JPH0442857B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a satellite communication reference station device, and more particularly to a satellite communication reference station device that centrally controls a satellite communication system formed by a plurality of ground stations that perform communication using a time division multiple access method via a communication satellite. Regarding.

First, an outline of a satellite communication system based on a time division multiple access system using communication satellites, which requires the present invention, will be explained.

The name of this satellite communication method is usually SS/TMDA.
(Satellite Switching／Time Division Multiple
It is one of the most anticipated future forms of satellite communication. What is shown in Figure 1 is this SS/TDMA
This is a conceptual diagram of the system, showing the relationship between the main components of the repeater inside the communication satellite and the corresponding earth station.

In FIG. 1, on the communication satellite side, spot beam antennas 1-1 to 4 and receiver 4
-1 to 4, transmitters 5-1 to 4, and matrix
A switch circuit 6 and a matrix switch control circuit 7 are provided.
1 to 4 are provided. What is shown in FIG. 1 is for the purpose of explaining the outline of the SS/TDMA system.
As an example, a comparison is made in which a communication satellite is equipped with four spot beam antennas for both transmitting and receiving, the corresponding earth side is divided into four spot regions, and each spot region is equipped with only one earth station. FIG. 2 is a conceptual diagram quoting a case with a simple configuration. However, in general, it is formed with a more diversified configuration than the cited example above, depending on operational requirements.

Now, earth station 3-1 in spot area A is
It is assumed that this station is a satellite communication reference station (hereinafter abbreviated as reference station) in this SS/TDMA system. Earth station 3-1 in each spot area A, B, C and D
The communication radio waves transmitted from ~4 are received by the corresponding spot beam antennas 1-1~4, respectively, and are transmitted to RA, RB, RC and
On-board receiver 4-1, indicated by the abbreviation RD
4, the frequency is converted and amplified. These received signals are outputted from the receivers 4-1 to 4-4, and passed through a matrix switch circuit 6 whose switching is controlled by a matrix switch control circuit 7, and are converted into abbreviations of TA, TB, TC, and TD. The signals are inputted to the transmitters 5-1 to 4 shown in , are amplified to a predetermined transmission power, and then transmitted via the spot beams 2-1 to 2-4 by the corresponding spot beam antennas 1-1 to 4, respectively. and is sent to the corresponding spot areas A to D.

In this case, the switch switching control for the matrix switch circuit 6 on the communication satellite side is executed according to a predetermined connection mode synchronized with a reference time signal generated inside the matrix switch control circuit 7. Therefore, earth station 3 within the four spot areas A to D mentioned above
- From 1 to 4, the communication satellite side receiver RA or
Up link communication signal sent to RD,
Regarding the correspondence between the down link communication signals transmitted from the transmitters TA or TD on the communication satellite side to the earth stations 3-1 to 3-4 in the corresponding four spot areas A to D, respectively, Communication via communication satellites between earth stations within the four spot areas A to D requires time control corresponding to time-division communication, synchronized and compatible with the predetermined connection mode.

For this purpose, in the SS/TDMS method, connection modes such as those shown in FIG. 2 a and b are set in advance, and
Using this as a TDMA frame, a method is used in which communication line switching control is periodically time-divisionally controlled. Figure 2a shows which spot area the signal from each spot area is connected to the down link corresponding to, from the perspective of receivers RA, RB, RC, and RD on the uplink within this TDMA frame. Figure 2b shows transmitters TA, TB, TC and
Viewed from the TD, it shows which spot area the signal to be sent to each spot area is supplied from the corresponding up link.
Therefore, in the case of the example shown in FIG. 2, communication lines between spot areas formed in a time-division manner via communication satellites are as follows, corresponding to the connection modes, and.

...A→A, B→B, C→C, D→D ...A→B, B→C, C→D, D→A ...A→C, B→D, C→A, D→ B...A→D, B→A, C→B, D→C In other words, the four spot areas A to D are
It is clear that connection is periodically switched and connected in a time-division manner via a communication satellite, and the communication method is a method compatible with TDMA, that is, a time-division multiple access method, as described above.

Generally, in the case of a TDMA satellite communication system, one of the participating earth stations serves as the reference station.
In accordance with the reference time signal provided in this reference station, a reference burst signal is transmitted in a TDMA cycle,
By receiving this reference burst signal at the participating station via a communication satellite, a time division standard for the TDMA system is established.

