JPH11183585A - Satellite navigation receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a satellite navigation receiver in which a group-delay-time difference can be corrected more precisely and by which positioning operation can be performed more precisely by a method wherein, only regarding the phase of a PN code, the group-delay-time difference is measured and corrected by a pseudo signal which is different from an actual signal. SOLUTION: A signal whose frequency is converted by a frequency conversion part 3 is input to an A/D conversion part 5 so as to be converted into a digital signal by a demodulation part 6. Then, the signal is input to the demodulation part 6 so as to be demodulated in such a way that a signal computing and tracking control part 7 is operated with reference to a satellite selected by a satellite selection part 8. An actual demodulated signal from the satellite is detected by a carrier-frequency and vector detection part 9 and a PN-code frequency and phase detection part 10. Data on it is sent to a code-delay-time measuring and control part 11. The control part 11 controls a pseudo signal, for group-delay-time measurement, which is generated by a pseudo-signal generation part 20 on the basis of the data. When a group-delay- time difference in a route to the input of the pseudo signal to a mixer 2 from its generation is made zero, a measuring time difference can be made similar to the time difference between satellites to be found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite navigation receiver, and more particularly, to a satellite navigation receiver that corrects a signal delay time in a receiver without disturbing a normal signal receiving operation and performs an accurate positioning operation.

[0002]

2. Description of the Related Art United States GPS and Russian GLONASS
In satellite navigation systems such as, as is well known,
From the difference between the transmission time of the signal transmitted from the satellite and the reception time at which the signal is received by the user receiver, the distance between the satellite and the receiver is calculated, and the distance from a plurality of satellites calculated simultaneously is calculated. The position of the user receiver is calculated based on the distance. At this time, since the satellite time and the user time are not synchronized, an offset generally occurs between the satellite time and the user time. Therefore, the calculated distance between the satellite and the receiver includes a distance error corresponding to this time offset, and the calculated distance is not a true distance, and is therefore called a pseudo distance.

[0003] The pseudorange is obtained from the navigation data obtained by demodulating a signal transmitted from a satellite and the phase of the PN code used for demodulation, and at the same time it is built into the user receiver. It is obtained by reading the time on the clock and calculating the difference.
As described above, the pseudo distance for each satellite includes a uniform distance error corresponding to the offset between the common satellite time and the user time for all satellites, but the common distance corresponding to the clock offset is used. By adding the error to the unknown and solving the simultaneous equations, accurate positioning is possible.

However, if the group delay time differs depending on the signal of each satellite on the path in the receiver until the signal received by the antenna is demodulated by the signal processing unit, a positioning error corresponding to the difference in the delay time is generated. Will be included. The reason that the group delay time differs depending on the satellite signal is mainly due to the fact that the group delay time frequency characteristic of the filter inserted in the frequency conversion unit is not constant, that is, the signal is different due to the difference in frequency through the filter. Therefore, this is not a significant problem when signals of the same frequency are transmitted due to the configuration of the GPS satellite navigation system (strictly speaking, a GPS satellite navigation system). The group delay time is slightly different because the Doppler frequency shift of each signal is different even in the navigation system), but in the GLONASS satellite navigation system in which the signal of each satellite is divided by changing the transmission frequency, However, since the transmission frequencies are different by 562.5 kHz, this poses a serious problem.

Therefore, conventional satellite navigation receivers, especially GLO
In the NASS satellite navigation receiver, a method for minimizing the difference in the group delay time is being studied. For example, adopting a circuit design that makes the group delay time frequency characteristic of the filter for signal frequency selection constant, or measuring the difference in the group delay time different depending on the frequency in advance and performing the positioning calculation beforehand A method of performing positioning with a small error by correcting the pseudorange of each satellite with the set group delay time difference is being studied.

[0006]

As described above, in the satellite navigation receiver, a method for minimizing the group delay time difference has been studied, but the group delay time frequency characteristic of the signal frequency selection filter is kept constant. The following problems arise when adopting such a circuit design. For example, it is necessary to apply a special design using a LC filter or the like to a narrow-band filter (a filter after the intermediate frequency) in which it is difficult to make the group delay time frequency characteristic the most constant among filters used in the receiver. However, for this purpose, it is necessary to select a frequency configuration in which the intermediate frequency of the receiver is set in a frequency band in which the LC filter can be used, and the flexibility of the frequency configuration is lost. In addition, the degree of freedom of the filter design itself is limited.

