JP3730387B2 - Satellite navigation receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a satellite navigation receiver, and more particularly to a satellite navigation receiver that calibrates a signal delay time in the receiver without disturbing a normal signal reception operation and performs an accurate positioning operation.
[0002]
[Prior art]
As is well known, in satellite navigation systems such as GPS in the US and GLONASS in Russia, the satellite is determined 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 position of the user receiver is calculated based on the distance from a plurality of satellites calculated simultaneously.
At this time, since the satellite time and the user time are not synchronized, it is common that an offset is generated between each other. Therefore, the calculated distance between the satellite and the receiver includes a distance error corresponding to the offset of this time, and the calculated distance is not a true distance, and thus is called a pseudo distance.
[0003]
This pseudo-range is obtained from the navigation data obtained by demodulating the signal transmitted from the satellite and the phase of the PN code used for demodulation, and at the same time the time of the clock built in the user receiver. Is calculated by calculating the difference.
As described above, the pseudorange for each satellite includes an equal distance error corresponding to the offset between the satellite time common to all satellites and the user time, but the common distance corresponding to this clock offset. Accurate positioning is possible by adding simultaneous errors to unknowns and solving simultaneous equations.
[0004]
However, in the path in the receiver until the signal received by the antenna is demodulated by the signal processor, if the group delay time differs depending on the signal of each satellite, a positioning error corresponding to the difference in this delay time is included. End up.
The reason why 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 converter is not constant, that is, the signal due to the difference in frequency through the filter. Therefore, it is not a big problem when signals of the same frequency are transmitted due to the structure of the system like a GPS satellite navigation system (strictly speaking, GPS satellites In the navigation system, the Doppler frequency shift of each signal is different, so the group delay time is slightly different.) However, in the GLONASS satellite navigation system in which the signal of each satellite is divided by changing the transmission frequency, However, the transmission frequency is different every 562.5 kHz, which is a big problem.
[0005]
Therefore, in a conventional satellite navigation receiver, particularly a GLONASS satellite navigation receiver, a method for reducing the difference in the group delay time as much as possible has been studied.
For example, adopt circuit design that makes the frequency characteristics of the group delay time of the signal frequency selection filter constant, or measure in advance when performing positioning calculation by measuring the difference in group delay time depending on the frequency in advance. A method of performing positioning with little error by correcting the pseudorange of each satellite with the difference in the group delay time is being studied.
[0006]
[Problems to be solved by the invention]
As described above, in the satellite navigation receiver, a method for reducing the group delay time difference as much as possible has been studied. However, the following circuit design is adopted to adopt a circuit design that makes the group frequency characteristics of the signal frequency selection filter constant. Such a problem arises.
For example, a narrow-band filter (filter after the intermediate frequency) where it is most difficult to make the group delay time frequency characteristics the most constant among the filters used in the receiver needs to be specially designed using an LC filter or the like. 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 degree of freedom of the frequency configuration is deprived. In addition, the degree of freedom of the filter design itself is limited.
[0007]
In general, in order to make the group delay time frequency characteristic within the signal pass band of the filter constant, the bandwidth is set wide to make the group delay frequency characteristic of the signal pass frequency band constant, It is necessary to make the group delay time of the signal pass frequency band constant by using a filter of a type that makes the delay characteristic constant, but since either method is used, the cutoff characteristic outside the signal band is sacrificed, The anti-jamming characteristic outside the signal band is degraded.
Even when a SAW band limiting filter is used in the receiver to make the group delay time frequency characteristic as constant as possible, multiple reflections at the input and output parts cause a delay of about 10 nsec (3 m in terms of distance) within the pass band. 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 is generated.
[0008]
In addition, the following problems arise in the method of correcting the pseudorange of each satellite with the group delay time difference measured in advance when measuring the difference in group delay time depending on the frequency and performing the positioning calculation. .
In other words, the group delay time difference inside the receiver is measured in advance at a certain temperature and stored as data, and measured in advance to the pseudo distance obtained by receiving the satellite navigation system signal actually used for positioning. In the method of correcting the group delay time difference and reducing the error given to the measurement result by the group delay time difference depending on the satellite signal, positioning with less error is possible under the temperature where 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.
[0009]
Therefore, in this method, a means for keeping the temperature constant by controlling the temperature of the receiver is added, or the difference in the group delay time in the entire temperature range used in advance is measured and stored as data so that any temperature can be corrected. However, by detecting the temperature of the receiver when actually measuring the pseudorange, it must be configured to enable pseudorange correction corresponding to the temperature. In the former case, the heater and its control are required. Since it is necessary to provide a circuit, the receiver becomes larger and more complicated. In the latter case, there is a problem in reproducibility including the secular change of measured data.
[0010]
The present invention has been made to solve such a problem, and is a satellite navigation reception capable of performing accurate positioning by correcting a difference in group delay time based on a difference in frequency generated in a receiver due to a change in ambient environment in real time. The purpose is to provide a machine.
[0011]
The present applicant filed a patent application (Japanese Patent Application No. 9-283192) entitled “GLONASS receiver” on October 1, 1997 as an invention for solving the above-mentioned problems.
In this prior application, signals from a plurality of satellites having different carrier frequencies are received and their arrival times are calculated. At the same time, the transmission delay of the signal generated inside the receiver is different from each other. In a GLONASS receiver that calibrates, a pseudo signal (pilot signal) having the same frequency as each of the carrier frequencies is generated inside the receiver, and the delay time for each frequency of the pseudo signal is constantly measured. The positioning error based on the difference in group delay time is corrected by calibrating signal data from the satellite signal being received in real time using the delay time.
An object of the present application is to provide a satellite navigation receiver that performs more accurate correction and outputs accurate positioning data using the technology of the above-mentioned prior application.
[0012]
[Means for Solving the Problems]
The satellite navigation receiver according to the present invention is:
In the satellite navigation receiver that receives signals from multiple satellites and performs positioning calculation based on the arrival time of each signal and corrects the difference in group delay time of signals generated inside the receiver, each of the signals from each satellite Satellite signal detection means for detecting the carrier frequency, signal level, PN code, PN code frequency and PN code phase, and the same frequency, same signal level, same PN code, same as each signal detected by the satellite signal detection means A pseudo signal generating means for generating a pseudo signal having a different PN code phase at a PN code frequency, and a group for measuring a group delay time generated in the receiver by each pseudo signal generated by the pseudo signal generating means. Each signal from each satellite is generated inside the receiver using the delay time measuring means and the group delay time measured by the group delay time measuring means. Characterized in that a difference in that the group delay time and a correction means for correcting the real time.
[0013]
Each of the pseudo signals generated by the pseudo signal generating means is a signal obtained by separating the phase of the actual signal from the corresponding satellite and the PN code by one chip or more.
[0014]
Since the satellite navigation receiver of the present invention is configured to measure and correct the group delay time difference with a pseudo signal different from the actual signal only in the phase of the PN code as described above, the group delay time difference can be corrected more accurately, and more Accurate positioning is possible.
Further, since the pseudo signal is a signal in which the phase of the real signal and the PN code is separated by one chip or more, the difference in group delay time can be measured without disturbing the positioning operation with the real signal.
Further, the present invention can be applied to both a GPS satellite navigation receiver and a GLONASS satellite navigation receiver, and can also be applied to a dual-purpose satellite navigation receiver.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of a device configuration of a satellite navigation receiver of the present invention.
In FIG. 1, reference numeral 1 denotes an antenna unit that performs an operation of receiving radio signals transmitted from each satellite of the satellite navigation system, converting them into electrical signals, and sending them to the mixer 2.
In the mixer 2, a real signal from the satellite and a pseudo signal (also referred to as a group delay time measuring pseudo signal) described later are mixed and sent to the frequency conversion unit 3.
The frequency converting unit 3 limits the band of the transmitted signal with a band limiting filter and converts the frequency to a frequency that can be demodulated.
At this time, the local oscillation signal used for frequency conversion is generated by the local oscillation unit 4, and a synthesizer circuit is configured in the local oscillation unit 4 to perform phase synchronization with reference to a highly stable signal source.
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 converter 3.
[0016]
The signal frequency-converted by the frequency converter 3 is input to the A / D converter 5 and converted to a 1-bit digital signal by the demodulator 6 so that digital data can be processed.
The digitized signal is input to the demodulator 6 and the signal acquisition / tracking controller 7 operates on the satellite selected by the satellite selector 8 to perform demodulation.
The real signal from the demodulated satellite is detected by detecting the carrier frequency, signal level, PN code, PN code frequency and phase thereof by the carrier frequency / level detector 9 and the PN code frequency / phase detector 10. These pieces of data are sent to the code delay time measurement control unit 11.
[0017]
The code delay time measurement control unit 11 controls the group delay time measurement pseudo signal generated by the pseudo signal generation unit 20 from these data. That is, in the pseudo signal generation unit 20, each real signal from each satellite and a signal having the same carrier frequency, the same signal level, the same PN code, and the same PN code frequency, which are demodulated by the demodulation unit 6. In order not to affect the reception positioning operation of the real signal, the carrier wave in the pseudo signal generation unit 20 is generated so that the phase of the PN code is varied by one chip or more and each group delay time measurement pseudo signal is generated. The frequency controller 12 and the PN code frequency / phase controller 13 are controlled.
[0018]
The carrier frequency control unit 12 controls the carrier generation unit 14 to generate a carrier wave 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 interfere with satellite signal reception as described above. Generate code.
The carrier wave generated by the carrier wave generation unit 14 is controlled to the same output level as the carrier wave of the actual satellite signal whose delay time is to be measured by the carrier wave level control unit 16 under the control of the code delay time measurement control unit 11. Input to the modulation unit 17. The modulation unit 17 modulates the input carrier wave with the PN code input from the PN code generation unit 15, generates a group delay time measurement pseudo signal, and sends it to the mixer 2.
[0019]
The group delay time measurement pseudo signal input to the mixer 2 is sent from the frequency conversion unit 3 to the demodulation unit 6 through the same path as the path through which the actual signal from the satellite passes inside the receiver.
