JP2005110030A - Cell search method, receiving apparatus, and mobile communication terminal apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a performance of an initial cell search even when the SNR of a received signal from a base station is low without using a linear amplifier having a large dynamic range, and a receiving apparatus and a mobile for implementing the method To provide a body communication terminal device.
A receiving apparatus 100 linearly converts a received signal into a saturated amplifier 115 that saturates and amplifies a received signal until the synchronization with the base station is established, and after the synchronization with the base station is established. A linear amplifier 116 for amplifying, and an analog / digital converter 120 for analog / digital conversion of the saturation-amplified received signal or the linearly amplified received signal with a relatively small dynamic range.
[Selection] Figure 1

Description

  The present invention relates to a cell search method used in a cellular radio communication system, and a receiving apparatus and a mobile communication terminal apparatus that implement the cell search method.

  2. Description of the Related Art Conventionally, in a wireless communication system having mobile communication terminal devices such as mobile phones as components, in order to effectively use a limited frequency band, a communication area is divided into a plurality of cells, and a base station is assigned to each cell. A cellular system is provided.

  FIG. 5 shows an outline of a cellular radio communication system. A base station 51 is installed in the cell 50, and a base station 61 is installed in a cell 60 adjacent to the cell 50. The mobile stations 52 and 53 in the communication area of the cell 50 need to form a channel with the base station 51 when starting wireless communication. The mobile stations 52 and 53 acquire a pilot signal periodically transmitted from the base station 51, establish synchronization with the base station 51, perform code identification, etc. To form a channel. A series of signal processing performed until the mobile stations 52 and 53 in the communication area of the cell 50 form a channel with the base station 51 is referred to as “cell search”. In particular, the case where the mobile stations 52 and 53 form a channel for the first time after activation is referred to as “initial cell search”, and after the channel is formed with the base station 51, the communication of the cell 60 from the communication area of the cell 50 is performed. A cell search performed based on a pilot signal transmitted from the base station 61 by the mobile stations 52 and 53 in preparation for moving into an area is referred to as a “neighbor cell search”.

  By the way, a TD-SCDMA (Time Division Synchronous Code Division Multiple Access) system, which is a standard originated in China, has been formulated as a third generation mobile phone communication system. The TD-SCDMA scheme is a scheme in which a TDMA (Time Division Multiplexing Access) scheme technique is incorporated into a CDMA (Code Division Multiple Access) scheme, and includes an uplink and a base station that transmit radio signals from a mobile station to a base station. This is a TDD (Time Division Duplex) system in which a downlink that transmits a radio signal to a mobile station is finely switched in a time division manner for communication.

  FIG. 6 shows a frame format of the TD-SCDMA system. The subframe of the TD-SCDMA system includes seven slots TS # 0 to # 6 having a slot time of 675 μs, a slot DwPTS (Downlink Pilot Time Slot physical channel) including a downlink pilot signal, and an uplink pilot signal. The slot includes a slot UpPTS (Uplink Pilot Time Slot physical channel) and two guard slots GP (Guard Period). Therefore, in the TD-SCDMA wireless communication system, the mobile stations 52 and 53 perform cell search by transmitting and receiving DwPTS and UpPTS pilot signals to and from the base stations 51 and 61. In the TD-SCDMA wireless communication system, the mobile stations 52 and 53 share the UpPTS.

  Further, in a TD-SCDMA wireless communication system, a cell search method called 4-step cell search is adopted. In the 4-step cell search, based on the beacon channel midamble code included in TS # 0 and the SYNC-DL code included in DwPTS, the mobile stations 52 and 53 acquire and synchronize with the base stations 51 and 61. Perform code identification.