However, in the case of the SS/TDMA system, as mentioned above, the switching control of the matrix switch circuit 6 according to the predetermined connection mode is performed in synchronization with the reference time signal built in the matrix switch control circuit 7. Therefore, unlike the TDMA system, it is first necessary for the reference station to generate its own time reference in synchronization with the reference time signal of the matrix switch control circuit 7 on the artificial satellite. Needless to say, the distance between the communication satellite and the reference station varies slowly over time even when a geostationary satellite is used as the communication satellite, and therefore, the above-mentioned synchronization means that the distance between the reference station and the communication satellite varies slowly over time. In order to ensure that the signal transmitted according to the time reference of the own station is always in synchronization with the time reference within the communication satellite, the time reference of the own station is determined with reference to the time reference within the communication satellite. This means that it is constantly controlled and adjusted.

Therefore, in the SS/TDMA system, the local station receives the return signal of the signal sent to the communication satellite, and uses the received signal as a clue to establish the time standard of the local station through the synchronization effect described above. This is a necessary condition. Once this synchronization state is secured and the time reference of the own station is established and maintained, each participating earth station other than the reference station uses the reference burst signal sent from the reference station as a reference and uses the normal TDMA method. It becomes possible to participate in the satellite communication system using exactly the same procedure as in the case of . Therefore, generating and establishing a time reference synchronized with the time reference within the satellite at the reference station is one of the most important items for realizing the SS/TDMA system.

Shown in Figure 3 a, b and c is the SS/
In the TDMA system, this is an example of a synchronized burst signal used in a reference station to establish its own time reference with reference to the time reference of a communication satellite. Figure 3a is an example of a synchronized burst signal sent from a reference station to a communication satellite.The most commonly used modulation method is 2-phase or 4-phase PSK (Phase Shift Keying). Depending on the case, the leading edge of the synchronized burst signal includes an unmodulated carrier wave portion (continuous wave: abbreviated as CW) that serves for carrier extraction on the receiving side and a predetermined portion that serves for clock pulse extraction. Bit Timing
Recovery (abbreviated as BTR) and a preamplifier that consists of a part modulated by a predetermined synchronization signal (Unique Word: abbreviated as UW).
and a predetermined coded time series signal used to generate a synchronized time reference with respect to the communication satellite time reference.
Pattern (Metric Pattern: abbreviated as METRIC)
The modulation part continues. In this case, the synchronization signal UW and the metric pattern described above
It is also possible to insert time slots corresponding to other purposes, such as transmission of inter-station control data, between the METRIC and the METRIC.

The concept of the connection mode in the SS/TDMA system has already been explained with reference to Fig. 2.The connection mode shown in Fig. 2 is a communication signal transmitted from an earth station in a certain spot area. , the connection mode is such that the data is always sent back to the same spot area. Therefore, when a predetermined reference station transmits the synchronization burst signal in this connection mode, it is clear that the synchronization burst signal is received again at the reference station via the communication satellite. Moreover, what is important here is that the reason why the synchronized burst signal is received again at the reference station is because the time synchronization relationship corresponding to the connection mode is different between the time reference on the communication satellite side and the time reference on the ground reference station side. This means that it is limited to cases where it has been established between The specific reason for this is that on the communication satellite side, in connection with switching control corresponding to each connection mode, the communication signal sent back to the ground side is turned on or off by a gate signal generated from a built-in time reference. This is due to the fact that it is temporally controlled. This gate signal is called a synchronization window, and an example thereof is shown in FIG. 3b. Generally, this synchronization window is a narrow synchronization window that allows only the synchronization burst signal to pass, in order to achieve time synchronization between the communication satellite side and the reference station side, and may be separately prepared as one of the connection modes. . Figure 4 shows the SS/
This is a specific example of the structure of a TDMA frame in the TDMA system, and shows a synchronization window 100 that forms a time slot for time synchronization between the communication satellite side and the reference station side, and a predetermined station of the participating earth station. Data windows 101, 102, 103 forming time slots for connecting between
and 104.

