JPH03296327A - Travelling object satellite communication/position measuring system - Google Patents

Abstract

PURPOSE:To allow the system not to be made large in the circuit scale even when a mobile station is used as a reception section by using a chirp signal so as to measure the position thereby solving a problem of synchronization. CONSTITUTION:A chirp signal from a base station is multiplied with a modulated position measuring signal, the result is synthesized with an SCPC signal, the result is arranged in a prescribed frequency interval location and then sent to a transmission IF section for a communication satellite. Signals from three communication satellites are received by an antenna high frequency section, branched into three by a branching device 14 and inputted to a demodulation circuit (15-1-15-3). A correlation device 20 multiplies a received chirp signal and a local chirp signal to take the correlation of the both. A timing signal generating circuit 22 adjusts the output timing of a clock signal so that a frequency error is made zero thereby controlling a local chirp signal generating circuit 21. A position measuring signal demodulator 24 receiving the output of the correlation device 20 reproduces accurately a timing signal required for measuring the position.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mobile satellite communication/positioning system in which one base station and a large number of mobile stations perform communication and positioning via a plurality of communication satellites.

(Prior Art) The mobile satellite communication/positioning system to which the present invention is directed is, for example, as shown in FIG.
3(N)), one base station 2 and many mobile stations (3(N)) are used.
, 3, . . .), and also provides mobile station positioning services.

As is well known, this type of mobile satellite communication/positioning method is
Intensive research and development is being carried out in various fields. Conventionally, base stations have been configured as shown in Figure 7, and mobile stations have been configured as shown in Figure 8.
A device configured as shown in the figure is known. In addition, in FIGS. 7 and 8, there are three communication satellites (N=3>, A and B, respectively).

Suppose that they are distinguished by a code C.

Figure 7 shows the transmission system of the base station, which basically consists of the communication positioning system control unit 4 and the modulation circuits (29-1 to 29-3) provided corresponding to each communication satellite (A, B, C). It is composed of

The communication positioning system control unit 4 transmits the communication signal to a modulation circuit (2).
9-1 to 29-3), it also holds the latest orbit information of the communication satellites (A, B, C), generates a positioning signal to be transmitted to the corresponding satellite, and outputs the positioning signal to the modulation circuit (
29-1 to 29-3).

The modulation circuit (29-1 to 29-3> is the modulation circuit 29-1
The details are as follows. Frame generation circuit 6 receives the communication signal and generates a data signal and a clock signal in a predetermined format. 5cpC(Sfngle Chan
The modulator 7 performs a modulation operation for each communication signal based on the data signal and the clock signal.

The PN signal generator 28 receives the clock signal and generates a high-speed P
An N signal (pseudorandom signal) is generated and output to one input of the multiplier 10. The positioning signal modulator 9 receives the positioning signal and the clock signal, performs a modulation operation, and transmits the modulated signal to the multiplier 10.
output to the other input of The multiplier 10 performs a multiplication operation on the PN signal and the modulated positioning signal, that is, spread spectrum (S
S) Modulate.

The output of the 5cpc modulator 7 and the output of the multiplier 10 are combined by a signal combiner 11 and input to a frequency converter 12, where the output is converted into a transmission channel frequency signal based on the output of a synthesizer 13, and the signal is transmitted to the corresponding communication satellite. The data is sent to the designated transmission IF section.

As a result, communication satellites (A, B) are transmitted from the base station.

For each of C), an FDMA signal obtained by frequency division multiplexing a normal 5 cpc signal and a code division multiplexing (CDMA) signal obtained by SS modulating a modulated positioning signal with a high-speed PN signal are superimposed and transmitted ( Figure 9).

In other words, the base station is equipped with a highly directional antenna having a sufficient degree of separation from each other for each communication satellite, and establishes an independent communication path for each communication satellite.

On the other hand, the mobile station has a sufficiently wide directional antenna,
It is possible to simultaneously transmit and receive signals to and from three communication satellites, and as shown in FIG.
4 and input to the SS demodulators (30-1 to 30-3).

The 5cpc modem 34 extracts one 5cpc signal in FDMA from the input signal, demodulates it, and transmits it to the communication terminal 3.
Output to 3. Note that the communication signal generated by the communication terminal 33 is modulated by the 5cpc modulator/demodulator 34 and sent from the antenna high frequency section to the satellite line.

Each 5Sfx modulator (30-1 to 30-3>t-G, t, CDMA using local PN signal specific to the corresponding communication satellite)
While selectively demodulating the corresponding positioning signal from the signal, P
The timing of the received positioning signal is reproduced in units of chips of the N signal, and a reproduced positioning signal consisting of the precise timing is output to the time difference detection circuit 31.

In the time difference detection circuit 31, under the control of the positioning calculation section 32,
Detecting the propagation time differences from the three communication satellites based on the three reproduced positioning signals (fine timing) and the timing signal (coarse timing) from the 5cpc modem 34,
The detected content is output to the positioning calculation unit 32 as a position information signal.

The positioning calculation unit 32 determines the position of the mobile station based on the principle of triangulation.

Here, in the conventional positioning method described above, since a broadband SS signal is used, it is possible to measure the propagation time difference with high accuracy, and high-precision positioning can be performed. That is, the chip speed of the PN signal generated by the PN signal generator 28 is the data speed of the communication signal M.
If it is doubled, as shown in FIG. 10, the autocorrelation characteristic of the PN signal has a time accuracy that is M times the data rate, and measurement becomes possible with that much precision.

(Problems to be Solved by the Invention) In the conventional positioning method described above, since the PN code is used as the SS signal, it takes a long time to synchronize the PN signal in the SS demodulators (30-1 to 3O-3). There is a problem that it is necessary.

Further, as a method for quickly synchronizing, there is a method of using a matched filter using a tapped delay line, but this method has the problem of increasing the circuit scale.

The present invention has been made in view of these problems, and its purpose is to provide a mobile satellite communication/positioning system that allows quick synchronization and positioning with a simple configuration and without increasing the circuit scale of the mobile station. Our goal is to provide the following.

(Means for Solving the Problem) In order to achieve the above object, the mobile satellite communication/
The positioning method has the following configuration.

That is, in the mobile satellite communication/positioning system of the present invention, one base station has highly directional antennas having sufficient separation from each other to establish independent communication paths for each of a plurality of communication satellites; means for constantly holding the latest orbit information of the plurality of communication satellites in order to perform station positioning;
The plurality of mobile stations are equipped with antennas with sufficiently wide directional characteristics to enable simultaneous communication with the plurality of communication satellites;
A positioning method in a mobile satellite communication/positioning system in which one base station and many mobile stations communicate via multiple communication satellites using the SCPC/FDMA method; and a transmitting section provided on one side of each of the large number of mobile stations; and a receiving section provided on the other side; means for generating a chirp signal whose frequency is swept within the entire bandwidth of a communication satellite; means for modulating a positioning signal; and SCPC/FDMA communication on a modulated chirp signal obtained by multiplying the chirp signal by a modulated positioning signal. The receiving section includes: means for superimposing and transmitting signals;
A plurality of demodulators are provided corresponding to each communication satellite; Receiving the reproduced positioning signals from each demodulator, the difference in signal propagation time from the plurality of communication satellites is determined, and the geographical positioning of the mobile station is determined based on the principle of triangulation. a positioning calculation unit that determines a value 1; and each demodulation unit generates a precise timing signal by adjusting the timing of a regenerated clock signal regenerated from a communication signal in a received signal based on a timing error signal. and;
Means for generating a local chirp signal having the same format as the chirp signal generated by the transmitting section based on the precise timing signal; Means for detecting the correlation between the modulated chirp signal in the received signal and the local signal; and Correlation detection result. means for narrowband filtering; means for detecting a timing error between both chirp signals based on the narrowband filtered correlation result signal and outputting the timing error signal; demodulating the reproduced positioning signal from the correlation result. It is characterized by comprising: a means for outputting; and a means for outputting.

(Function) Next, the mobile satellite communication system of the present invention configured as described above will be described.
The operation of the positioning method will be explained.

The transmitter transmits the chirp signal carrying the positioning signal to the normal SC
It is sent out superimposed on the PC/FDMA communication signal. here,
When the base station is the transmitter, the positioning signal includes orbit information of the communication satellite. On the other hand, when the mobile station is a transmitter, the positioning signal includes the identification code of the mobile station and does not include orbit information.

The receiving section generates a local chirp signal based on the clock signal recovered from the communication signal in the received signal, and detects the frequency error between the chirp signal in the received signal and the local chirp signal, that is,
Control is performed so that the timing error is zero, and the positioning signal is regenerated. When the receiving unit is a mobile station, the positioning signal includes satellite orbit information, so positioning is performed at the mobile station. On the other hand, when the receiving unit is a base station, it determines the position of the mobile station using pre-held satellite orbit information, and transmits the result to the mobile station through a 5cpc channel.

Here, the receiving section demodulates and reproduces the correlation result output, but since the correlation signal can be obtained even when the timings of the chirp signals do not match, the synchronization operation during demodulation is quickly performed. Furthermore, when the mobile station serves as a transmitter, the configuration of the mobile station becomes very simple.

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

The mobile satellite communication/positioning system of the present invention is configured as shown in FIG.
/FDMA system, and mobile station positioning is performed as described below. Hereinafter, the positioning method of the present invention using three communication satellites as in the conventional example will be explained. In this embodiment, the base station serves as a positioning signal transmitter, and the mobile station serves as a positioning signal receiver.

For example, as shown in FIG. 2, the base station has a conventional circuit (P
A chirp signal generator 8 is provided in place of the N signal generator 28). The rest is the same as the conventional example (7th ward).

Here, the chirp signal is a signal whose frequency is swept within the entire bandwidth F of the communication satellite based on the period T of the clock signal used in SCPC/FDMA digital modulation, and the mode of the frequency sweep is There are various types as shown in FIGS. 3 and 4. Figures 3 and 4
Figures (a) and (b) show cases in which the period T of the clock signal is one period, and figures (c) and (d) show cases in which the total period is one period, and the frequency is changed in the positive direction (negative direction). When it sweeps and reaches the upper limit (lower limit) of the total bandwidth F, it instantly moves to the lower limit (upper limit) and repeats the sweep.

Such a chirp signal is multiplied by the modulated positioning signal,
It is combined with the 5cpc signal, arranged at predetermined frequency intervals, and sent to the transmission IF section for the corresponding communication satellite.

Next, the reception system of the mobile station includes demodulation circuits (15-1 to 15-3) provided corresponding to the satellites and a communication and positioning calculation section 26, as shown in FIG. 5, for example.

Signals from three communication satellites are received by the antenna high frequency section, branched into three by the splitter 14, and sent to the demodulation circuits (15-1 to 15-1).
15-3).

In the demodulation circuits (15-1 to 15-3), the input signal is first converted by the frequency converter 16 into a signal at the reception channel frequency based on the output of the synthesizer 17, and input to the 5cpc demodulator 19 and correlator 20. .

The 5cpc demodulator 19 converts the input signal into 1 in FDMA.
s'cpc signals, regenerates a data signal and a clock signal, and outputs them to the communication and positioning calculation section 26, as well as outputs the clock signal to the timing signal generation circuit 22.

The timing signal generation circuit 22 adjusts the timing of the clock signal based on the output of the timing error detection circuit 23, and outputs the adjusted fine timing signal to the communication and positioning calculation section 26 and the local chirp signal generation circuit 21.

The local chirp signal generation circuit 21 generates a chirp signal of the same format as that on the transmitting side in response to the inputted fine timing signal. Here, in the local chirp signal generation circuit 21,
Initially, it occurs at any timing. Therefore, correlator 2
The local chirp signal outputted to 0 has a moderate timing relationship with the received chirp signal (correctly, the modulated chirp signal) which is the other input of the correlator 20, as shown in, for example, ■ to ■ in FIG. 6(a). becomes.

The correlator 20 multiplies the received chirp signal and the local chirp signal and correlates them. When the received chirp signal and local chirp signal have the relationship shown in FIG. 6<a>, the correlation result is as shown in FIG. 6(b). As illustrated in FIG. 6(a), it is assumed that within one cycle of the received chirp signal, the timing of the local chirp signal is sequentially shifted by a predetermined timing from ■ to ■. At the timing when the received chirp signal is inverted from the sweep end point frequency to the sweep start point frequency, the local chirp signal is being swept, and there is a large frequency error f between the two, but after the local chirp signal is inverted, there is a small frequency error f8. becomes. These frequency errors correspond to the errors (■ to ■) in the generation timing of the local chirp signal (Figure 6 (b)).
.

Therefore, the output of the correlator 20 is passed through a narrow band low pass filter (LP).
F) Timing with small frequency error f, leading to 25 ■
Or with the same frequency error. is extracted, its frequency is discriminated by a timing error detection circuit, and the frequency error f0
Detect timing errors corresponding to The timing signal generation circuit 22 controls the local chirp signal generation circuit 21 by adjusting the output timing of the clock signal so that the frequency error becomes zero.

Now, if the data length of the 5cpc channel (i.e., clock period) is T (seconds) and the total bandwidth of the satellite is F (I (z)), the sweep speed is at least F/T (Hz/second), so the correlation is If the signal frequency error in the output of the device 20 is f8, the timing error t is 1, = 1°F (1) Since f can be detected very precisely compared to F, 70 is 5 cpc. This allows for much more detailed timing control than the data length.

Thus, the positioning signal demodulator 2 receiving the output of the correlator 20
4, it is possible to accurately reproduce the timing signal necessary for positioning.

In addition, since the correlator 20 outputs a correlation signal even when the timings of both chirp signals do not match, the positioning signal demodulator 24 can easily perform synchronized operation, which is different from the conventional method using a PN signal. It doesn't take much time to synchronize.