The specific procedure of signal processing performed by the mobile stations 52 and 53 in the 4-step cell search is as follows.
(Step 1) Synchronization acquisition and code group identification Delay profiles for each of the 32 types of SYNC-DL codes are acquired based on the received signal of one subframe.
2. By detecting the maximum correlation value, the SYNC-DL code and the DwPTS timing are detected simultaneously.
(Step 2) Identification of basic midamble code and scrambling code Correlation between the beacon channel or the P-CCPCH (Primary Common Control Physical Channel) midamble part included in TS # 0 and the four basic midambles of the code group detected in Step 1 is taken.
2. The one with the largest correlation value is identified as the basic midamble of the cell that is performing the cell search.
3. 2. The scrambling code corresponding to the basic midamble identified in step 1 is identified.
(Step 3) Frame synchronization and multi-frame control synchronization A phase difference between the beacon channel included in TS # 0 or the midamble part of P-CCPCH and DwPTS is calculated.
2. The head of a frame is detected from a phase difference pattern with a period of 2 frames (4 subframes).
3. It is detected whether “S1” or “S2” in which the P-CCPCH is present in the next four subframes.
(Step 4) Broadcast channel (BCH) information acquisition 1. Demodulate BCH.

  FIG. 7 is a block diagram showing a configuration of receiving apparatus 10 that performs cell search in a TD-SCDMA wireless communication system. Both the mobile stations 52 and 53 are assumed to include the receiving device 10. It should be noted that, by using the receiving apparatus 10 shown in FIG. 7, a technique for accurately performing synchronization acquisition even when the reception level of the received signal at the mobile stations 52 and 53 is large or the frequency offset is large. Is described in Patent Document 1.

  The receiving apparatus 10 includes an antenna element 11, a low noise amplifier 12, a frequency converter 13, a linear amplifier 14, an auto gain controller (AGC) 15, an analog / digital converter (A / D converter) 16, a correlator 17, and a standard. And a correlation peak detector 19, a reception timing output terminal 20, a reference power supply terminal 21, a demodulator 22, and a demodulated signal output terminal 23.

  A radio signal from the base station 51 captured by the antenna element 11 is subjected to predetermined signal processing by the low noise amplifier 12 and the frequency converter 13 and then input to the linear amplifier 14. In the linear amplifier 14, the received signal is linearly amplified with a gain value adjusted by the AGC 15 according to the reception level. The linearly amplified received signal is input to the A / D converter 16 and converted into a digital signal, and then input to the correlator 17 and the demodulator 22. In the correlator 17, the received signal is correlated with a known code prepared in advance, and the correlation value is input to the normalization unit 18. In the normalization unit 18, the correlation value of the reception signal is normalized with the reception level based on the reception level information input from the AGC 15, and then input to the correlation peak detector 19. The correlation peak detector 19 performs peak detection of the standardized correlation value of the received signal. Information about the position (timing) of the correlation peak detected by the correlation peak detector 19 is extracted from the reception timing output terminal 20.

  Here, it is assumed that the correlation value of the received signal input from the correlator 17 to the normalization unit 18 in the mobile station 52 is in the form shown in FIG. The reason why the correlation value of the received signal at the mobile station 52 is as shown in FIG. 8A is that the mobile station 53 is physically closer to the base station 51. This is because the radio signal transmitted from the mobile station 53 using UpPTS is received at a higher reception level than the radio signal transmitted using DwPTS.

  If the mobile station 52 does not include the normalization unit 18, the correlation value in the form illustrated in FIG. 8A is input to the correlation peak detector 19. If the mobile station 52 performs an initial cell search under this assumption, the correlation peak detector 19 erroneously detects the correlation peak PU in UpPTS as the correlation peak PD in DwPTS. This is because in the initial cell search, the mobile station 52 cannot distinguish DwPTS from DwPTS because synchronization with the base station 51 has not yet been established. If the correlation peak PU in UpPTS is erroneously detected as the correlation peak PD in DwPTS as described above, the mobile station 52 cannot naturally acquire synchronization with the base station 51, and must perform the initial cell search again. No longer.

On the other hand, if the mobile station 52 includes the normalization unit 18, the standardization unit 18 standardizes the correlation value in DwPTS according to the reception level in DwPTS, and similarly the correlation value in UpPTS also corresponds to the reception level in UpPTS. Standardized. FIG. 8B shows an aspect of the correlation value of the received signal after normalization by the normalization unit 18. In FIG. 8B, the correlation value in UpPTS is generally lower than that in FIG. 8A, and the correlation peak PD in DwPTS is higher than the correlation peak PU in UpPTS. Therefore, by comparing FIG. 8B with FIG. 8A, if the mobile station 52 includes the normalization unit 18, the correlation peak detector 19 can correctly detect the correlation peak PD in DwPTS. It turns out that it will be possible.
Japanese Patent Laid-Open No. 9-162943

