JP2007187462A - Gps receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a GPS receiving apparatus capable of shortening the time required for correlation. <P>SOLUTION: The GPS receiving apparatus is provided with a means for generating a synchronization signal to be added to an L1 band positioning signal and an L2 band positioning signal having frequencies different from each other; a means for determining timing on the basis of the L1 band positioning signal and correlating the L1 band positioning signal added with the synchronization signal with a P-code replica signal at the timing; a means for correlating the L2 band positioning signal added with the synchronization signal with the P-code replica signal at the timing; and a means for demodulating the L1 and L2 band positioning signals on the basis of the L1 band positioning signal and the L2 band positioning signal added with the synchronization signal and a phase determined on the basis of their correlation with the P-code replica signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a GPS receiver that measures the position of its own device by using positioning signals (both L1 and L2 positioning signals) having different frequencies transmitted from a GPS (Global Positioning System) satellite.

  GPS satellites transmit radio signals in two frequency bands called L1 and L2. In this radio signal, a pseudo noise code (hereinafter referred to as PN code) and a navigation message are modulated by the DS spread spectrum modulation method.

  The center frequencies of the carrier waves of the L1 and L2 signals are 1575.42 MHz and 1227.6 MHz, respectively. The PN code that modulates the L1 wave is a C / A code (Coarse / Acquisition code) with a chip rate of 1.023 Mbps and a code length of 1 ms, and a P code (Precision code) with a chip rate of 10.23 Mbps and a code length of 7 DAYS. is there. Further, the L2 wave is normally modulated only by the P code.

  Regarding a GPS receiver, there is a GPS receiver that can receive a C / A code and a P code in the L1 and L2 frequency bands (see, for example, Patent Document 1).

  In such a GPS receiver, at the time of a cold start, the C / A codes of more satellites than the number of channels can be demodulated simultaneously by causing the P code reception channel to function as a C / A code reception channel.

  In the GPS receiver, the positioning signals in the L1 and L2 wavebands are frequency-resolved by the subband dividing circuit. Thereafter, synchronization is achieved by the signal processing circuit. When this synchronization is achieved, synchronization detection is performed by separately processing the L1 band and the L2 band with the P code.

  For example, since one bit of the navigation data on the positioning signal in the L1 waveband is 20 ms, an appropriate one point is selected from the starting points every 1 ms of the C / A code, and reception is performed for 20 ms therefrom. Synchronously add signals.

  Next, a start point 1 ms next to the currently selected start point is selected, and the received signal for 20 ms is similarly synchronously added therefrom.

  In this way, 20 types of synchronous addition values shifted by 1 ms are measured. Since the bit boundary of the navigation data is synchronized with the start point of the C / A code, and one bit of the navigation data is 20 ms, one of these 20 types of synchronous addition sections coincides with the bit boundary of the navigation data. ing. For example, when bit synchronization cannot be achieved, the added value is canceled and becomes smaller in the addition interval. On the other hand, when bit synchronization can be achieved, the added value does not cancel out in the addition section because it coincides with the bit boundary of the navigation data, and becomes larger. By utilizing this property, bit synchronization is performed by detecting a synchronous addition section in which the addition value is maximum.

Further, for example, a pseudorange and a carrier phase are extracted from the positioning signal in the L2 waveband. For example, the L2 waveband positioning signal multiplied by the P code is multiplied by a replica P code generated in the GPS receiver, and square detection is performed through a low-frequency filter about 1/20 of the P code. The timing of the generated P code replica is controlled so as to maximize the signal power.
JP-A-11-142501

  However, the background art described above has the following problems.

  Since the GPS signal is a spectrum-spread signal, it can be processed only by correlation with the replica signal. For this reason, when bit synchronization is performed on a positioning signal in the L1 waveband, it is necessary to measure 20 types of synchronization addition values shifted by 1 ms, and when the signal strength of the received signal is weak, S In order to improve / N, it is necessary to increase the number of synchronous additions. For this reason, there is a problem that the time required for bit synchronization becomes long.

  In addition, when a pseudorange and a carrier phase are extracted from a positioning signal in the L2 waveband, there is a problem that the device configuration becomes complicated.

  In addition, there is a problem including an error because the synchronization detection is separately performed for the L1 band and the L2 band.

  The present invention has been made in view of the above-described points, and an object of the present invention is to provide a GPS receiver capable of reducing the time required for correlation processing.

  In order to solve the above-described problem, the GPS receiver of the present invention includes a synchronization signal generating unit that generates a synchronization signal to be added to a positioning signal in the L1 wave band and a positioning signal in the L2 wave band having different frequencies, and the synchronization signal. Is determined based on the positioning signal of the L1 waveband to which the synchronization signal is added and the synchronization signal, and the correlation processing between the positioning signal of the L1 waveband to which the synchronization signal is added and the P code replica signal at the timing L1 band positioning signal correlation processing means for performing L2 band positioning signal correlation processing for performing correlation processing between the positioning signal of the L2 band to which the synchronization signal is added and the P code replica signal based on the timing L1 and L1 based on the phase determined based on the correlation processing between the L1 band positioning signal and the L2 band positioning signal to which the synchronization signal is added, and the P code replica To one of the comprising: a demodulating means performs demodulation processing of the positioning signals of two waves band.

  With this configuration, when processing the positioning signals in the L1 wave band and the L2 wave band transmitted by the GPS satellite, a reference synchronization signal can be added to the positioning signal, and the timing error can be corrected. It can be performed.

  Further, the L1 waveband positioning signal correlation processing means obtains a phase at which a correlation value between the positioning signal of the L1 waveband to which the synchronization signal is added and the P code replica signal becomes a predetermined value, and the demodulation means, Based on the phase, the L1 waveband positioning signal may be demodulated.

  With this configuration, when processing the positioning signal in the L1 wave band transmitted by the GPS satellite, the L1 wave to which the synchronization signal is added based on the reference synchronization signal added to the positioning signal. Synchronization correction of the band positioning signal and the P code replica signal can be performed.

  Further, the L1 waveband positioning signal correlation processing means is determined based on the phase at which the correlation value between the positioning signal of the L1 waveband to which the synchronization signal is added and the P code replica signal becomes a predetermined value, and the timing. The L2 waveband positioning signal correlation processing means obtains the L2 waveband positioning signal and the P code replica signal to which the synchronization signal is added based on the timing and the phase difference. One of the features is to obtain the correlation value of.

  With this configuration, when processing the positioning signal in the L2 band transmitted from the GPS satellite, the timing obtained when processing the positioning signal in the L1 band and the synchronization signal added L1 Synchronization correction can be performed based on the phase difference between the phase where the correlation value between the positioning signal in the waveband and the P code replica signal is a predetermined value and the phase determined based on the timing.

  According to the embodiment of the present invention, it is possible to realize a GPS receiver that can shorten the time required for the correlation processing.

Next, the best mode for carrying out the present invention will be described based on the following embodiments with reference to the drawings.
In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

  A GPS receiver 100 according to an embodiment of the present invention will be described with reference to FIG.

  The GPS receiver 100 according to this embodiment includes a receiving antenna 102, a mixing circuit 104 connected to the receiving antenna 102, a subband dividing circuit 106 connected to the mixing circuit 104, and a synchronization connected to the mixing circuit 104. A reference synchronization signal generation circuit 108 as a signal generation unit, down-conversion circuits 110a and 110b to which an L1 band subband signal and an L2 band subband signal output from the subband division circuit 106 are input, A / D conversion circuits 112a and 112b to which the output signals of the down-conversion circuits 110a and 110b are respectively input, and L1 waveband positioning signal correlation processing means to which the output signals of the A / D conversion circuits 112a and 112b are input, L2 Waveband positioning signal correlation processing means and demodulation means; And a signal processing circuit 114 of Te. The reference synchronization signal generation circuit 108 is connected to the signal processing circuit 114.