The above is an overview of the SS/TDMA system and this SS/TDMA system.
The technical background that necessitates the present invention in the satellite communication reference station in the TDMA system has been explained, but as mentioned above, in order to realize the SS/TDMA system, the time standard on the communications satellite side and the time at the ground reference station are required. It is quite clear that establishing and maintaining a synchronization relationship with the reference within the time slot of the synchronization window is an essential element.

An object of the present invention is to generate a synchronized burst signal that is synchronized with the time reference of a communication satellite and send it to the communication satellite, and to receive the synchronized establishing a synchronization relationship between the communication satellite side time reference and the reference station side time reference by receiving the burst signal and detecting the trailing edge of the synchronization window through a predetermined band-limiting filter; An object of the present invention is to provide a satellite communication reference station device that maintains and sets a synchronization window and a predetermined number of data windows that comply with a predetermined TDMA frame.

The satellite communication reference station device of the present invention includes a plurality of spot beams corresponding to one or both of the up link and the down link, and connects the line connection between the up link and the down link to a predetermined connection. In a satellite communication standard station that centrally controls a satellite communication system formed by a communication satellite that has a function of switching control via a mode and a plurality of earth stations that communicate using a time division multiple access method via this communication satellite, means for transmitting a synchronization burst signal including a synchronization signal compatible with a time division multiple access system and a metric pattern having a predetermined time relationship with respect to the synchronization signal to the communication satellite; and returning the synchronization burst signal via the communication satellite. A metric pattern is determined by a gate-off trailing edge of the metric pattern that is gated off by a synchronization window that is generated based on a reference time within the communication satellite upon receiving the incoming synchronization burst signal. a metric pattern trailing edge reproducing means for detecting and reproducing the metric pattern trailing edge through a band limiting filter adapted to the code time series signal to be formed; and frame synchronization control means for controlling and adjusting the transmission time period.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

As mentioned above, FIGS. 3a, b, and c show the synchronization burst signal sent from the reference station to the communication satellite, the synchronization window generated within the communication satellite, and the synchronization window sent back from the communication satellite to the reference station, respectively. shows a synchronized burst signal received by For convenience, it is assumed that these three signals correspond on the same time axis. The state in which these three signals have a temporal relative relationship as shown in Figure 3 is an essential condition for establishing time synchronization between the communications satellite and the reference station. of the synchronous burst signal sent back from the communication satellite through the procedure
The METRIC area is the synchronization window (Figure 3b)
The trailing edge of the synchronized burst signals is timed to be partially gated off as shown in FIG. 3c. In Figure 3c, the preamble portion consisting of the CW and BTR regions is indicated by dotted lines because these portions are only related to the signal demodulation function related to the reproduction of the carrier wave and clock pulse, respectively. This is because only the synchronization signal UW and the metric pattern METRIC function as a synchronization burst signal after the demodulator in the reference station.

In FIGS. 3b and 3c, corresponding to the trailing edge 50 of the synchronization window on the communications satellite, the synchronization burst signal received and demodulated at the reference station is
It is gated off at a certain time position 51 in the METRIC region, and this time position 51
corresponds to the boundary point between the remaining part and the erased part of the METRIC area. Therefore, at the reference station,
If it is possible to receive and demodulate the synchronized burst signal as shown in FIG. By comparing and contrasting the above, it is possible to form a time synchronization control system for synchronizing the time reference at the reference station with the time reference on the communication satellite.

However, in order to specifically apply the above-mentioned method, consideration must be given to two important constraints. That is, in the reference station device,
As a condition for generating and maintaining the own station's time reference in synchronization with the communication satellite's time reference, even if the communication status between the reference station equipment and the communication satellite deteriorates for some reason, the communication system operates normally until it reaches an extreme state, and a given
This is due to the need to reliably maintain the time slot corresponding to the TDMA frame and the fact that the rise at the trailing edge of the synchronization window in Figure 3b does not necessarily have a steep rise characteristic. There are two issues that need to be considered. Therefore, as a practical matter, in the reference station equipment, the METRIC in Fig. 3 c corresponds to the synchronization window of the communication satellite.
Accurately detecting the time positions 51 corresponding to the boundary points of the regions is a prerequisite for establishing a time reference within the reference station device as described above.

FIG. 5 is a block diagram showing the main parts of the first embodiment of the present invention.