  However, even if the mobile station 52 includes the conventional receiving apparatus 10, if the SNR (Signal to Noise Ratio) of the radio signal transmitted from the base station 51 is further reduced, the correlation peak detector 19 causes the correlation peak in the UpPTS to be correlated. PU is erroneously detected as a correlation peak PD of DwPTS. That is, when the SNR of the received signal further decreases in the mobile station 52, the correlation value of the received signal input from the normalization unit 18 to the correlation peak detector 19 is in the form shown in FIG. As a specific example in which the SNR of the radio signal from the base station 51 is lowered, when the mobile station 52 moves, an obstacle is interposed between the base station 51 and the mobile station 52, or when the base station 51 And the physical distance between the mobile station 52 and the mobile station 52 is increased.

  Here, the reason why the correlation value of the received signal input to the correlation peak detector 19 of the mobile station 52 becomes the mode shown in FIG. 8C when the SNR of the radio signal from the base station 51 is further lowered is shown in FIG. And it demonstrates referring FIG. 10 suitably. In the TD-SCDMA wireless communication system, since the phase modulation method is adopted as the signal modulation method, a wireless signal modulated by the QPSK (Quadrature phase shift keying) method is transmitted from the base station 51, and the wireless signal is transmitted. Is received by the mobile station 52 including noise. 9 shows a radio signal 70 at the time of transmission from the base station 51, a range 71 in which the radio signal 70 at the time of transmission deviates due to the influence of noise, and an average reception level 72 of the received signal at the mobile station 52. A quadrature component (Quadrature component) and an in-phase component (In-phase component) are shown on a rectangular coordinate plane having coordinate axes. In FIG. 9, since the radio signal 70 at the time of transmission does not include noise, the radio signal 70 is evenly arranged as dots in each of the four quadrants. The signal 70 is indicated by a hatched circle centered on the signal 70, and the average reception level 72 of the received signal is indicated by a circle passing through four points of the radio signal 70 at the time of transmission. If it is assumed that the SNR of the radio signal from the base station 51 is lowered using FIG. 9, the diameter of the hatched circle is made larger.

  When a received signal including a large noise, that is, a received signal having a low SNR, is linearly amplified by the linear amplifier 14 and then input to the A / D converter 16, the received signal is shown in FIG. 10 by the A / D converter 16. It is focused on the inside or the periphery of the rectangular frame 80. That is, in the mobile station 52, the received signal observed in the hatched portion protruding from the rectangular frame 80 was observed by the A / D converter 16 at a point on the periphery of the rectangular frame 80 having the shortest linear distance. Impersonated as a thing. As the SNR of the received signal decreases, the shaded area becomes larger as described above, and the amount of fluctuation in the phase and reception level of the received signal that relies on A / D conversion also increases. As described above, if the received signal after A / D conversion is greatly different from the radio signal 70 at the time of transmission, it is obvious that the correlation peak PD is lowered even if the correlation value is obtained by the correlator 17. .

  In the mobile station 52, the dynamic range of the A / D converter 16 is usually designed in accordance with the average reception level of the reception signal linearly amplified by the linear amplifier 14. If an A / D converter having a dynamic range that is large enough to encompass the entire range 71 shifted by the influence of noise is used as the A / D converter 16 of the mobile station 52, various problems depending on the A / D conversion described above. However, since such an A / D converter is very expensive and consumes a large amount of power, it is not suitable as a component of the mobile station 52. Therefore, the A / D converter 16 of the mobile station 52 has to adopt a relatively small dynamic range, and when an A / D converter with a relatively small dynamic range is used, Since it must also be noted that the amount of fluctuation in the phase and reception level of the received signal depending on the / D conversion must be reduced, the dynamic range of the A / D converter 16 inevitably becomes the average reception level of the received signal. It will be set together.

  The present invention has been made in view of the above points, and a cell search method for improving the performance of an initial cell search even when the SNR of a received signal from a base station is low without using a linear amplifier having a large dynamic range. An object of the present invention is to provide a receiving apparatus and a mobile communication terminal apparatus that implement the method.

