JP2007267087A - Spread spectrum signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spread spectrum signal receiver which allows a demodulation process with no increase in the scale of a circuit. <P>SOLUTION: The spread spectrum signal receiver receives reception signals containing a first reception signal of which the carrier wave is data-modulated and subjected to spread spectrum with a first code which is a first BOC code and a first PN code. It also contains a second reception signal of which the carrier wave is synchronized with the first BOC code with no data modulation and subjected to spread spectrum with a second code containing a second BOC code in a specified relationship, and a second PN code. The code for correlation process, and first and second reception signals are switched when capturing and tracking the reception signals. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a spread spectrum signal receiving apparatus that demodulates a spread spectrum received signal using a binary offset carrier code or a pseudo noise code.

  A code in which a subcarrier that is a rectangular wave repeating 0 and 1 is superimposed on a pseudo-noise code (hereinafter referred to as PN code) is called a binary offset carrier code (hereinafter referred to as BOC code).

  There are cases where a signal in which two synchronized BOC codes having a predetermined relationship are transmitted on a carrier wave (hereinafter referred to as a carrier) is received. For example, the Galileo satellite in Europe plans to transmit a signal that transmits the above-mentioned two BOC codes having a predetermined relationship called L1F signal in the L1 band (center frequency 1575.42 MHz). (Refer nonpatent literature 1).

  The L1F signal includes an L1F data signal (hereinafter referred to as L1Fd signal) and an L1F pilot signal (hereinafter referred to as L1Fp signal).

  The L1Fd signal is modulated by an L1Fd code, which is a PN code, and a first code obtained by adding modulo 2 (modulo 2) subcarriers, and navigation data is superimposed on the L1Fd signal. The L1Fd code has a bit rate of 1.023 Mbps, a code length of 4092 chips, a repetition period of 4 ms, navigation data has a baud rate of 250 sps, and a subcarrier has a bit rate of 1.023 Mbps.

  On the other hand, the L1Fp signal is modulated by an L1Fp code that is a PN code, an auxiliary code (Secondary code) having a code length of 25 bits having a pattern unique to the Galileo system, and a second code obtained by modulo-2 addition of subcarriers. Navigation data is not superimposed. The L1Fp code has a bit rate of 1.023 Mbps, a code length of 4092 chips, a repetition period of 4 ms, and the subcarrier has a bit rate of 1.023 Mbps. The L1Fd code and the L1Fp code have different code patterns depending on the Galileo satellite.

  In the Galileo receiver, in order to demodulate the navigation data, the received signal including each of these codes is despread by the code generated by the code generator in the receiver, and the local frequency signal supplied to the carrier correlator Must match the phase and frequency of the received signal. For this purpose, the code phase and frequency scan applied to the code correlator and the phase and frequency scan applied to the carrier frequency signal are performed in parallel, and the correlation peak points of both the code and the carrier are searched and captured. When these peaks are detected, the code and the carrier are tracked so that the peak points are not shifted.

  Based on the existing spread spectrum signal demodulation technology and the disclosure of Non-Patent Document 1, a spread spectrum signal receiving apparatus that demodulates a received signal that has been spread spectrum by the Galileo L1F signal, for such an L1F signal, The present inventor considered the following reference examples.

  FIG. 3 is a diagram illustrating a reference example of a spread spectrum signal receiving apparatus for a Galileo L1F signal. The antenna unit 1, the frequency converting unit 2, the code processing unit 10, the carrier processing unit 20, and the adding units 31a, 31b, and 32a. 32b, an auxiliary code processing unit 50, and a control unit 40. In the following description, description of the code DLL is omitted for simplification.

  The antenna unit 1 receives a signal from the Galileo satellite, and the frequency conversion unit 2 performs frequency conversion on the received signal to generate an IF signal.

  The code processing unit 10 includes a code generation unit 13, a first code correlation unit 11, and a second code correlation unit 12, and a BOC code obtained by superimposing a subcarrier on the L1Fd code (hereinafter referred to as a BOCd code), A code correlation is obtained for each BOC code (hereinafter referred to as a BOCp code) in which a subcarrier is superimposed on an L1Fp code.

  Based on the code control signal Cc from the control unit 40, the code generation unit 13 generates a generated BOCd code BOCdg, which is a replica BOC code, and a generated BOCp code BOCpg. The first code correlator 11 performs correlation between the received BOCd code of the IF signal and the generated BOCd code BOCdg, and outputs a first code correlation value. The second code correlator 12 performs correlation between the received BOCp code of the IF signal and the generated BOCp code BOCpg, and outputs a second code correlation value.

  The carrier processing unit 20 includes a first I carrier correlation unit 21a, a first Q carrier correlation unit 21b, a second I carrier correlation unit 22a, a second Q carrier correlation unit 22b, a local signal generation unit 23, and a π / 2 phase delay. And a carrier correlation is obtained for the IF signal.

  The local signal generator 23 generates a local frequency signal ωg based on the local signal control signal LOc from the controller 40.

  The first I carrier correlation unit 21a obtains a correlation between the first code correlation value and the in-phase local frequency signal, and outputs a first I carrier correlation value. The first Q carrier correlation unit 21b obtains a correlation between the first code correlation value and the local frequency signal delayed by the π / 2 phase by the π / 2 phase delay unit 28, and outputs a first Q carrier correlation value. The second I carrier correlation unit 22a obtains a correlation between the second code correlation value and the local frequency signal and outputs a second I carrier correlation value. The second Q carrier correlation unit 22b obtains a correlation between the second code correlation value and the local frequency signal delayed by π / 2 phase by the π / 2 phase delay unit 28, and outputs a second Q carrier correlation value.

  The first I signal addition unit 31a performs addition processing for a certain time on the input first I carrier correlation value, and outputs the processing result as a first I addition correlation value. Similarly, the first Q addition unit 31b performs addition processing for a certain time on the input first Q carrier correlation value, and outputs the processing result as the first Q addition correlation value. Similarly, the second I addition unit 32a and the second Q addition unit 32b perform addition processing over a certain period of time on the input second I carrier correlation value and second Q carrier correlation value, and output the processing results.

  Note that two different types of codes are superimposed on the Galileo L1F signal as compared to the case of a BPSK modulated signal on which only one type of code is superimposed on the carrier signal, for example, a GPS L1C / A signal. Therefore, double addition units 31a to 32b are required for demodulation.

