JPH0363583A - Position measuring instrument for satellite - Google Patents

Abstract

PURPOSE:To reduce a calculation quantity by measuring an epoch signal with a data signal from the satellite or timing signal synchronized with it and a measurement start signal and calculating a dummy distance. CONSTITUTION:A signal which is demodulated by a reverse spread spectrum circuit part passes through a band-pass filter 9 and is inputted to a date demodulation part 14 and the signal is RBSK-demodulated and transferred to dummy distance measurement parts 25 and 26 to generate the timing signal. Further, the epoch signal which is synchronized with a PN (pseudo noise) code 7 is generated with the PN code. A rough time measurement part 23 transfers its counting result which is obtained by using the data timing signal as a start signal and the measurement start signal as an end signal to an arithmetic unit 25. Further, a detailed time measurement part 24 counts a fast clock by using the measurement start signal as a start and the epoch signal as an end signal to measure its time interval and transfers the result to the arithmetic unit 25. The arithmetic unit 25 knows the time when the satellite sends the signal and the internal time to calculate the dummy distance between the satellite and a user.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a ranging system using a positioning satellite.

[Conventional technology]

In the spread spectrum method used in positioning systems using positioning satellites, the time interval at which the epoch signal indicating the special position of the spreading code (PN code) is generated is the time interval from when the signal sent from the positioning satellite reaches the receiver. Since the propagation time is shorter than the propagation time required for By calculating the approximate distance between the satellite and the positioning device based on the information, and also by measuring the time difference between the epoch signal and the measurement start signal! M-similar distance was determined. If you do this for four satellites in the same way, the positions will be calculated.

Furthermore, when measuring the speed at a certain time, it was necessary to measure the speed for a certain period of time centered on that time.

[Problem to be solved by the invention]

The above technology requires the user's approximate position information to be input in advance when the positioning system is initially started up, and there is a problem in that the calculation of the approximate national position between the satellite and the user becomes a burden on the microcomputer.

An object of the present invention is to eliminate the need for initial position information that was conventionally required for positioning, simplify operations, and reduce the burden on the microcomputer.

Another object of the present invention is to simplify the procedure and device for positioning and reduce the number of required circuits.

[Means to solve the problem]

The above objectives are as follows: (1) The data signal sent from the satellite contains information such as the time when the satellite sent the data, and is completely synchronized with the epoch signal.

Therefore, if the epoch signal is measured using the data signal or a timing signal and measurement start signal synchronized with this, the time when a certain signal was sent from the satellite can be measured based on the clock inside the positioning device. Pseudoranges are easily calculated.

(2) Simultaneously start position and velocity measurements using the measurement start signal described above.

(3) This is achieved by generating a position and velocity measurement start signal using a clock that manages the time inside the positioning device.

[Effect]

(1) Since it is possible to know the time when a satellite transmitted a certain signal without the user's initial position information, which was required in the past, the pseudo distance between the satellite and the user can be easily calculated. Furthermore, since it is not necessary to calculate the approximate distance between the satellite and the positioning device, the amount of calculation is reduced and accuracy is improved.

(2) Since position and velocity measurements are started simultaneously with a single measurement start signal, the number of times a timing signal is generated can be reduced, and the circuit can be simplified.

(3) Generating a measurement start signal using a clock held within the positioning device eliminates the need for a measurement start signal generation circuit, and also makes it easier to know the time when measurement is started.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows NAVSTAR/GP for explaining the present invention.
2 is a timing chart of each signal when the present invention is applied to an S receiver. In the figure, (a) is a data signal sent from the satellite, (b) is an epoch signal inside the satellite, and (c) is
is the epoch signal reproduced inside the positioning device, (d)
is a received data signal, (e) is a timing signal synchronized with the data signal, and (f) is a positioning start signal. NA
The data inversion timing of the data signal (a) sent from the VSTAR satellite is P N which is a spread spectrum code.
(Pseud.

