JPS61107836A - Communication equipment - Google Patents

Abstract

PURPOSE:To detect a unique word correctly with simple means by detecting a non-modulation carrier synchronizing pattern in the TDMA communication system and detecting the unique word incoming after a prescribed time. CONSTITUTION:A received PSK signal passes through a BPF1, noise is eliminated and the result is inputted to a carrier synchronizing pattern detection circuit 2 and a demodulator 4. The demodulator 4 regenerates a reference carrier from the input signal, a unique word detector 5 uses an aperture control signal SC based on the reference carrier to apply aperture window with a prescribed time width and extract the unique word, which is inputted to an AND circuit 6, The circuit 2 applies envelope detection 22 to a signal subject to improvement of the C/N through a narrow band BPF21, and an output signal S22 is compared with a prescribed threshold level by a voltage comparator 23. A signal S23 exceeding the threshold level is retarded for a prescribed time by a delay circuit 3, its output signal S3 is inputted to the circuit 6, from which the unique word detected by the detector 5 is outputted effectively.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a communication device, and more specifically to a “phase shift key/time division multiple access (hereinafter referred to as PSk)”.
The present invention relates to a communication device that detects a unique word of a communication method (abbreviated as -TDM^) and receives predetermined data.

[Problems to be solved by conventional technology and invention]

The TDM^ communication system is used, for example, when a large number of stations communicate with each other by transmitting information in pre-assigned time segments using an artificial satellite. Especially PSK-
In the TDMA communication system, a unique word is used to recognize the arrival of a received signal and establish frame synchronization. That is, the unique word is detected and the data following the unique word is received, and the detection of the unique word is considered to be the most important.Therefore, the PS
In the K-TDMA communication system, there are cases of so-called "non-detection", in which the corresponding unique word cannot be detected even though it exists, or "error", in which it is detected as a unique word even though the corresponding unique word does not exist. "detection" must not occur.

Conventional unique word detection generally involves receiving a reference burst signal in a frame synchronization state, and opening an aperture window at the time when a unique word is expected to arrive based on the allocation information of the reference burst signal. A method is adopted in which the detected information is used as a unique word.

However, with this unique word extraction method,
If a station to which transmission is assigned is unable to transmit due to a failure, etc.
Or, in cases where transmission is assigned to a large number of stations but the equipment is not actually transmitted, the signal received within the aperture window on the receiving side is generally random noise. However, there is a probability that it will be detected as a corresponding unique word.In such a case, the following data is random noise, but if it is incorrectly determined as a unique word as described above, it will be detected as a random noise. There is a problem that noise is taken in as normal data.

Especially when performing logical processing based on that data,
There is a problem in that the system operates based on noise, causing random operation or system failure.

Such false detections tend to increase as the number of stations participating in the TDMA network increases.

One possible way to prevent malfunctions caused by such false detections is to check the validity of the data on the receiving side, but this is not practical when dealing with high-speed, huge amounts of data, and many types of data. Not.

- In the case of perpetual detection, the system will not be able to handle it.
System reliability and responsiveness decrease.

In view of the above, it is desired to be able to accurately detect unique words using relatively simple means.

[Means and effects for solving the problem] In the present invention, a signal containing an unmodulated carrier synchronization pattern and a unique word transmitted based on the TDMA communication system is received, and predetermined data is demodulated using the unique word as a reference. A communication device comprising: means for demodulating the received signal to extract a unique word; and means for detecting an unmodulated carrier synchronization pattern of the received signal and enabling extraction of the unique word after a certain period of time. ↓ That is, in the present invention, in addition to the means for demodulating the received signal and extracting the unique word, means for validating the extraction of the unique word is provided, and the PSK-TDMA communication This method focuses on the fact that a non-modulated carrier synchronization pattern exists a certain time before a unique word, and first detects the non-modulated carrier synchronization pattern and then effectively detects a unique word that arrives after a certain time.

〔Example〕

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

FIG. 1 is a diagram showing a circuit configuration of a portion of a communication device as an embodiment of the present invention relating to unique word detection, which is directly related to the present invention.

In FIG. 1, the communication device includes a reception bandpass filter l that passes only signals in a predetermined frequency band for a 5PSK PSK signal received via an antenna, a low noise amplifier, a down converter, etc. (all not shown). , and a demodulator 4 and a unique word detector 5 as means for receiving the output signal from the filter 1, demodulating it, and extracting a unique word. The communication device also includes a non-modulated carrier synchronization pattern detection circuit 2, a delay circuit 3, and an AND circuit 6 as means for validating unique word extraction. The non-modulated carrier synchronization pattern detection circuit 2 includes a bandpass filter 21, an envelope detector 22, and a voltage comparator 23 connected in series.

The operation of the apparatus shown in FIG. 1 will be described below with reference to FIG.

FIG. 2(a) shows the format of a normal PSK received signal, with an unmodulated or sinusoidal carrier synchronization pattern: CR, discrete "0".

