JPH0552931A - Tracking method of gps receiver - Google Patents

Abstract

PURPOSE:To realize a small-sized GPS receiver having excellent characteristics as a GPS receiver which is used for measuring positions at the time of navigating aircraft, marine vessels, automobiles by receiving radio waves from an artificial satellite by means of a plurality of antennas by commonly using a code generator without deteriorating the code tracking accuracy. CONSTITUTION:The code generator 31 of a demodulation circuit is commonly used among a plurality of receiving sections which receive the same satellite signal and, by approximately setting the phase of the generator 31, the measured results obtained when the phase is accurately set against each receiving section are presumed from the difference between the approximately set phase and the phase of the generator 31 to be set by each receiving section, characteristic of a correlator, and correlated results obtained with the correlator. When the presumed value is used as a measured result, the code generator 31 can be commonly used among the receiving sections without deteriorating the code tracking accuracy of the generator 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS receiver tracking method for measuring the position by receiving satellite radio waves by a plurality of antennas in the navigation field of aircrafts, ships and automobiles.

[0002]

2. Description of the Related Art In recent years, a GPS for simultaneously receiving the same satellite signal with a plurality of antennas for the purpose of measuring absolute azimuth and avoiding interruption of reception due to changes in the angle of a moving body.
Receivers are receiving attention.

A conventional GPS receiver tracking method will be described below. FIG. 6 shows a GPS to which a conventional tracking method is applied.
3 shows a configuration of a receiver. In FIG. 6, reference numeral 1 denotes two independent receivers that respectively receive the radio waves of satellites, and 2
Is a control unit for controlling these receiving units, measuring satellite signals to obtain the position and direction, and 3 is a reference oscillator.

FIG. 7 shows a more detailed structure of one of the receivers 1 shown in FIG. Reference numeral 11 is an antenna for receiving the radio waves of the satellite. Reference numeral 12 is a high-frequency unit that amplifies, filters, and frequency-converts the signal from the antenna, and 13 is a demodulation circuit, which is five independent identical circuits. In this demodulation circuit, 14 is a code generator for generating a pseudo-noise code peculiar to the satellite, 15 is a correlator for despreading the satellite signal spread by the pseudo-noise code, and 16 is a phase detector for the despread signal. The demodulator 17 is an oscillator for reproducing the carrier wave of the satellite signal.

The operation of tracking a satellite signal in the GPS receiver configured as described above will be described below. First, the receiving unit 1 of FIG. 6 receives the radio waves of up to five satellites simultaneously under the control of the control unit 2 independently, measures the pseudo noise code and the carrier wave with the reference oscillator 3, and measures the orbit of the satellite. Receive information and time data. It is possible to simultaneously receive signals from the same satellite at each of the receivers and compare them to obtain the bearing. Also, attach the antenna 11 to different parts of the moving body,
When the moving body changes its angle due to rolling or the like, and one receiving unit cannot receive the satellite signal required for measurement, the other unit compensates for it and continuous measurement can be performed. Next, FIG.
The operation of the receiving unit will be described. The signal received by the antenna 11 is amplified, filtered and frequency-converted by the high frequency section 12,
Five independent demodulation circuits 13 perform pseudo-noise code and carrier tracking and demodulate data for different satellite signals. Pseudo-noise code tracking is performed by the code generator 1
The output of 4 and the satellite signal are compared by the correlator 15, the result is evaluated by the control unit via the demodulator 16, and the result is fed back to the code generator 14. The carrier wave is tracked by the demodulator 1 using the output of the oscillator 17 and the despread signal.
The quadrature detection is performed at 6, the control unit evaluates the result, and the result is fed back to the oscillator 17.

[0006]

However, the above-mentioned conventional method has the problems that the circuit scale is large, the power consumption is large, and the cost is high because the plurality of independent receiving units 1 are provided. In addition, the code generator 14 of the demodulation circuit 13 that receives the same satellite signal among the plurality of receivers 1.
Although it is possible to share the same, there is a problem that the pseudo noise code cannot be tracked with high precision because the installation position of the antenna 11 is different.

The present invention solves the above-mentioned problems of the prior art. A plurality of receiving sections share a code generator, which is a main part of a demodulation circuit for receiving the same satellite signal, and an antenna is installed. It is an object of the present invention to provide a tracking method for a GPS receiver, which enables accurate tracking even when the positions are different.