This group delay time measurement pseudo signal is the same as the actual signal from the satellite for which the group delay time is to be obtained, except for the phase of the PN code. Therefore, the satellite for which the group delay time is to be measured inside the receiver. Group delay time similar to the actual signal from
In other words, the group delay time measurement pseudo signal according to the present invention matches not only the carrier frequency but also the signal level, the PN code, and the PN code frequency with the actual signal as in the above-described prior art. The difference in group delay time closer to the difference in delay time can be measured.
Further, this signal in this path including the frequency conversion unit 3 is compared by comparing the phase of the PN code generated by the control of the code delay time measurement control unit 11 with the phase of the PN code when the pseudo signal is demodulated. Group delay time can be measured.
In addition, the group delay time measurement pseudo signal is different from the actual signal from the satellite by one or more chips, so that the correlation of the PN code prevents the reception operation of the actual signal from the currently received satellite. And can be demodulated as a completely different signal.
By performing the above operation on the signals of the satellites whose group delay times are to be measured, the difference in the group delay times of the actual signals from the satellites can be obtained.
[0020]
Then, 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, the measured time difference becomes the delay from the input to the mixer 2 to the demodulator 6. It can be made similar to the time difference, that is, the difference in the group delay time that differs between the signals of the satellites to be obtained.
In order to make the group delay time difference from the generation of the pseudo signal for group delay measurement by the pseudo signal generator 20 to the input to the mixer 2 constant, the path from the modulator 17 to the input to the mixer 2 In addition, it is possible to connect directly without inserting a circuit such as a filter having frequency characteristics.
[0021]
The time difference from generation of the group delay time measurement pseudo signal thus obtained to demodulation is obtained for the actual signal of each satellite used for positioning.
As a specific method, for each satellite signal currently received (for example, satellites 1 to N), for example, the time is divided every 100 msec to obtain satellite 1, satellite 2, satellite 3,. , Satellite N, etc., are generated in the order of group delay time measurement, and the group delay time is determined within the allocated time using the generated 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 detector 18.
The delay time detection unit 18 obtains the difference from the group delay time for each satellite obtained by the operation as described above, and sends the difference to the positioning calculation unit 19 as delay time difference data in the frequency conversion unit 3.
The positioning calculation unit 19 corrects the pseudo distance using the difference in the group delay time as an offset value of the pseudo distance measured by the signal from each satellite, and performs the positioning calculation at the corrected pseudo distance.
In this case, correction may be performed so that the group delay times of the actual satellite signals are each zero, or correction may be performed so that the difference between the group delay times is zero.
[0022]
The apparatus configuration shown in FIG. 1 is one embodiment, and the present invention detects the carrier frequency, signal level, PN code, PN code frequency and PN code phase of the signal from each satellite, and the same frequency, the same signal level, Generate a pseudo signal with the same PN code and the same PN code frequency and different PN code phases, measure the group delay time generated inside the receiver with this pseudo signal, and use the measured group delay time from each satellite. The gist is to correct the difference in the group delay time of each signal, and it goes without saying that the apparatus configuration is not limited to the embodiment of FIG.
[0023]
【The invention's effect】
As described above, the satellite navigation receiver of the present invention detects a real signal received from each satellite, generates a pseudo signal for group delay time measurement that differs from the real signal by the phase of the PN code, and The delay time measurement pseudo signal detects the difference in the group delay time and corrects the difference in the group delay time of the actual signal, so it can be used without using a special filter that makes the group delay characteristic constant. High-precision positioning is possible under certain conditions.
For this reason, there is an effect that the degree of freedom of design is not limited with respect to the frequency configuration of the band limiting filter and the receiver, and a receiver that does not impair the anti-jamming wave characteristics outside the band can be configured .
[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 and tracking control part 8 Satellite selection part 9 Carrier frequency and level detection part 10 PN code frequency and 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 level control unit 17 Modulation unit 18 Delay time detection unit 19 Positioning calculation unit 20 Pseudo signal generation unit

Claims (2)

In a satellite navigation receiver that receives signals from multiple satellites and performs positioning calculation at the arrival time of each signal, and corrects the difference in group delay time of signals generated inside the receiver,
Satellite signal detection means for detecting the carrier frequency, signal level, PN code, PN code frequency and PN code phase of each signal from each satellite;
Pseudo signal generating means for generating pseudo signals having the same frequency, the same signal level, the same PN code, and the same PN code frequency as the respective signals detected by the satellite signal detecting means, but having different PN code phases;
Group delay time measuring means for measuring the group delay time generated in the receiver by each pseudo signal generated by the pseudo signal generating means;
Correction means for correcting in real time a difference in group delay time generated by each signal from each satellite using the group delay time measured by the group delay time measurement means. Satellite navigation receiver. 2. The satellite navigation receiver according to claim 1, wherein each of the pseudo signals generated by the pseudo signal generating means is a signal obtained by separating a phase of a real signal from a corresponding satellite and a PN code by one chip or more.

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