In FIG. 5, the first embodiment of the present invention includes an antenna 8, a transmitter 9, a modulator 10, a synthesis circuit 11, a synchronization signal generation circuit 12, a metric pattern generation circuit 13, and various Signal generation circuit 14, transmission timing generation circuit 15, receiver 16, and metric pattern trailing edge reproduction means 1
7, a transmission timing error detection circuit 18, a transmission timing control circuit 19, a demodulator 20, a synchronization signal detection circuit 21, a reception synchronization control circuit 22,
It includes a reception timing generation circuit 23 and a clock generator 24. Further, the main parts of the metric pattern trailing edge reproduction means included in the first embodiment in FIG. 5 are a signal branching circuit 25 and a delay circuit 26, as shown in the block diagram of FIG. , a multiplication circuit 27, a band filter 28,
It includes a detector 29, a reference voltage generation circuit 30, and a gate signal generation circuit 31.

In FIG. 5, the clock generator 24 is
Dozens to hundreds of megahertz (MHz), which corresponds to the information transmission speed of the communication system in the SS/TDMA system.
A clock signal is generated and sent to each time-related circuit within the reference station device. The transmission timing generation circuit 15 is equipped with a frame counter driven by this clock signal, and has a frame counter driven by this clock signal.
At the period corresponding to the TDMA frame shown in the figure, various timing signals such as gate signals and trigger signals involved in transmission of communication signals are generated and sent to a predetermined signal generation circuit, a predetermined signal processing circuit, etc. . The synchronization signal generation circuit 12 generates a synchronization signal in response to the timing signal output from the transmission timing generation circuit 15, and this synchronization signal is combined with the outputs of the metric pattern generation circuit 13 and various signal generation circuits 14. It is formed into a burst signal by circuit 11, PSK modulated by modulator 10, and transmitted via transmitter 9 and antenna 8 to a communication satellite.

On the other hand, a signal sent from a communication satellite is received via an antenna 8 and a receiver 16, converted into a signal in a predetermined intermediate frequency band, and sent to a demodulator 20.
and metric pattern trailing edge reproduction means 17
sent to. The demodulator 20 demodulates this intermediate frequency band PSK signal and outputs a digital code time series signal. As mentioned above, in the demodulation of the PSK signal, the CW (carrier wave part) shown in FIG. 3c plays an effective role as carrier wave regeneration. In addition, a synchronization signal is detected in the synchronization signal detection circuit 21 via the BTR (code time series signal for clock extraction) which forms part of the preamble together with the CW, and the synchronization signal is detected as a synchronization signal detection pulse by the reception synchronization control circuit 22 and the transmission timing. The signal is sent to the error detection circuit 18. The reception synchronization control circuit 18 inputs this synchronization signal detection pulse and establishes a reception frame period through its control action. The reception timing generation circuit 23 has a built-in frame counter, and as described above, after the reception frame synchronization is determined, the reception timing generation circuit 23 transmits a gate signal that predicts the detection position of the synchronization signal to the synchronization signal detection circuit 2.
1 to prevent error detection in the synchronization signal detection circuit 21 and maintain a correct reception frame period. In addition, the metric pattern trailing edge reproduction means 17 extracts a reproduction gate signal of the metric pattern trailing edge of the synchronized burst signal, which has been gated off by the synchronization window in the communication satellite, according to the operating principle described later. , and sent to the transmission timing error detection circuit 18. In response to the synchronization detection pulse sent from the synchronization signal detection circuit 21, the transmission timing error detection circuit 18 starts counting clock pulses input from the clock generator 24, and detects the existence of a metric pattern. The counting is continued for a period of time, and the counting is stopped at the time when the reproduction gate signal of the trailing edge of the metric pattern is input, and the time between the synchronization signal detection pulse and the reproduction gate signal is measured. This measured time corresponds to the time between time positions 51 and 52 in FIG. 3c.
The transmission timing error detection circuit 18 compares and checks this measured time with a predetermined time value that should originally exist, detects a time error in the transmission timing, and outputs it to the transmission timing control circuit 19. The transmission timing control circuit 19 generates a transmission timing control signal corresponding to the time error in the transmission timing and sends it to the transmission timing generation circuit 15.
5, a modified timing time is generated in response to the control signal, and an uplink communication signal, including a synchronized burst signal, is then transmitted to the communication satellite in the course of operation as described above. That is, in the embodiment shown in FIG. 5, the metric pattern trailing edge reproduction means 17, the synchronization signal detection circuit 21, the transmission timing error detection circuit 18, and the transmission timing control circuit 19 play a central role, and the TDMA frame is It forms a time synchronization system for the synchronization window on the communication satellite for establishing the synchronization window, and it can be seen that each of them plays an important role. In particular, regarding the synchronization accuracy of the time synchronization system, the metric pattern trailing edge reproduction means 17
The role played by this function is important.