  Further, the fixed time to be added by the adders 31a to 32b is set to 4 ms, which is a normal L1Fd code period. That is, in the L1Fd code, a start state is entered every time 4092 chips are repeated. In addition, the L1Fd code and the navigation data are synchronized, and the navigation data transitions in synchronization with the time when the L1Fd code is in the start state. Since the received signal from the artificial satellite is a signal generated by modulo-2 addition processing of the navigation data, the L1Fd code, and the subcarrier, the sign of the L1Fd code is inverted when the navigation data changes. Since the transition state of the navigation data is unpredictable, the value after the addition process is canceled unless the addition process is performed in synchronization with 4 ms that is the repetition period of the L1Fd code. Therefore, the addition processing time is normally set to the L1Fd code period (4 ms).

  The auxiliary code processing unit 50 includes an auxiliary code generation unit 53, an I auxiliary code correlation unit 51, and a Q auxiliary code correlation unit 52, and obtains a code correlation for the received auxiliary code.

  The auxiliary code generation unit 53 generates a generated auxiliary code CCg that is an auxiliary code of the replica based on the auxiliary code control signal CCc from the control unit 40. The I auxiliary code correlator 51 and the Q auxiliary code correlator 52 respectively correlate the output result of the second I adder 32a, the output result of the second Q adder 32b, and the generated auxiliary code CCg to obtain the second I adder correlation. Value and the second Q addition correlation value are output.

  The control unit 40 generates a code control signal Cc, a local signal control signal LOc, and an auxiliary code control signal CCc based on the first I addition correlation value, the first Q addition correlation value, the second I addition correlation value, and the second Q addition correlation value. To do. The control contents of these control signals Cc, LOc, CCc are for the spread spectrum signal receiving apparatus to perform initial acquisition and stable tracking of the Galileo L1F signal. , The phase and frequency of the generation auxiliary code CCc are included.

  FIG. 4 is a block diagram showing an example of the internal configuration of the code generator 13. The code generation unit 13 includes a code clock generation unit 60, an L1Fd code generation unit 61, an L1Fp code generation unit 62, a BOCd code correlation unit 63, and a BOCp code correlation unit 64.

  Based on the generated BOCd code and the code control signal Cc indicating the phase and frequency of the generated BOCp code from the control unit 40, the code clock generation unit 60 is a clock signal having a chip rate of 1.023 MHz for the L1Fd code and the L1Fp code. Is output.

The L1Fd code generator 61 and the L1Fp code generator 62 output an L1Fd code and an L1Fp code having a bit rate of 1.023 Mbps and a repetition period of 4 ms based on the clock signal. The BOCd code correlator 63 and the BOCp code correlator 64 correlate the L1Fd code and the L1Fp code with the clock signal and output the generated BOCd code BOCdg and the generated BOCp code BOCpg.
L1 band of Galileo Signal in Space ICD (SIS ICD), Galileo joint Undertaking, 2005

  Compared with the GPS L1C / A signal, the Galileo L1F signal has two synchronized codes superimposed on it, so the circuit scale is doubled.

  The present invention has been made for such a problem, and receives a reception signal in which two synchronized codes having a predetermined relationship are superimposed on a carrier wave, such as an L1F signal of a Galileo satellite. An object of the present invention is to provide a spread spectrum signal receiving apparatus capable of performing demodulation processing without increasing the circuit scale.

The spread spectrum signal receiving apparatus according to claim 1, wherein the carrier wave is data-modulated and the first received signal is spread spectrum with a first code which is a first binary offset carrier code (hereinafter referred to as a BOC code), and the carrier wave is data. In a spread spectrum signal receiving apparatus that receives a reception signal including a second reception signal that is spread with a second code including a second BOC code that is synchronized with the first BOC code and is not modulated. ,
A reception signal switching unit that switches between a signal component of the first reception signal and a signal component of the second reception signal used for data demodulation during tracking and acquisition of the reception signal, and superimposed on the signal component of the reception signal A superimposing signal switching unit that switches superimposing signal components to be
At the time of acquisition, the received signal switching unit and the superimposed signal switching unit are switched so as to use the signal component of the second received signal that has not undergone data modulation, and the carrier wave and the second code are acquired,
At the time of tracking, the reception signal switching unit and the superimposition signal switching unit are switched so as to use the signal component of the data-modulated first reception signal, and the tracking of the carrier wave and the first code is continued and the data is demodulated. It is characterized by that.

The spread spectrum signal receiving apparatus according to claim 2, wherein the carrier wave is data-modulated and the first received signal is spectrum-spread with a first code that is a first BOC code, and the carrier wave is not data-modulated and the first BOC code is In a spread spectrum signal receiving apparatus that receives a received signal including a second received signal that is spread spectrum with a second code including a second BOC code that is synchronized and has a predetermined relationship,
Decide whether to use both the signal component of the first received signal and the signal component of the second received signal or only the signal component of the second received signal when tracking and capturing the received signal In order to do so, it has a superimposed signal switching unit that switches the superimposed signal component to be superimposed on the signal component of the received signal,
At the time of acquisition, the superimposition signal component to be superimposed on the signal component of the reception signal is switched by the superimposition signal switching unit so that only the signal component of the second reception signal is used, and the second signal that is not affected by data modulation. Capture the carrier wave and the second code using the signal component of the received signal,
At the time of tracking, the superimposed signal switching unit switches the superimposed signal component to be superimposed on the signal component of the received signal so that both the signal component of the first received signal and the second received signal signal component are used. The second received signal is pulled in by loop control using the signal component of the second received signal that is not affected by the modulation, while the data component is used by using the signal component of the data-modulated first received signal. Are demodulated in parallel.

The spread spectrum signal receiving apparatus according to claim 3 is the spread spectrum signal receiving apparatus according to claim 1 or 2, wherein a BOC code generation unit that generates a replica BOC code that is one of the superimposed signal components, and the received signal A BOC code correlator for correlating a signal component with the replica BOC code;
A local signal generator that generates a local frequency signal that is one of the superimposed signal components, and a carrier correlation unit that correlates the signal component of the received signal and the local frequency signal,
The superimposition signal switching unit selects a type of the replica BOC code to be given to the BOC code correlator at the time of acquisition and at the time of tracking, a second replica BOC code corresponding to a second BOC code included in the second code, and Switching to the first replica BOC code corresponding to the first BOC code included in the first code is performed.