The focus timing reproduction pattern in which rlJ is set alternately is composed of BTR, unique word signal UW, and data DATA. There is a certain amount of time from CR to UW, and the unique word UW is followed by data DATA.

When a signal including the PSK signal shown in FIG. 2(a) is applied to the bandpass filter 1, signals from which noise has been removed are output to the narrowband filter 21 and the demodulator 4, respectively.

The signal applied to the demodulator 4 is regenerated into a reference carrier wave within the demodulator. Using this reference carrier wave as a reference, a unique word detector 5 extracts a unique word by applying an aperture window with a fixed time width using an aperture control signal Sc.

On the other hand, the signal applied to the narrowband filter 21 is further band-limited by the filter 21 and has a C/N ratio (signal-to-noise ratio).
We are working to improve this. For example, if the bandwidth of the bandpass filter 1 is B and the bandwidth of the narrowband filter 21 is BNL (B>BNL), the C/N ratio is -1104! og (B
NL/B) dB.

The unmodulated signal whose C/N ratio has been improved in this way is detected by the envelope detector 22. The output waveform is shown in FIG. 2 (bl). The output of the envelope detector 22 is applied to the voltage comparator 23, and it is determined whether the output signal S exceeds the threshold level V. When the threshold level ■ is exceeded, the output St3 is output from the voltage comparator 23 (Fig. 2 (C1),
Activate delay circuit 3. The delay circuit 3 outputs the "on" output signal S3 after a certain period of time τ from the rise of the signal S.
is output and turns off after a certain period of time from this on. The predetermined time τ is determined taking into account that the UW will arrive a predetermined time after the CR damage signal.

The AND circuit 6 performs a logical product of the output of the unique word detector 5 and the output S of the delay circuit 3, and outputs an effective unique word detection signal S6 (FIG. 2(e)).

That is, not only the detection signal from the unique word detector 5 but also the arrival timing of the UW multiplied signal that arrives after a certain period of time from the CR defect signal is detected by the bandpass filter 21 to the delay circuit 3.
The unique words detected above are validated. Therefore, if the timings match, an effective detection signal can be obtained as shown in FIG. .

Therefore, since the signal S6 detected in this manner is valid, the communication device can take in the data following the unique word (UW) as valid.

The bandwidth BNL of the narrowband filter 21 is determined by the CR flaw signal time length, and if that time length is T, then at least 1/T
It is desirable to make it as narrow as possible.

When implementing the present invention, modifications of the outer fences described above may be adopted. For example, FIG. 3 shows another embodiment.

In the communication device shown in FIG. 3, the bandpass filter 1, carrier synchronization pattern detection circuit 2, delay circuit 3, and demodulator 4 are the same as those shown in FIG. In this embodiment, the timing of the aperture window in the unique word detector 5' is controlled based on the signal detected by the delay circuit 3, thereby achieving substantially the same effect as in FIG. be. In this case, since it is desirable to interlock the control signal Sc such as the TDMA synchronization signal when applying the aperture window, the unique word detector 5' is operated via the AND gate 7. That is, an aperture window is created by ANDing the aperture control signal Sc according to the conventional method and the carrier synchronization pattern detection signal according to the present invention.

Note that better synchronization can be achieved by using TDMA clock timing as the time reference for the delay circuit 3.

〔Effect of the invention〕

As described above, according to the present invention, erroneous unique word detection is prevented, and the reliability of received data is improved.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an apparatus as an embodiment of the present invention, FIG. 2 is a timing diagram showing the operation of the apparatus shown in FIG. 1, and FIG. 3 is a configuration diagram of an apparatus as another embodiment of the invention. . DESCRIPTION OF SYMBOLS 1... Bandpass filter, 2... Carrier synchronization pattern detection circuit, 21... Narrowband filter, 22... Envelope detector, 23... Voltage comparator, 3... Delay circuit 4... Demodulator, 5... Unique word detector, 6... AND circuit.

Claims (1)

[Claims] 1. A communication device that receives a signal containing an unmodulated carrier synchronization pattern and a unique word transmitted based on a TDMA communication system, and demodulates predetermined data using the unique word as a reference. A communication device comprising: means for demodulating the received signal to extract a unique word; and means for detecting an unmodulated carrier synchronization pattern of the received signal and enabling extraction of the unique word after a certain period of time. 2. The means for enabling the unique word extraction includes a circuit for detecting a non-modulated carrier synchronization pattern, a delay circuit connected after the detection circuit, and an output of the unique word extraction means using the output of the delay circuit. The communication device according to claim 1, comprising a gate circuit for gating. 3. The means for enabling the unique word extraction includes a circuit for detecting a non-modulated carrier synchronization pattern, and a delay circuit connected to the downstream of the detection circuit, and the unique word extraction is performed at least on the condition of the output of the delay circuit. 2. The communication device according to claim 1, wherein the extraction means extracts a unique word. 4. The circuit for detecting the unmodulated carrier synchronization pattern,
Claims 2 or 3 include a filter having a predetermined bandwidth, a detector provided after the filter, and a signal level detector provided after the detector. communication equipment.