Generally, in order to make the group delay time frequency characteristics in the signal pass band of the filter constant, the bandwidth is set wide to make the group delay frequency characteristics in the signal pass frequency band constant. Alternatively, it is necessary to make the group delay time in the pass band of the signal constant by using a type of filter that makes the group delay characteristic constant, but the cutoff characteristic outside the signal band is sacrificed with either method. Therefore, the anti-jamming wave characteristic outside the signal band is reduced. Even when the SAW band limiting filter is used for the receiver to make the group delay time frequency characteristic as constant as possible, the reflection is approximately 10 nsec (3 m in distance) within the pass band due to multiple reflection of the input and output portions. As a result, a large positioning error corresponding to the accuracy obtained by multiplying the time difference by the geometric accuracy of the satellite navigation system occurs.

A method of measuring the difference of the group delay time different depending on the frequency in advance and correcting the pseudorange of each satellite by the previously measured group delay time difference when performing positioning calculation is as follows. Problems arise. That is, the group delay time difference inside the receiver is measured in advance at a certain temperature and stored as data, and the pseudo distance obtained by receiving the signal of the satellite navigation system actually used for positioning is measured in advance. In the method of correcting the group delay time difference, and reducing the error that the group delay time difference depending on the satellite signal gives to the measurement result, positioning with less error is possible at a temperature at which the group delay time difference is measured in advance, Since the group delay time frequency characteristic of the filter changes due to the temperature change of the receiver, the influence of the group delay time difference cannot be removed when the ambient temperature changes.

Therefore, in this method, means for controlling the temperature of the receiver to keep the temperature constant is added, or the difference in group delay time in the entire temperature range used in advance is measured so that correction can be performed at any temperature. By storing it as data and detecting the temperature of the receiver when actually measuring the pseudorange,
Although it must be configured to enable pseudo-range correction corresponding to temperature, in the former case, it is necessary to provide a heater and its control circuit, so that the receiver becomes large and complicated. In the latter case, there is a problem in the reproducibility of the measured data including the secular change.

The present invention has been made to solve such a problem, and corrects a difference in group delay time based on a difference in frequency generated in a receiver due to a change in an ambient environment in real time, thereby enabling accurate positioning. It aims to provide a satellite navigation receiver.

[0011] The applicant of the present invention disclosed "GLON on October 1, 1997" as an invention for solving the above problems.
ASS Receiver ”(Japanese Patent Application No. 9-2831)
No. 92). This prior application receives signals from a plurality of satellites each having a different carrier frequency, calculates the arrival time thereof, and delays the transmission delay of a signal generated inside the receiver depending on each carrier frequency. In a GLONASS receiver for calibrating, a pseudo signal (pilot signal) having the same frequency as each of the carrier frequencies is generated inside the receiver, and the delay time of each frequency of the pseudo signal is constantly measured. By calibrating the signal data from the satellite signal being received in real time using the delay time, the positioning error based on the difference in the group delay time is corrected. An object of the present application is to provide a satellite navigation receiver that outputs more accurate positioning data by performing more accurate correction using the technology of the above-mentioned prior application.

[0012]

SUMMARY OF THE INVENTION A satellite navigation receiver according to the present invention receives signals from a plurality of satellites, performs positioning calculation based on the arrival time of each signal, and also generates a group delay of a signal generated inside the receiver. In a satellite navigation receiver for correcting a time difference, a satellite signal detecting means for detecting a carrier frequency, a signal level, a PN code, a PN code frequency and a PN code phase of each signal from each satellite; At the same frequency, the same signal level, the same PN code, and the same PN code frequency as the detected signals,
Pseudo signal generating means for generating pseudo signals having different phases of PN codes; group delay time measuring means for measuring group delay times in which each pseudo signal generated by the pseudo signal generating means is generated inside the receiver; Correction means for correcting, in real time, a difference between group delay times in which signals from the respective satellites are generated inside a receiver using the group delay time measured by the group delay time measurement means. And

Each of the pseudo signals generated by the pseudo signal generating means includes a real signal from a corresponding satellite and a PN signal.
It is characterized in that the signal is a signal having a code phase separated by one chip or more.

