JPH04129432A - Aperture gate type unique word detection method - Google Patents

Abstract

PURPOSE:To improve the accuracy of synchronization maintenance by shifting a phase by a half clock only with respect to a system clock while an aperture gate signal is synchronized with the system clock. CONSTITUTION:A correlation detector 1 uses a burst clock in a satellite communication TDMA(Time Division Multiple Access) terminal station equipment, extracts a signal having a unique word pattern from a reception data by using a burst clock, and an AND gate 2 passes an output of the correlation detector 1 for a prescribed period specified by an aperture gate signal synchronously with the system clock used in a TDMA terminal station equipment. Then while the aperture gate signal is synchronously with the system clock, the phase is shifted by a half clock with respect to the system clock. Thus, the measured position of the unique word detection position required for synchronization maintenance is not biased to one value and the accuracy of the synchronization maintenance is improved.

Description

[Detailed Description of the Invention] [Summary] Regarding the aperture gate type unique word detection method, by devising the phase relationship between the system clock and the aperture gate signal to be suitable for actual operation, the unique word detection method necessary for maintaining synchronization is achieved. The purpose is to prevent the detected position measurement value from being biased to one side and improve the accuracy of synchronization maintenance. In the aperture gate type unique word detection method, which detects a unique word by passing the signal obtained from the correlation of , the aperture gate signal is configured to be synchronized with the system clock and shifted in phase by a half clock with respect to the system clock.

[Industrial Application Field] The present invention relates to an aperture gate type unique word detection method.

Generally, TDMA (Time D
ivision, the terminal station equipment extracts the unique word (UW) from the received data.
D) is detected to perform synchronization detection, etc.

However, in satellite communications, signals are sent and received via geostationary satellites, but even geostationary satellites move slightly, so the apparent distance on the receiving side fluctuates, which makes it difficult to use unique words. It cannot be detected at a certain fixed time. Therefore, a certain time range is given to unique word detection, and if a unique word is included within this period, it can be detected. Such a method is called an aperture gate type unique word detection method.

[Prior Art] FIG. 6 is a block diagram for explaining a conventional aperture gate type unique word detection method. In FIG. 6, 1 is a correlation detector, and this correlation detector 1 is In TDMA terminal equipment for communication, using the burst clock, the ■ channel, Q channel receive data I/
This is to extract a signal having a unique word pattern from Q.

2A and 2B are AND gates, and these AND gates 2
A and 2B allow the output of the correlation detector 1 to pass only for a required period defined by an aperture gate signal synchronized with the system clock used within this TDMA terminal equipment.

Note that the system clock is vC based on the frame signal.
The aperture gate signal is generated by a timing generator 5 based on the system clock.

3 is a clock transfer circuit, and this clock transfer circuit 3 is
This is for transferring the signal that has passed through the AND gate 2B from the burst clock to the system clock.

With such a configuration, in the TDMA terminal device for satellite communication, the correlation detector 1 receives a signal obtained from the correlation between the received data I/Q including the unique word and the burst clock, and the AND gate 2A.

At 2B, a unique word is detected by passing the aperture gate signal for a required period defined by an aperture gate signal synchronized with the system clock used in the TDMA terminal equipment, but the unique word obtained at AND gate 2A UWD1 is used as a write reset signal for an elastic clock converter (FCC) that performs clock switching to synchronize received data I/Q with the system clock.

Also, the unique word UW obtained by AND gate 2B
D2 is synchronized with the system clock by the clock transfer circuit 3 and sent to the synchronization detection/synchronization protection section.

By the way, in the circuit configuration shown in FIG. 6, if we consider a case where the received burst position fluctuates around ±4 symbols with the aperture gate signal as a reference, the time relationship between the aperture gate signal and the correlation detector output is When the burst falls on the leading edge of the gate signal (see Figure 7), when the burst falls on the trailing edge of the aperture gate signal (see Figure 8).
There are three possible cases: (see figure) and a case where the burst falls within the aperture gate signal (see figure 9).

First, if the burst is applied to the leading edge of the aperture gate signal, -
Normally unique word UWDI only in the range of 3 to +4,
It can be seen that UWD2 is detected, and when the burst falls on the trailing edge of the aperture gate signal and when the burst falls within the aperture gate signal, Figs. 8(a) to (f) and Fig. 9(a) respectively. As is clear from ~(f), the unique word U is successfully generated in the range of -4 to +4.
It can be seen that WDI and UWD2 are detected.

That is, the unique word detection signal (correlation detector quantity)
If the unique word detection signal (correlation detector output) is slower than the aperture gate signal or if the unique word detection signal (correlation detector output) is within the aperture gate signal, the unique word can be detected. If the correlation detector output) is faster than the aperture gate signal, even if some correlation detector output is present within the aperture gate, it is not considered to have been detected and is discarded.

[Problems to be Solved by the Invention] Therefore, in the conventional aperture gate type unique word detection method described above, the unique word detection position measurement value necessary for maintaining synchronization is biased to one side.

The present invention was devised in view of these problems, and by devising the phase relationship between the system clock and the aperture gate signal to be suitable for actual operation, the unique word detection position measurement value necessary for maintaining synchronization can be obtained. It is an object of the present invention to provide an aperture gate type unique word detection method that can improve the accuracy of synchronization maintenance without being biased to one side.

[Means to solve the problem] FIG. 1 is a block diagram of the principle of the present invention.

In this figure, 1 is a correlation detector, and this correlation detector 1 extracts a signal having a unique word pattern from received data using a burst clock in a TDMA terminal equipment for satellite communication. It is.

2 is an AND gate, and this AND gate 2 allows the output of the correlation detector 1 to pass for only the required period specified by the aperture gate signal synchronized with the system clock used in this TDMA terminal equipment. .

