JP2007142679A - Receiving machine - Google Patents

Abstract

To reduce the current consumption of a local oscillation circuit with a simple configuration by detecting the strength of a received signal and setting the current of the local oscillation circuit to an optimum value.
A demodulation circuit 101 demodulates an RF signal input from an antenna into baseband signals orthogonal to Ich and Qch, and a filter circuit 102 suppresses only interference waves from the baseband signals of Ich and Qch. Input to the gain control circuit 104. The gain control circuit 104 inputs a baseband signal whose level is kept constant to the baseband signal processing circuit 103. The local oscillation circuit 105 supplies a local signal to the demodulation circuit 101. At this time, the current source of the local oscillation circuit 105 is varied in conjunction with a control signal for controlling the gain of the gain control circuit 104. In this way, by changing the current of the local oscillation circuit 105, C / N is changed, and the average power of the local oscillation circuit 105 is reduced.
[Selection] Figure 1

Description

  The present invention relates to a receiver applied to a mobile phone or the like used in a digital mobile communication system.

  FIG. 8 is a block diagram showing an example of a conventional receiver used in a digital mobile communication system. This receiver includes a demodulating circuit 1 that demodulates an RF (Radio Frequency) signal input from an antenna into baseband signals of Ich and Qch orthogonal to each other, and interference waves from the baseband signals of Ich and Qch. A filter circuit 2 that suppresses only the signal, a baseband signal processing circuit 3 that converts the baseband signal demodulated by the demodulation circuit 1 into a digital signal, and an A / D converter included in the baseband signal processing circuit 3 A gain control circuit 4 that performs control to keep the level of the input baseband signal constant, a local oscillation circuit 5 that supplies a local signal to the demodulation circuit 1, and a baseband signal that is input to the baseband signal processing circuit 3 And a control I / F circuit 6 for converting the gain level into gain setting data of the gain control circuit 4.

  With such a configuration, in the demodulation circuit 1, the desired wave is normally frequency-converted with the local signal and demodulated into the baseband signal, and at the same time, the interference wave is also frequency-converted into the baseband band. At this time, a noise signal such as phase noise superimposed on the local signal (hereinafter, such noise signal is referred to as a phase noise signal) is superimposed on the interference wave that has been frequency-converted when the demodulation operation is performed, and its phase When the spread of the noise signal reaches the band of the desired wave, the S / N (Sound Noise Ratio) of the desired wave is deteriorated. Since this causes deterioration of the quality of the received signal, it is necessary to ensure a sufficiently high C / N (Carrier Noise Ratio) of the local oscillation circuit 5.

Various techniques for ensuring a sufficiently high value without deteriorating the C / N of the local oscillation circuit are known. For example, by detecting the frequency shift of the intermediate frequency filter and changing the frequency of the local oscillator by frequency control, the frequency shift of the intermediate frequency filter is corrected to prevent C / N degradation, and the demodulator operation clock is simultaneously set. A technique is known in which the frequency deviation of the intermediate frequency filter is corrected to prevent the deterioration of C / N by changing it (see, for example, Patent Document 1).
JP-A-9-247030

  In recent years, mobile devices (for example, mobile phones) of mobile communication systems have been strongly demanded to reduce power consumption in addition to downsizing and cost reduction. However, in the above prior art, in order to ensure a sufficiently high C / N of the local oscillation circuit for the purpose of preventing noise, it is necessary to sufficiently increase the current flowing through the local oscillation circuit itself. In other words, there is a trade-off relationship between noise prevention measures and lowering the current of the local oscillation circuit. Therefore, in conventional receivers, noise prevention measures greatly hinder the reduction in current, and further reduction in power consumption cannot be achieved.

  The present invention has been made in view of the above points, and by detecting the strength of the received signal and setting the current flowing through the local oscillation circuit to an optimum value, the current consumption of the local oscillation circuit can be reduced with a simple configuration. An object of the present invention is to provide a receiver that can realize the above.