Finally, the communication and positioning calculation unit 26 processes the received communication signals from each SCPC demodulator 19, and
A reproduced positioning signal and a timing signal are obtained from each positioning signal demodulator 24, and the propagation time for each satellite is determined based on the satellite position information included in the reproduced positioning signal, and the geographical position of the mobile station is determined based on the principle of triangulation. seek.

In the above explanation, the base station transmits a positioning signal and the mobile station independently performs its own positioning. However, in contrast, the mobile station transmits a modulated chirp signal carrying a 5 cpc digitally modulated signal and a modulated side signal. It is also possible for the base station to transmit and perform reception positioning processing in exactly the same way.

In this case, the mobile station should be equipped with a switch to turn on and off the chirp signal generation circuit, and the chirp signal generation circuit should be turned on when positioning. It includes a sign. Since satellite orbit information is always held by the base station, there is no problem with positioning.With this method, the mobile station cannot identify the satellite, so the number of channels that can be used for simultaneous positioning is limited. However, it has the advantage of simplifying the configuration of the mobile station.

(Effects of the Invention) As explained above, according to the mobile satellite communication/positioning method of the present invention, since positioning is performed using chirp signals, the synchronization problem can be solved, and the mobile station can Even in the case of
This has the advantage that it can be provided simultaneously with communication services based on the DMA method.

[Brief explanation of drawings]

FIG. 1 is a general configuration block diagram of a mobile satellite communication/positioning system targeted by the present invention, FIG. 2 is a configuration block diagram of a base station (transmission system) according to an embodiment of the present invention, and FIG. The diagram is 5
A time-frequency relationship diagram of a chirp signal carrying a positioning signal on the modulated side of a CPC digital modulation signal, FIG. 4 is a diagram showing various aspects of frequency sweep of the chirp signal, and FIG. Figure 6 is a diagram of the timing error measurement principle; Figure 7 is a diagram of the configuration of a conventional base station (transmission system); Figure 8 is a diagram of the configuration of a conventional mobile station; Figure 9 is a signal spectrum diagram in a conventional communication positioning system using CDMA/FDMA combination, and Fig. 10 is an autocorrelation characteristic diagram of a PN signal. 1-1 to 1-3...Communication satellite, 2...・・・
- Base station, 3...Mobile station, 4...Communication positioning system control unit, 5-1 to 5-3...Modulation circuit, 6... Frame generation circuit 57...
...5 cpc modulator, 8... chirp signal generator, 9... positioning signal modulator, 10...
... Multiplier, 11 ... Signal combiner, 1
2... Frequency converter, 13... Transmission channel frequency synthesizer, 14...
Brancher, 15-1 to 15-3... Demodulation circuit,
16... Frequency converter, core...
Receive channel frequency synthesizer, 18...
・Brancher, 19...5cpc demodulator, 20
... Correlator, 21 ... Local chirp signal generation circuit, 22 ... Timing signal generation circuit, 23 ... Timing error detection circuit, 24.
... Positioning signal demodulator, 25 ... Low pass filter (LPF), 26 ... Communication and positioning calculation section.

Claims (1)

[Claims] One base station includes highly directional antennas having sufficient separation from each other to establish independent communication paths for each of the plurality of communication satellites; means for constantly maintaining orbital information of the plurality of mobile stations; and the plurality of mobile stations are equipped with antennas with sufficiently wide directional characteristics to enable simultaneous communication with the plurality of communication satellites; A positioning method in a mobile satellite communication/positioning system in which a station communicates via multiple communication satellites using the SCPC/FDMA method; a transmitter provided on one side; a receiver provided on the other side; means for generating a frequency-swept chirp signal; means for modulating the positioning signal; superimposing an SCPC/FDMA communication signal on the modulated chirp signal obtained by multiplying the chirp signal and the modulated positioning signal and transmitting the signal; means; and a receiving section; a plurality of demodulation sections provided corresponding to each communication satellite; and; receiving a reproduced positioning signal from each demodulation section to obtain a signal propagation time difference from a plurality of communication satellites; a positioning calculation unit that determines the geographical position of a mobile station based on the principles of surveying; means for generating an adjusted fine timing signal; means for generating a local chirp signal in the same format as the chirp signal generated by the transmitting section based on the fine timing signal; and means for generating a local chirp signal based on the fine timing signal; means for detecting the correlation between the two chirp signals; means for filtering the correlation detection result in a narrow band; and means for detecting a timing error between both chirp signals based on the narrow band filtered correlation result signal and outputting the timing error signal. A mobile satellite communication/positioning method, comprising: means for demodulating and outputting the reproduced positioning signal from the correlation result.