The spread spectrum signal receiving apparatus according to claim 4, wherein the carrier wave is data-modulated and the first received signal is spectrum-spread with a first pseudo-noise code (hereinafter referred to as PN code) and the carrier wave is not data-modulated. In a spread spectrum signal receiving apparatus that receives a reception signal including a second reception signal that is spread with a second PN code that is synchronized with the first PN code and has a predetermined relationship,
A reception signal switching unit that switches between a signal component of the first reception signal and a signal component of the second reception signal used for data demodulation during tracking and acquisition of the reception signal, and superimposed on the signal component of the reception signal A superimposing signal switching unit that switches superimposing signal components to be
At the time of acquisition, the received signal switching unit and the superimposed signal switching unit are switched so as to use the signal component of the second received signal that has not undergone data modulation, and the carrier wave and the second PN code are acquired,
At the time of tracking, the reception signal switching unit and the superimposition signal switching unit are switched so as to use the signal component of the data-modulated first reception signal, and the tracking of the carrier wave and the first PN code is continued and the data is demodulated. It is characterized by that.

The spread spectrum signal receiving apparatus according to claim 5, wherein the carrier wave is data-modulated and the first received signal is spectrum-spread with the first PN code, and the carrier wave is not data-modulated and the first PN code is synchronized with the predetermined signal. In a spread spectrum signal receiving apparatus that receives a received signal including a second received signal that has been spread spectrum with a second PN code in relation,
Whether to use both the signal component of the first received signal and the signal component of the second received signal or only the signal component of the second received signal at the time of tracking of the received signal and at the time of capturing and capturing In order to determine, a superimposition signal switching unit that switches a superimposition signal component to be superimposed on the signal component of the reception signal,
At the time of acquisition, the superimposition signal component to be superimposed on the signal component of the reception signal is switched by the superimposition signal switching unit so that only the signal component of the second reception signal is used, and the second signal that is not affected by data modulation. The carrier component and the second PN code are captured using the signal component of the received signal,
At the time of tracking, the superimposed signal switching unit switches the superimposed signal component to be superimposed on the signal component of the received signal so that both the signal component of the first received signal and the second received signal signal component are used. The second received signal is pulled in by loop control using the signal component of the second received signal that is not affected by the modulation, while the data component is used by using the signal component of the data-modulated first received signal. Are demodulated in parallel.

The spread spectrum signal receiving apparatus according to claim 6 is the spread spectrum signal receiving apparatus according to claim 4 or 5, wherein a PN code generation unit that generates a replica PN code that is one of superimposed signal components; A PN code correlation unit that correlates a signal component and the replica PN code; and
A local signal generator that generates a local frequency signal that is one of the superimposed signal components, and a carrier correlation unit that correlates the signal component of the received signal and the local frequency signal,
The superimposition signal switching unit selects a type of the replica PN code to be given to the PN code correlation unit at the time of acquisition and at the time of tracking, a second replica PN code corresponding to a second PN code included in the second code, and Switching to the first replica PN code corresponding to the first PN code included in the first code is performed.

  According to the spread spectrum signal receiving apparatus of the present invention, the first received signal in which the carrier wave is data-modulated and the spectrum is spread by the first code or the first PN code as the first BOC code, and the carrier wave is not data-modulated. A spread spectrum signal receiving apparatus that receives a received signal including a second received signal that is spread with a second code and a second PN code that are synchronized with the first BOC code and have a predetermined relationship with a second BOC code and an auxiliary code In this case, the circuit scale can be reduced by switching between the code for performing correlation processing and the first and second received signals at the time of capturing and tracking the received signal.

Furthermore, without increasing the circuit scale, the acquisition performance can be improved by extending the addition time, and the tracking performance can be improved by extending the pull-in range.
it can.

  According to the spread spectrum signal receiving apparatus of the present invention, the first received signal whose carrier wave is data-modulated and spectrum-spread by the first code which is the first BOC code is synchronized with the first BOC code without the carrier wave being data-modulated. In addition, a received signal including a second received signal that is spectrum-spread with a second code consisting of a second BOC code and an auxiliary code having a predetermined relationship is received. Further, the first and second PN codes may be used instead of the first and second codes.

  As a first embodiment, a received signal switching unit that switches between a signal component of a first received signal and a signal component of a second received signal used for data demodulation during tracking and capturing of the received signal, and a received signal A superimposed signal switching unit that switches a superimposed signal component to be superimposed on the signal component of the second received signal, and at the time of acquisition, the received signal switching unit and the superimposed signal switching unit are configured to use the signal component of the second received signal that has not undergone data modulation. Switching to capture the carrier wave and the second code, and at the time of tracking, the received signal switching unit and the superimposed signal switching unit are switched so that the signal component of the data-modulated first reception signal is used. Some continue to track and demodulate data.

  In the second embodiment, both the signal component of the first received signal and the signal component of the second received signal are used at the time of tracking and capturing of the received signal, or the signal of the second received signal is used. In order to determine whether to use only the component, it has a superimposed signal switching unit that switches the superimposed signal component to be superimposed on the signal component of the received signal, and at the time of acquisition, the superimposed signal is used so that only the signal component of the second received signal is used. The switching unit switches the superimposed signal component to be superimposed on the signal component of the received signal, captures the carrier wave and the second code using the signal component of the second received signal that is not affected by data modulation, The superimposition signal switching unit switches the superimposition signal component to be superimposed on the signal component of the reception signal so that both the signal component of the first reception signal and the second reception signal signal component are used. While the second received signal is pulled in by loop control using the signal component of the second received signal that is not present, the data is demodulated in parallel using the signal component of the first received signal that has been data modulated. is there.

  The following embodiments of the present invention are described according to a structure using a BOC code, such as the L1F signal of the Galileo system. However, according to the present invention, in another system in which two synchronized PN codes having a predetermined relationship are transmitted using a carrier wave, even when data is superimposed on only one PN code, the replica PN code is switched, This can be easily realized by appropriately switching the first and second received signals.

