JPH0423534A - Transmission system for mwd - Google Patents

Abstract

PURPOSE:To make it possible to quickly obtain synchronism by using a modulated wave in a sequence having a sharp self-correlation as a synchronizing signal. CONSTITUTION:When an input waveform X(t) is inputted to a detector at the time of selecting a barker code with length '5' as a code string, the output waveforms of respective delay circuits 13a to 13d respectively become X(t-tau) to X(t-4tau). The output waveforms of the delay circuits 13a to 13d are added by an adder 14 though the output waveform of the circuit 13a is added after being inverted at its code, and when a waveform corresponding to the final symbol of a barker code is inputted to the detector, the a sine waveform having 5 times the amplitude of an input wave is outputted from the adder 14 as an output waveform y(t) only for time tau. Thereby, the sine wave is detected and its detecting timing is used for reproducing a carrier and symbol timing. Since synchronism is executed by using a sequence having a sharp correlating function such as a barker code, time required for the synchronism can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission system for MWD in a communication system.

[Prior Art] Figure 4 shows, for example, ``Digital Satellite Communication,'' published by Jadi Publishing, written by V. K. BHARGAVA, translated by Ken Tsukamoto et al.

This is a frame configuration diagram of a transmission signal used in conventional satellite communication as shown in "Published in May 1986". In the figure, 1 is a carrier wave recovery signal, 2 is a signal for symbol timing recovery, and 3 is a burst synchronization signal. 4 is the transmission data.

Figure 5 is, for example, a block diagram of a BPSK demodulator shown in [Satellite Communications, Tokyo Denki University Press, co-authored by Miyauchi, Sarata, and Yamamoto, published October 1985], and in the figure, 5 is the band pass filter, 6 is a carrier wave regeneration circuit, 7 is a multiplier, 8
9 is a low-pass filter, 9 is a clock recovery circuit, and 10 is a discriminator.

Next, the operation will be explained. In the conventional transmission system, a frame of a transmission signal is composed of a carrier wave reproduction signal 1, a symbol timing reproduction signal 2, a burst synchronization code 3, and transmission data 4. The carrier wave reproduction signal 1 is composed of a sine wave that continues for a predetermined period of time. The symbol timing reproduction signal 2 is a waveform in which the phase or bits are changed at a timing synchronized with the symbol of the transmission data. The burst synchronization code 3 is a waveform obtained by modulating a known code string. Further, the transmission data 4 is a waveform obtained by modulating the data to be transmitted.

The transmitted wave transmitted from the transmitter is distorted due to the characteristics of the transmission path, and becomes a received signal as a waveform with noise added. After passing through the bandpass filter 5, the received signal is input to the carrier recovery circuit 6.

In the carrier wave reproducing circuit 6, a sine wave whose phase is synchronized with the carrier wave reproducing signal 1 is reproduced. The reproduced sine wave and the received signal are multiplied by a multiplier 7. The multiplication result is input to a clock recovery circuit 9 after passing through a low-pass filter 8 . The clock regeneration circuit 9 regenerates a clock from the symbol timing regeneration signal 2 at a timing synchronized with the symbol of the transmission data, and the discriminator 10 outputs a regeneration signal using the regenerated clock. Thereafter, the burst synchronization code 3 is detected, and subsequent data can be recognized.

[Problem to be solved by the invention]

Conventional transmission is performed using the above method, but when the frequency of the carrier wave is low, there is a problem that it takes time to achieve synchronization.

Furthermore, it is impossible to compress signals for synchronization, and it is not possible to improve the detection accuracy of synchronization signals by signal compression.

This invention was made to solve the above-mentioned problems, and not only shortens the signal required for synchronization, but also improves the ratio of the signal necessary for synchronization to noise.

[Means to solve the problem]

In the transmission system according to the present invention, a series of modulated waves having a sharp autocorrelation is used as a synchronization signal of the MWD transmission system.

[For production]

In the transmission method according to the present invention, by detecting a series of modulated waves with sharp autocorrelation, the regeneration timing of the carrier wave and the regeneration of the clock synchronized with the bit period are performed at the same time, thereby reducing the time required for synchronization. Ru. In addition, a delay circuit, an inversion circuit,
Since the adder circuit compresses the signal necessary for synchronization, the amplitude ratio of the signal to noise is improved.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
Figures (a) and (b) are diagrams showing the frame structure of a transmission signal in the present invention, where 11.12 is a preamble and 4 is transmission data. Furthermore, 11 is a signal that serves both as a carrier wave recovery signal and a symbol timing recovery signal necessary for synchronous detection, and uses a waveform obtained by modulating a Barker sequence code using a phase modulation method. Reference numeral 12 indicates a pause period in which no transmission is performed, which is placed before and after 11 in order to improve detection accuracy.