  The receiver of the present invention includes a demodulation circuit that demodulates a received signal and converts it into a baseband signal, a baseband signal processing circuit that converts the baseband signal into a digital signal, and a local oscillation that supplies a local signal to the demodulation circuit Circuit, a gain control circuit that keeps the level of the baseband signal input to the baseband signal processing circuit constant, a filter circuit that suppresses the level of the interference wave input to the baseband signal processing circuit, and a baseband signal A receiver comprising a first control I / F circuit that detects a level of a baseband signal input to a processing circuit and converts it into gain setting data for setting a gain of the gain control circuit. The I / F circuit interlocks with the gain setting data to change the current of the local oscillation circuit according to the strength of the received signal and change the C / N. It adopts a configuration to reduce power.

  Further, an interference wave level detection circuit for detecting the level of the interference wave is provided, and the first control I / F circuit interlocks with the gain setting data to detect the interference of the received signal and the interference detected by the interference wave level detection circuit. It is also possible to adopt a configuration in which the average power of the local oscillation circuit is reduced by changing the current of the local oscillation circuit and changing the C / N according to the strength of the wave level. Alternatively, the received signal quality data calculated by the baseband signal processing circuit is obtained separately from the first control I / F circuit, and converted into data for setting the current value of the local oscillation circuit based on the received signal quality data. 2 control I / F circuit, the second control I / F circuit varies the current of the local oscillation circuit according to the received signal quality data to change the C / N, thereby reducing the average power of the local oscillation circuit A configuration can also be adopted. Of course, in this case, the first control I / F circuit only needs to have a function of converting the gain setting data.

  That is, according to the receiver of the present invention, the operating current of the local oscillation circuit is varied in conjunction with the control signal for controlling the gain of the gain control circuit, and the C / N of the local oscillation circuit is changed. Alternatively, the operating current of the local oscillation circuit is varied according to the level of the interference wave detected on the output side of the demodulation circuit or the received signal quality data calculated by the baseband signal processing circuit, and the C / N Is changing. As a result, the average power can be reduced while ensuring the C / N of the local oscillation circuit at a sufficiently high level.

  According to the receiver of the present invention, the S / O at the input terminal of the baseband signal processing circuit required for the digital mobile communication system is obtained by linking the control signal to the gain control circuit and the current change of the local oscillation circuit. By ensuring the C / N of the local oscillation circuit to an optimum value while ensuring a good value for N, it is possible to reduce the current consumption of the receiver with a relatively simple configuration. Further, by detecting the level of the interference wave by the interference wave level detection circuit, the current of the local oscillation circuit can be adjusted according to the state of the interference wave in addition to the current adjustment of the local oscillation circuit according to the operating state of the gain control circuit. It becomes possible. As a result, more precise current control of the local oscillation circuit can be performed, and as a result, further reduction of current consumption can be realized while taking measures against noise of the receiver. In the case of a digital mobile communication system in which the received signal quality data can be calculated from the S / N of the received signal by the baseband signal processing circuit, the calculation result of the received signal quality data is used as the current of the local oscillation circuit. By interlocking with the control, it is possible to realize both low noise and power saving of the receiver by a relatively simple method.

<Summary of invention>
The receiver of the present invention changes the C / N of the local oscillation circuit by varying the operating current of the local oscillation circuit in conjunction with a control signal for controlling the gain of the gain control circuit. Alternatively, the operating current of the local oscillation circuit is varied according to the level of the interference wave detected on the output side of the demodulation circuit or the received signal quality data calculated by the baseband signal processing circuit, and the C / N Is changing. In this way, by detecting the strength of the received signal and setting the current flowing through the local oscillation circuit to an optimum value, the average current of the local oscillation circuit can be reduced with a simple circuit configuration, resulting in low current consumption and low power consumption. Both noise generation can be realized.

  Hereinafter, several embodiments of the receiver of the present invention will be described in detail with reference to the drawings. In the drawings used in the embodiments, the same components are denoted by the same reference numerals, and redundant description is omitted as much as possible.

<Embodiment 1>
FIG. 1 is a block diagram showing a configuration of a receiver according to Embodiment 1 of the present invention. The receiver of Embodiment 1 shown in FIG. 1 includes a demodulation circuit 101 that demodulates an RF signal input from an antenna (not shown) into baseband signals orthogonal to Ich and Qch, and baseband signals of Ich and Qch, respectively. Filter circuit 102 that suppresses only the interference wave from the baseband signal, a baseband signal processing circuit 103 that converts the baseband signal demodulated by the demodulation circuit 101 into a digital signal, and an A / B included in the baseband signal processing circuit 103 A gain control circuit 104 that performs control so as to keep the level of the baseband signal input to the D converter constant, a local oscillation circuit 105 that supplies a local signal to the demodulation circuit 101, and a baseband signal processing circuit 103 Detects baseband signal level and converts to gain setting data of gain control circuit 104 And a first control I / F circuit 106 that. The first control I / F circuit 106 is configured to change the operating current of the local oscillation circuit 105 according to the strength of the received signal in conjunction with the gain setting data. Thus, the average power of the local oscillation circuit 105 can be reduced by changing the C / N of the local oscillation circuit 105.

  Next, the operation of the receiver shown in FIG. 1 will be described. An RF signal input from an antenna (not shown) is demodulated by the demodulation circuit 101 into a baseband signal in which Ich and Qch are orthogonal to each other. Then, only the interference wave is suppressed from the baseband signals of Ich and Qch by the filter circuit 102, and the level of the baseband signal is kept constant by the gain control circuit 104. The baseband signal in which the interference wave is suppressed in this way and held at a constant level is input to an A / D converter included in the baseband signal processing circuit 103.

  On the other hand, since the local oscillation circuit 105 supplies a local signal to the demodulation circuit 101, the demodulation circuit 101 converts the frequency of the desired wave by the local signal and demodulates it into a baseband signal. Frequency converted to band. Thereby, the phase noise signal such as phase noise superimposed on the local signal from the local oscillation circuit 105 is superimposed on the interference wave frequency-converted during the demodulation operation, and the spread of the phase noise signal is in the band of the desired wave. Reach up to. Hereinafter, this state will be described with reference to the drawings.

  FIG. 2 is a schematic diagram illustrating the relationship between the desired wave, the interference wave, and the noise at the input unit of the demodulation circuit 101 in a state where the desired signal level of the RF signal is relatively low and the interference wave level is relatively high. In FIG. 2, the horizontal axis represents frequency and the vertical axis represents signal level. That is, this figure shows a case where the gain (gain) of the AGC (Automatic Gain Controller) and LNA (Low Noise Amplifier) of the gain control circuit 104 is large, and the desired wave when the desired wave level is low and the interference wave level is high. And the noise of the interference wave.

  In FIG. 2, the interference wave itself is suppressed by the filter circuit 102 and input to the baseband input unit (not shown) of the baseband signal processing circuit 103, but phase noise such as phase noise superimposed on the interference wave The signal has reached the band of the desired wave. In this case, since the level of the baseband signal input to the baseband signal processing circuit 103 decreases, generally, the gain of the gain control circuit 104 is increased so that the input level of the baseband signal does not decrease. To the baseband signal processing circuit 103.

  Here, the phase noise signal such as the phase noise superimposed on the interference wave is mainly amplified by the demodulating circuit 101, the filter circuit 102, and the gain control circuit 104, and the baseband input of the baseband signal processing circuit 103. Is superimposed on a noise signal that has arrived at this section (hereinafter, such a noise signal is referred to as a thermal noise signal), and is input to the baseband signal processing circuit 103 as a total noise signal. That is, the total noise signal in which the phase noise signal and the thermal noise signal are superimposed is input to the baseband signal processing circuit 103.

  Further, it is desirable that the phase noise signal of the local oscillation circuit 105 is sufficiently lower than the thermal noise signal obtained by amplifying the thermal noise. For this purpose, the C / N of the local oscillation circuit 105 should be secured at a sufficiently high value. It is necessary to keep.