  In order to receive a plurality of satellites, there are a plurality of reception channels inside, but for the sake of simplicity of explanation, the operation will be described as one channel.

  FIG. 1 is a block diagram illustrating a configuration example of a spread spectrum signal receiving apparatus according to the first embodiment. In addition, the same code | symbol is attached | subjected to the thing corresponding to what was shown in FIG. 3 of the reference example.

  As shown in FIG. 1, the spread spectrum signal receiving apparatus includes an antenna unit 1, a frequency conversion unit 2, a code processing unit 10a, a carrier processing unit 20a, addition units 31 and 32, and an auxiliary code processing unit 50a. And a control unit 40a. The antenna unit 1 receives a signal from the Galileo satellite, performs frequency conversion on the signal received by the frequency conversion unit 2, and generates an IF (Intermediate Frequency) signal.

  The code processing unit 10 a includes a code generation unit 13, a code switching unit 14, a first code correlation unit 11, and a second code correlation unit 12. The code generator 13 outputs a generated BOCd code BOCdg and a generated BOCp code BOCpg based on the code control signal Cc from the controller 40a. The code generator 13 is generally composed of a numerically controlled oscillator (NCO) and a shift register.

  The code switching unit 14 switches the generated BOCd code BOCdg and the generated BOCp code BOCpg based on the switching control signal CCs from the control unit 40a, and outputs it to the first code correlation unit 11 and the second code correlation unit 12. When in the capture state, the generated BOCp code BOCpg is selected by setting the code switching unit to 1 side as shown in FIG. 1, and when in the tracking state, the generated BOCd code BOCdg is set by setting to 2 side. select.

  The first code correlation unit 11 and the second code correlation unit 12 obtain a correlation between the received BOC code of the IF signal and the generated BOCd code BOCdg or the generated BOCp code BOCpg selected by the code switching unit 14, and the first code correlation The value and the second code correlation value are output.

  The carrier processing unit 20a includes a local signal generation unit 23, a π / 2 phase delay unit 28, a first carrier switching unit 24 and a second carrier switching unit 25 that are reception signal switching units, a first I carrier correlation unit 21a, and a first Q. It has a carrier correlation unit 21b, a second I carrier correlation unit 22a, and a second Q carrier correlation unit 22b.

  The local signal generator 23 generates a local frequency signal ωg based on the local signal control signal LOc from the controller 40a. The local signal generator 23 is configured by a numerically controlled oscillator (NCO). The π / 2 phase delay unit 28 delays the phase of the local frequency signal by π / 2.

  The first carrier switching unit 24 switches the output result of the first I carrier correlation unit 21a and the output result of the second I carrier correlation unit 22a based on the switching control signal CCs from the control unit 40a. Similarly, the second carrier switching unit 25 switches the output result of the first Q carrier correlation unit 21b and the output result of the second Q carrier correlation unit 22b based on the switching control signal CCs from the control unit 40a.

  Here, when in the acquisition state, by setting both the first carrier switching unit 24 and the second carrier switching unit 25 to one side, carrier correlation is performed only for the second code correlation value, and the tracking state is set. In some cases, both are set to 2 so that carrier correlation is performed only for the first code correlation value.

  The first I carrier correlation unit 21a obtains a correlation between the first code correlation value and the local frequency signal ωg, and outputs a first I carrier correlation value. The first Q carrier correlation unit 21b obtains a correlation between the first code correlation value and the local frequency signal ωg phase-delayed by π / 2, and outputs a first Q carrier correlation value. The second I carrier correlation unit 22a obtains a correlation between the second code correlation value and the local frequency signal ωg, and outputs a second I carrier correlation value. The second Q carrier correlation unit 22b obtains a correlation between the second code correlation value and the local frequency signal ωg phase-delayed by π / 2, and outputs a second Q carrier correlation value.

  The I addition unit 31 performs addition processing for a certain period of time on the output result of the first carrier switching unit 24 and outputs the processing result. Similarly, the Q addition unit 32 performs addition processing for a certain period of time on the output result of the second carrier switching unit 25 and outputs the processing result.

  The auxiliary code processing unit 50 a includes an auxiliary code generation unit 53, an auxiliary code switching unit 54, an I auxiliary code correlation unit 51, and a Q auxiliary code correlation unit 52. The auxiliary code generator 53 outputs the generated auxiliary code CCg based on the auxiliary code control signal CCc from the controller 40a. The auxiliary code generator 53 is generally composed of a numerically controlled oscillator (NCO) and a shift register.

  The auxiliary code switching unit 54 is turned on at the time of acquisition based on the switching control signal CCs from the control unit 40a, and outputs the generated auxiliary code to the I auxiliary code correlation unit 51 and the Q auxiliary code correlation unit 52. At the time of tracking, the value is fixed to +1 so that the auxiliary code switching unit 54 is turned off.

  The I auxiliary code correlation unit 51 and the Q auxiliary code correlation unit 52 take the correlation between the output results of the I addition unit 31 and the Q addition unit 32 and the generated auxiliary code CCg at the time of acquisition, and add the I signal addition correlation value and the Q signal addition. Output the correlation value. At the time of tracking, the output results of the I adder 31 and the Q adder 32 are output as they are as the I signal addition correlation value and the Q signal addition correlation value.

  The control unit 40a includes a switching control unit 41, a data demodulation unit 42, a loop control unit 43, a control unit switching unit 44, and an inversion unit 46. The loop control unit 43 generates a code control signal Cc, a local signal control signal LOc, and an auxiliary code control signal CCc based on the I addition correlation value and the Q addition correlation value. The control contents of these control signals Cc, LOc, and CCc are for the spread spectrum signal receiving apparatus to perform initial acquisition and stable tracking of the L1F signal. The generated BOCd code BOCdg, the generated BOCp code BOCpg, the local frequency signal ωg, The phase and frequency of the generated auxiliary code CCg are included.

  The control unit 40a captures the BOC code, the carrier, and the auxiliary code based on the I addition correlation value and the Q addition correlation value. When the correlation peak is detected, the control unit 40a determines that the received signal is captured, and the correlation is shifted. Track so that there is no. In addition, the determination of acquisition of the received signal may be made when the correlation values of the BOC code, the carrier, and the auxiliary code based on the I addition correlation value and the Q addition correlation value each exceed a predetermined threshold value.

  In the switching control unit 41, a switching control signal CCs is output, and the code switching unit 14, the first carrier switching unit 24, and the second carrier switching unit 25 are set to one side at the time of acquisition and set to the second side at the time of tracking. Control. Further, the auxiliary code switching unit 54 is controlled to be turned on during capture and to be turned off during tracking. On the other hand, the control unit switching unit 44 is controlled to be turned off at the time of capturing and turned on at the time of tracking through the inverting unit 46 that inverts the signal.

  The data demodulator 42 operates only during tracking, and demodulates the navigation data using the I-added correlation value output from the controller switching unit 44 during tracking.

  The spread spectrum signal receiving apparatus according to the first embodiment is configured as described above, and the operation when an L1F signal is received from an unillustrated artificial satellite will be specifically described using equations.

The IF signal generated by performing frequency conversion on the received L1F signal using the frequency converting unit 2 is the first received signal [BOCd (t) · D (t) · α · cos (ωt)] and the first received signal. 2 is a composite signal of the received signal [-BOCp (t) · CC (t) · α · cos (ωt)], and can be expressed by the following equation (1), for example.
So = {BOCd (t) · D (t) · α-BOCp (t) · CC (t) · α} · cos (ωt) (1)
So: IF signal, BOCd (t): reception BOCd code, BOCp (t): reception BOCp code, D (t): navigation data, CC (t): reception auxiliary code, α: signal amplitude, ω: reception carrier frequency

First, the operation during signal acquisition will be described. At the time of acquisition, only the pilot signal component is selected by the first carrier switching unit 24 and the second carrier switching unit 25, and the data signal component is not selected. Therefore, only the second code correlation value from the second code correlation unit 12 is considered. When the generated BOCp code is BOCpg (t), the second code correlation value SS1 is represented by the following equation.
SS1 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt) (2)

When the local frequency signal is 2 cos (ωgt + φ), the second I carrier correlation value SS2 is expressed by the following equation.
SS2 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt)
・ 2cos (ωgt + φ) (3)

When the phase is delayed by π / 2, 2 cos (ωgt + φ−π / 2) = 2sin (ωgt + φ), so the second Q signal carrier correlation value SS3 is expressed by the following equation.
SS3 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt)
・ 2sin (ωgt + φ) (4)

Further, the second I carrier correlation value SS2 and the second Q signal carrier correlation value SS3 are added in the I adder 31 and Q adder 32, and the result is correlated with the auxiliary code CCg (t). The I signal addition correlation value SS4 and the Q signal addition correlation value SS5 can be expressed by the following equations.
SS4 = −α · cos (φ) (5)
SS5 = −α · sin (φ) (6)

Here, ideally, the phase and frequency of the generated BOCp code BOCpg, the generated auxiliary code CCg, and the frequency of the local frequency signal ωg are the same as the BOCp code, auxiliary code, and carrier frequency of the received signal,
BOCpg (t) = BOCp (t), ωg = ω, CCg (t) = CC (t) (7)
Is assumed.

Using the I signal addition correlation value SS4 (Equation (5)) and the Q signal addition correlation value SS5 (Equation (6)), the loop control unit 43 detects a phase error so that φ = 0 in the following equation. .
δΦ = SS4 · SS5 = 1/2 · α ² · sin (2φ) (8)

  Here, the second I carrier correlation value SS2 (formula (3)) input to the I adder 31 and the second Q carrier correlation value SS3 (formula (4)) input to the Q adder 32 are superimposed with navigation data. It has not been. Therefore, it is possible to set an addition time of 4 ms or more without being influenced by the navigation data, and the initial acquisition performance can be improved.

  Next, the operation during signal tracking will be described. At the time of tracking, each correlation value is ST1 to ST5 and is shown in parentheses in the figure. At the time of tracking, only the data signal component is used by the first carrier switching unit 24 and the second carrier switching unit 25, and the pilot signal component is not used. Therefore, only the first code correlation value from the first code correlation unit 11 is considered.

When the generated BOCd code is BOCdg (t), the first code correlation value ST1 is expressed by the following equation.
ST1 = BOCdg (t) · BOCd (t) · D (t) · α · cos (ωt) (9)
At this time, the first I carrier correlation value ST2 is represented by the following equation when the local frequency signal is 2 cos (ωgt + φ).
ST2 = BOCdg (t) · BOCd (t) · D (t) · α · cos (ωt)
・ 2cos (ωgt + φ) (10)

The first Q carrier correlation value ST3 is represented by the following equation.
ST3 = BOCdg (t) · BOCd (t) · D (t) · α · cos (ωt)
・ 2sin (ωgt + φ) (11)

Furthermore, when the first I carrier correlation value ST2 (equation (10)) and the first Q carrier correlation value ST3 (equation (11)) are added in the I addition unit 31 and the Q addition unit 32, the I addition correlation value ST4 , Q addition correlation value ST5 can be expressed by the following equation.
ST4 = D (t) · α · cos (φ) (12)
ST5 = D (t) · α · sin (φ) (13)

Here, ideally, the frequency of the generated BOCd code BOCdg and the local frequency signal ωg is the same as the BOCd code and carrier frequency of the received signal,
BOCdg (t) = BOCd (t), ωg = ω (14)
It is said.

For example, when a Costas Loop is configured to cancel the navigation data, the loop control unit 43 uses the I addition correlation value ST4 (Equation (12)) and the Q addition correlation value ST5 (Equation (13)). In the following equation, the phase error is controlled so that φ = 0.
δΦ = ST4 · ST5 = 1/2 · α ² · sin (2φ) (15)
The data demodulator 42 monitors ST4 and obtains navigation data D when φ = 0.

As described above, in the spread spectrum signal receiving apparatus according to the first embodiment, the signal used at the time of signal acquisition and signal tracking is switched. Thereby, since the pilot signal component and the data signal component in the L1F signal are selectively used, the circuit scale can be reduced.
In addition, since the circuit scale can be reduced, power consumption can be reduced.

  Note that the code processing unit 10a and the carrier processing unit 20a may be replaced, and demodulation processing may be performed in the order of carrier correlation and code correlation.

  FIG. 2 is a block diagram showing the configuration of the spread spectrum signal receiving apparatus according to the second embodiment. Components corresponding to those shown in FIG. 1 are given the same reference numerals.

  In the first embodiment, only the pilot signal component of the L1F signal is used when the received signal is captured, and only the data signal component of the L1F signal is used during tracking. On the other hand, the spread spectrum signal receiving apparatus in the second embodiment is different from the spread spectrum signal receiving apparatus in the first embodiment in that the pilot signal component of the L1F signal is used even during tracking of the received signal.

  As shown in FIG. 2, the spread spectrum signal receiving apparatus includes an antenna unit 1, a frequency conversion unit 2, a code processing unit 10b, a carrier processing unit 20b, adders 31, 32, and an auxiliary code processing unit 50b. And a control unit 40b. The antenna unit 1 receives a signal from the Galileo satellite, performs frequency conversion on the received signal received by the frequency conversion unit 2, and generates an IF signal.

  The code processing unit 10 b includes a code generation unit 13, a code switching unit 14, a first code correlation unit 11, and a second code correlation unit 12.

  The code generator 13 outputs the generated BOCd code BOCdg and the generated BOCp code BOCpg based on the code control signal Cc from the controller 40b. The code switching unit 14 that is a superimposition signal switching unit switches the generated BOCp code BOCpg and the generated BOCd code BOCdg based on the switching control signal CCs from the control unit 40 b and outputs the switched BOCp code BOCdg to the first code correlation unit 11. At this time, at the time of acquisition, the generated BOCp code BOCpg is selected by setting the code switching unit 14 to 1 side, and at the time of tracking, the generated BOCd code BOCdg is selected by setting it to 2 side.

  The first code correlator 11 correlates the received BOCp code or received BOCd code of the IF signal with the generated BOCp code BOCpg or generated BOCd code BOCdg selected by the code switching unit 14 and outputs the first code correlation value To do. The second code correlator 12 correlates the received BOCp code of the IF signal with the generated BOCp code BOCpg and outputs a second code correlation value.

  The carrier processing unit 20 b includes a local signal generation unit 23, a π / 2 phase delay unit 28, an I carrier correlation unit 21, and a Q carrier correlation unit 22. The local signal generation unit 23 generates a local frequency signal ωg based on the local signal control signal LOc from the control unit 40b.

  The I carrier correlation unit 21 obtains a correlation between the first code correlation value from the first code correlation unit 11 and the local frequency signal ωg, and outputs an I carrier correlation value. The Q carrier correlator 22 correlates the second code correlation value from the second code correlator 12 with the local frequency signal ωg phase-delayed by π / 2 by the π / 2 phase delay unit 28, and Q carrier Output the correlation value.

  The I addition unit 31 and the Q addition unit 32 perform addition processing over a certain period of time on the input I carrier correlation value and Q carrier correlation value, and output the processing results.

  The auxiliary code processing unit 50b includes an auxiliary code generation unit 53, an auxiliary code switching unit 54 that is a superimposition signal switching unit, an I addition correlation unit 51, and a Q addition correlation unit 52. The auxiliary code generator 53 outputs the generated auxiliary code CCg based on the auxiliary code control signal CCc from the controller 40b.

  Based on the switching control signal CCs from the control unit 40b, the auxiliary code switching unit 54 is turned on at the time of acquisition, and outputs the generated auxiliary code to the I auxiliary code correlation unit 51. Further, the auxiliary code switching unit 54 fixes the value to +1 so that it is turned off during tracking.

  The I auxiliary code correlation unit 51 obtains a correlation between the output result of the I addition unit 31 and the generated auxiliary code CCg at the time of acquisition, and outputs an I addition correlation value. At the time of tracking, the output result of the I adder 31 is output as it is as an I signal addition correlation value. The Q auxiliary code correlator 52 correlates the output result of the Q adder 32 and the generated auxiliary code CCg, and outputs a Q addition correlation value.

  The control unit 40b includes a switching control unit 41, a data demodulation unit 42, a loop control unit 43a, and a control unit switching unit 45. The loop control unit 43a generates a code control signal Cc, a local signal control signal LOc, and an auxiliary code control signal CCc based on the I addition correlation value and the Q addition correlation value. The control contents of these control signals Cc, LOc, CCc are for the spread spectrum signal receiving apparatus to perform initial acquisition and stable tracking of the L1F signal, and the generated BOCd code BOCdg, the generated BOCp code BOCpg, the local frequency signal ωg, The phase and frequency of the generated auxiliary code CCg are included.

  The control unit 40b captures the BOC code, the carrier, and the auxiliary code based on the I addition correlation value and the Q addition correlation value. When a correlation peak is detected, the control unit 40b determines that the received signal is captured, and the correlation is determined. Tracking so as not to shift. In addition, the determination of acquisition of the received signal may be made when the correlation values of the BOC code, the carrier, and the auxiliary code based on the I addition correlation value and the Q addition correlation value each exceed a predetermined threshold value.

  The switching control unit 41 outputs a switching control signal CCs, and controls the code switching unit 14 and the control unit switching unit 45 to be set to 1 side at the time of capture and to 2 side at the time of tracking. Further, the auxiliary code switching unit 54 is controlled to be turned on during capture and to be turned off during tracking. The data demodulator 42 operates only during tracking, and demodulates the navigation data using the I-added correlation value output from the controller switching unit 45.

  The spread spectrum signal receiving apparatus according to the second embodiment is configured as described above, and the operation when an L1F signal is received from an unillustrated artificial satellite will be specifically described using equations. The IF signal generated by performing frequency conversion on the received L1F signal using the frequency conversion unit 2 is expressed by the above-described equation (1).

The operation at the time of signal acquisition will be described. At this time, since the generated BOCp code BOSpg is selected by the code switching unit 14, when the generated BOCp code is set to BOCpg (t), the first code correlation value SS1 from the first code correlation unit 11 is expressed by the following equation: It becomes.
SS1 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt) (16)

When the local frequency signal is 2 cos (ωgt + φ), the I carrier correlation value SS2 is expressed by the following equation.
SS2 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt)
・ 2cos (ωgt + φ) (17)

Further, since the auxiliary code switching unit 54 is on at the time of acquisition, the correlation between the generated auxiliary code CCg (t) and the result of adding the I carrier correlation value in the I adding unit 31 is performed. SS3 can be expressed by the following equation.
SS3 = −α · cos (φ) (18)

Here, ideally, the phase and frequency of the generated BOCp code BOCpg and the generated auxiliary code CCg and the frequency of the local frequency signal ωg are the same as the BOCp code, carrier, and auxiliary code of the received signal,
BOCp (t) = BOCpg (t), ω = ωg, CC = CCg (19)
It is said.

Similarly, the second code correlation value SS4 from the second code correlation unit 12 is the same as the first code correlation value SS1 (formula (16)).
SS4 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt) (20)

The Q carrier correlation unit 22 takes a correlation between 2 cos (ωgt + φ−π / 2) = 2 sin (ωgt + φ) obtained by delaying the local frequency signal by π / 2 and the second code correlation value SS4, and the Q carrier correlation value SS5 is The following formula.
SS5 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt)
・ 2sin (ωgt + φ) (21)

Further, when the result of the addition processing in the Q addition unit 32 is correlated with the generated auxiliary code CCg, the Q addition correlation value SS6 can be expressed by the following equation.
SS6 = −α · sin (φ) (22)

Using the I addition correlation value SS3 (formula (18)) and the Q addition correlation value SS6 (formula (22)), the loop control unit 43a detects a phase error so that φ = 0 in the following formula.
δΦ = SS3 · SS6 = 1/2 · α ² · sin (2φ) (23)

  Here, the I carrier correlation value SS2 (formula (17)) input to the I adder 31 and the Q carrier correlation value SS5 (formula (21)) input to the Q adder 32 are superimposed with navigation data. Absent. Therefore, it is possible to set an addition time of 4 ms or more without being influenced by the navigation data, and the initial acquisition performance can be improved.

Next, the operation during tracking of the received signal will be described. At the time of tracking, each correlation value is ST1 to ST6 and is shown in parentheses in the figure. At this time, since the generated BOCd code BOCdg is selected by the code switching unit 13, the first code correlation value ST1 is expressed by the following equation.
ST1 = BOCdg (t) · BOCd (t) · D (t) · α · cos (ωt) (24)

The I carrier correlation value ST2 is represented by the following equation.
ST2 = BOCdg (t) · BOCd (t) · D (t) · α · cos (ωt)
・ 2cos (ωgt + φ) (25)
Further, since the auxiliary code switching unit 54 is off at the time of tracking, the I addition correlation value ST3 can be expressed by the following equation.
ST3 = D (t) · α · cos (φ) (26)
Also here, ideally, the phase and frequency of the generated BOCd code BOCdg and the frequency of the local frequency signal ωg are the same as the BOCd code and carrier of the received signal,
BOCdg (t) = BOCd (t), ω = ωg (27)
It is said.

Similarly, the second code correlation value ST4, the Q carrier correlation value ST5, and the Q addition correlation value ST6 are the values SS4 (formula (20)), SS5 (formula (21)), and SS6 (formula (22)) at the time of acquisition. Similarly, the following equation is obtained.
ST4 = −BOCpg (t) · BOCp (t) · CC (t)
・ Α ・ cos (ωt) (28)
ST5 = −BOCpg (t) · BOCp (t) · CC (t) · α · cos (ωt)
・ 2sin (ωgt + φ) (29)
ST6 = −α · sin (φ) (30)

  When a PLL is configured using the Q addition correlation value ST6, the loop control unit 43a performs control so that φ = 0 in ST6 (Equation (30)). However, since the polarity is opposite to that at the time of capture, phase control is performed in the opposite direction. The data demodulator 42 monitors the I-added correlation value ST3 (formula (26)), and obtains navigation data D when φ = 0.

  In the first embodiment, a Costas loop is used when tracking a received signal. This is because the navigation data is multiplied by both the I-added correlation value and the Q-added correlation value so that the carrier tracking can be continued even if the polarity of the navigation data is reversed. On the other hand, in the spread spectrum signal receiving apparatus according to the second embodiment, the PLL can be used independently of the demodulation of the navigation data and independently. Therefore, compared with the first embodiment, the tracking pull-in range is wide and more accurate tracking is possible.

  Note that the code processing unit 10b and the carrier processing unit 20b may be interchanged, and demodulation processing may be performed in the order of carrier correlation and code correlation.

  In the above description, the structure using a BOC code such as the Galileo L1F signal has been described. However, the present invention transmits two synchronized PN codes in a predetermined relationship on a carrier wave. In other systems, even when data is superimposed on only one PN code, it can be easily realized by appropriately switching the generated PN code and the local signal. In this case, the auxiliary code may or may not be included in addition to the PN code.

  In that case, the L1Fd code and the L1Fp code output from the L1Fd code generation unit 61 and the L1Fp code generation unit 64 are not provided in the code generation unit of FIG. 4 by not providing the BOCd code correlation unit 63 and the BOCp code correlation unit 64. Output without superimposing subcarriers.

It is a block diagram which shows the internal structure of the principal part of the spread spectrum signal receiver which concerns on 1st Embodiment. It is a block diagram which shows the internal structure of the principal part of the spread spectrum signal receiver which concerns on 2nd Embodiment. It is a block diagram which shows the internal structure of the principal part of the spread spectrum signal receiver of a prior art. It is a block diagram which occupies the internal structure of the code generation part of FIG.1, FIG.2, FIG.3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna part, 2 ... Frequency conversion part 10, 10a, 10b ... Code processing part 11 ... 1st code correlation part, 12 ... 2nd code correlation part, 13 ... Code generation unit 14 ... code switching unit 20, 20, 20a, 20b ... carrier processing unit, 21 ... I carrier correlation unit, 21a ... first I carrier correlation unit, 21b ... first Q carrier correlation , 22 ... Q carrier correlation unit, 22a ... second I carrier correlation unit, 22b ... second Q carrier correlation unit, 23 ... local signal generation unit, 24 ... first carrier switching unit, 25... Second carrier switching unit, 28... Π / 2 phase delay unit, 31... I addition unit, 31 a... First I addition unit, 31 b. Q adder, 32a, second I adder, 32b, second Q Calculation unit, 40, 40a, 40b ... control unit, 41 ... switching control unit, 42 ... data demodulation unit, 43, 43a ... loop control unit, 44 ... control unit switching unit, 45 ... control unit switching unit, 46... Inverting unit, 50, 50 a, 50 b... Auxiliary code processing unit, 51... I auxiliary code correlation unit, 52... Q auxiliary code correlation unit, 53. ... Auxiliary code switching unit, 60 ... Code clock generation unit, 61 ... L1Fd code generation unit, 62 ... L1Fp code generation unit, 63 ... BOCd code correlation unit, 64 ... BOCp code Correlator

Claims (6)

The first received signal whose spectrum is spread with a first code whose carrier is data-modulated and is a first binary offset carrier code (hereinafter referred to as a BOC code) and the first BOC code without the carrier being data-modulated In a spread spectrum signal receiving apparatus that receives a received signal including a second received signal that is spread spectrum with a second code including a second BOC code that is synchronized and has a predetermined relationship,
A reception signal switching unit that switches between a signal component of the first reception signal and a signal component of the second reception signal used for data demodulation during tracking and acquisition of the reception signal, and superimposed on the signal component of the reception signal A superimposing signal switching unit that switches superimposing signal components to be
At the time of acquisition, the received signal switching unit and the superimposed signal switching unit are switched so as to use the signal component of the second received signal that has not undergone data modulation, and the carrier wave and the second code are acquired,
At the time of tracking, the reception signal switching unit and the superimposition signal switching unit are switched so as to use the signal component of the data-modulated first reception signal, and the tracking of the carrier wave and the first code is continued and the data is demodulated. A spread spectrum signal receiving apparatus. The first received signal, the carrier wave of which is data-modulated and spectrum-spreaded by the first code which is the first BOC code, and the second BOC code which is synchronized with the first BOC code without being data-modulated of the carrier wave A spread spectrum signal receiving apparatus for receiving a received signal including a second received signal that is spread spectrum with a second code including:
Decide whether to use both the signal component of the first received signal and the signal component of the second received signal or only the signal component of the second received signal when tracking and capturing the received signal In order to do so, it has a superimposed signal switching unit that switches the superimposed signal component to be superimposed on the signal component of the received signal,
At the time of acquisition, the superimposition signal component to be superimposed on the signal component of the reception signal is switched by the superimposition signal switching unit so that only the signal component of the second reception signal is used, and the second signal that is not affected by data modulation. Capture the carrier wave and the second code using the signal component of the received signal,
At the time of tracking, the superimposed signal switching unit switches the superimposed signal component to be superimposed on the signal component of the received signal so that both the signal component of the first received signal and the second received signal signal component are used. The second received signal is pulled in by loop control using the signal component of the second received signal that is not affected by the modulation, while the data component is used by using the signal component of the data-modulated first received signal. A spread spectrum signal receiving apparatus characterized by performing demodulation in parallel. A BOC code generation unit that generates a replica BOC code that is one of the superimposed signal components, a BOC code correlation unit that correlates the signal component of the received signal and the replica BOC code, and
A local signal generator that generates a local frequency signal that is one of the superimposed signal components, and a carrier correlation unit that correlates the signal component of the received signal and the local frequency signal,
The superimposition signal switching unit selects a type of the replica BOC code to be given to the BOC code correlator at the time of acquisition and at the time of tracking, a second replica BOC code corresponding to a second BOC code included in the second code, and The spread spectrum signal receiving apparatus according to claim 1, wherein the spread spectrum signal receiving apparatus is switched to a first replica BOC code corresponding to a first BOC code included in the first code. The first received signal in which the carrier wave is data-modulated and spectrum-spread by a first pseudo-noise code (hereinafter referred to as PN code) is synchronized with the first PN code and the carrier wave is not data-modulated and has a predetermined relationship A spread spectrum signal receiving apparatus for receiving a received signal including a second received signal that has been spread spectrum with a second PN code
A reception signal switching unit that switches between a signal component of the first reception signal and a signal component of the second reception signal used for data demodulation during tracking and acquisition of the reception signal, and superimposed on the signal component of the reception signal A superimposing signal switching unit that switches superimposing signal components to be
At the time of acquisition, the received signal switching unit and the superimposed signal switching unit are switched so as to use the signal component of the second received signal that has not undergone data modulation, and the carrier wave and the second PN code are acquired,
At the time of tracking, the reception signal switching unit and the superimposition signal switching unit are switched so as to use the signal component of the data-modulated first reception signal, and the tracking of the carrier wave and the first PN code is continued and the data is demodulated. A spread spectrum signal receiving apparatus. The first received signal in which the carrier wave is data-modulated and spectrum-spread by the first PN code and the carrier wave is not data-modulated and the first PN code is synchronized and spread-spectrum by the second PN code having a predetermined relationship In a spread spectrum signal receiving apparatus that receives a received signal including a second received signal,
Decide whether to use both the signal component of the first received signal and the signal component of the second received signal or only the signal component of the second received signal when tracking and capturing the received signal In order to do so, it has a superimposed signal switching unit that switches the superimposed signal component to be superimposed on the signal component of the received signal,
At the time of acquisition, the superimposition signal component to be superimposed on the signal component of the reception signal is switched by the superimposition signal switching unit so that only the signal component of the second reception signal is used, and the second signal that is not affected by data modulation. The carrier component and the second PN code are captured using the signal component of the received signal,
At the time of tracking, the superimposed signal switching unit switches the superimposed signal component to be superimposed on the signal component of the received signal so that both the signal component of the first received signal and the second received signal signal component are used. The second received signal is pulled in by loop control using the signal component of the second received signal that is not affected by the modulation, while the data component is used by using the signal component of the data-modulated first received signal. A spread spectrum signal receiving apparatus characterized by performing demodulation in parallel. A PN code generation unit that generates a replica PN code that is one of the superimposed signal components, a PN code correlation unit that correlates the signal component of the received signal and the replica PN code, and
A local signal generator that generates a local frequency signal that is one of the superimposed signal components, and a carrier correlation unit that correlates the signal component of the received signal and the local frequency signal,
The superimposition signal switching unit selects a type of the replica PN code to be given to the PN code correlation unit at the time of acquisition and at the time of tracking, a second replica PN code corresponding to a second PN code included in the second code, and 6. The spread spectrum signal receiving apparatus according to claim 4, wherein the spread spectrum signal receiving apparatus is switched to a first replica PN code corresponding to a first PN code included in the first code.

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