JPH11231036A - Gps receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To introduce the degree of stability of code phase tracking so as to accurately measure a position, in the code phase tracking of a GPS(global positioning system) receiving device. SOLUTION: Radio wave from a CPS satellite received with an antenna 1 is amplified by an amplifier 2 and input to an inverse diffusion circuit 4 inversely diffusing the spectrum of a control block 3. The inversely diffused signal is integrated for a fixed time by an integrator 8, and output to a CPU 7 as one component and Q component. In satellite signal tracking, because carrier frequency and code phase required to be synchronized are changed accompanying movement of the satellite and a GPS receiving device itself, they are necessary to follow to it. From the value of Early, Late to be the material of code phase tracking, the degree of stability of the code phase tracking is computed, and the tracking method is made different from each other at being stable and at being unstable. Further, at being abnormally unstable, the tracking information is not used for computation of position measurement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a Global P
The present invention relates to a GPS receiving apparatus that accurately receives and tracks radio waves from a positioning system satellite and obtains an accurate current position by performing positioning calculation.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a conventional GPS receiver.
FIG. 6 is a diagram showing the correlation between the shift of the tracking code phase and the despread integral value, and FIG. 7 is a diagram showing the correlation between the code phase shift and the despread integral value when the tracking code phase is shifted by a certain amount. FIG. In FIG. 5, this GPS receiving apparatus includes an amplifier 2 for amplifying a GPS satellite signal received by an antenna 1.
And a control block 3. The control block 3 includes a despreading circuit 4 for performing spectrum despreading, a code phase control circuit 5 for controlling a code phase and a carrier frequency to be synchronized at the time, and a carrier frequency control circuit 6, and is obtained by despreading. And a CPU 7 for determining whether or not the synchronization of the signals is correct based on the integrated signals and feeding back control to the control circuit to correct the deviation.

The offset to be corrected is a code phase and a carrier frequency.
e, detected using the I and Q components. Early and Late respectively denote the code phase currently being tracked by-
This is the integral value of the signal when shifted by ２ Chip and + ／ Chip, and the smaller the shift of the code phase is, the earlier the signal is shifted.
The difference between ly and Late becomes smaller. The I component and the Q component are a sine component and a cos component, respectively. The smaller the shift of the carrier frequency, the larger the I component and the smaller the Q component. Control for reducing the deviation of the carrier frequency is referred to as carrier tracking, and control for reducing the deviation of the code phase is referred to as code tracking.

FIG. 6 shows the correlation between the code phase shift and the despread integral value. The despread integral value is maximum when the code phase shift is 0, and linearly increases as the shift increases. The despread integrated value at Early and Late becomes 1/2 of the maximum value, and the despread integrated value becomes 0 at a shift of ± 1 chip.

At this time, the shift amount Δ of the code phase is given by (Equation 1)
Is calculated by

[0006]

(Equation 1)

In code tracking, this Δ is calculated,
Code phase tracking is realized by setting a phase shifted by Δ from the currently tracked phase in the code phase control circuit 5 of FIG.

[0008]

However, Early,
Since both the values Late include noise, Δ obtained by one calculation also includes an error. Therefore, in order to remove the influence of noise, some average processing must be performed to calculate this Δ. However, if the average time is long, it takes time to track the correct code phase,
If the average time is short, accurate code phase tracking cannot be realized.

In this GPS receiver, erroneous control due to noise causes a positioning error. Therefore, it is required to track a satellite signal with a correct carrier frequency and a correct code phase. In particular, the code phase shift is 1ch
Since the displacement of ip results in a positioning error equivalent to 300 m, it is necessary to quickly capture and accurately track.

The present invention solves the above-mentioned problems. By improving the accuracy of code tracking, it is possible to prevent erroneous control due to noise and improve the positioning accuracy.
It is intended to provide a PS receiver.

