JP7675564B2 - Positioning signal receiving device, positioning signal receiving method, and positioning program - Google Patents

Description

This disclosure relates to a positioning signal receiving device, a positioning signal receiving method, and a positioning program.

A Global Navigation Satellite System (GNSS), typified by the Global Positioning System (GPS), broadcasts signals using various modulation methods such as Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Keying (QPSK). Among them, signals using the Binary Offset Carrier (BOC) modulation method using a subcarrier have multiple peaks in the autocorrelation characteristics, so that it is difficult to track the positioning signal using a typical method using a Delay Lock Loop (DLL), and when a side lobe is captured, the side lobe continues to be tracked.
Various research institutes have proposed methods for tracking BOC signals. Patent Document 1 proposes a system that adds a Sub-Carrier Lock Loop (SLL) that tracks the subcarrier to remove side peaks, enables positioning signal tracking with a normal DLL, and also provides resistance to multipath and noise.

US Patent Publication No. 2010104046

When tracking a BOC signal modulated by a subcarrier signal with a high chip rate, if a side lobe far away from the main lobe is captured, there is a technical problem that it is not possible to pull in to the main lobe and to maintain tracking of the positioning signal. Even if it is possible to pull in to the main lobe, there is a technical problem that the code phase cannot be corrected and it is not possible to improve the accuracy of tracking the positioning signal.
In particular, when a positioning signal receiving device is attached to a highly maneuverable target, a large Doppler is generated, and there is a very high possibility that a side lobe far removed from the main lobe of the BOC signal is captured, making it difficult to apply conventional methods to targets with high maneuverability.

The positioning signal receiving device of the present disclosure is a positioning signal receiving device that receives a positioning signal of a BOC (Binary Offset Carrier) modulation method,
a correlation unit which generates a correlation value with a BOC signal from a subcarrier replica signal at a subcarrier prompt phase and a code replica signal at a code prompt phase as a PP correlation value, generates a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at an early phase which is more advanced in phase than the code prompt phase as a PE correlation value, and generates a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at a late phase which is more advanced in phase than the code prompt phase as a PL correlation value;
a side peak detection unit which receives the PP correlation value, the PE correlation value, and the PL correlation value, and compares the PP correlation value, the PE correlation value, and the PL correlation value to determine whether a main peak or a side peak has been captured;
and a sample shift section for shifting the processing start position of the correlation section based on the determination result of the side peak detection section.

According to the present disclosure, when capturing a BOC signal, even if a side lobe far away from the main lobe is captured, the main lobe can be searched for and captured.

FIG. 1 is a configuration diagram of a positioning signal receiving device 100 according to a first embodiment. FIG. 4 is an autocorrelation characteristic diagram of the BOC signal according to the first embodiment. FIG. 4 is an autocorrelation characteristic diagram of the DLL of the first embodiment. FIG. 4 is an autocorrelation characteristic diagram of the SLL of the first embodiment. FIG. 11 is an autocorrelation characteristic diagram of a BOC signal when a side lobe is captured in the first embodiment. FIG. 13 is an autocorrelation characteristic diagram of the DLL in the case where a side lobe is captured according to the first embodiment. FIG. 11 is an autocorrelation characteristic diagram of the SLL when a side lobe is captured in the first embodiment. 4 is a flowchart showing the operation of a positioning signal receiving method according to the first embodiment. FIG. 4 is a diagram of a sample shift in the first embodiment. FIG. 4 is a diagram of a sample shift in the first embodiment.

In the following description of the embodiments and drawings, the same reference numerals indicate the same or corresponding parts.

Embodiment 1.
***Description of the Configuration of Positioning Signal Receiving Device 100***
The configuration of a positioning signal receiving device 100 will be described with reference to FIG.
The positioning signal receiving device 100 is a receiving device that receives a positioning signal 41 modulated by a BOC (Binary Offset Carrier) method from a satellite.
The positioning signal receiving device 100 receives the positioning signal 41 , and after synchronization with the positioning signal 41 is completed, maintains synchronization with the positioning signal 41 .
The positioning signal receiving device 100 captures the positioning signal 41 by demodulating the code modulated from the positioning signal 41 and correlating it with a replica signal generated locally by the positioning signal receiving device 100. The code has a fixed pattern repeated at a code period Tp.

The positioning signal receiving device 100 has a preprocessing unit 51, a sample shift unit 52, a correlation unit 60, a sub-carrier lock loop (SLL) unit 81, a delay lock loop (DLL) unit 83, a phase lock loop (PLL) unit 85, a side peak detection unit 90, and a phase correction unit 91.

The pre-processing unit 51 receives the positioning signal 41 transmitted from the satellite via an antenna, and converts the positioning signal 41 into an intermediate frequency signal.
The pre-processing unit 51 outputs an IF signal 42 obtained by analog-to-digital conversion of an intermediate frequency signal at a sampling frequency.
The IF signal 42 is a signal in which a carrier, a subcarrier, and a code are superimposed.

The sample shift unit 52 shifts the processing start position of the correlation unit 60 based on the determination result 98 .
The sample shift section 52 shifts the processing start position of the IF signal 42 , thereby shifting the processing start position of the correlation section 60 .

The correlation unit 60 internally creates replica signals of the carrier signal, the subcarrier signal, and the code signal superimposed on the IF signal 42 .
The correlation unit 60 generates the following replica signals:
1. Carrier replica signal 2. Subcarrier replica signal 3. Code replica signal

The carrier replica signal is a signal that imitates the carrier signal.
The subcarrier replica signal is a signal that imitates the subcarrier signal.
The code replica signal is a signal that imitates the code signal.

The correlator 60 obtains correlations between the carrier signal, the subcarrier signal, the code signal superimposed on the IF signal 42 and each replica signal.
The correlation unit 60 outputs an EP correlation value, an LP correlation value, a PE correlation value, a PP correlation value, and a PL correlation value. These correlation values have positive values.

The SLL section discriminator 81, the DLL section discriminator 83, and the PLL section discriminator 85 each have a function of outputting a phase error.
The SLL section discriminator 81 performs frequency search and phase detection of the subcarrier.
The SLL section discriminator 81 receives the EP correlation value and the LP correlation value, and outputs a subcarrier phase error τsc to track the subcarrier.

The DLL section discriminator 83 performs frequency search and phase detection of the code.
The DLL section discriminator 83 receives the PE correlation value and the PL correlation value and tracks the code.
The DLL section discriminator 83 outputs the code phase error τc.

The PLL section discriminator 85 performs a carrier frequency search and phase detection.
The PLL section discriminator 85 receives the PP correlation value and tracks the carrier wave.
The PLL section discriminator 85 outputs the carrier phase error τφ.
The PLL section discriminator 85 may be a FLL section discriminator that performs FLL (Frequency Locked Loop) processing.

The side peak detection unit 90 inputs the PE correlation value, PP correlation value, and PL correlation value, and determines whether it is capturing the main peak of the main lobe or the side peak of the side lobe.

The phase correction unit 91 generates a correction value for the replica signal created by the correlation unit 60 .
The phase correction unit 91 receives the subcarrier phase error τsc from the SLL unit discriminator 81 and outputs a subcarrier phase signal 96 to track the subcarrier. The subcarrier phase signal 96 is a signal indicating the phase difference between the subcarrier signal and the subcarrier replica signal of the BOC signal.
The phase correction unit 91 receives the code phase error τc from the DLL unit discriminator 83 and outputs a code phase signal 97 to track the code. The code phase signal 97 is a signal indicating the phase difference between the code signal of the BOC signal and the code replica signal.
A carrier phase correction unit 92 of the phase correction unit 91 receives the carrier phase error τφ from the PLL unit discriminator 85 and outputs a carrier phase signal 95 to track the carrier. The carrier phase signal 95 is a signal indicating the phase difference between the carrier signal and the carrier replica signal of the BOC signal.

The correlation unit 60 of the positioning signal receiving device 100 will be described with reference to FIG. 1.

The carrier NCO 54 is a numerically controlled oscillator that generates a carrier replica signal.
The carrier NCO 54 sets the carrier phase in response to the carrier phase signal 95 to generate a carrier clock signal.
The carrier NCO 54 generates a carrier replica signal of an intermediate frequency according to the carrier replica phase.
The carrier replica phase is the phase of the current reference carrier replica signal.
The carrier replica phase is a phase that is changed in response to the carrier phase signal 95 and approaches the carrier phase of the BOC signal.
The carrier NCO 54 generates a carrier replica signal based on the carrier clock signal, and outputs the carrier replica signal.

The subcarrier NCO 56 is a numerically controlled oscillator that generates a subcarrier replica signal.
The subcarrier NCO 56 sets the subcarrier phase in response to the subcarrier phase signal 96 to generate a subcarrier clock signal.
The subcarrier NCO 56 generates a subcarrier replica signal based on the subcarrier clock signal, and outputs the subcarrier replica signal.

The subcarrier NCO 56 outputs the following subcarrier replica signals:
1. Prompt subcarrier replica signal at the subcarrier Prompt phase; 2. Early subcarrier replica signal in which the subcarrier phase is advanced by a period Tds/2 from the subcarrier Prompt phase relative to the Prompt subcarrier replica signal; 3. Late subcarrier replica signal in which the subcarrier phase is delayed by a period Tds/2 from the subcarrier Prompt phase relative to the Prompt subcarrier replica signal.

The subcarrier prompt phase is the phase of the current reference subcarrier replica signal.
The subcarrier prompt phase is a phase that is changed in response to the subcarrier phase signal 96 and approaches the subcarrier phase of the BOC signal.
The period Tds is in the range of 0<Tds<Ts.

The code NCO 58 is a numerically controlled oscillator that generates a code replica signal.
The code NCO 58 sets the code phase in response to the code phase signal 97 and generates a code clock signal.
The code NCO 58 generates a code replica signal based on the code clock signal, and outputs the code replica signal.

The code NCO 58 outputs the following code replica signals:
1. A prompt code replica signal at the code prompt phase; 2. An early subcarrier replica signal in which the subcarrier phase is advanced by a period Tdc/2 from the code prompt phase relative to the prompt code replica signal; 3. A late subcarrier replica signal in which the subcarrier phase is delayed by a period Tdc/2 from the code prompt phase relative to the prompt code replica signal.

The code prompt phase is the phase of the current reference code replica signal.
The code prompt phase is a phase that is changed in response to the code phase signal 97 and approaches the code phase of the BOC signal.
The period Tdc is 0<Tds<Tc or Ts<Tds<Tc.

Multiplication units 61 to 69 form a mixer that mixes signals.
The integrating units 71 to 75 are integrators that integrate signals every certain period (integration period). The integration period is an integral multiple of the code period Tp.
The multiplier 61 mixes the carrier replica signal with the IF signal 42 and outputs the BOC signal 43. The BOC signal 43 is a signal in which a subcarrier and a code are superimposed.

The multiplier 62 mixes the BOC signal 43 with the Prompt subcarrier replica signal, and demodulates the code signal (BCP signal).
The multiplier 65 mixes the Prompt code replica signal with the code signal (BCP signal) demodulated by the multiplier 62 , and outputs to an accumulator 74 a correlation value (BCPP signal) obtained by demodulation with the Prompt code replica signal.
The accumulator 74 accumulates the correlation value (BCPP signal) output from the multiplier 65 for a certain period of time, and outputs the "correlation value of the Prompt subcarrier and Prompt code replica signal" (PP correlation value).

The multiplier 66 mixes the early code replica signal with the code signal (BCP signal) demodulated by the multiplier 62 , and outputs the correlation value (BCPE signal) obtained by demodulation with the early code replica signal to an accumulator 73 .
The accumulator 73 accumulates the correlation value (BCPE signal) output from the multiplier 66 for a certain period of time, and outputs the "correlation value of the Prompt subcarrier and Early code replica signal" (PE correlation value).

The multiplier 67 mixes the late code replica signal with the code signal (BCP signal) demodulated by the multiplier 62 , and outputs the correlation value (BCPL signal) obtained by demodulation with the late code replica signal to an accumulator 75 .
The accumulator 75 accumulates the correlation value (BCPL signal) output from the multiplier 67 for a certain period of time, and outputs the "correlation value of the Prompt subcarrier and Late code replica signal" (PL correlation value).

The multiplier 63 mixes the BOC signal 43 with the early subcarrier replica signal, and demodulates the code signal (BCE signal).
The multiplier 68 mixes the Prompt code replica signal with the code signal (BCE signal) demodulated by the multiplier 63 , and outputs to an accumulator 71 a correlation value (BCEP signal) obtained by demodulation with the Prompt code replica signal.
The accumulator 71 accumulates the correlation value (BCEP signal) output from the multiplier 68 for a certain period of time, and outputs the "correlation value of the Early subcarrier and Prompt code replica signal" (EP correlation value).

The multiplier 64 mixes the BOC signal 43 with the late subcarrier replica signal, and demodulates the code signal (BCL signal).
The multiplier 69 mixes the Prompt code replica signal with the code signal (BCL signal) demodulated by the multiplier 64 , and outputs the correlation value (BCLP signal) obtained by demodulation with the Prompt code replica signal to an accumulator 72 .
The accumulator 72 accumulates the correlation value (BCLP signal) output from the multiplier 68 for a certain period of time, and outputs the "correlation value of the late subcarrier and prompt code replica signal" (LP correlation value).

The accumulator 71 generates, as an EP correlation value, a correlation value between the BOC signal and the subcarrier replica signal at an Early phase that is ahead of the subcarrier Prompt phase and a code replica signal at a code Prompt phase.
The accumulator 72 generates, as an LP correlation value, a correlation value with the BOC signal from the subcarrier replica signal at a Late phase that lags behind the subcarrier Prompt phase and the code replica signal at a code Prompt phase.
The accumulator 73 generates, as a PE correlation value, a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and the code replica signal at the early phase that is ahead of the code prompt phase.
The accumulator 74 generates a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and the code replica signal at the code prompt phase as a PP correlation value.
The accumulator 75 generates, as a PL correlation value, a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and the code replica signal at a late phase that lags behind the code prompt phase.
Accumulators 71 to 75 accumulate correlation values for a certain period of time, output the accumulated values, and then reset the accumulated values to zero.
After resetting the accumulated values to zero, accumulators 71 to 75 repeat the operation of accumulating correlation values for a certain period of time.

The side peak detection unit 90 inputs the PP correlation value, the PE correlation value, and the PL correlation value, and compares the PP correlation value, the PE correlation value, and the PL correlation value to determine whether a main peak or a side peak has been captured.

When the PL correlation value is greater than the PP correlation value, the side peak detector 90 determines that a side peak that is in a phase leading phase with respect to the main peak has been captured.
When the PE correlation value is greater than the PP correlation value, the side peak detector 90 determines that a side peak that is delayed in phase from the main peak has been captured.
If the PP correlation value is greater than the PE correlation value and the PL correlation value, the side peak detection unit 90 determines that the main peak has been captured.

The sample shifter 52 shifts the processing start position of the IF signal 42 based on the determination result of the side peak detector 90 .
The sample shift unit 52 shifting the processing start position of the IF signal 42 means that the sample shift unit 52 shifts the processing start position of the BOC signal.
The sample shift section 52 shifting the processing start position of the IF signal 42 means that the correlation section 60 shifts the processing start position to generate the PP correlation value, the PE correlation value, and the PL correlation value.

If the side peak detection section 90 determines that it has captured a side peak that is in a phase that is more advanced than the main peak, the sample shift section 52 delays the processing start position by one sub-chip period.
If the side peak detection unit 90 determines that it has captured a side peak that is delayed in phase from the main peak, the sample shift unit 52 advances the processing start position by one sub-chip period.
If the side peak detector 90 determines that the main peak has been captured, the sample shifter 52 does not change the processing start position.

When it is determined that the side peak detector 90 has captured a side peak whose phase is more advanced than the main peak, the carrier phase corrector 92 delays the carrier phase of the carrier replica signal by one sub-chip period.
When it is determined that the side peak detector 90 has captured a side peak whose phase is delayed from that of the main peak, the carrier phase corrector 92 advances the carrier phase of the carrier replica signal by one sub-chip period.

***Hardware and Software of Positioning Signal Receiving Device 100***
The positioning signal receiving device 100 can be realized by a computer including a processor, a main memory, a storage device, an input/output interface, and storage, and a positioning program executed by the computer.

The processor executes a positioning program while executing an operating system, network drivers, and storage drivers.
The positioning program, the operating system, the network driver, and the storage driver stored in the storage device are loaded into the main memory and executed by the processor.

The data, information, signal values and variable values used, processed or output by the positioning program are stored in main memory, a storage device, or in registers or cache memory within the processor.

The "part" of each part of the positioning signal receiving device 100 may be read as a "process," a "procedure," or a "step." Also, the "process" of each process of the positioning signal receiving device 100 may be read as a "program," a "program product," or a "computer-readable storage medium on which a program is recorded."
The positioning program causes the computer to execute each process, procedure or step of the positioning signal receiving device 100, where the "part" is replaced with a "process,""procedure" or "step."
The positioning signal receiving method is a method carried out by the positioning signal receiving device 100 executing a program.
The positioning program may be provided in a state stored in a computer-readable recording medium, or as a program product.

The positioning signal receiving device 100 may also be realized, in whole or in part, by a processing circuit such as a logic IC (integrated circuit), a GA (gate array), an ASIC (application specific integrated circuit), or an FPGA (field-programmable gate array).

The higher-level concept of a processor, a combination of a processor and memory, and a processing circuit is called processing circuitry. In other words, a processor, a combination of a processor and memory, and a processing circuit are each specific examples of processing circuitry.

***Explanation of autocorrelation properties***
The autocorrelation characteristics will be described with reference to FIG. 2 to FIG.
It is assumed that the positioning signal 41 is modulated by BPSK (Binary Phase Shift Keying) and BOC (15, 2.5).
BOC modulation is commonly written as BOC(m,n), where m denotes the subcarrier frequency in units of 1.023 MHz, and n denotes the chip rate of a pseudo random noise (PRN) code in units of 1.023 MHz.
The period Tc of one chip and the period Ts of one subchip of BOC(15,2.5) can be calculated as follows.

One chip period Tc
=1/(n*1.023MHz)
=1/(2.5*1.023MHz)

Period of one subchip Ts
=1/(2*m*1.023MHz)
=1/(2*15*1.023MHz)
=1/(30*1.023MHz)

FIG. 2 is a diagram showing the autocorrelation characteristics of BPSK and BOC of a BOC signal.
The horizontal axis represents the code phase difference, and the unit of the horizontal axis is the number of chips.
The vertical axis represents the correlation strength, and the units of the vertical axis are amplitudes.
ML is the main lobe.
SL are side lobes appearing on both sides of the main lobe ML.
The SC is a subchip.
In BOC(15,2.5), there are 12 sub-chips SC per chip, and 6 sub-chips SC per 0.5 chip.

The autocorrelation characteristic of a signal modulated by BPSK has a mountain shape, as shown by the thick line.
The correlation value of a signal modulated by BPSK is maximum when the code phase difference is 0 chips, and is 0 when the code phase difference is ±1.0 chips.

The autocorrelation characteristics of a signal modulated with BOC(15,2.5) are wavy, like a thin line.
The autocorrelation characteristic of a signal modulated with BOC(15,2.5) has 11 positive peaks and 12 negative peaks.
The correlation value of a signal modulated with BOC(15,2.5) is maximum when the code phase difference is 0 chips, and is 0 when the code phase difference is ±1.0 chips.
The correlation value of a signal modulated with BOC(15,2.5) becomes gradually smaller as the code phase difference varies between 0 chip and ±1.0 chip six times in units of subchip SC.

FIG. 3 shows the DLL autocorrelation properties of the BOC(15,2.5) code.
The horizontal axis represents the code phase difference, and the unit of the horizontal axis is the number of chips.
The vertical axis represents the correlation strength, and the units of the vertical axis are amplitudes.
The autocorrelation characteristic of the DLL has a peak shape centered at 0 chip.
PP is the correlation value of the Prompt subcarrier and Prompt code replica signals.
PE is the correlation value of the Prompt subcarrier and Early code replica signals.
PL is the correlation value between the prompt subcarrier and the late code replica signal.
When the main lobe ML is captured, the code phase difference becomes 0, PP is at the peak position of the 0th chip, and PP>PE and PP>PL.

FIG. 4 is a diagram showing the SLL autocorrelation characteristics of the subcarriers of BOC(15,2.5).
The horizontal axis represents the subcarrier phase difference, and the unit of the horizontal axis is the number of chips.
The vertical axis represents the correlation strength, and the units of the vertical axis are amplitudes.
The autocorrelation characteristic of the SLL is a waveform with constant amplitude.
The autocorrelation characteristic of a signal modulated with BOC(15,2.5) is a repetition of positive and negative peaks, with the positive and negative peak values having the same absolute value.
When the main lobe ML is captured, the subcarrier phase difference becomes 0, and PP exists at the peak position of the 0 chip.

Figure 5 shows an example of a case where the main lobe ML cannot be captured, and instead a side lobe SL that is -0.5 chips away is captured.

FIG. 6 is a diagram showing a case where a side lobe SL that is −0.5 chips away is captured.
The PP is located at -0.5 chips.
The PE is located before the -0.5 chip position.
The PL is located after the -0.5 chip position.
When a side lobe SL that is −0.5 chips away is captured, PE<PP<PL.

Although not shown, when capturing a side lobe SL that is +0.5 chips away, the equation becomes as follows.
The PP is located at +0.5 chips.
The PE is located before the +0.5 chip position.
The PL is located after the +0.5 chip position.
PE>PP>PL.

FIG. 7 is a diagram showing a case where a side lobe SL that is −0.5 chips away is captured.
The PP is at the peak position of -0.5 chips.
Although not shown, when a side lobe SL that is separated by +0.5 chips is captured, PP exists at the peak position of +0.5 chips.

*** Operation Description ***
FIG. 8 is a diagram showing how positioning signal receiving device 100 changes from a state in which it has captured side lobe SL, which is −0.5 chips away, as shown in FIGS. 5 to 7, to the state shown in FIGS. 2 to 5 by capturing main lobe ML.

Step S10: Correlation Value Calculation Step The correlation unit 60 calculates a PP correlation value, a PE correlation value, and a PL correlation value.
Step S11: Correlation Value Input Process The side peak detection unit 90 receives the PP correlation value, the PE correlation value, and the PL correlation value as input.
At this time, each correlation value is smoothed by filtering.

Step S12: Correlation Value Comparison Step The side peak detection unit 90 detects side peaks from the PP correlation value, the PE correlation value, and the PL correlation value according to the following determination conditions and results.

Judgment condition 1: When the PL correlation value is greater than the PP correlation value Judgment result 1: It is judged that a side peak that is in a phase leading phase to the main peak has been captured.

Judgment condition 2: When the PE correlation value is greater than the PP correlation value Judgment result 2: It is judged that a side peak that is delayed in phase from the main peak has been captured.

Judgment condition 3: When the PP correlation value is greater than the PE correlation value and the PL correlation value. Judgment result 3: It is judged that the main peak has been captured.

The side peak detection unit 90 outputs the determination result 98 to the sample shift unit 52 and the phase correction unit 91.

Based on the judgment result 98, the side peak detection unit 90 uses the sample shift unit 52 and the phase correction unit 91 to track the positioning signal while moving the side lobe SL until the main peak is detected when the side peak is captured.

Tracking Process Based on the determination result 98 output from the side peak detection unit 90, the sample shift unit 52 shifts the analog-to-digital converted BOC signal input from the pre-processing unit 51 by a period of one sub-chip.
The sample shift unit 52 delays or advances the processing start position of the IF signal 42 based on the decision result 98, thereby moving the side lobe SL.
When the sample shift unit 52 performs a sample shift on the IF signal 42, a phase error occurs, and therefore the phase correction unit 91 corrects the code phase, subcarrier phase, and carrier phase.
The phase correction unit 91 corrects the carrier phase signal 95 , the subcarrier phase signal 96 , and the code phase signal 97 .
The phase correction unit 91 inputs the subcarrier phase error τsc from the SLL unit discriminator 81, adds the subcarrier phase error (G1*τsc) obtained by multiplying the previous carrier phase signal 95 by a gain constant G1, and outputs a new subcarrier phase signal 96.
The phase correction section 91 inputs the code phase error τc from the DLL section discriminator 83, adds the code phase error (G2*τc) obtained by multiplying the previous code phase signal 97 by a gain constant G2, and outputs a new code phase signal 97.
The phase correction unit 91 inputs the carrier phase error τφ from the PLL unit discriminator 85, adds the carrier phase accumulated error (G3*Στφ) obtained by multiplying the previous carrier phase signal 95 by a gain constant G3 to the carrier phase error (G4*τφ) multiplied by a gain constant G4, and outputs a new carrier phase signal 95.
The carrier phase correction unit 92 of the phase correction unit 91 performs correction by delaying or advancing the carrier phase of the carrier replica signal by a period of one subchip (Ts) based on the judgment result output from the side peak detection unit 90.

Step S13: Post-movement process In the case of judgment result 1:
The sample shift unit 52 delays the processing start position of the IF signal 42 by one sub-chip period (Ts).
The carrier phase correction unit 92 outputs a carrier phase signal 95 that delays the carrier phase of the carrier replica signal by one subchip period (Ts).
The phase correction section 91 outputs a subcarrier phase signal 96 and a code phase signal 97 for correcting the subcarrier phase of the subcarrier replica signal and the code phase of the code replica signal.
The phase correction section 91 corrects the code phase, subcarrier phase, and carrier phase of each replica signal.

Step S14: Forward Shift Step In the case of decision result 2, the sample shift unit 52 advances the processing start position of the IF signal 42 by one sub-chip period (Ts).
The carrier phase correction unit 92 outputs a carrier phase signal 95 that advances the carrier phase of the carrier replica signal by one subchip period (Ts).
The phase correction section 91 outputs a subcarrier phase signal 96 and a code phase signal 97 for correcting the subcarrier phase of the subcarrier replica signal and the code phase of the code replica signal.

Step S15: Maintenance step In the case of the determination result 3, the sample shift unit 52 does not perform a sample shift while the side peak detection unit 90 determines that the main lobe ML is captured. In other words, the sample shift unit 52 does not change the processing start position of the IF signal 42.
When the sample shift unit 52 does not sample shift the IF signal 42 (capturing the main lobe ML) but has not yet captured the main peak, the phase correction unit 91 corrects the code phase, subcarrier phase, and carrier phase of each replica signal.
The phase correction section 91 determines that the main peak has been captured when the phase errors output from the SLL section discriminator 81, the DLL section discriminator 83, and the PLL section discriminator 85 become (almost) zero.
When the sample shift section 52 does not sample-shift the IF signal 42 and when the main peak is captured, the phase correction section 91 does not correct the code phase, subcarrier phase, and carrier phase of each replica signal.
The phase correction unit 91 outputs the code phase, subcarrier phase, and carrier phase of each replica signal as the code phase, subcarrier phase, and carrier phase of the received positioning signal 41. That is, the phase correction unit 91 outputs the code phase indicated by the latest code phase signal 97, the subcarrier phase indicated by the latest subcarrier phase signal 96, and the carrier phase indicated by the latest carrier phase signal 95 as the code phase, subcarrier phase, and carrier phase of the received positioning signal 41, respectively.

Loop process After steps S13, S14, and S15, the process returns to step S11.

6, when a side lobe SL that is -0.5 chips away from the main lobe ML is captured, since PL is larger than PP in the autocorrelation characteristics output by the DLL, the side peak detector 90 determines that a side peak that is in a phase that leads the main peak has been captured. Based on the determination result of the side peak detector 90, the sample shifter 52 delays the processing start position of the IF signal 42 by one subchip period (Ts), as shown by the arrows in FIGS. 9 and 10.
In BOC(15,2.5), there are six subchips per 0.5 chip, so the main lobe ML is reached after six determinations by the side peak detection unit 90 and six sample shifts by the sample shift unit 52 (six executions of steps 11, 12, and 13). At the main lobe ML, PP becomes larger than PL and PE in the autocorrelation characteristic output by the DLL, so it is determined that the main peak has been captured. Therefore, after the main peak has been captured, steps 11, 12, and 15 are executed.

When a side lobe SL that is +0.5 chips away from the main lobe ML is captured, the main lobe ML is reached after six determinations by the side peak detection unit 90 and six sample shifts by the sample shift unit 52 (six executions of steps 11, 12, and 14).

***Features of the First Embodiment***
As described above, in this embodiment, in capturing a positioning signal using the BOC modulation method, a method has been described in which the side peak detection unit 90, the sample shift unit 52, and the phase correction unit 91 are used to track the positioning signal while moving the side lobe SL until the main peak is detected even after capturing a side peak.

***Advantages of First Embodiment***
According to the positioning signal receiving apparatus 100 of the first embodiment, in capturing a BOC signal, even if a side lobe SL far away from the main lobe ML is captured, the main lobe ML can be searched for and captured.
In addition, the tracking accuracy is improved by phase correction processing.
In particular, it is possible to track a BOC signal modulated by a high-frequency subcarrier signal, such as the BOC (15, 2.5) modulation method.

***Modification of the First Embodiment***
The BOC modulation of the positioning signal may be other BOC(m,n) modulation instead of BOC(15,2.5). In particular, BOC modulation with a subcarrier frequency of m≧15 is preferable, and BOC modulation with m≧17 or BOC modulation with m≧20 may also be used.
The modulation method of the code does not have to be the BPSK modulation method, but may be the QPSK modulation method or other modulation methods.
The code does not have to be a pseudorandom noise (PRN) code, but may be some other code.

Although the embodiments have been described above, several of the embodiments may be combined for implementation. Alternatively, parts of the embodiments may be combined for implementation.

41 Positioning signal, 42 IF signal, 43 BOC signal, 51 Preprocessing unit, 52 Sample shift unit, 54 Carrier NCO, 56 Subcarrier NCO, 58 Code NCO, 60 Correlation unit, 61, 62, 63, 64, 65, 66, 67, 68, 69 Multiplication unit, 71, 72, 73, 74, 75 Integration unit, 81 SLL unit discriminator, 83 DLL unit discriminator, 85 PLL unit discriminator, 90 Side peak detection unit, 91 Phase correction unit, 92 Carrier phase correction unit, 95 Carrier phase signal, 96 Subcarrier phase signal, 97 Code phase signal, 98 Judgment result, 100 Positioning signal receiving device, ML Main lobe, SL Side lobe, SC Subchip, τφ Carrier phase error, τc Code phase error, τsc Subcarrier phase error.

Claims (6)

In a positioning signal receiving device that receives a positioning signal of a BOC (Binary Offset Carrier) modulation method,
a correlation unit which generates a correlation value with a BOC signal from a subcarrier replica signal at a subcarrier prompt phase and a code replica signal at a code prompt phase as a PP correlation value, generates a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at an early phase which is more advanced in phase than the code prompt phase as a PE correlation value, and generates a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at a late phase which is more advanced in phase than the code prompt phase as a PL correlation value;
a side peak detection unit which receives the PP correlation value, the PE correlation value, and the PL correlation value, and compares the PP correlation value, the PE correlation value, and the PL correlation value to determine whether a main peak or a side peak has been captured;
and a sample shift unit that shifts a processing start position of the correlation unit based on a determination result of the side peak detection unit. The side peak detection unit
If the PL correlation value is greater than the PP correlation value, it is determined that a side peak that is in a phase leading phase to the main peak has been captured;
If the PE correlation value is greater than the PP correlation value, it is determined that a side peak that is delayed in phase from the main peak has been captured;
2. The positioning signal receiving device according to claim 1, wherein when the PP correlation value is greater than the PE correlation value and the PL correlation value, it is determined that a main peak has been captured. The sample shift unit includes:
When it is determined that the side peak detection unit has captured a side peak that is in a phase leading phase to the main peak, the processing start position is delayed by one subchip;
When it is determined that the side peak detection unit has captured a side peak that is delayed in phase from the main peak, the processing start position is advanced by one subchip.
3. The positioning signal receiving device according to claim 2, wherein the processing start position is not changed when the side peak detecting section determines that the main peak has been captured. The correlation unit generates a carrier replica signal based on a carrier phase of the carrier replica signal and demodulates the BOC signal;
The positioning signal receiving device includes:
4. The positioning signal receiving device according to claim 2, further comprising a carrier phase correction unit that delays a carrier phase of the carrier replica signal by one subchip period when it is determined that the side peak detection unit has captured a side peak having a phase that is more advanced than the main peak, and that advances the carrier phase of the carrier replica signal by one subchip period when it is determined that the side peak detection unit has captured a side peak having a phase that is more advanced than the main peak. A positioning signal receiving method for receiving a positioning signal of a BOC (Binary Offset Carrier) modulation method,
a PP correlation value is generated as a correlation value with a BOC signal from a subcarrier replica signal at a subcarrier prompt phase and a code replica signal at a code prompt phase, a PE correlation value is generated as a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at an early phase which is more advanced in phase than the code prompt phase, and a PL correlation value is generated as a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at a late phase which is more delayed in phase than the code prompt phase,
the PP correlation value, the PE correlation value, and the PL correlation value are input, and the PP correlation value, the PE correlation value, and the PL correlation value are compared to determine whether a main peak or a side peak has been captured;
A positioning signal receiving method in which a processing start position is shifted to generate the PP correlation value, the PE correlation value, and the PL correlation value based on a result of determining whether the main peak or the side peak is being captured . A computer that receives a positioning signal using the BOC (Binary Offset Carrier) modulation method is
a correlation process for generating a correlation value with a BOC signal from a subcarrier replica signal at a subcarrier prompt phase and a code replica signal at a code prompt phase as a PP correlation value, generating a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at an early phase which is more advanced in phase than the code prompt phase as a PE correlation value, and generating a correlation value with the BOC signal from the subcarrier replica signal at the subcarrier prompt phase and a code replica signal at a late phase which is more advanced in phase than the code prompt phase as a PL correlation value;
a side peak detection process for inputting the PP correlation value, the PE correlation value, and the PL correlation value, and comparing the PP correlation value, the PE correlation value, and the PL correlation value to determine whether a main peak or a side peak has been captured;
and a sample shift process for shifting a start position of the correlation process based on a result of the side peak detection process .

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