency of the received signal to a specific frequency or conversion to frequency zero is performed by multiplying the received signal by the carrier removal signal. However, it may be performed by software by digital signal processing. Similarly, the correlation calculation for a specific frequency signal and the correlation calculation for a zero frequency signal may be performed in software by digital signal processing instead of hardware by a circuit configuration using a correlator. Good.

  DESCRIPTION OF SYMBOLS 1 Portable telephone, 10 GPS receiving part, 11 RF receiving circuit part, 20 Baseband processing circuit part, 21 Multiplication part, 22 Carrier removal signal generation part, 23 Correlation part, 24 Replica code generation part, 25 Processing part, 27 Storage unit, 30 host CPU, 40 operation unit, 50 display unit, 60 mobile phone antenna, 70 mobile phone wireless communication circuit unit, 80 storage unit, 211 first multiplier, 212 second multiplier, 221 first carrier A signal generator for removal, 222 a signal generator for second carrier removal, 231 a first correlator, and a 232 second correlator.

Claims (6)

Converting the frequency of the received signal, which is a satellite signal received from the positioning satellite, to a specific frequency corresponding to the bit length of the navigation message data carried in the satellite signal;
Performing a first correlation operation on the frequency-converted signal of the specific frequency;
Integrating the results of the first correlation operation over a predetermined time longer than the bit length;
Using the integrated result to capture the satellite signal;
A signal acquisition method comprising: Converting the frequency of the received signal to a frequency of zero;
Performing a second correlation operation on the frequency-converted zero-frequency signal;
Integrating the results of the second correlation operation over the predetermined time;
Further including
Capturing the satellite signal includes capturing the satellite signal using a sum value obtained by summing up the result of summing up the results of the first correlation calculation and the result of summing up the results of the second correlation computation. Including,
The signal capturing method according to claim 1. Converting the frequency of the received signal to a frequency of zero;
Performing a second correlation operation on the frequency-converted zero-frequency signal;
Integrating the results of the second correlation operation over the predetermined time;
Further including
Capturing the satellite signal means that the satellite signal is obtained using a result obtained by integrating one of a result obtained by integrating the results of the first correlation calculation and a result obtained by integrating the result of the second correlation calculation. Including capturing,
The signal capturing method according to claim 1. The specific frequency is 25 Hz.
The signal acquisition method as described in any one of Claims 1-3. A receiver for receiving satellite signals from a positioning satellite;
A frequency converter that converts the frequency of the received signal received by the receiver to a specific frequency corresponding to the bit length of the navigation message data carried in the satellite signal;
A correlation calculation unit that performs a correlation calculation on the signal of the specific frequency that has been frequency converted by the frequency conversion unit;
An accumulating unit that accumulates the results of the correlation calculation over a predetermined time longer than the bit length;
Using the result of the correlation operation integrated by the integration unit, a capture unit that captures the satellite signal;
A signal capturing device comprising:   An electronic apparatus comprising the signal capturing device according to claim 5.

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