No.1se (pseudo noise) is completely synchronized with the epoch signal (b) indicating the start position of the code. The radio waves sent from the satellite reach the user with a delay in time proportional to the distance between the satellite and the user, as shown in the epoch signal (C) and data signal (d) in the figure. By the way, NAVST
Since the data transfer rate of the data signal sent from the AR satellite is 50 Bps, a timing signal (e) with a period of 20 m5 and whose timing is synchronized with the demodulated data inversion is created. Also, the time of data reversal, ie.

The generation time of the timing signal (e) can be easily determined by analyzing the sent data (d). Here, that time is assumed to be t. The timing signal starts counting epoch signals, and the positioning start signal (
f), the count is stopped. Here, the count number is assumed to be n.

For example, in the case shown in FIG. 1, n is 3.

Since the epoch signal of the NAVSTAR satellite has a period of 1 ms, the time when the epoch signal was sent from the satellite one time before the positioning start signal (f) was generated is:

It is calculated as t+n$1ms (1). Next, a clock with a shorter period is used to measure the time interval between the positioning start signal (f) and the next epoch signal (d). Here, it is set as Δt. At this time, the time when the received signal corresponding to the timing when the positioning start signal (f) was generated is sent from the satellite is t + (n-1) 1 ms + Δt (2)
is easily calculated. Furthermore, it is clear that even if the time interval between the positioning start signal (f) and the immediately preceding epoch signal (d) is measured, the time at which the signal was sent from the satellite can be calculated in the same way as described above.

Figure 2 shows NAVSTAR/G P to which the present invention is applied.
This is an example of the configuration of the S receiver. An antenna 1 receives a spread spectrum modulated signal on a 1.5 GHz carrier wave sent from a NAVSTAR satellite, and amplifies it with a low-noise amplifier.A local oscillator 4 and a frequency converter 3 convert the received signal to an intermediate frequency. Convert to This intermediate frequency signal is demodulated by the inverse spread spectrum circuit section 12, and the signal processing section 1
Incorporate into 3. Inside the inverse spread spectrum circuit section 12,
PN code is generated by PN code and N CO (N
The intermediate frequency generated by the carrier NCOIO is mixed by the mixer 6, mixed with the received signal by the mixer 3, passed through the bandpass filter 9, and subjected to inverse spread spectrum demodulation. The signal is taken into the signal processing section 13, and the signal processing section 13 converts the Doppler shift frequency calculated by the Doppler shift calculation section 15 into the carrier N
C010 to correspond to Doppler changes in the signal sent from the NAVSTAR satellite.

Further, in the signal processing unit 13, the data demodulation unit 14 demodulates the inverse spread spectrum signal into a 50 Bps signal sent from the NAVSTAR satellite, and the synchronization detection unit 18 detects synchronization and controls the PN code NCO3. TeP
Synchronous control is performed by changing the phase of the N code. Furthermore, the signal processing unit 13 performs positioning calculations based on the pseudo distance to the user, and calculates the user's position.

Next, an embodiment in which the present invention is applied to a NAVSTAR/GPS receiver will be described with reference to FIG. The signal demodulated by the inverse spread spectrum circuit section passes through the bandpass filter 9 and is taken into the data demodulation section 14 . Here P B S K (Binary Phase Shi
ftKeying) is demodulated and transferred to the pseudo distance measurement unit 25. That signal is input to the data timing signal 21. The data transfer rate of the data signal sent from the NAVSTAR satellite is 50Bps, so here it is 20m.
A timing signal is generated once every five times, and its timing is synchronized with the demodulated data inversion. Also, P
In N-coco generation 7, an epoch signal synchronized with the PN code of the received spread spectrum signal is created. This epoch signal is counted in the approximate time measurement 23 by using the data timing signal as a start signal and the measurement start signal as an end signal, respectively, and transfers the result to the arithmetic unit 25. Further, the detailed time section 24 measures the time interval by counting the high speed clock using the measurement start signal as the start signal and the epoch signal as the end signal, and sends the result to the arithmetic unit 2.
Transfer to 5. At the same time, the internal time when the measurement start signal is generated is read and output to the arithmetic unit 25. The arithmetic unit 25 uses the above-mentioned means from these measurement results to know the time when the satellite emitted the signal and the internal time, and calculates the pseudo distance between the satellite and the user. Further, the user's speed is measured by counting the signal that has passed through the bandpass filter 9 using the speed measurement 22, and the result is sent to the arithmetic unit 25.
will be forwarded to. Incidentally, although these pseudo-range measuring sections 26 are constructed of the above-mentioned hardware, it is clear that they can also be realized by software having similar functions.