By the way, the phase of the aperture gate signal is shifted by half a clock with respect to the system clock.

3 is a clock transfer circuit, and this clock transfer circuit 3 is
This is for transferring the signal that has passed through the AND gate 2 from the burst clock to the system clock.

[Function] In the aperture gate type unique word detection method of the present invention described above, the phase of the aperture gate signal is shifted by half a clock with respect to the system clock while being synchronized with the system clock. A unique word can be detected as long as the part is within the aperture gate.

[Example] The present invention will be described in detail below with reference to one drawing.

FIG. 2 is a block diagram showing one embodiment of the present invention, and the embodiment shown in FIG. 2 also includes a correlation detector 1, AND gates 2A and 2B, and a clock transfer circuit 3.

Here, the correlation detector 1 extracts a signal having a unique word pattern from the received data I/Q of channel 1 and Q channel using a burst clock in a TDMA terminal equipment for satellite communication. Gate 2A
, 2B allows the output of the correlation detector 1 to pass through for a required period defined by an aperture gate signal synchronized with the system clock used in this TDMA terminal equipment, and the clock transfer circuit 3 is an AND gate. This is for transferring the signal that has passed through 2B from the burst clock to the system clock.

Incidentally, the system clock is generated by an oscillator 4 such as a vCO based on a frame signal, and the aperture gate signal is generated by a timing generator 5 based on the system clock. A flip-flop 7 is provided which latches the signal inverted by the circuit 6, so that the output of the flip-flop 7 is as follows.
An aperture gate signal whose phase is shifted by half a clock with respect to the system clock is obtained while being synchronized with the system clock. In this embodiment, the phase of the aperture gate signal is delayed by 0.5 clock with respect to the system clock.

With such a configuration, in the TDMA terminal device for satellite communication, the correlation detector 1 receives a signal obtained from the correlation between the received data I/Q including the unique word and the burst clock, and the AND gate 2A.

At 2B, a unique word is detected by passing the aperture gate signal for a required period defined by an aperture gate signal synchronized with the system clock used in the TDMA terminal equipment, but the unique word obtained at AND gate 2A UWD1 is used as a write reset signal for the elastic clock converter, while the unique word UWD2 obtained by the AND gate 2B is synchronized with the system clock by the clock transfer circuit 3, and is used for synchronization detection and synchronization. Sent to the Protection Department.

Now, in the circuit configuration shown in Fig. 2, if we consider a case where the received burst position fluctuates around ±4 symbols with the aperture gate signal as a reference, as in the case of the conventional example, the aperture gate signal and the correlation detector output As before, the time relationship between the burst and the aperture gate signal is the same as in the past. There are three possible cases in which the signal falls within the signal range (see FIG. 5).

However, if the burst falls on the leading edge of the aperture gate signal, as is clear from FIGS. 3(a) to (f),
It can be seen that if the phase shift between the aperture gate signal and the burst clock is within 0.5 clocks, the unique words UWDI and UWD2 can be normally detected in the range of -4 to +4.

Note that when the burst is applied to the trailing edge of the aperture gate signal (the phase shift between the aperture gate signal and the burst clock must be within 0.5 clocks)
As is clear from Fig. 4(a) to (f), -4 to
Unique word UWDI is successfully detected in the range of +3,
It can be seen that the unique word UWD1 is normally detected in the range of -4 to +4. Here, the unique word UW
Since D1 is used as a write reset signal for the elastic clock converter, detection in the range of -4 to +3 is sufficient.

In addition, when the burst falls within the aperture gate signal, as is clear from FIGS. 5(a) to 5(f), the unique word UWDI is normally output in the range of -4 to +4, as in the past.
, UWD2 is detected.

In other words, according to this embodiment, regarding the unique word UWD 2 used for synchronization detection/synchronization protection, if the unique word detection signal (correlation detector output) is slower than the aperture gate signal, Not only when the word detection signal (correlation detector output) is within the aperture gate signal, but also when the unique word detection signal (correlation detector output) is earlier than the aperture gate signal, If the correlation detector output is somewhat different from (0,
(within a range of 5 clocks or less), the unique word UWD2 can be detected. This prevents the unique word detection position measurement value from being biased to one side, making it possible to greatly improve the accuracy of synchronization maintenance.

[Effects of the Invention] As detailed above, according to the aperture gate type unique word detection method of the present invention, the phase of the aperture gate signal can be shifted by half a clock with respect to the system clock while being synchronized with the system clock. Since the unique word detection position measurement value is not biased to one side, there is an advantage that the accuracy of synchronization maintenance can be greatly improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the principle of the present invention, Figure 2 is a block diagram showing an embodiment of the present invention, and Figures 3 to 5.
Each figure is an operation timing diagram explaining the operation of an embodiment of the present invention, FIG. 6 is a block diagram showing the conventional example, and FIGS. 7 to 9 are operation timing diagrams explaining the operation of the conventional example. . In the figure, 1 is a correlation detector, 2.2A and 2B are AND gates, 3 is a clock transfer circuit, 4 is an oscillator, 5 is a timing generator, 6 is an inversion circuit, and 7 is a flip-flop.

Claims (1)

[Claims] In a TDMA terminal device for satellite communication, an aperture gate that synchronizes a signal obtained from a correlation between received data including a unique word and a burst clock with a system clock used in the TDMA terminal device. In an aperture gate type unique word detection method that detects the unique word by allowing the signal to pass for a required period specified by the signal, the aperture gate signal is synchronized with the system clock, and the aperture gate signal is synchronized with the system clock. An aperture gate type unique word detection method characterized by shifting the phase by half a clock.