[0008]

In order to achieve this object, the present invention shares a code generator of a demodulation circuit between a plurality of receiving units that receive the same satellite signal, and the code generator is Perform an approximate phase setting, and make correct settings for each receiving unit based on the difference between the phase of the code generator to be set in each receiving unit, the characteristics of the correlator, and the correlation result obtained by the correlator. In this case, there is a processing method of predicting the measurement result in the case of the above, and using this predicted value as the measurement result.

[0009]

According to the present invention, a phase different from the phase of the code generator to be set is set by the above method, and the difference in the measured values caused by the setting difference is determined by the correlation characteristic if the tracking is accurate. Becomes Then, the measured values obtained by setting the different phases are back-calculated to obtain the measured values when the measurement is performed at the original set values.

[0010]

【Example】

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the GPS in one embodiment of the present invention.
It is a block diagram of the receiver which applies the tracking method of a receiver.

In FIG. 1, 21 is two antennas for receiving radio waves from the satellite, 22 is two high-frequency parts for amplifying, filtering and frequency converting signals from the antennas, and 23 is a demodulation circuit, which is five independent parts. The same circuit, 24 is a control unit that controls these demodulation circuits, measures a satellite signal to obtain the position and azimuth, and 25 is a reference oscillator.

FIG. 2 is a block diagram showing a more detailed structure of the demodulation circuit 23 shown in FIG. In this demodulation circuit, 31 is a code generator for generating a pseudo-noise code peculiar to the satellite, 32-1 and 32-2 are correlators for despreading the satellite signal spectrum-spread with the pseudo-noise code.
-1, 33-2 are demodulators for phase-detecting the despread signal, and 34-1, 34-2 are oscillators for reproducing the carrier wave of the satellite signal.

The operation of tracking a satellite signal in the GPS receiver configured as described above will be described with reference to the correlation characteristics shown in FIG. First, the two antennas 21 of FIG. 1 are installed at different positions corresponding to less than half of the chip which is the code rate, and the signals received by these antennas are amplified, filtered and After the conversion, in each of the five independent demodulation circuits 23, the pseudo noise code and the carrier wave are tracked and the data is demodulated for each different satellite signal. In each demodulation circuit in FIG. 2, the pseudo noise code tracking is performed by using the output of the code generator 31 and
The satellite signal input from each antenna is input to the correlator 3 respectively.
2-1 and 32-2 are compared, the result is evaluated by the control unit via the demodulators 33-1 and 33-2, and the result is fed back to the code generator 32.
For tracking the carrier wave, the outputs of the oscillators 34-1 and 34-2 and the despread signal are orthogonally detected by the demodulators 33-1 and 33-2,
The control unit evaluates the result, and the oscillators 34-1, 34-2 are evaluated.
By returning to. The pseudo-noise code and the carrier wave are independently tracked by the control unit 24 so that the radio waves of up to five satellites are simultaneously received, the pseudo-noise code and the carrier wave are measured by comparison with the reference oscillator 3, and the orbit of the satellite is also measured. Receive information and time data. One demodulation circuit simultaneously receives signals from the same satellite from two antennas. In this tracking of carrier waves, the code generator 31 is shared by the same satellite for signals from two antennas. The code generator 31 has two correlators, 2
The phase τ n to be set next is independently determined according to the measurement results of the demodulators and the oscillators. Note that n is 1 or 2 and corresponds to two antennas. τ n is the code phase measured by tracking the pseudo-noise code of the received signal. Calculate the average value for this τ n,
The difference is set in the code generator 31 and the difference Δτn between the average value and the phase to be set is stored in the control unit. FIG. 3 shows the characteristics of the correlator. If the tracking to the satellite signal is accurate, the maximum amplitude is obtained at τn. The horizontal axis is the phase of the pseudo-noise code, the unit is the code rate chip, and the vertical axis is the correlation result, and the signal strength is An. Phase error is τn + 1/2
It is measured by examining the correlation between the chip and τ n -1/2 chip and comparing the two. Data reception and carrier phase measurement are performed at the code phase τn. The phase actually set in the code generator is τn + 1/2 chip and τn
It is the value obtained by adding Δτn to −½ chip and τn. The correlator has a linear characteristic with respect to the input.
It can be expected that Δτ n will be a value smaller than 1/2 chip. Therefore, the ratio of the measured value obtained at the central value (Δτn = 0) to the measured value obtained when shifted by Δτn for +1/2, 0, and −1/2 chips, respectively, is Δτ independent of n. Function F + (Δτ),
It can be expressed by F0 (Δτ) and F- (Δτ). The control unit has these characteristics as a table, reads each function value according to the value of Δτ n, and reads this as +1/2, 0, -1
The measured value at the center value (Δτn = 0) is obtained by multiplying the measured value of each / 2 chip. If the measurement value of 0 chip does not require accuracy, conversion to this measurement value is unnecessary.