In the first embodiment shown in FIG. 5, the essential components for applying the present invention include a metric pattern generation circuit 13, which transmits a synchronous burst signal having a metric pattern as one component to a communication satellite. means, metric pattern trailing edge reproducing means 17, and transmission timing error detection circuit 18.
and frame synchronization control means including a transmission timing control circuit 19 and the like. Among these essential components, the first feature of the present invention is that the metric pattern trailing edge regeneration means 17 is capable of regenerating metrics within a synchronized burst signal gated off by a synchronization window within a communications satellite. - The principle is that the trailing edge of the pattern is detected and reproduced through a band-limiting filter adapted to the code time series signal forming this metric pattern. Below, the 6th
The metric pattern trailing edge reproduction means will be described with reference to FIGS. a, 7 and 9.

FIG. 6a is a block diagram showing the main parts of the metric pattern trailing edge reproduction means in the first embodiment of the present invention. In FIG. 6a, the metric pattern trailing edge reproduction means includes the signal branching circuit 25, the delay circuit 26, the multiplication circuit 27, the bandpass filter 28, and the detector 29, as described above.
, a reference voltage generation circuit 30 , and a gate signal generation circuit 31 .

In FIG. 6a, a synchronized burst signal in an intermediate frequency band is inputted from a terminal 61, the frequency of which is converted in a receiver in the reference station device and amplified to a predetermined level. This synchronous burst signal is branched into two in the signal branching circuit 25, one of which is sent to the multiplication circuit 27, and the other is input to the multiplication circuit 27 via the delay circuit 26. The delay time of the delay circuit 26 corresponds to the time of 1/2 bit of the code time series signal forming the metric pattern.

7a, b and c are conceptual diagrams of signal waveforms for explaining the operation of the metric pattern trailing edge reproducing means in the first embodiment, and FIG. 7a is an intermediate frequency input from the terminal 61 described above. 7b is the synchronous burst signal at the output of the delay circuit 26. FIG. Figure 7 a and b
, the synchronous burst signal is 1, 0, 1, 0,
The synchronized burst signal in the intermediate frequency band is a two-phase PSK (Phase
Shift Keying).

In FIG. 6a, the synchronous burst signals shown in FIGS. 7a and 7b having a time difference corresponding to 1/2 bit are input to the multiplication circuit 27 as described above, and the phase is adjusted through mutual multiplication. The wave is detected and output. What is shown in FIG. 7c is the multiplication circuit 2
7 shows the waveform of the output signal. That is, if the bit rate of the code time series signal forming the metric pattern in the synchronous burst signal is f _b , then the multiplier 27 outputs a signal with a frequency f _b . This is because the phase detector represented by the multiplier 27 has an effect completely similar to that of an exclusive OR circuit. This signal at frequency f _b has its signal-to-noise ratio improved by a band-limited bandpass filter 28 and is input to a detector 29 in order to improve the accuracy of the gate-off trailing edge detection time of the metric pattern. and amplitude detection.
This detection output is input to the gate signal generation circuit 31 and corresponds to the gate-off trailing edge of the metric pattern by referring to a predetermined reference voltage supplied from the reference voltage generation circuit 30 to the gate signal generation circuit 31. A reproduction gate signal for detecting synchronization time is generated and outputted from the terminal 62.

Metrics in the first embodiment of FIG. 6a
FIGS. 9a, b, c and d conceptually show the main signal waveforms at each stage in the pattern trailing edge reproduction means. FIG. 9a is a signal waveform diagram at the output stage of the multiplier 27 in FIG. A pattern is formed in which the thermal noise gradually decreases at a certain slope and, instead, increases gradually. FIG. 9b is a signal waveform diagram at the output stage of the bandpass filter 28, in which the level of thermal noise is reduced compared to the signal due to the bandlimiting characteristic of the bandpass filter 28. FIG. 9b is a signal waveform diagram at the output stage of the detector 29. The gate output signal shown in FIG. d is output from the gate signal generation circuit 31.