  The cell search method according to the present invention includes a reception step of receiving a radio signal transmitted from a base station, and a saturation type amplification step of performing saturation type amplification of the received signal until synchronization with the base station is established. After the synchronization with the base station is established, a linear amplification step for linearly amplifying the received signal, and a conversion step for analog / digital conversion of the saturation-amplified received signal or the linearly amplified received signal A correlation step for obtaining a correlation value between the received signal converted into a digital signal and a known code, a normalization step for normalizing the correlation value at a reception level, and a correlation based on the normalized correlation value And a detection step for detecting a peak.

  According to this method, after the initial cell search is performed based on the saturation-amplified received signal, and after synchronization with the base station is established by the initial cell search, based on the linearly amplified received signal, Since wireless communication is performed with this base station, even if the SNR of the received signal from the base station is low, the performance of the initial cell search is improved and the high reception performance as before is maintained after synchronization is established. can do.

  The receiving apparatus according to the present invention includes a receiving unit that receives a radio signal transmitted from a base station, a saturation amplifier that saturates and amplifies the received signal until synchronization with the base station is established, After synchronization with the base station is established, a linear amplifier that linearly amplifies the received signal, and an analog / digital converter that performs analog / digital conversion of the saturation-amplified received signal or the linearly amplified received signal A correlator for obtaining a correlation value between the received signal converted into a digital signal and a known code, a normalizing means for normalizing the correlation value at a reception level, and a correlation based on the normalized correlation value And a detecting means for detecting a peak.

  According to this configuration, after the initial cell search is performed based on the saturation-amplified received signal and synchronization with the base station is established by the initial cell search, the linearly amplified received signal is used. Since wireless communication is performed with this base station, even if the SNR of the received signal from the base station is low, the performance of the initial cell search is improved and the high reception performance as before is maintained after synchronization is established. can do.

  The receiving apparatus according to the present invention includes a receiving unit that receives a radio signal transmitted from a base station, and saturation-amplifies the received signal in a saturation region until synchronization with the base station is established, After synchronization with the station is established, a linear amplifier that linearly amplifies the received signal in a linear region, and an analog / digital converter that performs analog / digital conversion on the saturation-amplified received signal or the linearly amplified received signal. A converter, a correlator for obtaining a correlation value between the received signal converted into a digital signal and a known code, a normalizing means for normalizing the correlation value at a reception level, and based on the normalized correlation value And detecting means for detecting a correlation peak.

  According to this configuration, in the initial cell search, the received signal is saturated and amplified in the saturation region of the linear amplifier. After the initial cell search, the received signal is amplified in the linear region of the linear amplifier. Therefore, it is not necessary to use a different amplifier for the wireless communication, and the circuit configuration of the receiving apparatus can be simplified, and the performance of the initial cell search can be improved.

  The mobile communication terminal apparatus according to the present invention employs a configuration including the receiving apparatus according to the present invention.

  According to this configuration, since the A / D converter having a relatively small dynamic range and low power consumption is used, a long-time call with low manufacturing cost and low power consumption is possible. A mobile communication terminal device is obtained. Further, according to this configuration, since the performance of the initial cell search is improved, a mobile communication terminal device capable of wireless communication even in a place where radio waves cannot reach can be obtained.

  According to the present invention, the performance of the initial cell search can be improved even when the SNR of the received signal from the base station is low, without using a linear amplifier having a large dynamic range.

  The essence of the present invention is that the received signal is saturated and amplified until synchronization with the base station is established, and after the synchronization with the base station is established, the received signal is linearly amplified, and further saturated and amplified. The received signal or the linearly amplified received signal is converted into a digital signal by using an A / D converter having a relatively small dynamic range.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of receiving apparatus 100 according to Embodiment 1 of the present invention. The receiving apparatus 100 includes an antenna element 111, a low noise amplifier 112, a frequency converter 113, switches 114 and 119, a saturation amplifier 115, a linear amplifier 116, an AGC 117, a state management unit 118, an A / D converter 120, and a correlator 121. , A normalization unit 122, a correlation peak detector 125, a reception timing output terminal 126, a demodulator 127, a demodulated signal output terminal 128, and a reference power supply terminal 129. The receiving apparatus 100 is incorporated in a mobile communication terminal apparatus that can be used in a cellular radio communication system such as a mobile phone or a PDA (Personal Digital Assistant).