According to the tracking method of the GPS receiver according to the present embodiment, the code generator can be shared as compared with the conventional example without lowering the measurement accuracy, the circuit scale becomes smaller, the size becomes smaller and the price is lower. And power saving can be achieved.

As is clear from the above description, the tracking method of the GPS receiver according to this embodiment has an excellent effect in terms of circuit scale.

As described above, according to the present embodiment, the phase is roughly set in the code generator between a plurality of receiving units that receive the same satellite signal, and the code to be set in each demodulation circuit is set. From the difference between the phase of the generator, the characteristics of the correlator, and the correlation result obtained by the correlator, predict the measurement result when the correct settings are made for each receiver, and use this predicted value as the measurement result. By doing so, the code generator of the demodulation circuit can be shared without degrading the measurement accuracy, and downsizing, cost reduction, and power saving can be achieved.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a block diagram of a receiver to which the tracking method of the GPS receiver in one embodiment of the present invention is applied.
In FIG. 4, 41 is two antennas, 42 is two high frequency parts, 43 is five independent demodulation circuit circuits, 44 is a control part, and 45 is a reference oscillator. The configuration is almost the same as that of the first embodiment of FIG. 1, but the installation range between the two antennas is within the distance corresponding to two chips. FIG. 5 is a block diagram showing the detailed structure of the demodulation circuit 43 in the second embodiment of the present invention. 51 is a code generator, 52-
Reference numerals 1 and 52-2 are correlators, 53-1 and 53-2 are demodulators, and 54-1 and 54-2 are oscillators. The above is the same as the configuration of FIG. The difference from the configuration of FIG. 2 is that code phase shifters 55-1 and 55-2 are provided between the code generator 51 and the demodulators 54-1 and 54-2.

The operation of the GPS receiver tracking method applied to the above-mentioned structure will be described with respect to the difference from the first embodiment. First, by installing the antenna at a position separated by a distance equal to or more than half of the chip which is the code rate, the phase set in the code generator 51,
When the phase difference Δτn to be set approaches ½ chip, in the first embodiment, the functions F + (Δτ), F0 (Δτ),
The error in F- (Δτ) increases rapidly. In the present embodiment, the code phase shifter 55-
1, 55-2 adjusts to the approximate phase. The phase may be adjusted in units of 1/2 chip or less. If it is corrected in units of 1/2 chip, Δτ can be reduced to 1/4 chip or less.

As described above, the code generator 51 and the demodulator 5
Code phase shifters 55-1 and 55-2 are provided between 4-1 and 54-2.
By providing the antenna, even if the antennas are separated by 1/2 chip or more, the code generator of the demodulation circuit can be shared without deteriorating the measurement accuracy, thereby achieving downsizing, cost reduction, and power saving. be able to.

(Embodiment 3) Hereinafter, a third embodiment of the present invention will be described with reference to the drawings.

The structure of the receiver to which the tracking method of the GPS receiver in one embodiment of the present invention is applied is substantially the same as that of the first embodiment, and therefore the drawings are omitted. The difference is that the components of the demodulation circuit 23 in FIG. 1 and the phase setting of the code generator 31 in FIG. 2 are quantized in 1/8 chip units. The code generation is then made with a fixed timing signal that is eight times the pseudo-noise code rate generated by the reference oscillator 25.

The operation of the tracking method of the GPS receiver applied to the above-mentioned structure will be described with respect to the difference from the first embodiment. By quantizing the code generator, the difference Δ between the phase set in the code generator 31 and the phase to be set Δ
In the first embodiment, τ n is the difference from the average value, but an error due to quantization is also added. In the present embodiment, the added Δτ n is stored in the control unit. Then, as in the first embodiment, the function F + (Δ
τ), F0 (Δτ), F- (Δτ) +1/2, 0,-
An accurate measured value is obtained by multiplying each measured value of 1/2 chip.