The trailing edge 53 of the gate signal in FIG. 9d has an uncertainty time region in consideration of the signal-to-noise ratio.
Narrowing this uncertainty time region is a factor in improving the synchronization accuracy by the synchronization burst signal. Therefore, taking into account the signal-to-noise ratio of the signal input from the terminal 61, the gate-off time period _δT shown in FIG. The passband characteristics of the bandpass filter 14 are set so that the error rate is below a predetermined value. With this method, the reference station device can receive the synchronization burst signal sent back from the communication satellite and extract the reproduction gate signal that is directly synchronized with the synchronization window on the communication satellite. Therefore,
The present invention can be positioned as a much superior method compared to conventionally proposed methods in which reproduction gate signals are obtained over several frames and a reproduction gate signal is selected by majority decision.

Next, a second embodiment of the present invention will be described. The main parts of the second embodiment are shown in the same configuration as the block diagram showing the main parts of the first embodiment shown in FIG. The difference between the first and second embodiments is due to the difference in the configuration and operation of the metric pattern trailing edge detection means 17.

FIG. 6b is a block diagram showing the main part of the metric pattern trailing edge detecting means in the second embodiment of the present invention.
, a delay circuit 33 , a multiplication circuit 34 , a reduction filter 35 , a gate signal generation circuit 36 , and a reference voltage generation circuit 37 .

In FIG. 6b, a synchronized burst signal in an intermediate frequency band, which has been frequency-converted in a receiver in the reference station device and amplified to a predetermined level, is inputted from a terminal 63. This synchronous burst signal is branched into two in the signal branching circuit 32, one of which is sent to the multiplication circuit 34, and the other is input to the multiplication circuit 34 via the delay circuit 33. The delay time of the delay circuit 33 corresponds to the time of one bit of the code time series signal forming the metric pattern.

8a, b, and c are conceptual diagrams of signal waveforms for explaining the operation of the metric pattern trailing edge reproduction means in the second embodiment, and FIG. 8a shows the intermediate frequency input from the aforementioned terminal 63. FIG. 8b is the synchronous burst signal at the output of the delay circuit 33. Figure 8 a and b
In the same way as in the first embodiment, the synchronization burst signal is formed by a code time series signal of 1, 0, 1, 0..., and the synchronization burst signal in the intermediate frequency band is formed by 1→ 0 radians,
It is modulated by two-phase PSK from 0 to π radians.

In FIG. 6b, the synchronized burst signals shown in FIGS. 8a and 8b having a time difference of 1 bit are input to the multiplication circuit 34 as described above, and the signals are phase-detected through mutual multiplication. is output. Shown in FIG. 8c is the multiplication circuit 34
The waveform of the output signal is shown. In this case,
In the phase detector shown as the multiplier circuit 34, the two input intermediate frequency signals are mixed in a mutually opposite phase state and subjected to synchronous phase detection, so that a negative signal is detected as shown in FIG. 8c. A direct voltage is generated. This DC voltage output is passed through the low-pass filter 3.
5, the signal-to-noise ratio is improved and the signal is input to the gate signal generation circuit 36. Gate signal generation circuit 3
At step 6, a regenerated gate signal for synchronization time detection corresponding to the gate-off trailing edge of the metric pattern is generated with reference to a predetermined reference voltage supplied from the reference voltage generation circuit 37. Output from

Regarding the metric pattern trailing edge reproducing means in this second embodiment, as in the case of the first embodiment, the signal at each stage in the process of generating a reproduction gate signal as shown in FIG. Although the conceptual waveform diagram will not be presented again, in principle, the waveform diagram in FIG. 9c corresponds to the waveform at the output stage of the low-pass filter 35, and the waveform diagram in FIG. It corresponds to the output signal of the generating circuit 36.

In the case of this second embodiment, as in the case of the first embodiment, by providing an optimal band-limiting filter corresponding to the code time series signal forming the metric pattern, the input signal is By improving the signal-to-noise ratio and accurately reproducing and extracting the reproduction gate signal corresponding to the synchronization window on the communication satellite, it is possible to accurately set the TDMA frame in the SS/TDMA system and maintain it stably. becomes.

