JP6860971B2 - Signal processing device and receiving device and code tracking method - Google Patents

Description

The present invention relates to a signal processing device and a receiving device and a code tracking method.

As a background of this technical field, there is Japanese Patent Application Laid-Open No. 2013-246017 (Patent Document 1). In Patent Document 1, "GPS (Global Positioning System) is widely known as a positioning system using satellite signals, and is used in a receiving device built in a portable telephone, a car navigation device, or the like. In GPS, position calculation is performed to obtain the position coordinates of the receiving device and the clock error based on information such as the positions of a plurality of GPS satellites and the pseudo distance from each GPS satellite to the receiving device. "

The satellite signal transmitted from the GPS satellite is spread spectrum by a CDMA (Code Division Multiple Access) method using a C / A (Coarse and Acquisition) code which is a kind of spreading code. In addition, the navigation message including the trajectory information necessary for calculating the position of the GPS satellite is conveyed by BPSK (Binary Phase Shift Keying) modulation of the C / A code in units of 20 PN frames. The C / A code is a pseudo-random noise code having a code length of 1023 chips as a 1PN frame. Then, the navigation message is obtained by generating a replica signal of the same format as the C / A code and measuring the correlation value with the C / A code while changing the phase of the replica signal.

In order for the receiving device to demodulate the satellite signals transmitted from each GPS satellite and calculate the time when the GPS satellites launched the satellite signals, it is necessary to accurately track the C / A code. Non-Patent Document 1 describes a DLL (Delay Lock Loop) method, which is a general method for tracking a C / A code.

Japanese Unexamined Patent Publication No. 2013-246017

W. J. Gill, "A Comparison of Binary Delivery-Lock Tracking-Loop Implementations", IEEE Transitions on Aerospace and Electrical Systems, vol. ARS-2, No. 4, July, 1966.

In the techniques described in Patent Document 1 and Non-Patent Document 1, it is not considered to reduce the tracking error due to the influence of multipath. Therefore, there is a possibility that the followability of the replica signal to the C / A code may decrease due to the influence of multipath.

An object of the present invention is to provide a technique capable of improving the followability of a replica signal to a C / A code.

A brief description of typical inventions disclosed in the present application is as follows.

The signal processing device according to the embodiment of the present invention is a signal processing device for making a replica signal follow the C / A code of a satellite signal, and has a signal holding unit that holds the satellite signal as a digital signal. Further, a sample point for extracting a sample point in which the deviation amount of the replica signal is changed by a predetermined value and the correlation value between the C / A code of the satellite signal held by the signal holding unit and the replica signal changes. It has an extraction unit. In addition, it has a rearrangement data generation unit that generates rearrangement data in which the sample points extracted by the sample point extraction unit are rearranged in the order of extraction. Further, it has a correlation value calculation unit that calculates the correlation value for each deviation amount from which the sample points are extracted based on the rearrangement data generated by the rearrangement data generation unit. It also has a code timing determination unit that determines the amount of deviation at which the correlation value is maximized as the code timing of the satellite signal.

Further, the receiving device according to the embodiment of the present invention is a receiving device having a signal processing device for making the replica signal follow the C / A code of the satellite signal, and is a signal that holds the satellite signal as a digital signal. It has a holding part. Further, a sample point for extracting a sample point in which the deviation amount of the replica signal is changed by a predetermined value and the correlation value between the C / A code of the satellite signal held by the signal holding unit and the replica signal changes. It has an extraction unit. In addition, it has a rearrangement data generation unit that generates rearrangement data in which the sample points extracted by the sample point extraction unit are rearranged in the order of extraction. Further, it has a correlation value calculation unit that calculates the correlation value for each deviation amount from which the sample points are extracted based on the rearrangement data generated by the rearrangement data generation unit. It also has a code timing determination unit that determines the amount of deviation at which the correlation value is maximized as the code timing of the satellite signal.

Further, the code tracking method according to the embodiment of the present invention is a code tracking method in a signal processing device for making a replica signal follow the C / A code of a satellite signal, and the signal holding unit of the signal processing device , Has a signal holding step of holding the satellite signal as a digital signal. Further, the sample point extraction unit of the signal processing device changes the deviation amount of the replica signal by a predetermined value, and the correlation between the C / A code of the satellite signal held by the signal holding unit and the replica signal. It has a sample point extraction step that extracts sample points whose values change. Further, the relocation data generation unit of the signal processing device has a relocation data generation step of generating relocation data in which the sample points extracted in the sample point extraction step are rearranged in the extracted order. .. Further, the correlation value calculation unit of the signal processing device calculates the correlation value for each deviation amount from which the sample points are extracted based on the rearrangement data generated in the rearrangement data generation step. It has a value calculation step. Further, the code timing determination unit of the signal processing device has a code timing determination step of determining the deviation amount at which the correlation value is maximized as the code timing of the satellite signal.

Among the inventions disclosed in the present application, the effects obtained by representative ones will be briefly described as follows.

According to a typical embodiment of the present invention, the followability of the replica signal to the C / A code is improved.

It is a figure which shows the relationship between the correlation value and the phase difference. It is a figure which shows the relationship between the correlation value and the phase difference in a 0.5 chip correlator. When the code timing to be determined is 0, it is a diagram showing the positions of the Z _L of Z _E. When the code timing to be determined is 0.2, it is a diagram showing the positions of the Z _L of Z _E. And the difference between Z _E and Z _L, is a diagram showing the correlation between the code timing. It is a figure which shows the relationship between the correlation value, Z _E, and Z _L. It is a figure which shows the outline of the structural example of the receiving apparatus in one Embodiment of this invention. It is a figure for demonstrating the process of rearranging sample points in the order of extraction in one Embodiment of this invention. It is another figure for demonstrating the process of rearranging sample points in the order of extraction in one Embodiment of this invention. It is a figure which shows an example of the correlator waveform output by mounting the sort correlator in one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in all the drawings for explaining the embodiment, in principle, the same reference numerals are given to the same parts, and the repeated description thereof will be omitted.

First, the conventional DLL method will be described with reference to FIGS. 1 to 6. First, the satellite signal r (t) obtained by normalizing and down-converting the GPS signal received from the GPS satellite satisfies the following (Equation 1). As shown in (Equation 1), the satellite signal r (t) includes an error ε.

FIG. 1 is a diagram showing the relationship between the correlation value (correlation value between the C / A code and the replica signal) and the phase difference. The correlation value c (u) satisfies the following (Equation 2). Note that x (t) in (Equation 2) represents a code of period N, and is a function whose correlation becomes 0 when the time deviates by 1. Further, x (t-u) is a function representing a C / A code when the deviation amount u is shifted.

Then, as shown in FIG. 2, a general DLL type correlator has a code (replica signal) that is 1/2 chip ahead of the satellite signal and a code (replica signal) that is 1/2 chip behind the satellite signal. Is generated, and the timing of the codes is controlled so that the correlation values of the satellite signals for these two codes are equal. Further, such a correlator is called a 0.5 chip correlator.

Z (u) in (Equation 3), which is a mathematical formula for calculating the correlation value, indicates the correlation value, u indicates the amount of deviation, t indicates the time, and ε indicates satellite signals from other GPS satellites and other satellite signals. The sum of the error components caused by noise is shown. Further, (Equation 3) is used to calculate the code timing τ at which the correlation value Z (u) is maximized. Also, the absolute value of τ, which is the code timing value to be obtained if the prediction is correct, approaches 0.

That is, in the 0.5 chip correlator, the equation (3), and _{Z L} is Z (0.5), and a _{Z E} is Z (-0.5) is calculated. Further, as shown in FIG. _3, Z E, _{Z L} can be understood as a point on Z (u).