  FIG. 3 is a schematic diagram showing the relationship between the desired wave, the disturbing wave, and the noise at the input unit of the demodulation circuit 101 in a state where both the desired wave level and the disturbing wave level are relatively high. In FIG. 3, the horizontal axis represents frequency and the vertical axis represents signal level. That is, this figure shows the relationship between the noise of the desired wave and the interference wave when the gain (gain) of the AGC and LNA of the gain control circuit 104 is small and the desired wave level is high and the interference wave level is high. Yes.

  That is, as shown in FIG. 3, the signal level of the desired wave of the RF signal and the signal level of the interference wave are substantially equal. In such a case, the gain of the gain control circuit 104 is generally small because the input level of the baseband signal input to the baseband signal processing circuit 103 is lowered.

  In general, in such a state, the ratio of the desired wave at the baseband input unit of the baseband signal processing circuit 103 and the thermal noise signal obtained by amplifying the thermal noise is sufficiently large, and digital mobile communication There is enough noise margin on the system. Therefore, in such a state, the phase noise signal of the local oscillation circuit 105 superimposed on the interference wave is sufficiently lower than the thermal noise signal, so that the desired signal level of the RF signal shown in FIG. It is not necessary to ensure the C / N of the local oscillation circuit 105 at a sufficiently high value as in the case where the wave level is relatively high, up to the ratio between the desired wave and the total noise signal allowed on the digital mobile communication system. Noise level can be degraded. This is realized by lowering the current of the local oscillation circuit 105. In other words, the operating current of the local oscillation circuit 105 can be lowered by the amount that the ratio between the desired wave and the total noise signal is degraded to a level that can be tolerated by the digital mobile communication system.

  FIG. 4 is a schematic diagram illustrating the relationship between the desired wave, the disturbing wave, and the noise at the input unit of the demodulation circuit 101 in a state where the desired wave level is relatively high and the disturbing wave level is relatively low. In FIG. 4, the horizontal axis represents frequency and the vertical axis represents signal level. That is, this figure shows the relationship between the noise of the desired wave and the interference wave when the gain (gain) of the AGC and LNA of the gain control circuit 104 is small and the desired wave level is high and the interference wave level is low. Yes.

  That is, as shown in FIG. 4, the desired wave of the RF signal is sufficiently higher than the interference wave. In such a case, the input level of the baseband signal input to the baseband signal processing circuit 103 is lowered, In general, the gain of the gain control circuit 104 is small.

  In general, in such a state, the ratio of the desired wave at the baseband input unit of the baseband signal processing circuit 103 and the thermal noise signal obtained by amplifying the thermal noise is sufficiently large, and digital mobile communication There is enough noise margin on the system. Further, most of the phase noise signal of the interference wave is buried in the thermal noise signal in which the thermal noise is amplified. In such a state, since the phase noise signal of the local oscillation circuit 105 superimposed on the interference wave is sufficiently lower than the thermal noise signal, the desired signal level of the RF signal shown in FIG. It is not necessary to ensure the C / N of the local oscillation circuit 105 at a sufficiently high value as in the case where the level is relatively high, and the noise is reduced to the ratio between the desired wave and the total noise signal allowed on the digital mobile communication system. The level can be degraded. This is realized by lowering the current of the local oscillation circuit 105. In other words, the operating current of the local oscillation circuit 105 can be lowered by the amount that the ratio between the desired wave and the total noise signal is degraded to a level that can be tolerated by the digital mobile communication system.

  As described above, in the receiver according to Embodiment 1 of the present invention, when the gain of the gain control circuit 104 is relatively small, the operating current of the local oscillation circuit 105 can be lowered. This can be realized by the first control I / F circuit 106 controlling the control signal for controlling the gain of the gain control circuit 104 and the current source of the local oscillation circuit 105 in conjunction with each other. As a result, it is possible to realize both low noise and low current consumption of the receiver.

<Embodiment 2>
FIG. 5 is a block diagram showing a configuration of a receiver according to Embodiment 2 of the present invention. The receiver of the second embodiment shown in FIG. 5 compares the level of the interference wave with the reference value using the level comparator 108 compared to the receiver of the first embodiment shown in FIG. An interference wave level detection circuit 107 for detecting a level interference wave is added. With such a configuration, the first control I / F circuit 106 operates in conjunction with the gain setting data, depending on the strength of the received signal and the level of the interference wave level detected by the interference wave level detection circuit 107. C / N is changed by changing the operating current 105, and the average power of the local oscillation circuit is reduced.

  FIG. 6 is a schematic diagram showing the relationship between the desired wave, the disturbing wave, and the noise at the input unit of the demodulation circuit 101 in a state where both the desired wave level and the disturbing wave level are relatively low. In FIG. 6, the horizontal axis represents frequency and the vertical axis represents signal level. That is, this figure shows the relationship between the noise of the desired wave and the disturbing wave when the gain (gain) of the AGC and LNA of the gain control circuit 104 is large and both the desired wave level and the disturbing wave level are low. Yes.

  That is, as shown in FIG. 6, when the desired signal level of the RF signal and the interference signal level are both substantially equal and low, the input level of the baseband signal input to the baseband signal processing circuit 103 is In general, the gain of the gain control circuit 104 is large as in the case of FIG. However, most of the phase noise signal of the interference wave is buried in the thermal noise signal in which the thermal noise is amplified.

  In such a state, since the phase noise signal of the local oscillation circuit 105 superimposed on the interference wave is sufficiently lower than the thermal noise signal, the desired signal level of the RF signal shown in FIG. It is not necessary to ensure the C / N of the local oscillation circuit 105 at a sufficiently high value as in the case where the level is relatively high, and the noise is reduced to the ratio between the desired wave and the total noise signal allowed on the digital mobile communication system. The level can be degraded. This can be realized by reducing the current of the local oscillation circuit 105. In other words, the operating current of the local oscillation circuit 105 can be lowered by the amount that the ratio between the desired wave and the total noise signal is degraded to a level that can be tolerated by the digital mobile communication system.

  As described above, in the receiver according to Embodiment 2 of the present invention, when the gain of the gain control circuit 104 is relatively large and the interference wave level is relatively low, the operating current of the local oscillation circuit 105 is lowered. Can do. This is because the level of the interference wave is detected by the interference wave level detection circuit 107, and the first control I / F circuit 106 is detected by the control signal for controlling the gain of the gain control circuit 104 and the interference wave level detection circuit 107. This can be realized by linking the level of the disturbing wave with the current source of the local oscillation circuit 105. As a result, it is possible to realize both low noise and low current consumption of the receiver.

<Embodiment 3>
FIG. 7 is a block diagram showing a configuration of a receiver according to Embodiment 3 of the present invention. The difference between the receiver of the third embodiment shown in FIG. 7 and the receiver of the first embodiment shown in FIG. 1 is that the first control I / F circuit 106 uses the received signal in conjunction with the gain setting data. Rather than changing the operating current of the local oscillation circuit 105 depending on the strength, the first control I / F circuit 106 only has a gain data setting function. The second control I / F circuit 106a for changing the operating current is provided.

  That is, in the receiver according to the third embodiment, the baseband signal processing circuit 103 calculates the quality data of the received signal, and the second control I / F circuit 106a uses the local oscillation circuit according to the calculation result of the quality data of the received signal. 105 is converted into data for setting the operating current value. In this way, the second control I / F circuit 106a changes the C / N by changing the operating current of the local oscillation circuit 105 according to the quality data of the received signal, thereby reducing the average power of the local oscillation circuit 105. I am letting.

  That is, in the receiver of the third embodiment, the RF signal input from the antenna is demodulated by the demodulation circuit 101 into baseband signals of Ich and Qch that are orthogonal to each other, and further, the baseband signals of Ich and Qch are respectively obtained by the filter circuit 102. Only the interference wave is suppressed from the signal and the baseband signal maintained at a constant level by the gain control circuit 104 is input to the A / D converter included in the baseband signal processing circuit 103. The local oscillation circuit 105 supplies a local signal to the demodulation circuit 101. At this time, in the demodulation circuit 101, the desired wave is frequency-converted with the local signal and demodulated into the baseband signal, and at the same time, the interference wave is also frequency-converted into the baseband band. Then, the phase noise signal such as phase noise superimposed on the local signal is superimposed on the interference wave frequency-converted during the demodulation operation, and the spread of the phase noise signal reaches the desired wave band as shown in FIG. Reach.