Note that in the metric pattern trailing edge reproducing means in the first and second embodiments described above, the delay circuit is used for the code time series signals 1, 0, 1, 0, . . . The delay times are set to the times corresponding to 1/2 bit and 1 bit, respectively, but these delay times are not necessarily limited to the above two times, and are generally 2n each. It is possible to set the time corresponding to -1/2 bit and n bit as the delay time. Here, n is an integer of 1 or more.

Further, the configuration of the code time series signal forming the metric pattern and the corresponding adaptive filter is not limited as in the case of the above-mentioned embodiment, and various code time series signals and corresponding filters can be used. It goes without saying that a metric pattern trailing edge reproducing means is also formed by a combination with an adaptive filter, and each reference station apparatus in the SS/TDMA system is configured with these.

As explained in detail above, the present invention provides SS/
In the reference station equipment in the TDMA system, the gate-off trailing edge of the metric pattern included in the synchronized burst signal sent back from the communication satellite is filtered by a band-limiting filter that matches the code time sequence signal forming the metric pattern. By reproducing and extracting the signal through the communication satellite, it is possible to accurately reproduce the synchronization signal for the synchronization window within the communication satellite within one received frame.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the SS/TDMA satellite communication system, Figure 2 a and b are diagrams of combinations of connection modes using matrix switches in communication satellites, and Figure 3 a, b and c are synchronized burst signals and Figure 4 is an explanatory diagram of the relative relationship with the synchronization window.
FIG. 5 is a block diagram showing the main parts of the first and second embodiments of the present invention, and FIGS. 6a and b are diagrams for explaining the TDMA frame pattern, respectively. Figures 7a, b and c, which are block diagrams showing the main parts of the metric pattern trailing edge reproduction means, and Figures 8a, b and c, respectively, are block diagrams showing the main parts of the metric pattern trailing edge reproduction means in the first and second embodiments of the present invention. - Waveform diagrams for explaining the operation of the pattern trailing edge reproduction means. FIGS. 9a, bc and d are waveform diagrams for explaining the operation of the metric pattern trailing edge reproduction means in the first embodiment of the present invention.
In the figure, 1-1 to 4...spot beam
Antenna, 2-1 to 4...Spot beam, 3
-1 to 4...Earth station, 4-1 to 4...Onboard receiver, 5-1 to 4...Onboard transmitter, 6...Matrix switch circuit, 7...Matrix switch control circuit, 8... ...Antenna, 9...Transmitter, 10
... Modulator, 11 ... Synthesis circuit, 12 ... Synchronization signal generation circuit, 13 ... Metric pattern generation circuit, 14 ... Various signal generation circuits, 15 ... Transmission timing generation circuit, 16 ... Receiver, 17...
Metric pattern trailing edge reproduction means, 18...
Transmission timing control circuit, 20... Demodulator, 21
... Synchronization signal detection circuit, 22 ... Reception synchronization control circuit, 23 ... Reception timing generation circuit, 24 ...
Clock generator, 25, 32...signal branch circuit,
26, 33... Delay circuit, 27, 34... Multiplication circuit, 28... Band filter, 29... Detector, 3
0, 37... Reference voltage generation circuit, 31, 36...
Gate signal generation circuit, 35...low-pass filter, 6
1 to 64...Terminal.

Claims (1)

[Claims] 1 A function that includes a plurality of spot beams corresponding to one or both of the up link and the down link, and switches and controls the line connection between the up link and the down link via a predetermined connection mode. A satellite communication standard station that provides overall control of the satellite communication system formed by a communication satellite with means for transmitting a synchronization burst signal including a synchronization signal and a metric pattern having a predetermined time relationship with the synchronization signal to the communication satellite; and the synchronization burst signal that is returned via the communication satellite. a gate-off trailing edge of the metric pattern, which is gated off by a synchronization window generated based on a reference time within the communications satellite, to a code time series signal forming the metric pattern. A filter circuit (filter) is used to reduce the uncertain time region of the gate-off trailing edge detection time.
frame synchronization control means for controlling and adjusting the sending time period of the synchronized burst signal with reference to the time of the reproduced gate-off trailing edge; A satellite communication reference station device comprising: