JPS58171143A - Spread spectrum communication system - Google Patents

Abstract

PURPOSE:To simplify the constitution in the spread spectrum communication system, by obtaining the correlation between a pseudo noise code, which is generated in the transmitter side, and a pseudo code generated in a receiver and comparing both correlated threshold level to obtain a demodulation output. CONSTITUTION:In a transmitter 1, a transmission data signal A impressed to a selective switching circuit 4 consists of binary code ''0'' and ''1''. A PN (pseudo noise) code B is a pseudo noise signal having a pulse width T and a period nT and is impressed to a delay circuit 3 and the selective switching circuit 4. A signal C outputted from the delay circuit 3 is the signal obtained by delaying the PN code B by deltaT. The selective switching circuit 4 switches and outputs the PN code B and the delay signal C in accordance with transmission data A. Correlations between a PN code B' generated in a receiver 6 and a reception signal D' and between a delay signal C' and the reception signal D' are obtained in the receiver 6, and demodulated transmission data is obtained by the output of the comparison between both correlation values.

Description

[Detailed description of the invention] The present invention relates to a spread spectrum communication system.

In recent years, the spread spectrum communication method (hereinafter referred to as S
This is called the S communication method. ) has been adopted and considered in many cases.

In the direct spread method, which is one of the SS communication methods.

Balanced modulation of the transmitted signal with a PN code (pseudo-noise code)
Transmit by expanding the frequency band and convert the received signal to PN on the receiver side
The transmitted signal is demodulated by mixing it with the code. In this communication method, the frequency band for one communication channel is wide, so even if noise mixes in some frequency bands.

It has excellent noise resistance because it can demodulate signals in other remaining frequency bands. However, this communication system has the disadvantage that it is necessary to keep the PN code series on the transmitter side and the PN code series on the receiver side completely synchronized, and that the synchronization circuit becomes complicated.

Therefore, an object of the present invention is to provide an SS communication system that allows communication even if the synchronization accuracy of the synchronization circuit is not so sufficient, that is, the synchronization circuit can be configured relatively easily.

In order to achieve the above object, the SS communication system of the present invention switches and transmits the PN code generated on the transmitting device side, either as is or with a predetermined time delay depending on whether the transmission data is 0 or 1, and the receiving device side The correlation between the signal from the transmitting device, that is, the received signal and the PN code generated within the receiving device, and the correlation between the received signal and the PN code generated within the receiving device.
The correlation between the N code and the signal delayed by a predetermined time is determined, and the comparison output of both correlation values is used to obtain υ demodulated transmission data.

The present invention will be explained in detail below with reference to embodiments shown in the drawings.

FIG. 1 is a block diagram showing the configuration of a transmitter of a communication system in which the present invention is implemented. In the figure, a transmitting device 1 includes a PN code generation circuit 2. Delay circuit 5. and a selection switching circuit 4. The signal A applied to the selection switching circuit 4 is transmission data, and this signal A is, for example, e Q *J:t 1 as shown in FIG. 6(a).
It consists of 97 binary numbers. PN code generation circuit 1
The signal B generated at is.

For example, there is a PN code shown in FIG. 6(b).

This is a pseudo noise signal having a puffless width T2 and period nT on this PNN code, and is applied to the delay circuit 3 and also to the selection switching circuit 4. The signal C output from the delay circuit 5 is a signal that is delayed by a period of 8T above the PNN code generated by the PN code generation circuit 2 and output as shown in FIG. 6(C). is also added to selection 5rJ path 4.

The selection switching circuit 4 selects P according to the applied transmission data A.
The delay signal C from the PNN code delay circuit 6 from the N code generation circuit 2 is switched and output. That is, when the transmission data A is 0'', it is output in PNN code, and when the transmission data A is ``1'', the delayed signal C is output. Therefore, if the transmitted data A shows the value of 0'' from time t1 to t2 as shown in FIG. 3(a), As the output signal of the selection switching circuit 4, the output signal shown in FIG.
), the PN signal B is output for 1 hour, 2 to 6, and the delayed signal C is output for 1 hour, 6 to 4, and the PN signal B is output for the time L1 to t2. The output signal is sent to the communication path 5.

FIG. 2 is a block diagram showing the configuration of a receiving device of a communication system in which the present invention is implemented. In the figure, a receiving device 6 includes a PN code generating circuit 7. Delay circuit 8. Correlation circuit (I)
9. Correlation circuit (n) 10 and differential amplifier circuit (comparison circuit)
11.

The PN code circuit 7 and the delay circuit 8 are the PN code circuit 2. Delay D] is the same type of circuit as circuit 6.