FIG. 2 shows a detector used for synchronization, and is an example of the configuration when a parity code of length 5 is selected as the code string. In the figure, 1
3 is a delay circuit, 14 is an addition circuit, 15 is an inversion circuit,
t) indicates an input waveform, and y(t) indicates an output waveform. The delay time in the delay circuit is the symbol interval.

Figure 3 shows the input waveform X(t) in Figure 2, and the output waveforms X(t-τ), X(t-3τ)X (
v-4τ) or the inverted waveform of the output waveform of the delay circuit -X
(t-2τ) and the adder circuit output waveform y (t).

Next, the operation will be explained. Here, a case will be described in which the parity code "+10-+" with a code length of 5 is used in the present invention. If the binary symbols of the Parr force code are made to correspond to sine waves with a phase difference of 180°, and the symbol interval is set to one period of the sine wave, τ, then the Parr force code of length 5 is shown in 11 in Figure 1. It becomes a waveform. Eleven waveforms are transmitted from the transmission point prior to the transmission data.

At the receiving point, the 11 waveforms are compressed by a detector having the configuration shown in FIG. 2, and a sine wave with a large amplitude is output for one hour. By detecting the compressed sine wave, the carrier wave and symbol timing required for coherent detection are recovered.

Next, the operation of the detector shown in FIG. 2 will be explained with reference to FIG.

When the waveform of X(t) is input to the detector, the delay circuit 13a
The output waveform of 13b is X (-τ), and the output waveform of 13b is X<L
-2τ), 13c output waveform is X(t-3r>, 13
d(7) The output waveform becomes CX(t-4r). The output waveforms of the respective delay circuits are added by the adder circuit 14, but the output waveforms of the delay circuit 13a are added after having their signs inverted by the inverter circuit 15. The output waveform of the adder circuit 14 is shown as y(t),
When the last symbol is input to the detector, a sine waveform having an amplitude five times that of the input wave is output from the adder circuit 14 for a time τ. Therefore, carrier wave reproduction and symbol timing reproduction are performed by detecting this sine wave and using the detected timing.

In the above embodiment, a case where a Parr code with a length of 5 is applied has been described, but it is also possible to use a Parr code with an arbitrary length. Further, the fundamental period of the transmission frequency and the symbol interval of the parity code are equal. That is, although the synchronization signal is expressed using one symbol of the Parr power code as one period of the transmission frequency, it can also be realized when one symbol of the Parr power code is encoded with several periods of the transmission frequency. Furthermore, in addition to Harker codes, for example, PN sequences (pseudo-rois
This is possible if the sequence has a sharp correlation function, such as a sign of ``Esequence'' or a chirp wave.

〔Effect of the invention〕

As described above, according to the present invention, since synchronization is performed using a sequence with a sharp correlation function, such as a Parr code,
The time required for synchronization is shortened, allowing more accurate synchronization even under poor reception conditions.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams showing an example of the waveform configuration of a synchronization signal according to the present invention, FIG. 2 is a diagram showing a synchronization waveform detector according to an embodiment of the present invention, and FIG. is a waveform diagram showing the operation of the wave detector, Figure 4 is a configuration diagram of a conventional synchronization signal,
FIG. 5 is a diagram showing an example of the configuration of a demodulator in a conventional transmission system. In the figure, 4 is the transmission data, 11 is the modulated wave of the Par power sequence, 1
2 is an oscillation pause period, 13 is a delay circuit, 14 is an addition circuit,
15 is an inverting circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (4)

[Claims] (1) A transmission system for MWD characterized by using a series of modulated waves having a sharp autocorrelation as a synchronization signal. (2) The MWD transmission system according to claim 1, wherein the synchronization signal is composed of a Barker series phase modulated wave and a pause period during which no oscillation is performed. (3) The transmission system for MWD according to claim 1, characterized in that a Barker sequence is used as the sequence with sharp autocorrelation. (4) The transmission system for MWD according to claim 1, characterized in that a PN sequence is used as the sequence having sharp autocorrelation.