The satellite navigation receiver of the present invention has a P
Since the configuration is such that the group delay time difference is measured and corrected using a pseudo signal different from the real signal only in the phase of the N code, the group delay time difference can be corrected more accurately, and more accurate positioning can be performed. Further, since the pseudo signal is a signal in which the phase of the real signal and the PN code are separated by one chip or more, the difference in group delay time can be measured without hindering the positioning operation with the real signal. G
The present invention can be applied to both the PS navigation receiver and the GLONASS satellite navigation receiver, and can be applied to a dual-purpose satellite navigation receiver.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the device configuration of the satellite navigation receiver of the present invention. In FIG. 1, reference numeral 1 denotes an antenna unit, which performs an operation of receiving a radio signal transmitted from each satellite of the satellite navigation system, converting the signal into an electric signal, and transmitting the electric signal to the mixer 2. The mixer 2 mixes a real signal from the satellite with a pseudo signal (also referred to as a group delay time measurement pseudo signal), which will be described later, and sends the mixed signal to the frequency converter 3. In the frequency conversion unit 3, the band of the transmitted signal is band-limited by the band-limiting filter, and the signal is frequency-converted to a frequency that can be demodulated. At this time, the local oscillation signal used for the frequency conversion is generated by the local oscillator 4, and inside the local oscillator 4, a synthesizer circuit for performing phase synchronization based on a highly stable signal source is configured. The main cause of the difference in the group delay time depending on the satellite frequency is due to the influence of the band limiting filter in the frequency conversion unit 3.

The signal whose frequency has been converted by the frequency conversion unit 3 is input to an A / D conversion unit 5 and converted into a 1-bit digital signal by a demodulation unit 6 so that digital data processing is possible. The digitized signal is supplied to the demodulation unit 6
The signal acquisition / tracking control unit 7 operates on the satellite selected by the satellite selection unit 8 to perform demodulation.
The actual signal from the demodulated satellite is calculated based on the carrier frequency
The level detector 9 and the PN code frequency / phase detector 10 determine the carrier frequency, signal level, PN code,
The PN code frequency and its phase are detected, and the detected data is sent to the code delay time measurement control unit 11.

The code delay time measurement control section 11 controls a pseudo signal for group delay time measurement generated by the pseudo signal generation section 20 from these data. That is, in the pseudo signal generating section 20, the real signal from each satellite and the signal of the same carrier frequency, the same signal level, the same PN code, and the same PN code frequency, The carrier wave in the pseudo signal generation unit 20 is generated so that the phase of the PN code is changed by one or more chips so as not to affect the reception positioning operation of the real signal of the real signal and generate pseudo signals for group delay time measurement. Frequency control unit 1
2. Control the PN code frequency / phase control unit 13.

The carrier frequency control unit 12 controls the carrier generation unit 14 to generate a carrier having the same frequency. The PN code frequency / phase control unit 13 and the code delay time measurement control unit 11 control the PN code generation unit 15 to control the phase so as not to hinder satellite signal reception as described above. Generate code. The carrier generated by the carrier generation unit 14 is controlled by the code delay time measurement control unit 11 to control the carrier level control unit 16.
Then, the delay time is controlled to the same output level as the carrier of the actual satellite signal for which the delay time is to be measured, and is input to the modulator 17. The modulator 17 modulates the input carrier with the PN code input from the PN code generator 15, generates a group delay time measurement pseudo signal, and sends it to the mixer 2.

The pseudo signal for measuring the group delay time input to the mixer 2 is transmitted from the frequency converter 3 to the demodulator 6 on the same path as the path through which the real signal from the satellite passes inside the receiver. Become. Since the pseudo signal for measuring the group delay time is the same as the real signal from the satellite for which the group delay time is to be obtained, except for the phase of the PN code, the satellite for which the group delay time is to be measured inside the receiver A group delay time similar to that of the actual signal from That is, the pseudo signal for measuring the group delay time of the present invention is such that not only the carrier frequency but also the signal level, the PN code and the PN code frequency are made to coincide with the real signal as in the prior art described above. The difference in group delay time closer to the difference in delay time can be measured. The code delay time measurement control unit 11
By comparing the phase of the PN code generated by the above control with the phase of the PN code when the pseudo signal is demodulated, the group delay time of this signal in this path including the frequency conversion unit 3 can be measured. it can. Since the pseudo signal for measuring group delay time differs from the real signal from the satellite by one or more chips in the PN code, the correlation of the PN code does not hinder the operation of receiving the real signal from the currently received satellite. And can be demodulated as a completely different signal. By performing the above operation on the signal of each satellite whose group delay time is to be measured,
The difference between the group delay times of the actual signals from each satellite can be determined.

By making the group delay time difference in the path from the generation of the pseudo signal for measuring the group delay time to the input to the mixer 2 zero, the measured time difference is obtained from the input to the mixer 2 to the demodulator 6. , That is, the difference in the group delay time between the signals of the respective satellites to be obtained. In order to make the group delay time difference between the generation of the pseudo signal for measuring the group delay time in the pseudo signal generation unit 20 and the input to the mixer 2 constant, the modulation unit 1
This can be achieved by directly connecting a circuit such as a filter having a frequency characteristic to the path from 7 to the input to the mixer 2 without inserting a circuit such as a filter having frequency characteristics.

The time difference from the generation of the pseudo signal for measuring the group delay time to the demodulation thus obtained is obtained for the actual signal of each satellite used for positioning. As a specific method, a signal of each satellite currently being received (for example, 1 to N
For example, the pseudo signals for measuring group delay time are generated and generated in the order of satellite 1, satellite 2, satellite 3,..., Satellite N in order of 100 msec. The group delay time is determined within the allocated time using the group delay time measurement pseudo signal. By repeating this measurement operation, it is possible to measure the difference in the group delay time generated in the receiver in real time with respect to the signal from each satellite that is receiving and positioning. The group delay time obtained in this way is sent to the delay time detecting unit 18. The delay time detecting section 18 obtains the difference from the group delay time for each satellite obtained by the above operation and obtains the difference as the data of the delay time difference in the frequency conversion section 3, and the positioning calculating section 19.
Send to The positioning calculation unit 19 corrects the pseudo distance using the difference in group delay time as an offset value of the pseudo distance measured by a signal from each satellite, and performs positioning calculation using the corrected pseudo distance. In this case, the correction may be performed such that the group delay time of the actual satellite signal is zero, or the correction may be performed such that the difference between the group delay times is zero.

The apparatus configuration shown in FIG. 1 is an embodiment, and the present invention detects the carrier frequency, signal level, PN code, PN code frequency and PN code phase of a signal from each satellite, and detects the same frequency, the same PN code phase. Signal level, same P
A pseudo signal having a different PN code phase at the N code and the same PN code frequency is generated, a group delay time generated inside the receiver is measured with the pseudo signal, and each of the satellites is transmitted from each satellite using the measured group delay time. The purpose of the present invention is to correct the difference in the group delay time of the signals of FIG.
It is needless to say that the present invention is not limited to the embodiment.

[0023]

As described above, the satellite navigation receiver of the present invention detects a real signal received from each satellite, and generates a group delay time measurement pseudo signal which is different from the real signal by the phase of the PN code. A special filter that keeps the group delay characteristic constant is used because it is configured to generate and detect the difference in the group delay time with the pseudo signal for measuring the group delay time and correct the difference in the group delay time of the real signal. High-precision positioning is possible under all use conditions without any problem. For this reason, there is an effect that the degree of freedom of design is not limited with respect to the band limiting filter and the frequency configuration of the receiver, and a receiver can be configured without impairing the anti-jamming characteristic outside the band. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a device configuration of a satellite navigation receiver of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna part 2 Mixer 3 Frequency conversion part 4 Local oscillation part 5 A / D conversion part 6 Demodulation part 7 Signal acquisition / tracking control part 8 Satellite selection part 9 Carrier frequency / level detection part 10 PN code frequency / phase detection part 11 Code delay time measurement control unit 12 Carrier frequency control unit 13 PN code frequency / phase control unit 14 Carrier generation unit 15 PN code generation unit 16 Carrier wave level control unit 17 Modulation unit 18 Delay time detection unit 19 Positioning calculation unit 20 Pseudo signal generation unit

Claims (2)

[Claims] 1. A satellite navigation receiver for receiving signals from a plurality of satellites, performing positioning calculation based on the arrival time of each signal, and correcting a difference in a group delay time of a signal generated inside the receiver. Satellite signal detecting means for detecting a carrier frequency, a signal level, a PN code, a PN code frequency and a PN code phase of each of the signals from the satellite, the same frequency, the same signal level as the respective signals detected by the satellite signal detecting means, Same PN code, same PN
Pseudo signal generating means for generating a pseudo signal having a different PN code phase at a code frequency; and a group delay for measuring a group delay time in which each pseudo signal generated by the pseudo signal generating means is generated inside a receiver. A time measuring unit; and a correcting unit that corrects, in real time, a difference in a group delay time in which a signal from each of the satellites is generated inside a receiver using the group delay time measured by the group delay time measuring unit. A satellite navigation receiver. 2. The apparatus according to claim 1, wherein each of the pseudo signals generated by said pseudo signal generation means is a signal having a phase of a PN code separated from a real signal from a corresponding satellite by one chip or more. Satellite navigation receiver.