FIG. 4 is a timing chart of each signal when the present invention is applied to a positioning system that measures speed. In the figure, (a) is a band-pass filter output signal, (b) is a positioning start signal, (c) is a conventional speed measurement timing, and (d) is a speed measurement timing according to the present invention. The user's speed is proportional to the amount of Doppler shift in the received radio waves. Therefore, the speed can be calculated by measuring the frequency of the inversely spread spectrum signal shown in FIG. By the way, to measure the speed, the inverse spectrum is spread for a certain period of time (in this case, ±t') centered around the positioning start signal shown in Figure (b), that is, the time shown in Figure (c). The signal must be measured. In the present invention, FIG.
As shown in d), start measurement with a positioning start signal,
After a certain period of time (t' in this case), the measurement is terminated, and the Doppler shift amount is measured to calculate the speed of the user. Even if speed is measured using this method, the error is small and poses no practical problem. In addition, Fig. 4 (b
) If the position and velocity measurements are started at the same time using the positioning start signal shown in ), the structure can be simplified.

The next embodiment will be explained using FIG. 5. The internal clock 27 in FIG. 5 receives the measurement start signal 19. in FIG. This replaces the internal clock 20.

A feature of the present invention is that the position and speed are measured using a time signal generated by the internal clock 27, such as a clock generated every - second, as a measurement start signal, thereby simplifying the circuit configuration. The measurement start signal generated by the internal clock 27 is
Inputted to the pseudo distance measurement unit 26 and the speed measurement 22,
Speed, approximate time.

The detailed time is measured and the result is input to the arithmetic device 25. In addition, the measurement start signal created at internal time 27 is
At the same time, the data is input to the arithmetic unit 25, and the time at which the measurement is started is grasped. Therefore, the pseudo distance between the satellite and the user can be easily calculated.

[Effects of the Invention] According to the present invention, the pseudo distance between the satellite and the user can be calculated without inputting the user's position information, and it is not necessary to calculate the approximate distance between the satellite and the positioning time. Therefore, the amount of calculation is reduced and accuracy is improved. Further, since the circuit that generates the position and velocity measurement start signal can be shared with other circuits, there is an effect that the circuit configuration can be simplified.

[Brief explanation of drawings]

FIG. 1 is a timing chart of each signal in an embodiment of the present invention, FIG. 2 is a block diagram of a GPS positioning device for realizing the present invention, and FIG. 3 is an embodiment in which the present invention is applied to a GPS positioning device. A block diagram of an example, FIG. 4 is a timing chart for measuring speed in the present invention, and FIG. 5 is a block diagram of an embodiment in which an internal clock is applied in place of the measurement start signal. l...Antenna, 5, 6...Mixer, 7...PN
Coco generation, 8...PN code NGO19...Band pass filter, 10...Carrier NGO111...
Pseudo-range measurement, 12... inverse spread spectrum circuit section,
13... Signal processing section, 14... Data demodulation, 15.
... Dotsupura shift calculation, 17... Positioning calculation, 18.
...Synchronization detection, 19...Measurement start signal, 20...Internal clock, 21...D Fig. 1 @ Fig. 4 TOI-→ Fig. 3 Fig. 5rgJ

Claims (1)

[Claims] 1. In order to reverse spectrum spread the signal sent from the positioning satellite, an epoch signal indicating a special position of the spreading code created inside the positioning device is applied to the received data or to this. A positioning device characterized by measuring using a synchronized timing lock and a positioning start signal. 2. A positioning device characterized in that it starts measuring position and velocity simultaneously with a single positioning start signal. 3. A positioning device characterized in that a clock that manages time inside the positioning device generates a signal indicating the start of positioning and speed measurement.