  The positioning signal transmitted from the GPS satellite is received by the receiving antenna and input to the mixing circuit 104. A positioning signal transmitted from a GPS satellite, that is, a positioning signal in the L1 and L2 wavebands is modulated by a P code. Further, the positioning signal in the L1 wave band is modulated by the C / A code.

  The reference synchronization signal generation circuit 108 generates a pulse signal having a constant period as a reference synchronization signal, and inputs the pulse signal to the mixing circuit 104 and the signal processing circuit 114.

  The mixing circuit 104 performs a mixing process of the positioning signal transmitted from the GPS satellite and the reference synchronization signal, adds the reference synchronization signal to the positioning signal, and inputs it to the subband division circuit 106.

  The subband dividing circuit 106 divides the positioning signal to which the reference synchronization signal is added into a plurality of subband signals for each frequency band, for example, an L1 waveband subband signal and an L2 waveband subband signal. The subband division circuit 106 inputs the L1 band subband signal to the down-conversion circuit 110a, and inputs the L2 band subband signal to the downconversion circuit 110b.

  The down-conversion circuit 110a performs processing to reduce the frequency to the speed of the signal that can be processed by the signal processing circuit 114, that is, the frequency, of the L1 subband signal. For example, the down-conversion circuit 110a converts a subband signal in the L1 wave band of 1575.42 MHz into an intermediate frequency of several MHz, and inputs it to the A / D conversion circuit 112a. The down-conversion circuit 110b performs processing to reduce the frequency to the speed of the signal that can be processed by the signal processing circuit 114, that is, the frequency, of the L2 waveband subband signal. For example, the down-conversion circuit 110b converts an L2 band subband signal of 1227.6 MHz into an intermediate frequency of several MHz and inputs the signal to the A / D conversion circuit 112b.

  The A / D conversion circuit 112 a digitally converts the intermediate frequency (IF) signal of the L1 band sub-band signal output from the down-conversion circuit 110 a for processing in the signal processing circuit 118 and inputs the signal to the signal processing circuit 114. To do. The A / D conversion circuit 112 b digitally converts the intermediate frequency (IF) signal of the L2 band subband signal output from the down-conversion circuit 110 b for processing in the signal processing circuit 118 and inputs the signal to the signal processing circuit 114. To do.

  The signal processing circuit 114 performs positioning processing based on the reference synchronization signal and the digitally converted intermediate frequency signal of the L1 band subband signal and the intermediate frequency signal of the L2 band subband signal.

  Next, the signal processing circuit 114 in the GPS receiver 100 according to the present embodiment will be described with reference to FIG.

  The signal processing apparatus 114 according to the present embodiment includes A / D conversion circuits 112a and 112b, a correlation processing unit 116a serving as an L1 waveband positioning signal correlation processing unit connected thereto, and an L2 waveband positioning signal correlation processing unit, respectively. 116b, a positioning processing unit 118 as demodulation means connected to the correlation processing units 116a and 116b, and a P code generator 120 connected to the correlation processing units 116a and 116b. The correlation processing unit 116a is connected to the correlation processing unit 116b. Further, the reference synchronization signal is input to the correlation processing unit 116a.

  The P code generator 120 generates a P code replica (hereinafter referred to as a P code replica) and inputs it to the correlation processing units 116a and 116b.

  The transmitted navigation message from the GPS satellite is transmitted as a spread spectrum signal. The P code is one of codes used for modulation of navigation messages. In order to extract the navigation message, it is necessary to detect the phase of the carrier on which the P code is carried. This is done by generating a P code replica of the same format as the P code of the GPS satellite to be captured, and measuring the correlation value with the received spread spectrum signal while changing the phase of the P code replica. Is called.

  The correlation processing unit 116a performs correlation processing between the intermediate frequency signal of the L1-band subband signal that is output from the A / D conversion circuit 112a and the reference synchronization signal, and measures the timing of the synchronization signal. By doing so, it is possible to determine the synchronization timing between the P code replica and the intermediate frequency signal of the digitally converted L1 subband signal, and to detect the phase on which the P code is multiplied The time required can be shortened.

  Further, the correlation processing unit 116a performs a correlation process between the intermediate frequency signal of the L1 band subband signal that has been digitally converted and the P code replica input by the P code generator 120 based on the timing of the synchronization signal. The P code signal is grasped. As a result, the phase and frequency of the P code replica signal are obtained and recorded.

  For example, the correlation processing unit 116a sets the initial phase of the P code replica based on the timing of the synchronization signal. Correlation processing section 116a measures the correlation value between the P code and the P code replica of the intermediate frequency signal of the L1-band subband signal that has been digitally converted.

  Here, when the set reception frequency is incorrect or the P code replica is not synchronized with the P code of the intermediate frequency signal of the subband signal of the L1 wave band that has been digitally converted, the correlation value is close to zero. However, if the reception frequency and the P code replica are both appropriate, the correlation value indicates a predetermined value.

  The correlation processing unit 116a measures a correlation value in a predetermined range of phases from the initial phase of the P code replica, and obtains a phase that maximizes the correlation value based on the correlation value in the predetermined range of phases. The correlation processing unit 116a inputs information indicating the phase at which the correlation value is maximized to the positioning processing unit 118.

  Further, the correlation processing unit 116a obtains a difference between the phase having the maximum correlation value and the initial phase, for example, time data, and inputs it as a timing correction value to the correlation processing unit 116b together with information indicating the timing of the synchronization signal.

  The correlation processing unit 116b corrects the timing of the synchronization signal with the timing correction value, and based on the corrected timing of the synchronization signal, the intermediate frequency signal of the L2 band subband signal that has been digitally converted and the P code generator 120. Correlation processing with the P-code replica input by is performed.

  For example, the correlation processing unit 116b sets the initial phase of the P code replica based on the corrected timing of the synchronization signal. Correlation processing section 116b measures the correlation value between the P code and the P code replica of the intermediate frequency signal of the L2 band subband signal that has been digitally converted.

  Here, if the set reception frequency is incorrect or the P code replica is not synchronized with the P code of the intermediate frequency signal of the subband signal in the L2 wave band that has been digitally converted, the correlation value is close to zero. However, if the reception frequency and the P code replica are both appropriate, the correlation value indicates a predetermined value.

  The correlation processing unit 116b measures the correlation value in a predetermined range of phases from the initial phase of the P code replica, and obtains the phase that maximizes the correlation value based on the correlation value in the predetermined range of phases. The correlation processing unit 116b inputs information indicating the phase with the maximum correlation value to the positioning processing unit 118. In this case, since the timing of the synchronization signal and its timing correction value are determined in advance in the correlation processing unit 116a and the phase and frequency of the P code replica are also grasped, the time required for the correlation determination process can be shortened.

  The positioning processing unit 118 performs demodulation processing based on the input phase.

  Next, correlation processing performed in the signal processing circuit 114 of the GPS receiver 100 according to the present embodiment will be described with reference to FIG. Here, P code correlation processing will be described.

  The correlation processing unit 116a performs a correlation process between the digitally converted intermediate frequency signal of the L1 band sub-band signal and the reference synchronization signal input by the reference synchronization signal generation circuit 108 (step S302). As a result, the timing of the synchronization signal between the digitally converted intermediate frequency signal of the L1 subband signal and the reference synchronization signal input by the reference synchronization signal generation circuit 108 is determined.

  Next, correlation processing section 116a performs correlation processing between the intermediate frequency signal of the L1 band subband signal that has been digitally converted based on the timing of the synchronization signal, and the P code replica generated by P code generator 120. Is performed (step S306). As a result, the phase having the maximum correlation value is obtained, and the phase and frequency of the P code replica signal are recorded. The correlation processing unit 116 a inputs information indicating the phase with the maximum correlation value, that is, information indicating the phase of the P code replica signal, to the positioning processing unit 118.

  Next, the correlation processing unit 116a obtains a difference between the phase where the correlation value is maximum and the phase corresponding to the timing of the synchronization signal, for example, time data, and correlates with information indicating the timing of the synchronization signal as a timing correction value. The data is input to the processing unit 116b (step S306).

  Next, the correlation processing unit 116b performs a correlation process between the digitally converted intermediate frequency signal of the L2 band subband signal and the P code replica generated by the P code generator 120 (step S308). Here, the timing correction of the P code replica is performed based on the timing of the input synchronization signal and the timing correction value. As a result of the correlation processing, the phase having the maximum correlation value is obtained. The correlation processing unit 116b inputs information indicating the phase with the maximum correlation value to the positioning processing unit 118.

  The timing of the synchronization signal and the timing correction value determine the timing, for example, phase difference (time difference) between the intermediate frequency signal of the L2 band subband signal that has been digitally converted and the P code replica. Since the phase and frequency are known, the time required for the correlation determination process can be shortened.

  Thereafter, the positioning processing unit 118 demodulates the positioning signal in the L1 waveband and the positioning signal in the L2 waveband according to the input phase, and performs the positioning process.

  In the present embodiment, the P code correlation processing has been described, but the present invention can also be applied to the case where C / A code correlation processing is performed.

  For example, correlation processing is performed between the intermediate frequency signal of the L1 band subband signal converted from the digital signal output from the A / D conversion circuit 112a and the reference synchronization signal added to the positioning signal of the L1 band, and the synchronization is performed. Measure the timing of the signal. By doing so, it is possible to determine the synchronization timing between the C / A code replica and the intermediate frequency signal of the L1-band subband signal that has been digitally converted, and the phase on which the C / A code is multiplied is determined. The time required for detection can be shortened.

  The GPS receiver according to the present invention can be applied to a positioning system.

It is a partial block diagram which shows the GPS receiver concerning one Example of this invention. It is a partial block diagram which shows the GPS receiver concerning one Example of this invention. It is a flowchart which shows operation | movement of the GPS receiver concerning one Example of this invention.

Explanation of symbols

  100 GPS receiver

Claims (3)

Synchronization signal generating means for generating a synchronization signal to be added to the positioning signal in the L1 band and the positioning signal in the L2 band having different frequencies;
A timing is determined based on the positioning signal in the L1 band to which the synchronization signal is added and the synchronization signal, and the positioning signal and the P code replica signal in the L1 band to which the synchronization signal is added at the timing. L1 waveband positioning signal correlation processing means for performing correlation processing of
L2 band positioning signal correlation processing means for performing correlation processing between the L2 band positioning signal to which the synchronization signal is added and the P code replica signal based on the timing;
Demodulation of positioning signals in the L1 and L2 bands based on the phase determined based on the correlation processing between the positioning signal in the L1 band and the positioning signal in the L2 band to which the synchronization signal is added and the P code replica A GPS receiving device comprising: demodulation means for performing processing. The GPS receiver according to claim 1,
The L1 waveband positioning signal correlation processing means obtains a phase at which the correlation value between the positioning signal of the L1 waveband to which the synchronization signal is added and the P code replica signal is a predetermined value,
The demodulation means performs a demodulation process of a positioning signal in the L1 waveband based on the phase. The GPS receiver according to claim 2, wherein
The L1 waveband positioning signal correlation processing means is determined based on the phase at which the correlation value between the positioning signal of the L1 band to which the synchronization signal is added and the P code replica signal is a predetermined value, and the timing. Find the phase difference from the phase,
The L2 waveband positioning signal correlation processing means obtains a correlation value between an L2 waveband positioning signal to which the synchronization signal is added and a P code replica signal based on the timing and the phase difference. GPS receiver.

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