As described above, by quantizing the code generator 31, further downsizing, cost reduction, and power saving can be achieved without degrading the measurement accuracy.

In the first embodiment, the antenna 21
The number of satellites is two and the number of satellites for simultaneous reception is five. However, the number of satellites is not limited to this, and the number may be plural. Further, the setting value of the code generator is an average of the setting values of a plurality of antennas, but the setting value is not limited to this, and the setting value of one antenna may be used, or other means may be used. further,
The configuration of the demodulation circuit is limited to that shown in FIG. 2. Even if the code generator is shared, for example, the output of the oscillator is supplied to the demodulator through the correlator for the code, even if the demodulation circuit for other spread spectrum signals is used. Good. In the third embodiment, the code phase shifters 55-1 and 55-2 of the second embodiment can be quantized. Also, the quantization is 1/8 chip,
It goes without saying that another value less than 2 may be used.

[0027]

As described above, according to the present invention, between the plurality of receiving units that receive the same satellite signal, the phase is roughly set in the code generator, and the code generation to be set in each demodulation circuit is performed. Predict the measurement result when the correct setting is made for each receiving unit from the difference between the phase of the receiver, the characteristics of the correlator, and the correlation result obtained by the correlator, and use this predicted value as the measurement result. Therefore, without lowering the measurement accuracy,
The code generator of the demodulation circuit can be shared, downsizing,
It is possible to realize an excellent tracking method for a GPS receiver, which can achieve cost reduction and power saving.

[Brief description of drawings]

FIG. 1 is a block connection diagram of a receiver to which a tracking system of a GPS receiver according to a first embodiment of the present invention is applied.

FIG. 2 is a detailed block diagram of the demodulation circuit of the GPS receiver according to the first embodiment.

FIG. 3 is a characteristic diagram of a correlator of the GPS receiver according to the first embodiment.

FIG. 4 is a block connection diagram of a receiver to which a GPS receiver tracking system according to a second embodiment of the present invention is applied.

FIG. 5 is a detailed block diagram of the demodulation circuit of the GPS receiver according to the second embodiment of the present invention.

FIG. 6 is a block connection diagram of a receiver to which a tracking method of a GPS receiver of a conventional GPS receiver is applied.

FIG. 7 is a detailed block connection diagram of a receiver of a conventional GPS receiver.

[Explanation of symbols]

 21 antenna 22 high frequency unit 23 demodulation circuit 24 control unit 25 reference oscillator 31 code generator 32 correlator 33 demodulator 34 oscillator 41 antenna 42 high frequency unit 43 demodulation circuit circuit 44 control unit 45 reference oscillator 51 code generator 52 correlator 53 demodulation 54 oscillator 55 code phase shifter

Claims (3)

[Claims] 1. A plurality of antennas installed at positions corresponding to a distance equal to or less than ½ of a pseudo noise code rate, a high frequency section for amplifying, filtering, and frequency converting signals from these antennas, respectively, and a high frequency section for this high frequency section. A correlator that despreads the output signals of the respective units, and a demodulator that performs phase detection,
An oscillator for reproducing a carrier wave corresponding to each of the antennas, and a code generator for generating a pseudo-noise code unique to the satellite common to the plurality of antennas are provided, the same satellite signal is received by the plurality of antennas, and each antenna receives the same satellite signal. The common phase of the code generator is set to the common code generator, and the difference between the phase of the code generator to be set in each receiving unit, the characteristics of the correlator, and the correlation obtained by the correlator. From the result, the GP that tracks the pseudo noise code by predicting the measurement result when the correct setting is made for each receiving unit and using this predicted value
S Receiver tracking method. 2. A plurality of antennas installed at a position corresponding to a distance equal to or less than twice the pseudo noise code rate, and a code phase shifter for correcting the phase of the pseudo noise code at the code input of each correlator. 2. The G according to claim 1, wherein the difference from the phase of the code generator to be set in each receiving section is adjusted to an approximate phase.
PS receiver tracking method. 3. A code generator for setting a phase in a quantized unit of ½ chip or less, wherein an approximate phase of a quantized pseudo noise code is set in a code generator common to antennas, From the difference between the phase that should be set in each receiving unit, including the error, the characteristics of the correlator, and the correlation result obtained by the correlator, obtain the measurement result when the correct setting is made for each receiving unit. 3. The GP according to claim 1, wherein the GP is predicted, and the pseudo noise code is tracked by using the predicted value.
S Receiver tracking method.