JP2007243626A - Spread spectrum signal receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a demodulation process to be practiced without increasing a circuit scale even in receiving a reception signal containing a first reception signal where data modulation has been practiced in one carrier wave and a spectrum spread has been practiced with a first code, and a second reception signal where the data modulation has been not practiced in the other carrier wave and the spectrum spread has been practiced with a second code, among two carrier waves whose frequencies are identical and whose phases are shifted by 90 degrees from each such as an L5 signal of a GPS. <P>SOLUTION: When catching the reception signal, a code and a carrier signal by which correlation processing is performed at the time of tracking, are changed over. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a spread spectrum signal receiving apparatus that demodulates a spread spectrum received signal using a pseudo noise code (hereinafter referred to as PN code).

  Of the two carriers having the same frequency and phases orthogonal to each other, the first received signal that is data-modulated to one carrier and spread-spectrum with the first code, and the second code without data modulation to the other carrier There is a system for receiving a reception signal including a second reception signal subjected to spread spectrum. For example, the signal is scheduled to be transmitted in the GPS L5 signal. (Refer nonpatent literature 1).

  The I5 code and Q5 code in the GPS L5 signal are two 13-bit code generators (I5 code is an XA code generator and XBI code generator, and Q5 code is an XA code generator and XBQ. 2 types of code sequences generated by a code generator), which are modulo 2 added, both of which have a bit rate of 10.23 Mbps, a code length of 10230 chips, a repetition period of 1 ms, and the timing of modulation is synchronized Yes. In addition, by changing the phase of the XBI code and the XBQ code with respect to the XA code, a unique code string can be obtained for each artificial satellite.

  The phases of the I5 code and the Q5 code are orthogonal to each other, and the I5 code and the Q5 code have a predetermined relationship in which the cycle start timing is synchronized. The L5 signal is configured to be modulated by an in-phase component I5 code and a quadrature component Q5 code. In addition, navigation data D with a baud rate of 100 sps is superimposed on the I5 code.

Further, each of the I5 signal and the Q5 signal is multiplied by an auxiliary code called a Neuman-Huffman code (hereinafter referred to as NH code). Specifically, the I5 code has a bit rate of 1 kbps, a code length of 10 chips, and a repetition period of 10 ms (hereinafter referred to as NHi code), while the Q5 code has a bit rate of 1 kbps and a code length of 20 The chip is multiplied by a code having a repetition period of 20 ms (hereinafter referred to as NHq code). These NHi code and NHq code have a predetermined relationship in which the cycle start timing is synchronized. The NHi code and NHq code pattern are shown below.
NHi (t) = 0000110101
NHq (t) = 00000100101101001110

  In the GPS, these signal codes are despread with a code generated by a code generator in the receiver to extract a signal. Further, in order to demodulate the signal, the local frequency given to the carrier correlator needs to match the phase and frequency of the GPS signal. Therefore, in the GPS receiver, the code phase and frequency scan given to the code correlator and the phase and frequency scan of the carrier wave (hereinafter also referred to as carrier) given to the carrier correlator are executed in parallel. Search and capture correlation peak points for both code and carrier. When these peaks are detected, the code and the carrier are tracked so that the peak points are not shifted.

  A spread spectrum apparatus for demodulating the received signal based on the existing QPSK signal demodulation technique and the contents disclosed in Non-Patent Document 1 with respect to a GPS received signal that has been spread spectrum by such an L5 signal. The following reference example was considered by a person.

  FIG. 3 is a diagram illustrating a reference example of the L5 signal spread spectrum signal receiving apparatus, in which the antenna unit 1, the frequency converting unit 2, the PN code processing unit 10, the carrier processing unit 20, the adding units 31a, 31b, 32a, 32b, NH code processing unit 50, and control unit 40. In the following description, description of the code DLL is omitted for simplification.

  The antenna unit 1 receives a signal from a GPS satellite, performs frequency conversion on the signal received by the frequency conversion unit 2, and generates an intermediate frequency (IF) signal.

  The PN code processing unit 10 includes a PN code generation unit 12, an I signal PN code correlation unit 11a, and a Q signal PN code correlation unit 11b, and obtains a code correlation for each of the received I5 code and Q5 code. .

  The PN code generator 12 generates a generated I5 code I5g and a generated Q5 code Q5g, which are replica codes. The I signal PN code correlation unit 11a performs correlation between the received I5 code of the IF signal and the generated I5 code I5g, and outputs an I signal PN code correlation value. Further, the Q signal PN code correlation unit 11b performs correlation between the received Q5 code of the IF signal and the generated Q5 code Q5g, and outputs a Q signal PN code correlation value.

  The carrier processing unit 20 includes a first I signal carrier correlation unit 21a, a first Q signal carrier correlation unit 21b, a second I signal carrier correlation unit 22a, a second Q signal carrier correlation unit 22b, a local signal generation unit 23, and π. A / 2 phase delay unit 28 and a -π / 2 phase delay unit 29 are provided, and a carrier correlation is obtained for each of the I signal component and the Q signal component of the L5 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 signal carrier correlation unit 21a obtains a correlation between the I signal PN code correlation value from the I signal PN code correlation unit 11a and the in-phase local frequency signal ωg, and outputs a first I signal carrier correlation value.