  The antenna element 111 captures a radio signal and inputs the captured radio signal to a low noise amplifier.

  The low noise amplifier 112 amplifies the reception signal input from the antenna element 111 while suppressing generation of noise due to amplification, and inputs the amplified reception signal to the frequency converter 113.

  The frequency converter 113 extracts a modulation signal from the reception signal input from the low noise amplifier 112 and inputs the extracted modulation signal to the switch 114.

  The switch 114 distributes and receives the received signal input from the frequency converter 113 to the saturation amplifier 115 or the linear amplifier 116 in accordance with the switching signal input from the state management unit 118. Similarly, the switch 119 selectively switches the input path of the reception signal in accordance with the switching signal input from the state management unit 118, so that the reception signal amplified by the saturation amplifier 115 or linear by the linear amplifier 116 is used. One of the amplified reception signals is input to the A / D converter 120.

  The saturation amplifier 115 performs saturation amplification on the reception signal input from the switch 114 and inputs the amplified reception signal to the switch 119.

  The linear amplifier 116 measures the reception level of the reception signal input from the switch 114 and inputs the measurement value to the AGC 117. Further, the linear amplifier 116 amplifies the reception signal input from the switch 114 with the gain value input from the AGC 117, and inputs the amplified reception signal to the switch 119.

  The AGC 117 compares the reception level of the reception signal input from the linear amplifier 116 with the reference power input from the reference power supply terminal 129, and performs linear amplification in the linear amplifier 116 to obtain the reception level of the reception signal, that is, The gain value input to the linear amplifier 116 is adjusted so that the power level is averaged. Further, the AGC 117 inputs the reception level of the reception signal input from the linear amplifier 116 to the standardization unit 122 as needed.

  The state management unit 118 constantly monitors the communication state of the receiving device 100 and switches to the switches 114 and 119 so that the received signal is saturated and amplified by the saturation amplifier 115 when the receiving device 100 starts an initial cell search. When a signal is input, and when the receiving apparatus 100 establishes synchronization with the base station and ends the initial cell search, a switching signal is input to the switches 114 and 119 so that the received signal is linearly amplified by the linear amplifier 116.

  The A / D converter 120 has a relatively small dynamic range, and the dynamic range matches the average reception level of a saturated amplified reception signal or a linearly amplified reception signal input from the switch 119. Adjusted. The A / D converter 120 converts the phase and reception level of the received signal input from the switch 119 into digital values, and inputs the digital signals to the correlator 121 and the demodulator 127, respectively.

  The correlator 121 obtains a correlation value between the received signal converted into the digital signal input from the A / D converter 120 and the known code specified in advance, and inputs the correlation value to the normalization unit 122. . In the above four-step cell search, the step of obtaining the correlation value by the correlator 121 is as follows: “Step 1. 2. Detect the maximum value of the correlation value to simultaneously detect the SYNC-DL code and the DwPTS timing. Process and “correlation between Step 2. 1. Beacon channel or P-CCPCH (Primary Common Control Physical Channel) midamble part included in TS # 0 and 4 types of basic midambles of code group detected at Step 1. Taking ”process.

  The normalization unit 122 normalizes the correlation value input from the correlator 121 based on the reception level of the reception signal input from the AGC 117. Here, normalization of the correlation value of the received signal by its reception level means that, for example, when the correlation value input from the correlator 121 is in the form shown in FIG. 8A, the correlation value in the DwPTS and the UpPTS 8 is obtained by subtracting an arbitrary value from the correlation value in FIG. In the standardization from the mode shown in FIG. 8 (a) to the mode shown in FIG. 8 (b), the average correlation value of UpPTS is higher than the average correlation value of DwPTS in FIG. Reflecting the difference in correlation value, the correlation value of UpPTS is much lower. Then, the correlation value normalized by the reception level by the normalization unit 122 is input to the correlation peak detector 125.

  The correlation peak detector 125 performs peak detection of the correlation value input from the normalization unit 122. Information about the position (timing) of the correlation peak detected by the correlation peak detector 125 is extracted from the reception timing output terminal 126. The information on the position of the correlation peak is effectively used, for example, from (Step 1) to (Step 3) in the 4-step cell search.