[0011]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention relates to a GPS receiver for measuring a position, which comprises a GPS receiver.
In code tracking that performs code phase synchronization control during tracking processing of satellite radio waves, Earl, which is a material for code tracking, is used as an index for measuring the stability of code synchronization.
y, Late signal values were used (Early + Lat
e) Use / (Early-Late).

[0012] With this configuration, it is possible to realize a GPS receiving apparatus capable of preventing erroneous control due to noise and improving positioning accuracy by improving code tracking accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 is a GPS receiver for measuring a position, in code tracking for performing code phase synchronization control during tracking processing of a GPS satellite radio wave, the code synchronization stability is reduced. As an index to be measured, a signal value of Early and Late, which is a material of code tracking, was used (Early + Late) / (Early-
Late) is used.

According to this configuration, Early and Late
, The stability of the code phase synchronization is calculated from the value of, and the stability of the code phase synchronization during code tracking can be quantitatively evaluated.

According to a second aspect of the present invention, a reciprocal of the stability is defined as a code tracking gain.

In this configuration, the gain of the shift amount of the code at the time of code tracking is calculated from the stability of the code phase synchronization, and the characteristic of the code tracking control can be changed according to the stability of the code phase synchronization. Improve tracking accuracy.

According to a third aspect of the present invention, a code tracking algorithm is selectively used depending on the stability.

According to this configuration, the code tracking algorithm is switched according to the stability of the code phase synchronization. When the code phase synchronization is stable, code tracking with an emphasis on accuracy is performed, and the code phase synchronization becomes unstable. At the time, code tracking is performed with emphasis on the pull-in speed of the code phase, and the accuracy of code tracking is improved.

According to a fourth aspect of the present invention, a channel having a high stability is prohibited from being used for positioning calculation.

With this configuration, it is determined whether or not the signal of the currently tracked satellite can be used for positioning calculation based on the stability of the code phase synchronization, and the positioning error is determined by using the signal in the unstable tracking state for positioning calculation. It can be prevented from occurring.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram of a GPS receiver according to an embodiment of the present invention, FIG. 2 is a diagram showing an example of a flow of a satellite signal tracking process, and FIG. 3 is a code tracking algorithm when the code phase tracking is unstable. FIG. 4 is a diagram showing a code tracking algorithm when the code phase tracking is stable.

The basic configuration shown in FIG. 1 is the same as that shown in FIG. 5, and a radio wave from a GPS satellite received by an antenna 1 is amplified by an amplifier 2 and supplied to a despreading circuit 4 of a control block 3 for despread spectrum. Is entered. The despread signal is integrated for a certain time by the integrator 8 and output to the CPU 7 as an I component and a Q component. 9 is a memory. Since the carrier frequency and code phase that need to be synchronized in the satellite signal tracking change with the movement of the satellite and the GPS receiver itself, it is necessary to follow them. This flow chart is shown in FIG.

The CPU 7 takes out the signal from the integrator 8 (step 1), calculates the deviation of the carrier frequency from the I and Q components obtained as a result of the despreading, and performs feedback control to the carrier frequency control circuit 6 (step 1). Step 2,
3). Further, in order to follow the code phase, the CPU 7 determines the despread integral values Early, Lat before and after the tracking code phase.
The code phase shift Δ is calculated from (Equation 1) based on e, and feedback control is performed to the code phase control circuit 5.

The reciprocal of Δ decreases as the code phase shift increases, and increases as the code phase shift decreases. Immediately after the start of tracking, the reciprocal of Δ is small because the code phase is inaccurate, and when the code phase tracking becomes accurate and stable, the reciprocal of Δ increases. Therefore, the reciprocal of Δ is calculated as a ratio r at the time of code tracking in each step 4.
ate can be used as the stability of the code phase tracking (hereinafter referred to as “stability”) (Equation 2).

[0025]

(Equation 2)

In steps 5 and 6, if the stability is high, it can be determined that the code phase tracking is stable. If the stability is low, it can be determined that the code phase tracking is unstable.