  In the first Q signal carrier correlator 21b, a local frequency signal obtained by delaying the I signal PN code correlation value from the I signal PN code correlator 11a and the local frequency signal ωg by π / 2 phase by the π / 2 phase delay unit 28. And the first Q signal carrier correlation value is output.

  In the second I signal carrier correlator 22a, the Q signal PN code correlation value from the Q signal PN code correlator 11b and the local frequency signal ωg are delayed by −π / 2 phase by the −π / 2 phase delay unit 29. The correlation with the frequency signal is taken, and the second I signal carrier correlation value is output.

  The second Q signal carrier correlation unit 22b obtains a correlation between the Q signal PN code correlation value from the Q signal PN code correlation unit 11b and the in-phase local frequency signal ωg, and outputs a second Q signal carrier correlation value.

  The first I signal adding unit 31a performs addition processing for a certain time on the input first I signal carrier correlation value, and outputs the processing result. Similarly, the first Q signal adder 31b, the second I signal adder 32a, and the second Q signal adder 32b receive the input first Q signal carrier correlation value, second I signal carrier correlation value, and second Q signal carrier correlation value, respectively. Depending on the repetition time of the PN code, for example, addition processing is performed over 1 ms, and the processing result is output.

  In addition, compared with the case of the L1 signal that is BPSK modulation, the L5 signal requires a double addition unit.

  Moreover, the fixed time added by the adders 31a to 32b is normally set to the I5 code cycle (both are 1 ms). That is, in the I5 code, the start state is entered every time 10230 chips are repeated. Further, the I5 code and the navigation data are synchronized, and the navigation data transitions in synchronization with the time when the I5 code becomes the start state. Since the received signal from the artificial satellite is a signal generated by adding modulo 2 to the navigation data and the I5 code, the sign of the I5 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 if the addition process of the I signal carrier correlation value is not performed in synchronization with 1 ms which is the I5 code repetition period. Therefore, the addition processing time is normally set to the I5 code period (1 ms).

  The NH code processing unit 50 includes an NH code generation unit 53, a first I signal NH code correlation unit 51a, a first Q signal NH code correlation unit 51b, a second I signal NH code correlation unit 52a, and a second Q signal NH code correlation unit 52b. The code correlation is obtained for each of the received NHi code and NHq code.

  The NH code generator 53 generates a generated NHi code NHig and a generated NHq code NHqg, which are replica-Neumann-Huffman codes.

  The first I signal NH code correlator 51a and the first Q signal NH code correlator 51b respectively correlate the output result of the first I signal adder 31a, the output result of the first Q signal adder 31b, and the generated NHi code NHig. The first I signal addition correlation value and the first Q signal addition correlation value are output.

  Similarly, the second I signal NH code correlator 52a and the second Q signal NH code correlator 52b are respectively the output result of the second I signal adder 32a, the output result of the second Q signal adder 32b, the generated NHq code NHqg, And the second I signal addition correlation value and the second Q signal addition correlation value are output.

The controller 40 includes a first I signal addition correlation value from the first I signal NH code correlation unit 51a, a first Q signal addition correlation value from the first Q signal NH code correlation unit 51b, and a second I signal NH code correlation unit 52a. Based on the 2I signal addition correlation value and the second Q signal addition correlation value from the second Q signal NH code correlation unit 52b, a PN code control signal PNc, a local signal control signal LOc, and an NH code control signal NHc are generated. The control contents of these control signals PNc, LOc, and NHc are for the spread spectrum signal receiving apparatus to perform initial acquisition and stable tracking of the L5 signal. The generated I5 code I5g and the generated Q5 code Q5g, the local frequency signal ωg, The phase and frequency of the NHi code NHig and the NHq code NHqg are included.
ARINC Incorporated, ICD-GPS-705 Navstar GPS Space Segment / User Segment L5 Intfaces, 02 December, 2002, p. 5-23

  Compared with a BPSK-modulated signal such as an L1C / A signal, the L5 signal is QPSK-modulated, and it is necessary to perform correlation processing on two types of signals, the I5 code and the Q5 code, which increases the circuit scale. .

  The present invention has been made for such a problem, and is data-modulated to one of two carriers having the same frequency and orthogonal to each other, such as a GPS L5 signal, and the first code. Even in the case of receiving a received signal including the first received signal spread in spectrum and the second received signal spread in spectrum with the second code without modulating the data to the other carrier, the circuit scale is not increased. An object of the present invention is to provide a spread spectrum signal receiving apparatus capable of performing demodulation processing.

The spread spectrum signal receiving apparatus according to claim 1, wherein a first received signal in which one of two carriers having the same frequency and phases orthogonal to each other is data-modulated and spread by a first code, and the other carrier In a spread spectrum signal receiving apparatus that receives a reception signal including a second reception signal that is spread with a second code that is not modulated with data and is in a predetermined relationship synchronized with the first 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 code are acquired,
At the time of tracking, the reception signal switching unit and the superimposition signal switching unit are switched so that the signal component of the data-modulated first reception signal is used, 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 a first received signal in which one of two carriers having the same frequency and phases orthogonal to each other is data-modulated and spectrum-spread with a first code, and the other carrier In a spread spectrum signal receiving apparatus that receives a reception signal including a second reception signal that is spread with a second code that is not modulated with data and is in a predetermined relationship synchronized with the first code,
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 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 with the replica PN code;
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 Switch to the first replica PN code corresponding to the first PN code included in the first code,
Furthermore, it has a local signal generation unit 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 reception signal and the local frequency signal,
The superimposed signal switching unit switches the phase of the local frequency signal applied to the carrier correlation unit between acquisition and tracking.

  According to the spread spectrum signal receiving apparatus of the present invention, the first received signal in which one of the two carriers having the same frequency and phases orthogonal to each other is data-modulated and spread by the first code, and the other A spread spectrum signal receiving apparatus for receiving a reception signal including a second reception signal that is spectrum-spread with a second code having a predetermined relationship in which a carrier wave is not subjected to data modulation and whose cycle start timing is synchronized In this case, it is possible to reduce the circuit scale by switching the code and the carrier signal for performing correlation processing at the time of capturing 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.

  The spread spectrum signal receiving apparatus of the present invention includes a first received signal in which one of two carriers having the same frequency and phases orthogonal to each other is data-modulated and spectrum-spread with a first code, and the other carrier is A received signal including a second received signal that is not subjected to data modulation and is spectrum-spread with a second code having a predetermined relationship with the first code is received.

  As a first embodiment, a reception signal switching unit that switches between a signal component of the first reception signal used for data demodulation and the second reception signal during tracking and acquisition of the reception signal, and the reception A received signal switching unit and a superimposed signal switching unit so as to use a signal component of the second received signal that has not been subjected to data modulation at the time of capture; The received signal switching unit and the second code are captured so that the carrier time and the second code are acquired by extending the addition time longer than the I5 code period, and the signal component of the data-modulated first received signal is used during tracking. Some devices switch the superimposition signal switching unit to continue tracking the carrier wave and the first code and demodulate the data.

  Further, as a second embodiment, in order to determine whether to use both the signal component of the first received signal and the second received signal or only the second received signal at the time of tracking and capturing of the received signal. In addition, a superimposition signal switching unit that switches a superimposition signal component to be superimposed on the reception signal is used, and at the time of acquisition, the superimposition signal switching unit switches the superimposition signal component to be superimposed on the reception signal so that only the second reception signal is used. The signal component of the received signal that is not affected by data modulation is used to acquire the carrier wave and the second code by extending the addition time longer than the I5 code period, and at the time of tracking, the signal component of the first received signal The superimposition signal switching unit switches the superimposition signal component to be superimposed on the reception signal so as to use both of the second reception signal and the signal component of the second reception signal not affected by the data modulation is used. While performing the pull-in of the second received signal by the loop control, there is one using a signal component of the first received signal data modulation performed in parallel demodulated data.

  The following embodiments of the present invention are described according to the structure of the GPS L5 signal. However, the present invention can be applied to the case where data is superimposed only on the in-phase component or the quadrature component in a signal that is spread spectrum independently on two carriers whose phases are orthogonal to each other, such as a Galileo system in Europe. However, it can be easily realized by appropriately switching the PN code and the local frequency signal.

  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 PN code processing unit 10a, a carrier processing unit 20a, adders 31, 32, and an NH code processing unit 50a. And a control unit 40a. The antenna unit receives a signal from a GPS satellite, performs frequency conversion on the signal received by the frequency conversion unit, and generates an IF signal.

  The PN code processing unit 10a includes a PN code generation unit 12, a PN code switching unit 13, an I signal PN code correlation unit 11a, and a Q signal PN code correlation unit 11b.

  The PN code generator 12 outputs a generated I5 code I5g and a generated Q5 code Q5g, which are one of the superimposed signal components, based on the PN code control signal PNc from the controller 40a. The PN code generator 12 is generally composed of a numerically controlled oscillator (NCO) and a shift register.

  The PN code switching unit 13 switches the generated I5 code I5g and the generated Q5 code Q5g based on the switching control signal CCs from the control unit 40a, and outputs it to the I signal PN code correlation unit 11a and the Q signal PN code correlation unit 11b. To do. When in the capture state, the generated Q5 code Q5g is selected by setting the PN code switching unit 13 to the 1 side as shown in FIG. In the tracking state, the generated I5 code I5g is selected by setting the PN code switching unit 13 to the 2 side.

  The I signal PN code correlation unit 11a and the Q signal PN code correlation unit 11b take a correlation between the received PN code of the IF signal and the generated Q5 code Q5g or the generated I5 code I5g selected by the PN code switching unit 13, respectively. PN code correlation values I1 and Q1 are output.

  The carrier processing unit 20a includes a local signal generation unit 23, a π / 2 phase delay unit 28, a −π / 2 phase delay unit 29, a first carrier switching unit 25, a second carrier switching unit 26, and a third carrier switching unit 27. A first I signal carrier correlation unit 21a, a first Q signal carrier correlation unit 21b, a second I signal carrier correlation unit 22a, and a second Q signal carrier correlation unit 22b.

  The local signal generator 23 generates a local frequency signal ωg, which is one of the superimposed signal components, 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 29 outputs a local frequency signal obtained by advancing the phase of the local frequency signal ωg by π / 2, and the π / 2 phase delay unit 28 delays the phase of the local frequency signal ωg by π / 2. Output a local frequency signal.

  The first carrier switching unit 25 that is a superimposed signal switching unit branches the local frequency signal ωg output by the local signal generating unit 23 into two based on the switching control signal CCs from the control unit 40a.

  The first carrier switching unit 25 can be omitted because the second carrier switching unit 26 and the third carrier switching unit 27, which are reception signal switching units, perform switching operations. In this case, the local frequency signal ωg output by the local signal generation unit 23 is supplied to the carrier correlation units 21a to 22b without passing through the switching unit. However, when the first carrier switching unit 25 is provided as shown in FIG. 1, either the carrier correlation unit 21 a or 21 b or the carrier correlation unit 22 a or 22 b is set in an inoperative state during acquisition or tracking. be able to.

  The second carrier switching unit 26, which is a reception signal switching unit, switches between 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 third carrier switching unit 27, which is a reception signal switching unit, outputs 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. Switch.

  Here, when in the acquisition state, as shown in FIG. 1, by setting all of the first, second, and third carrier switching units to the 1 side, the PN from the Q signal PN code correlation unit 11b is set. Carrier correlation is performed only on the code correlation value Q1. In the tracking state, carrier correlation is performed only on the PN code correlation value I1 from the I signal PN code correlation unit 11a by setting all of the first, second, and third carrier switching units to the 2 side. To.

  The first I signal carrier correlator 21a correlates the PN code correlation value I1 and the local frequency signal ωg, and outputs a carrier correlation value I21. The first Q signal carrier correlator 21b correlates the PN code correlation value I1 and the local frequency signal ωg phase-delayed by π / 2, and outputs a carrier correlation value Q21. The second I signal carrier correlator 22a correlates the PN code correlation value Q1 with the local frequency signal ωg phase-delayed by −π / 2, and outputs a carrier correlation value I22. The second Q signal carrier correlator 22b correlates the PN code correlation value Q1 and the local frequency signal ωg, and outputs a carrier correlation value Q22.

  The I signal adding unit 31 performs addition processing for a certain period of time on the output result of the second carrier switching unit 26 and outputs the processing result. Similarly, the Q signal addition unit 32 performs addition processing for a certain period of time on the output result of the third carrier switching unit 27 and outputs the processing result.

  The NH code processing unit 50 a includes an NH code generation unit 53, an NH code switching unit 54, an I signal NH code correlation unit 51, and a Q signal NH code correlation unit 52.

  The NH code generation unit 53 outputs the generated NHi code NHig and the generated NHq code NHqg based on the NH code control signal NHc from the control unit 40a. The NH code generation unit 53 is generally composed of a numerically controlled oscillator (NCO) and a shift register.

  The NH code switching unit 54, which is a superimposition signal switching unit, switches the generated NHi code NHig and the generated NHq code NHqg output by the NH code generating unit 53 based on the switching control signal CCs from the control unit 40a. The signals are output to the signal NH code correlation unit 51 and the Q signal NH code correlation unit 52.

  When it is during capture, the generated NHq code NHqg is selected by setting the NH code switching unit 54 to the 1 side as shown in FIG. During tracking, the generated NHi code NHig is selected by setting the NH code switching unit 54 to the second side.

  The I signal NH code correlator 51 and the Q signal NH code correlator 52 output results of the I signal adder 31 and Q signal adder 32 and the generated NHq code NHqg selected by the NH code switch 54 (generated during tracking). The correlation with the NHi code NHig) is taken, and the I signal addition correlation value I3 and the Q signal addition correlation value Q3 are output.

  The control unit 40 a includes a switching control unit 41, a data demodulation unit 42, a loop control unit 43, and an opening / closing unit 44. The loop control unit 43 generates a PN code control signal PNc, a local signal control signal LOc, and an NH code control signal NHc based on the I signal addition correlation value I3 and the Q signal addition correlation value Q3. The control contents of these control signals PNc, LOc, and NHc are for the spread spectrum signal receiving apparatus to perform initial acquisition and stable tracking of the L5 signal. The generated I5 code I5g and the generated Q5 code Q5g, the local frequency signal ωg, The generated NHi code NHig and the phase and frequency of the generated NHq code NHqg are included.

  The controller 40a captures the PN code, carrier, and NH code based on the I signal addition correlation value I3 and the Q signal addition correlation value Q3. When a correlation peak is detected for each of the PN code, carrier, and NH code, it is determined that the received signal has been captured, and tracking is performed so that the correlation does not shift. Further, the determination of the capture of the received signal may be made when the correlation values of the PN code, the carrier, and the NH code based on the I signal addition correlation value I3 and the Q signal addition correlation value Q3 each exceed a predetermined threshold.

  The switching control unit 41 outputs a switching control signal CCs, and at the time of acquisition, the PN code switching unit 13, the first carrier switching unit 25, the second carrier switching unit 26, the third carrier switching unit 27, The NH code switching unit 54 is controlled to the 1 side, and is controlled to be set to the 2 side during tracking. Further, the opening / closing unit 44 is controlled to be turned off during capture and to be turned on during tracking.

  The data demodulator 42 demodulates the navigation data using the I signal addition correlation value I3 at the time of tracking.

  The spread spectrum signal receiving apparatus according to the first embodiment is configured as described above, and the operation when an L5 signal is received from a GPS satellite (not shown) will be specifically described using equations.

The IF signal generated by performing frequency conversion on the received L5 signal using the frequency conversion unit 2 is the first received signal [I5 (t) · D (t) · NHi (t) · Ai · cos ( ωt)] and the second received signal [Q5 (t) · NHq (t) · Aq · sin (ωt)], which can be expressed by the following equation (1), for example.
IF = I5 (t) .D (t) .NHi (t) .Ai.cos (.omega.t) + Q5 (t) .NHq (t) .Aq.sin (.omega.t) (1)
However, IF: IF signal input, I5 (t): reception I5 code, Q5 (t): reception Q5 code,
D (t): Navigation data, NHi (t): Received NHi code, NHq (t): Received NHi code, Ai, Aq: Signal amplitude, ω: Received carrier frequency

  First, the operation during signal acquisition will be described. At the time of acquisition, only the Q signal component is selected by the second carrier switching unit 26 and the third carrier switching unit 27, and the I signal component is not selected. Therefore, only the Q signal PN code correlation value is considered.

When the generated Q5 code is Q5g (t), the Q signal PN code correlation value Q1 is expressed by the following equation.
Q1 = Q5 (t) · Q5g (t) · NHq (t) · Aq · sin (ωt) (2)
When the local frequency signal ωg is 2 cos (ωgt + φ), if the phase is delayed by −π / 2, 2 cos (ωgt + φ + π / 2) = − 2 sin (ωgt + φ), so the second I signal carrier correlation value I22 is expressed by the following equation .
I22 = Q5 (t) · Q5g (t) · NHq (t) · Aq · sin (ωt) · -2sin (ωgt + φ) (3)

The second Q signal carrier correlation value Q22 is expressed by the following equation.
Q22 = Q5 (t) · Q5g (t) · NHq (t) · Aq · sin (ωt) · 2cos (ωgt + φ) (4)

Further, I22 and Q22 are added in the I signal adder 31 and Q signal adder 32, and when the result is correlated with the generated NHq code NHqg, the I signal addition correlation value I3 and the Q signal addition correlation are obtained. The value Q3 can be expressed by the following equation.
I3 = Aq · −cos (φ) (5)
Q3 = Aq · −sin (φ) (6)

Here, ideally, the phase and frequency of the generated Q5 code Q5g, the generated NHq code NHqg, and the frequency of the local frequency signal ωg are the same as the Q5 code, NHq code, and carrier frequency of the received signal,
Q5 (t) = Q5g (t), ω = ωg, NHq (t) = NHqg (t) (7)

Further, using I3 (Expression (5)) and Q3 (Expression (6)), the loop control unit 43 detects the phase error so that φ = 0 in the following expression.
δΦ = I ・ Q = 1/2 ・ Aq ²・ sin (2φ) (8)

  Here, the navigation data D (t) is not superimposed on the carrier correlation value I22 input to the I signal adding unit 31 and the carrier correlation value Q22 input to the Q signal adding unit 32. Therefore, for example, it is possible to set an addition time of 10 ms or more of the navigation data rate instead of 1 ms without being influenced by the navigation data D (t), and the initial acquisition performance can be improved.

  Next, the operation during signal tracking will be described. At the time of tracking, only the I signal component is used by the second carrier switching unit 26 and the third carrier switching unit 27, and the Q signal component is not used. Therefore, only the I signal PN code correlation value is considered.

When the generated I5 code is I5g (t), the correlation value I1 of the I signal PN code correlator 11a is expressed by the following equation.
I1 = I5 (t) · I5g (t) · D (t) · NHi (t) · Ai · cos (ωt) (9)

At this time, the carrier correlation value I21 of the first I signal carrier correlation unit 21a is expressed by the following equation.
I21 = I5 (t) · I5g (t) · D (t) · NHi (t) · Ai · cos (ωt)
・ 2cos (ωgt + φ) (10)

Further, when the local frequency signal ωg is delayed by π / 2 phase, 2 cos (ωgt + φ−π / 2) = 2 sin (ωgt + φ), and therefore, the carrier correlation value Q21 of the first Q signal carrier correlation unit 21b is expressed by the following equation: Become.
Q21 = I5 (t) · I5g (t) · D (t) · NHi (t) · Ai · cos (ωt)
・ 2sin (ωgt + φ) (11)

Further, when I21 (formula (10)) and Q21 (formula (11)) are added in the I signal adder 31 and Q signal adder 32 and the result is correlated with the NHi code, the I signal The added correlation value I3 and the Q signal added correlation value Q3 can be expressed by the following equations.
I3 = D (t) · Ai · cos (φ) (12)
Q3 = D (t) · Ai · sin (φ) (13)

Also here, ideally, the phase and frequency of the generated I5 code I5g and generated NHi code NHig, and the frequency of the local frequency signal are the same as the I5 code, NHq code and carrier frequency of the received signal,
I5 (t) = I5g (t), ω = ωg, NHi (t) = NHig (t) (14)
It is said.

In order to cancel the navigation data, for example, when a Costas Loop is configured, the loop control unit 43 becomes φ = 0 in the following formula using I3 (formula (12)) and Q3 (formula (13)). The phase error is controlled as follows.
δΦ = I3 · Q3 = 1/2 · Ai ² · sin (2φ) (15)
The data demodulator 42 monitors I3 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. As a result, the I5 signal component and the Q5 signal component in the GPS L5 signal are selectively used, so that the circuit scale can be reduced. In addition, since the circuit scale can be reduced, power consumption can be reduced. Furthermore, the initial acquisition performance can be improved by setting an addition time equal to or longer than the I5 code period.

  Note that the PN 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 PN code correlation.

  FIG. 2 is a block diagram showing the configuration of the spread spectrum signal receiving apparatus according to the second embodiment. In addition, the same code | symbol is attached | subjected to the thing corresponding to what was shown in FIG.

  In the second embodiment, only the Q signal component of the L5 signal is used at the time of signal acquisition, and the Q signal component is also used together with the I signal component of the L5 signal at the time of tracking. On the other hand, in the first embodiment, only the Q signal component of the L5 signal is used during signal acquisition, and only the I signal component of the L5 signal is used during tracking. Therefore, in the second embodiment, signal tracking is performed. The usage form of the L5 signal at the time is different.

  As shown in FIG. 2, the spread spectrum signal receiving apparatus includes an antenna unit 1, a frequency converting unit 2, a PN code processing unit 10b, a carrier processing unit 20b, adding units 31 and 32, and an NH code processing unit 50b. And a control unit 40b.

  The antenna unit 1 receives a signal from a GPS satellite, the frequency conversion unit 2 performs frequency conversion on the signal, and generates an IF signal.

  The PN code processing unit 10b includes a PN code generation unit 12, a PN code switching unit 13, an I signal PN code correlation unit 11a, and a Q signal PN code correlation unit 11b.

  The PN code generator 12 outputs a generated I5 code I5g and a generated Q5 code Q5g based on the PN code control signal PNc from the controller 40b.

  The PN code switching unit 13 switches the generated I5 code I5g and the generated Q5 code Q5g based on the switching control signal CCs from the control unit 40b, and outputs it to the I signal PN code correlation unit 11a. At this time, when it is during capture, the generated Q5 code Q5g is selected by setting the PN code switching unit 13 to the 1 side as shown in FIG. On the other hand, at the time of tracking, the generated I5 code I5g is selected by setting the PN code switching unit 13 to the 2 side.

  The I signal PN code correlator 11a correlates the received PN code of the IF signal with the generated I5 code I5g or the generated Q5 code Q5g selected by the PN code switching unit 13, and outputs a PN code correlation value I1.

  The Q signal PN code correlator 11b correlates the received PN code of the IF signal with the generated Q5 code Q5g and outputs a PN code correlation value Q1.

  The carrier processing unit 20b includes a local signal generation unit 23, -π / 2 phase delay units 29-1 and 29-2, a carrier switching unit 25, an I signal carrier correlation unit 21, and a Q signal carrier correlation unit 22. Yes.

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

  Based on the switching control signal CCs from the control unit 40b, the carrier switching unit 25 sets the phase of the local frequency signal output by the local signal generation unit 23 to −π / 2 by the −π / 2 phase delay unit 29-1. Switching between a local frequency signal that has been phase-delayed and a local frequency signal that has been phase-delayed by -π by using two of the phases of the -π / 2 phase delay units 29-1 and 29-2. And output to the Q signal carrier correlation unit 22.

  At this time, when in the acquisition state, the local frequency signal delayed by −π / 2 is selected by setting the carrier switching unit 25 to 1 side as shown in FIG. By setting to 2 side, the local frequency signal delayed by −π is selected.

  The I signal carrier correlation unit 21 obtains a correlation between the PN code correlation value I1 from the I signal PN code correlation unit 11a and the local frequency signal, and outputs a carrier correlation value I2.

  The Q signal carrier correlation unit 22 selects the Q signal PN code correlation value Q1 from the Q signal PN code correlation unit 11b and the local frequency signal selected by the carrier switching unit 25 and delayed in phase by −π / 2 (at the time of acquisition). Or a local frequency signal (in the case of tracking) phase-delayed by −π, and outputs a Q signal carrier correlation value Q2.

  The I signal addition unit 31 and the Q signal addition unit 32 perform addition processing over a certain period of time on the input carrier correlation value I2 and Q signal carrier correlation value Q2, and output the processing results.

  The NH code processing unit 50 b includes an NH code generation unit 53, an NH code switching unit 54, an I signal NH code correlation unit 51, and a Q signal NH code correlation unit 52.

  The NH code generation unit 53 outputs the generated NHi code NHig and the generated NHq code NHqg based on the NH code control signal NHc from the control unit 40b.

  The NH code switching unit 54 switches the generated NHi code NHig output by the NH code generating unit 53 and the generated NHq code NHqg based on the switching control signal CCs from the control unit 40b, and the I signal NH code correlation unit 51. Output to. At this time, when in the capturing state, the generated NHq code NHqg is selected by setting the NH code switching unit 54 to the 1 side as shown in FIG. Further, when in the tracking state, the generated NHi code NHig is selected by setting the NH code switching unit 54 to the 2 side.

  The I signal NH code correlation unit 51 outputs the output result of the I signal addition unit 31, the generated NHi code NHig selected by the NH code switching unit 54 (when tracking), or the generated NHq code NHqg (when captured). And the added correlation value I3 is output. The Q signal NH code correlation unit 52 correlates the output result of the Q signal addition unit 32 with the generated NHq code NHqg, and outputs a Q signal addition correlation value Q3.

  The control unit 40 b includes a switching control unit 41, a data demodulation unit 42, a loop control unit 43, and a control unit switching unit 45.

  The loop control unit 43 generates a PN code control signal PNc, a local signal control signal LOc, and an NH code control signal NHc based on the I signal addition correlation value I3 and the Q signal addition correlation value Q3.

  The control contents of these control signals are for the spread spectrum signal receiving apparatus to perform initial acquisition and stable tracking of the GPS L5 signal. The generated I5 code I5g, the generated Q5 code Q5g, the local frequency signal ωg, and the generated NHi code NHig, phase and frequency of generated NHq code NHqg are included.

  The controller 40b captures the PN code, carrier, and NH code based on the I signal addition correlation value I3 and the Q signal addition correlation value Q3. When a correlation peak of each of the PN code, carrier, and NH code is detected, it is determined that the received signal has been captured, and tracking is performed so that the correlation does not shift. In addition, the reception signal acquisition may be determined when the correlation values of the PN code, the carrier, and the NH code based on the addition correlation value I3 and the Q signal addition correlation value Q3 each exceed a predetermined threshold.

  The switching control unit 41 outputs a switching control signal CCs, and controls the PN code switching unit 13, the first carrier switching unit 25, the NH code switching unit 54, and the control unit switching unit 45 to one side at the time of acquisition, and at the time of tracking Then, it controls to set to the 2 side. The data demodulator 42 demodulates the navigation data using the added correlation value I3 at the time of tracking.

  The spread spectrum signal receiving apparatus according to the second embodiment is configured as described above, and the operation when an L5 signal is received from a GPS satellite (not shown) will be specifically described using equations.

  The IF signal generated by performing frequency conversion on the received L5 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. Since the generated Q5 code I5q is selected by the PN code switching unit 13 at the time of acquisition, when the generated Q5 code is Q5q (t), the PN code correlation value I1 of the I signal PN code correlation unit 11a is It becomes an expression.
I1 = Q5 (t) · Q5q (t) · NHq (t) · Aq · sin (ωt) (16)

When the local frequency signal from the local signal generator 23 is 2 cos (ωgt + φ), the carrier correlation value I2 of the I signal carrier correlator 21 is expressed by the following equation.
I2 = Q5 (t) · Q5q (t) · NHq (t) · Aq · sin (ωt) · 2cos (ωgt + φ) (17)

Further, when the generated NHq code NHqg (t) selected by the NH code switching unit 54 is correlated with the result of adding the carrier correlation value I2 in the I signal adding unit 31, the I signal addition correlation value I3 Can be expressed as:
I3 = Aq · −sin (φ) (18)

Here, ideally, the phase and frequency of the generated Q5 code Q5g and the generated NHq code NHqg, and the frequency of the local frequency signal are the same as the Q5 code, carrier, and NHq code of the received signal,
Q5 (t) = Q5g (t), ω = ωg, NHq (t) = NHqg (t) (19)
It is said.

Similarly, the Q signal PN code correlation value Q1 from the Q signal PN code correlator 11b is the same as I1 (Expression (16)).
Q1 = Q5 (t) · Q5q (t) · NHq (t) · Aq · sin (ωt) (20)

Further, since the first carrier switching unit 25 selects 2 cos (ωgt + φ + π / 2) = − 2 sin (ωgt + φ) obtained by delaying the local frequency signal ωg by −π / 2 phase, the Q signal carrier correlation value Q2 is expressed by the following equation: Become.
Q2 = Q5 (t) .Q5g (t) .NHq (t) .Aq.sin (.omega.t) .- 2sin (.omega.g t + .phi.) (21)

Further, when the result of the addition processing in the Q signal addition unit 32 is correlated with the generated NHq code NHqg, the Q signal addition correlation value Q3 of the Q signal NH code correlation unit 52 can be expressed by the following equation.
Q3 = Aq · −cos (φ) (22)

Using I3 (Expression (18)) and Q3 (Expression (22)), the loop control unit 43 detects the phase error so that φ = 0 in the following expression.
δΦ = I3 · Q3 = 1/2 · Aq ² · sin (2φ) (23)

  Here, the carrier correlation value I2 (equation (17)) input to the I signal addition unit 31 and the Q signal carrier correlation value Q2 (expression (21)) input to the Q signal addition unit 32 are superimposed with navigation data. It has not been. Therefore, for example, it is possible to set an addition time of not less than 1 ms but a navigation data bit length of 10 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 this time, since the generated I5 code I5g is selected by the PN code switching unit 13, the PN code correlation value I1 of the I signal PN code correlation unit 11a is expressed by the following equation.
I1 = I5 (t) · I5g (t) · D (t) · NHi (t) · Ai · cos (ωt) (24)

The carrier correlation value I2 from the I signal carrier correlation unit 21 is expressed by the following equation.
I2 = I5 (t) · I5g (t) · D (t) · NHi (t) · Ai · cos (ωt)
・ 2cos (ωgt + φ) (25)

Further, when the generated NHi code NHig (t) selected by the NH code switching unit 54 is correlated with the result of adding the carrier correlation value I2 in the I signal adding unit 31, the I signal NH code correlating unit The added correlation value I3 from 51 can be expressed by the following equation.
I3 = D (t) · Ai · cos (φ) (26)

Also here, ideally, the phase and frequency of the generated I5 code I5g and generated NHi code NHig and the frequency of the local frequency signal ωg are the same as the I5 code, carrier, NHi code of the received signal,
I5 (t) = I5g (t), ω = ωg, NHi (t) = NHig (t) (27)
It is said.

Similarly, the Q signal PN code correlation value Q1 from the Q signal PN code correlation unit 11b is expressed by the following equation.
Q1 = Q5 (t) · Q5g (t) · NHq (t) · Aq · sin (ωt) (28)

Further, since the first carrier switching unit 25 is switched to the 2 side, 2 cos (ωgt + φ + π) = − 2 cos (ωgt + φ) obtained by delaying the local frequency signal by −π phase is selected. Thereby, the Q signal carrier correlation value Q2 from the Q signal carrier correlation unit 22 is expressed by the following equation.
Q2 = Q5 (t) · Q5g (t) · NHq (t) · Aq · sin (ωt)
-2cos (ωgt + φ) (29)

Further, when the result of the addition processing in the Q signal addition unit 32 is correlated with the generated NHq code NHqg, the Q signal addition correlation value Q3 from the Q signal NH code correlation unit 52 can be expressed by the following equation.
Q3 = Aq · sin (φ) (30)

  When a PLL is configured using the Q signal addition correlation value Q3, the loop control unit 43 performs control so that φ = 0 in Q3 (Equation (30)).

  Then, the data demodulator 42 monitors I3 (formula (26)), and obtains navigation data D when φ = 0.

  In the first embodiment (FIG. 1), a Costas loop is used during signal tracking. This is because the navigation data D is multiplied by the added correlation value I3 from the I signal NH code correlation unit 51 and the added correlation value Q3 from the Q signal NH code correlation unit 52 at the time of signal tracking, and the polarity of the navigation data is inverted. Even so, the carrier tracking can be continued. On the other hand, in the spread spectrum signal receiving apparatus according to the second embodiment, the PLL can be used using the loop control unit 43 independently of the demodulation of the navigation data D. Therefore, in addition to the effects of the first embodiment, in the second embodiment, the tracking pull-in range is wide and more accurate tracking is possible.

  Note that the PN 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 PN code correlation.

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 reference example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna part 2 ... Frequency conversion part 10, 10a, 10b ... PN code processing part 11a ... I signal PN code correlation part 11b ... Q signal PN code correlation part 11a ... I Signal PN code correlator 11b ... Q signal PN code correlator 12 ... PN code generator 13 ... PN code switching units 20, 20a, 20b ... carrier processing unit 21a ... first I signal carrier Correlator 21b ... 1st Q signal carrier correlator 22 ... Q signal carrier correlator 22a ... 2nd I signal carrier correlator 22b ... 2nd Q signal carrier correlator 23 ... Local signal generator 25 ... 1st carrier switching part 26 ... 2nd carrier switching part 27 ... 3rd carrier switching part 28 ... π / 2 phase delay part 29 ...-π / 2 phase delay part 31 ... I signal adder 31a ... 1st I signal addition part 31b ... 1st Q signal addition part 32 ... Q signal addition part 32a ... 2nd I signal addition part 32b ... 2nd Q signal addition part 40, 40a, 40b. ··· Control unit 41 ··· Switching control unit 42 ··· Data demodulating unit 43 ··· Loop control unit 44 ··· Opening and closing unit 45 ··· Control unit switching units 50, 50a and 50b ··· NH code processing unit 51 ··· I signal NH Code correlation unit 51a ... 1st I signal NH code correlation unit 51b ... 1st Q signal NH code correlation unit 52 ... Q signal NH code correlation unit 52a ... 2nd I signal NH code correlation unit 52b ... Second Q signal NH code correlation unit 53... NH code generation unit 54... NH code switching unit

Claims (3)

A first received signal in which one of two carriers having the same frequency and phases orthogonal to each other is data-modulated and spectrum-spread by the first code, and the other carrier is not data-modulated and the first code 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 code having a predetermined relationship synchronized with
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 that the signal component of the data-modulated first reception signal is used, and the tracking of the carrier wave and the first code is continued and the data is demodulated. A spread spectrum signal receiving apparatus. A first received signal in which one of two carriers having the same frequency and phases orthogonal to each other is data-modulated and spectrum-spread by the first code, and the other carrier is not data-modulated and the first code 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 code having a predetermined relationship synchronized with
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 PN code generation unit that generates a replica PN code that is one of the superimposed signal components, and a PN code correlation unit that correlates the signal component of the received signal and the replica PN code,
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 Switch to the first replica PN code corresponding to the first PN code included in the first code,
Furthermore, it has a local signal generation unit 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 reception signal and the local frequency signal,
3. The spread spectrum signal receiving apparatus according to claim 1, wherein the superimposed signal switching unit switches a phase of the local frequency signal given to the carrier correlation unit between acquisition and tracking. 4.

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