  The demodulator 127 generates a demodulated signal by demodulating the received signal converted into the digital signal input from the A / D converter 120 by, for example, the QPSK method. The demodulated signal generated by the demodulator 127 is extracted from the demodulated signal output terminal 128. Therefore, the demodulator 127 performs, for example, (Step 4) in the 4-step cell search.

  Next, the operation of each component of receiving apparatus 100 according to the present embodiment will be described in detail.

  When performing the above-described four-step cell search using the receiving apparatus 100, from (Step 1) to (Step 3) corresponding to the initial cell search, the received signal is saturated and amplified by the saturation amplifier 115, and after the initial cell search is completed. In the step (Step 4), the received signal is linearly amplified by the linear amplifier 116.

  Here, in the initial cell search using the receiving apparatus 100, FIG. 2 shows a state after the received signal containing noise represented by the orthogonal coordinate plane of FIG. As shown in FIG. 2, the reception signal that is saturated and amplified by the saturation amplifier 115 is all focused on a thick ring 200 that overlaps the average reception level 72 of the reception signal in FIG. When the received signal is saturated and amplified, even if there is a range 71 in which the received signal is shifted due to noise, the received signal is all focused on the ring 200 while retaining the phase information at the shifted position. The Therefore, if the dynamic range of the A / D converter 120 is set in accordance with the size of the ring 200 with respect to the saturation-amplified received signal input from the saturation amplifier 115 to the A / D converter 120, A / D Phase fluctuations caused by D conversion can be suppressed as much as possible. As a result of the A / D conversion with the phase information of the received signal held as much as possible, the peak of the correlation value generated in the correlator 121 becomes steeper, and the correlation peak detector 125 detects the correlation. Peak detection is more accurate and reliable.

  If the saturation amplifier 115 is used in this way, even when the A / D converter 120 having a relatively small dynamic range is used, the phase information of the received signal can be held as much as possible during the A / D conversion. This is the most different point from the case where the linear amplifier 116 is used, and is the most important advantage of using the saturated amplifier 115.

  By the way, in the initial cell search, it is easy to detect the correlation peak by saturating and amplifying the received signal using the saturating amplifier 115. However, after the initial cell search is completed, a high function such as an equalizer is provided. Therefore, it is necessary to amplify the received signal using the linear amplifier 116 instead of the saturation amplifier 115.

  Therefore, while monitoring the state of the initial cell search by the state management unit 118, the switches 114 and 119 are switched as appropriate so that the saturated amplifier 115 is used in the initial cell search and the linear amplifier 116 is used in the subsequent wireless communication. To.

  As described above, according to the cell search method according to the present embodiment, after the initial cell search is performed based on the saturation type amplified received signal and the synchronization with the base station is established by the initial cell search. Since wireless communication is performed with this base station based on the linearly amplified received signal, even if the SNR of the received signal from the base station is low, the performance of the initial cell search is improved and synchronization is achieved. After establishment, the conventional high reception performance can be maintained.

  Further, according to the embodiment of the present invention, since the A / D converter 120 having a relatively small dynamic range and a low power consumption is used, the manufacturing cost is low and the power consumption is low. A mobile communication terminal device capable of making a long-time telephone call with a small number can be obtained. Also, according to this mobile communication terminal device, the performance of the initial cell search is improved, so that wireless communication is possible even in places where radio waves are difficult to reach.

(Embodiment 2)
In Embodiment 2 according to the present invention, Embodiment 1 is used only in that the saturation amplifier 115 is removed from the receiving apparatus 100 and the receiving apparatus 300 in which the gain value adjustment signal S1 is input from the state management unit 118 to the AGC 117 is used. And different. Therefore, in the present embodiment, only the components and the operation of receiving apparatus 300 that are different from those in Embodiment 1 will be described in detail below.

  FIG. 3 is a block diagram showing a configuration of receiving apparatus 300 according to the present embodiment. The state management unit 118 constantly monitors the state of the initial cell search, and inputs the gain value adjustment signal S1 to the AGC 117 when the initial cell search is started. When the gain value adjustment signal S1 is input, the AGC 117 instructs the linear amplifier 116 to saturate and amplify the received signal in the saturation region.