  Here, the baseband signal processing circuit 103 calculates the received signal quality data from the S / N of the received signal, and the second control I / F circuit 106a determines the operating current value of the local oscillation circuit 105 based on the result. Setting, that is, when the S / N is good, the operating current of the local oscillation circuit 105 is decreased to the system allowable limit to degrade the C / N, thereby realizing the current reduction of the local oscillation circuit 105. . As a result, the receiver can realize both low noise and low current consumption.

  Since the receiver according to the present invention can realize both low noise and power saving, it can be effectively used for a mobile phone using a battery as a power source.

The block diagram which shows the structure of the receiver in Embodiment 1 of this invention Schematic diagram showing the relationship between the desired wave, jamming wave and noise at the demodulating circuit input section where the desired wave level is relatively low and the jamming wave level is relatively high Schematic diagram showing the relationship between the desired wave, jamming wave and noise at the demodulator input section where both the desired wave level and the jamming wave level are relatively high Schematic diagram showing the relationship between the desired wave, jamming wave, and noise at the demodulator circuit input section when the desired wave level is relatively high and the jamming wave level is relatively low. The block diagram which shows the structure of the receiver in Embodiment 2 of this invention. Schematic diagram showing the relationship between the desired wave, jamming wave and noise at the demodulator circuit input section where both the desired wave level and the jamming wave level are relatively low The block diagram which shows the structure of the receiver in Embodiment 3 of this invention. Block diagram showing an example of a conventional receiver used in a digital mobile communication system

Explanation of symbols

Reference Signs List 101 demodulation circuit 102 filter circuit 103 baseband signal processing circuit 104 gain control circuit 105 local oscillation circuit 106 first control I / F circuit 106a second control I / F circuit 107 jamming wave level detection circuit 108 level comparator

Claims (3)

A demodulation circuit that demodulates the received signal and converts it into a baseband signal;
A baseband signal processing circuit for converting the baseband signal into a digital signal;
A local oscillation circuit for supplying a local signal to the demodulation circuit;
A gain control circuit for maintaining a constant level of the baseband signal input to the baseband signal processing circuit;
A filter circuit for suppressing the level of an interference wave input to the baseband signal processing circuit;
A first control I / F circuit that detects a level of the baseband signal input to the baseband signal processing circuit and converts it into gain setting data for setting a gain of the gain control circuit;
A receiver comprising:
The first control I / F circuit changes the current of the local oscillation circuit according to the strength of the received signal in association with the gain setting data to change C / N, and the average power of the local oscillation circuit A receiver characterized by reducing noise. Furthermore, it has a jamming wave level detection circuit that detects the level of the jamming wave,
The first control I / F circuit operates in conjunction with the gain setting data so that the current of the local oscillation circuit is determined by the strength of the received signal and the level of the interference wave detected by the interference wave level detection circuit. The receiver according to claim 1, wherein the average power of the local oscillation circuit is reduced by changing the C / N by changing the C / N. A demodulation circuit that demodulates the received signal and converts it into a baseband signal;
A baseband signal processing circuit for converting the baseband signal into a digital signal;
A local oscillation circuit for supplying a local signal to the demodulation circuit;
A gain control circuit for maintaining a constant level of the baseband signal input to the baseband signal processing circuit;
A filter circuit for suppressing the level of an interference wave input to the baseband signal processing circuit;
A first control I / F circuit that detects a level of the baseband signal input to the baseband signal processing circuit and converts it into gain setting data for setting a gain of the gain control circuit;
A receiver comprising:
And a second control I / F circuit for obtaining the received signal quality data calculated by the baseband signal processing circuit and converting the received signal quality data into data for setting a current value of the local oscillation circuit according to the received signal quality data,
The second control I / F circuit varies the current of the local oscillation circuit by changing the current of the local oscillation circuit according to the received signal quality data, thereby changing the C / N to reduce the average power of the local oscillation circuit. Receiving machine.

Images