When the stability is low, the code phase tracking is in an unstable state, so the code phase must be quickly pulled in to the stable tracking state (step 7). When the stability is high, the tracking is performed sufficiently stably. Therefore, the code tracking must be performed accurately without performing the code phase shift unnecessarily (step 8). In the present invention, quick and accurate code tracking is realized by switching the code tracking algorithm depending on the degree of stability.

First, the code tracking algorithm when the stability is small, that is, when the code phase tracking is unstable, will be described with reference to FIG. The integrated values of Early and Late are taken out from the integrator 8 in FIG. 1 and integrated in the memory 9 (step 11).
(Step 12). When the number of times of integration reaches a predetermined number of times (step 13), Δ of (Equation 1) is calculated by dividing the integrated value of Early and Late by the predetermined number of times (step 14), and based on the phase currently being tracked. The value shifted by Δ is set in the code phase control circuit 5 of FIG. 1 (step 15), and the memory for integrating the integrated values of Early and Late and the memory for storing the number of integrations are cleared.
The predetermined number to be added is incremented by +5 (steps 16, 1
7, 18). By gradually increasing the number of times to be added, the code phase is pulled in immediately after the start of tracking, and the code phase tracking becomes more stable as the tracking progresses. This algorithm enables accurate code phase pull-in in a short time.

Next, the code tracking algorithm when the stability is high, that is, when the code phase tracking is stable will be described with reference to FIG.

From the integrator 8 of FIG.
Is taken out and the Δ of (Equation 1) is calculated (step 21). A new code phase is set in the code phase control circuit 5 of FIG. 1 by using a value obtained by multiplying Δ by the reciprocal of the stability as a code phase shift amount (steps 22 and 23). This is to reduce the influence of noise and the like, and does not feed back all Δ obtained by one calculation, but feeds a part of Δ. Since the stability is used for the feedback ratio, control according to the stability of the code phase tracking can be performed, and accurate code tracking can be performed.

When the stability is abnormally large, it is considered that the tracked code phase is largely shifted. Since a code phase tracking error of 1 chip corresponds to a position error of 300 m, a large positioning error may be generated when a satellite in such a tracking state is used for positioning calculation. Therefore, a satellite tracking in a state where the stability is equal to or higher than a certain value is not used for positioning calculation.

[0032]

As described above, according to the present invention, Earl
switching code tracking depending on the stability obtained from y and Late, using the reciprocal of the stability as a gain of code tracking, and, when the stability is abnormally large, positioning information of the satellite is calculated. , It is possible to perform a highly accurate positioning calculation that is not affected by noise.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a GPS receiver according to an embodiment of the present invention;

FIG. 2 is a diagram showing an example of a flow of a satellite signal tracking process according to one embodiment of the present invention;

FIG. 3 is a diagram showing a code tracking algorithm when code phase tracking is unstable in one embodiment of the present invention.

FIG. 4 is a diagram showing a code tracking algorithm when code phase tracking is stable according to one embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional GPS receiver.

FIG. 6 is a diagram showing a correlation between a conventional tracking code phase shift and a despread integral value.

FIG. 7 is a diagram showing a correlation between a conventional code phase shift when a tracking code phase shifts by a certain amount and a despread integral value.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 antenna 2 amplifier 3 control block 4 despreading circuit 5 code phase control circuit 6 carrier frequency control circuit 7 CPU 8 integrator

Claims (4)

[Claims] 1. A GPS receiver for measuring a position, comprising: a GPS receiver;
In code tracking that performs code phase synchronization control during tracking processing of satellite radio waves, Earl, which is a material for code tracking, is used as an index for measuring the stability of code synchronization.
y, Late signal values were used (Early + Lat
e) A GPS receiver using / (Early-Late). 2. The GPS receiver according to claim 1, wherein the reciprocal of said stability is a code tracking gain. 3. The GPS receiver according to claim 1, wherein a code tracking algorithm is selectively used depending on the degree of stability. 4. The GPS receiver according to claim 1, wherein the channel having a high degree of stability is prohibited from being used for positioning calculation.