  Here, FIG. 4 shows a characteristic curve relating to the power level of the input / output signal of the linear amplifier 116. In general, a linear amplifier amplifies an input signal in a range where the power level of the input signal is low, that is, in a linear region, but is almost directly proportional to the power level of the input signal. The input signal cannot be linearly amplified and is saturated. Accordingly, the linear amplifier 116 can function as a saturation amplifier by adjusting the power level of the input signal. Further, in this embodiment, the received signal is saturated and amplified in the initial cell search, and the received signal is linearly amplified after the initial cell search is completed. Therefore, the saturated amplification and the linear amplification of the received signal are performed simultaneously. There is no. Therefore, by using the linear amplification in the linear region of the linear amplifier 116 and the saturation region in the saturation region in time division, the saturation amplifier can be removed from the receiving apparatus 300.

  As described above, according to receiving apparatus 300 according to the present embodiment, when a gain value adjustment signal is input to linear amplifier 116, the received signal is saturated and amplified in its saturation region. Therefore, the circuit configuration of the receiving device can be simplified.

  The cell search method, receiver and mobile communication terminal according to the present invention improve the performance of the initial cell search even when the SNR of the received signal from the base station is low, without using a linear amplifier having a large dynamic range. This is advantageous for cellular radio communication systems and the like.

The block diagram which shows the structure of the receiver which concerns on Embodiment 1 of this invention. The figure which shows the received signal of saturation type amplification in this invention on a rectangular coordinate The block diagram which shows the structure of the receiver which concerns on Embodiment 2 of this invention. The figure which shows the characteristic curve regarding the power level of the input / output signal of the linear amplifier The figure which shows the outline of the cellular radio communication system The figure which shows the frame format in TD-SCDMA system Block diagram showing the configuration of a conventional receiving apparatus The figure which shows the outline | summary of the correlation peak detection of the correlation value of a received signal Diagram showing the received signal including linearly amplified noise on Cartesian coordinates The figure which shows the received signal containing the noise which carried out linear amplification and A / D conversion on a rectangular coordinate

Explanation of symbols

100, 300 Receiver 111 Antenna element 112 Low noise amplifier 113 Frequency converter 114, 119 Switch 115 Saturation type amplifier 116 Linear amplifier 117 Auto gain controller (AGC)
118 State Management Unit 120 A / D Converter 121 Correlator 122 Normalization Unit 125 Correlation Peak Detector 126 Reception Timing Output Terminal 127 Demodulator 128 Demodulated Signal Output Terminal 129 Reference Power Supply Terminal 200 Ring

Claims (4)

A receiving step of receiving a radio signal transmitted from the base station;
Until a synchronization with the base station is established, a saturation amplification step of saturation amplification of the received signal;
After synchronization with the base station is established, a linear amplification step for linearly amplifying the received signal;
A conversion step for analog / digital conversion of the received signal amplified by saturation type or the received signal linearly amplified;
A correlation step for obtaining a correlation value between the received signal converted into a digital signal and a known code;
A normalization step of normalizing the correlation value with a reception level;
And a detecting step for detecting a correlation peak based on the normalized correlation value. Receiving means for receiving a radio signal transmitted from the base station;
Until the synchronization with the base station is established, a saturation amplifier that amplifies the received signal,
After synchronization with the base station is established, a linear amplifier that linearly amplifies the received signal;
An analog / digital converter that performs analog / digital conversion of the received signal that has been subjected to saturation amplification or the linearly amplified received signal;
A correlator for obtaining a correlation value between the received signal converted into a digital signal and a known code;
Normalization means for normalizing the correlation value with a reception level;
And a detecting means for detecting a correlation peak based on the normalized correlation value. Receiving means for receiving a radio signal transmitted from the base station;
A linear amplifier that amplifies the received signal in a saturation region until synchronization with the base station is established, and linearly amplifies the received signal in a linear region after synchronization with the base station is established. ,
An analog / digital converter that performs analog / digital conversion on the received signal that has been subjected to saturation amplification or the linearly amplified received signal;
A correlator for obtaining a correlation value between the received signal converted into a digital signal and a known code;
Normalization means for normalizing the correlation value with a reception level;
And a detecting means for detecting a correlation peak based on the normalized correlation value.   A mobile communication terminal device comprising the receiving device according to claim 2.

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