_{Next, the positions of ZE} and Z _L when the value of the code timing τ is 0 and when the value of the code timing τ is 0.2 will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, when the value of the code timing τ is 0, _{Z d,} which is the difference between _ZE and Z _L , becomes small. On the other hand, when the value of the code timing τ increases from 0 to 0.2, _{Z d,} which is the difference between _ZE and Z _L , increases as shown in FIG. Incidentally, the difference between the _{Z E} and _{Z L} satisfies the equation (4).

Next, _{the relationship between Z d} , which is the difference between _{Z E} and Z _L, and the code timing τ will be described with reference to FIG. As shown in FIG. 5, if it is assumed that the value of τ exceeds −0.5 and is less than 0.5, τ that minimizes the absolute value of _{Z d can be calculated.}

Here, in the conventional DLL method, there is a problem that a tracking error occurs due to multipath. Here _{, the satellite signal satisfies that G m} indicates the relative gain of the _{multipath and τ m} indicates the relative delay amount of the multipath (Equation 5). The relative gain of the multipath, G _m, is greater than -1 (a _{negative G m} indicates that the multipath is out of phase) and less than 1, which is greater than the main path. The absolute value is small. _{In addition, τ m,} which is the relative delay amount of the multipath, exceeds 0 and arrives later than the main path. Further, Z (u), which is the above-mentioned correlation value under this condition, satisfies the following (Equation 6).

Next, the correlation between the correlation value Z (u) and _ZE and Z _L will be described with reference to FIG. As shown in FIG. 6, Z _E, Z _L becomes a different value under the influence of multipath, so that the error occurs in the estimated value of the code timing τ to be obtained. Further, in order to reduce the tracking error due to multipath, a method (narrow correlator) in which the code timing difference is narrowed to less than 0.5 is known, but there is a problem that it becomes difficult to track a weak satellite signal. is there.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 7 to 10. In one embodiment of the present invention, the deviation amount u is changed within a predetermined range (for example, −0.5 (lower limit value of the deviation amount) <u <0.5 (upper limit value of the deviation amount)), and the deviation is changed. The correlation value Z (u) is calculated for each quantity u. Then, τ is calculated based on the maximum value of each calculated correlation value Z (u). That is, all the correlation values Z (u) are calculated _{, and τ is calculated from the maximum value as a mathematical formula (τ = max arg u} Z (u)).

FIG. 7 is a diagram showing an outline of a configuration example of the receiving device 10 according to the embodiment of the present invention. As shown in FIG. 1, the receiving device 10 that performs the positioning calculation based on the satellite signal transmitted from the positioning satellite includes the antenna 101, the RF receiving circuit unit (reception circuit unit) 102, the signal processing device 200, and the signal processing device 200. It has a positioning calculation processing unit 300.

The antenna 101 is a GNSS (Global Navigation Satellite System) antenna or the like.

The signal processing device 200 causes the replica signal to follow the C / A code of the satellite signal. Further, the signal processing device 200 includes a signal holding unit 201, a sample point extraction unit 202, a rearrangement data generation unit 203, a correlation value calculation unit 204, and a code timing determination unit 205.

The RF receiving circuit unit 102 receives a satellite signal transmitted from a GPS satellite. The RF reception circuit unit 102 converts the received satellite signal into a digital signal. Then, the RF reception circuit unit 102 inputs the satellite signal converted into a digital signal to the signal holding unit 201 and the correlation value calculation unit 204.

The signal holding unit 201 holds the satellite signal transmitted from the GPS satellite as a digital signal.

The sample point extraction unit 202 changes the replica signal by a predetermined value, so that the correlation value between the C / A code of the satellite signal held by the signal holding unit 201 and the replica signal changes. Is extracted. Further, the sample point extraction unit 202 inputs the order in which the sample points are extracted and the information for specifying the position of the extracted sample points to the rearrangement data generation unit 203.

The rearrangement data generation unit 203 generates rearrangement data in which the sample points extracted by the sample point extraction unit 202 are rearranged in the order of extraction.

The correlation value calculation unit 204 calculates the correlation value for each deviation amount based on the rearrangement data generated by the rearrangement data generation unit 203. More specifically, the correlation value calculation unit 204 integrates the correlation value between the C / A code and the replica signal at the sample points into the previously calculated correlation value in the order in which the sample points are extracted, and the sample points are extracted. Calculate the correlation value for each amount of deviation.

The correlation value calculation unit 204 inputs the calculated correlation value for each deviation amount to the code timing determination unit 205.

The code timing determination unit 205 determines the deviation amount that maximizes the correlation value as the code timing of the satellite signal from the correlation values for each deviation amount input from the correlation value calculation unit 204. The code timing determination unit 205 inputs the determined code timing to the correlation value calculation unit 204.

The correlation value calculation unit 204 generates a replica signal based on the code timing input from the code timing determination unit 205. Then, the correlation value calculation unit 204 inputs the generated replica signal to the positioning calculation processing unit 300.

The positioning calculation processing unit 300 calculates the distance to the positioning satellite based on the replica signal input from the correlation value calculation unit 204.

Hereinafter, a method of calculating the correlation value Z (u) between the sample points constituting the satellite signal r (t) and the C / A code for each deviation amount u will be described in detail. Generally, the satellite signal r (t) is composed of a finite sample point r (t), and satisfies the following (Equation 7) in the calculation of Z (u).

Further, as shown in (Equation 8) below, r (u) can be considered as a function such that it is 0 other than the sample point by using the Dirac delta function.

The sample point extraction unit 202 obtains the correlation value of Z (u ₀ + Δ) by using the following (Equation 9), assuming that the correlation value Z (u _{0 ) at a certain u 0 is obtained.} Here, the value of x (τ−u ₀ + Δ) −x (τ−u ₀ ) constituting (Equation 9) becomes smaller as the value of Δ becomes smaller. Also, r (t) is a function of 0 everywhere. Therefore, as shown in (Equation 10), when the value of Δ is close to 0, the value of x (τ−u ₀ + Δ) −x (τ−u ₀ ) is also close to 0. By (Equation 9), the difference between the correlation value of _{Z (u 0} + Δ) and the correlation value of Z (u _{0) can be calculated.}

When the sample point extraction unit 202 gradually increases the value of Δ from a state close to 0, the value of x (τ−u ₀ + Δ) −x (τ−u ₀ ) becomes zero and r The value of any of the sample points constituting (t) is not 0. At that moment, the value of x (τ-u ₀ + Δ) -x (τ-u ₀ ) becomes either 0, -2, or 2, so the following (Equation 11) is satisfied. Note that Δ and p in (Equation 11) are values obtained by _{u 0.} Also, K is 2 / N or -2 / N.

The sample point extraction unit 202 extracts all the sample points whose values change by increasing the value of Δ little by little (predetermined value) and repeating the process of extracting the sample points whose values change. For example, the sample point extraction unit 202 gradually increases the value of Δ from the lower limit value to the upper limit value of the deviation amount, and repeats the process of extracting the sample points whose values change, so that all the sample points whose values change. Is extracted. The sample point extraction unit 202 changes the value by gradually reducing the value of Δ from the upper limit value to the lower limit value of the deviation amount by a small amount (predetermined value) and repeating the process of extracting the sample points whose values change. All sample points may be extracted.

After that, the rearrangement data generation unit 203 rearranges (sorts) the order of the sample points in the order extracted by the sample point extraction unit 202, and generates the rearrangement data.

The correlation value calculation unit 204 integrates the correlation values between the sample points and the C / A code in the order rearranged by the rearrangement data generation unit 203, so that the correlation values for each deviation amount u from which the sample points are extracted are integrated. The value Z (u) is calculated. In the implementation, only the argument that maximizes Z (u) is actually required, so K may be calculated as 1 or -1.

Next, a method of calculating the correlation value will be specifically described with reference to FIGS. 8 and 9. As the value of Δ is gradually increased, in the example shown in FIG. 8, _{the value of r 3 at} the sample point changes, then _{the value of r 7} changes, and then the value of _{r N changes.} It changes, and then the value of _{r 0 changes.}

Then, in the sort correlator according to the embodiment of the present invention, the sample points are sorted in the order in which the values change. In the example shown in FIG. 8, r ₃ whose _{value changed first is first, r 7} whose value changed _{second is second, and r N} whose value changed third is third and fourth. r ₀ the value is changed to is sorted in the fourth.

Further, as shown in FIG. 9, when the value of Δ is gradually increased and the replica signal is shifted, _{the value of the sample point r 6} changes (inverts) first, and then the value of _{r 0 changes.} Then the value of _{r 7} changes, then the value of _{r 1} changes, then the value of _{r 8} changes, then the value of _{r 2 changes. Then, r 6} whose value changed first is first, _{r 0} whose value changed _{second is second, r 7} whose value changed third is third, and r whose value changed fourth. ₁ is sorted 4th, r ₈ whose value changed 5th is sorted 5th, and _{r 2 whose value changed 6th is sorted 6th.} That is, the sample points whose values have changed are sorted by using the distance from the changing point of x (τ) as a key. If the distances are the same, all the sample points may be added.

FIG. 10 is a diagram showing an example of a correlator waveform output by mounting the sort correlator according to the embodiment of the present invention. The horizontal axis of FIG. 10 indicates the amount of deviation u, and the vertical axis indicates the correlation value Z (u).

As shown in FIG. 10, the correlation value before increasing the value of Δ is 0. Then, after that, the value of Δ is gradually increased, and the process of extracting the sample points whose values change is repeated. Then, the difference between the correlation value between the sample point whose value changes and the C / A code and the correlation value between the sample point before the value changes and the C / A code is added to the previously calculated correlation value. That is, by integrating the correlation values between the sample points whose values change and the C / A code, the correlation value Z (u) between the sample points and the C / A code for each deviation amount u is sequentially plotted. Then, the code timing τ to be obtained is calculated based on the maximum value (peak) of each calculated correlation value Z (u).

<Effect of embodiment>
According to the present embodiment described above, the correlation value calculation unit 204 can obtain the correlation value at once in a wide range by calculating the correlation value for each deviation amount from which the sample points are extracted. Then, theoretically, the limit value obtained when the difference in code timing is set to 0 is obtained regardless of the estimated value of τ. Moreover, the multipath error can be reduced. Further, in this case, the multipath may be in-phase or out-of-phase, may be single or plural, and does not depend on the amount of delay. In addition, it is possible to suppress the appearance of estimation errors and errors due to multipath due to errors and lack of high-frequency components.

Further, the correlation value calculation unit 204 integrates the correlation value between the C / A code and the replica signal at the sample points in the order in which the sample points are extracted into the previously calculated correlation value, and the deviation amount from which the sample points are extracted. By calculating the correlation value for each, the amount of calculation for calculating the correlation value for each deviation amount can be reduced as compared with the conventional case.

Although the invention made by the present inventor has been specifically described above based on the embodiment, the present invention is not limited to the embodiment and can be variously modified without departing from the gist thereof. Needless to say.

10 ... Receiver,
101 ... antenna, 102 ... RF receiving circuit section,
200 ... Signal processing device, 201 ... Signal holding unit, 202 ... Sample point extraction unit, 203 ... Relocation data generation unit, 204 ... Correlation value calculation unit, 205 ... Code timing determination unit,
300 ... Positioning calculation processing unit.

Claims (4)

A signal processing device for making a replica signal follow the C / A code of a satellite signal.
A signal holding unit that holds the satellite signal as a digital signal,
Wherein a shift amount of the replica signal is changed to be larger by a predetermined value, the signal holding section the C / A code and the correlation value deviation amount is calculated for each of said replica signal change in the satellite signal held by However, a sample point extraction unit that extracts the changing position as a sample point and outputs the extraction order and information for specifying the position of the sample point extracted at a plurality of sample points.
A rearrangement data generation unit that generates rearrangement data in which a plurality of the sample points extracted by the sample point extraction unit are rearranged in the order of extraction according to the above order.
The relocation data generated by the relocation data generation unit is input, and the deviation between the C / A code of the satellite signal held by the signal holding unit and the sample point specified by the relocation data. A correlation value calculation unit that calculates the correlation value for each replica signal whose amount has changed, and a correlation value calculation unit.
From the correlation values calculated by the correlation value calculation unit, a code timing determination unit that determines the correlation value of the replica signal in which the deviation amount that maximizes the correlation value has changed is determined as the code timing of the satellite signal.
A signal processing device. In the signal processing device according to claim 1,
The correlation value calculation unit integrates the correlation value between the C / A code and the replica signal at the sample points into the previously calculated correlation value in the order in which the sample points are extracted. A signal processing device that calculates the correlation value for each replica signal from which sample points have been extracted. A receiving device having a signal processing device for making a replica signal follow the C / A code of a satellite signal.
The signal processing device is
A signal holding unit that holds the satellite signal as a digital signal,
Wherein a shift amount of the replica signal is changed to be larger by a predetermined value, the signal holding section the C / A code and the correlation value deviation amount is calculated for each of said replica signal change in the satellite signal held by However, a sample point extraction unit that extracts the changed position as a sample point and outputs the extraction order and information for specifying the position of the sample point extracted at a plurality of sample points.
A rearrangement data generation unit that generates rearrangement data in which a plurality of the sample points extracted by the sample point extraction unit are rearranged in the order of extraction according to the above order.
The relocation data generated by the relocation data generation unit is input, and the deviation between the C / A code of the satellite signal held by the signal holding unit and the sample point specified by the relocation data. A correlation value calculation unit that calculates the correlation value for each replica signal whose amount has changed, and a correlation value calculation unit.
From the correlation values calculated by the correlation value calculation unit, a code timing determination unit that determines the correlation value of the replica signal in which the deviation amount that maximizes the correlation value has changed is determined as the code timing of the satellite signal.
Have,
Receiver. A code tracking method in a signal processing device for tracking a replica signal to the C / A code of a satellite signal.
A signal holding step in which the signal holding unit of the signal processing device holds the satellite signal as a digital signal,
Sample point extraction unit of the signal processing apparatus, the C / A code and the shift amount of the satellite signal, wherein the shift amount of the replica signal is changed to be larger by a predetermined value, is held by the signal holding unit is changed Sample point extraction that extracts the changed position of the correlation value calculated for each replica signal as a sample point and outputs the extraction order and the information for specifying the position of the sample point extracted at a plurality of sample points. Steps and
The rearrangement data generation unit of the signal processing device rearranges the plurality of extracted sample points in the order extracted by the sample point extraction unit according to the order output in the sample point extraction step. Relocation data generation steps to generate data and
The relocation data generated in the relocation data generation step is input to the correlation value calculation unit of the signal processing device, and the correlation value calculation unit is the satellite signal held by the signal holding unit. A correlation value calculation step for calculating the correlation value for each of the replica signals in which the deviation amount at the sample point specified by the C / A code and the rearrangement data has changed, and
The code timing determination unit of the signal processing device sets the correlation value of the replica signal in which the deviation amount that maximizes the correlation value from the correlation values calculated by the correlation value calculation unit is changed as the code timing of the satellite signal. With the code timing determination step to determine as
A code tracking method that has.

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