The PN code circuit 7 is synchronized with the transmitter 1. Signal B' (PN code) output from this PN code circuit 7
is the same as the output signal B of the PN code generation circuit 2, as shown in FIG. 6 (0)), and the output signal C of the delay circuit 8 is also the same as the output signal C of the delay circuit B, as shown in FIG. Suppose that it is the same as .

The signal D' received via the communication path 5 is sent to the correlation circuit (I) 9
and correlation circuit 1) are added to 10. Also, correlation circuit (I)
The output signal B' of the PN signal generation circuit 7 is added to 9,
The received signal D' and the correlation output E on the PNN code are derived from the output of the correlation circuit (I) 9. Similarly, correlation circuit (1) 1
The output signal C of the delay circuit 8 is added to 0.

Correlation 1] A correlation output F between the received value D and the output signal C of the delay circuit 8 is derived from the output of the path (II) 10.

Now, to simplify the explanation, the receiving signal D' is shown in Fig. 3 (d
), it is assumed that it is the same as the signal without noise. The autocorrelation function of the PN code still has a peak value of 1, as shown in FIG. 4, and remains constant in other parts.

Correlation circuit (1)9. If the t-th output of the correlation circuit (II) 10 is output every period nT (1, L2, L3, M4 in FIG. 6), the correlation output signal E of the correlation circuit (■) 9 is
, the correlation output of the correlation circuit (n) 10 (the difficulty F is shown in Fig. 6(e)
)(f).

One period (nT) before time t1, transmission data A is 0, and signal B and signal RI match.

The output signal E of the correlation circuit (I) 9 becomes 1. On the other hand, since signal C and signal RI do not match, correlation circuit ('1I) 1
The output signal F of 0 becomes a signal. Similarly, at time t2, signal B and signal B match between time t1 and t2, but signal C' and signal D' do not match, so output signal E is 1 and output signal F is 4. . Next, at time 171] t 3, signal B and signal RI do not match between 9 hours L2 and 6, and signal C and signal RI do not match, so output signal E becomes 4. F becomes 1. Further time t4
In this case, the signal JijB' and the signal D' match again between time t6 and t4, and since the signal C' and the signal D' do not match, the output signal E becomes 1 and the success signal F becomes 4. Therefore, by adding the output signal E and the output signal F to the differential amplifier 11 and adding the Ryokawa power signal, comparing the two times 1, t2, t3, and 4, an output is obtained only at time t3. Figure 6(g) shows the output signal G.
is obtained. This output signal G is a reproduction of the original transmission data A delayed by one period, and the transmission data is demodulated in this way.

According to the Nuvectrum spread communication system of this invention.

Based on the above principle, even if a synchronization difference occurs between the PN code sequence of the receiving device and the PN code sequence of the transmitting device, the transmitted data can be successfully demodulated as long as the deviation is within ±b. Therefore, there is no need to worry about ensuring precision in the synchronous circuit.

This can be handled with a simple synchronous circuit.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a transmitting device of a communication system in which the present invention is implemented, FIG. 2 is a block diagram showing the configuration of a receiving device of the same system, and FIG. 3 is a block diagram showing the configuration of a receiving device of the same system. FIG. 4 is a diagram showing the autocorrelation function characteristics of the PN code. 1: Transmitting device, 2.7: PN code generation circuit. 3/8: Delay circuit, 4: Selection switching circuit. 5: Communication path, 6: Receiving device, 9: Correlation circuit (I),
10: Correlation circuit (II), 11: Differential amplifier circuit. Patent Applicant Tateishi Electric Co., Ltd. Agent Patent Attorney Shigeru Nakamura

Claims (1)

[Claims] (1) The transmitting device includes a PN code generation circuit, a delay circuit that delays the output of the PN code generation circuit for a predetermined period of time, and outputs the PN code generation circuit by switching between the output of the PN code generation circuit and the output of the delay circuit. including a switching circuit, and transmit data O'
=! or 1 by operating the switching circuit according to the value of iJ.
Selecting either the output of the PN code generation circuit or the output of the delay circuit and transmitting it to the communication channel, while the receiving device includes a PN code generation circuit and a delay circuit of the same type as those included in the transmitting device; 1st. a second 4-11 circuit; a comparison circuit that compares the output of the second correlation circuit, the first correlation circuit calculates the correlation between the received signal from the communication path and the output of the PN code circuit, and the first correlation circuit calculates the correlation between the received signal and the output of the delay circuit. The +1 function of the first . A spread spectrum communication system characterized in that demodulated data is obtained by the output of the comparison circuit to which the output of the second correlation circuit is added.