JPS63196129A - Spread spectrum communication receiver - Google Patents

Abstract

PURPOSE:To correct the effect of signal distortion due to a signal transmission line and to demodulate data momentarily by a simple circuit by taking correlation between a signal retarding a reception signal by one period or a multiple of one period of a series of a pseudo noise signal and the reception signal itself and demodulating the result. CONSTITUTION:A correlation device 21 of a transmitter inverts the phase by 180 deg. and gives an output depending on '1', '0' of data 20 for a spread signal generated by a PN code (pseudo noise signal) generating means 19. One bit of the data has a time corresponding to one period of the PN code. A receiver 22 takes a correlation between a signal 25 retarding a reception signal 23 by one period of the PN code at a delay means 24 and the reception signal 23 by means of a correlation device 26. A delay means 24 consists of a delay line in case of an analog signal and a shift register in case of a digital signal. The output of the correlation device 26 is given to a low pass filter 27 and a data 28 is demodulated. Since the data 28 is information representing the level '1' or '0' to be inverted or the same before one preceding bit, the start bit is decided to be '0' or '1' in case of transmission and the actual data is sent from a 2nd bit.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a receiving device for spread spectrum communication.

BACKGROUND OF THE INVENTION FIG. 6 shows a block diagram of a conventional direct sequence receiving apparatus. The received signal 1 was correlated with the output of the pseudo-noise signal generating means 2 by a correlator 3, and passed through a low-pass filter 4 to demodulate data 5. Here, in order to match the phase of the output of the pseudo-noise generating means 2 with the pseudo-noise signal (hereinafter referred to as Pit code) included in the received signal, the operating frequency is controlled by the synchronization tracking means 6. FIG. 7 shows the relationship between the phase of the PM code and the output of the correlator 3. Here, the received signal is converted into a binary value, and the correlator 3 performs an exclusive OR. When the phase of the received signal 7 and the PN code 8 generated by the pseudo-noise generating means 2 are out of phase as in the example shown in FIG. Output 1o of filter 4 is "1"
It becomes an intermediate value between ``0'' and ``0'', and the data cannot be demodulated to output 9. However, as shown in B, when the received signal 11 and the enclosing code 12 are phase synchronized, the output 14 of the low-pass filter that receives the output 13 of the correlator 3 demodulates the data.

Problems to be Solved by the Invention As described above, in the conventional system, in order to demodulate data, it is necessary to synchronize the received signal with the PM code generated inside the receiver, but the synchronization tracking circuit There were problems in that the configuration was complicated and it took a long time to acquire synchronization. Furthermore, if the phase and gain frequency characteristics of the signal transmission path are poor and the phase of the received signal 150 changes as shown in FIG. 8, an error may occur in the correlation output 17 with the PM code 16. there were.

The present invention solves the conventional problems by providing a spread spectrum communication receiving device that can instantaneously demodulate data with a simple circuit and can also correct the effects of signal distortion caused by the signal transmission path. be.

Means for Solving the Problems In order to achieve the above object, the device of the present invention converts the received signal into P
The phase modulated data is demodulated by correlating the received signal with a signal delayed by one period or a multiple of one period of the N code.

Effect With the above configuration, the transmitter uses data “1” and “0” as P.
The phase of the H code is inverted by 1800 and output. The receiver receives a signal with the same waveform, or a signal with the same waveform but with an inverted phase, every cycle of the PN code. Therefore, demodulation is performed by correlating the received signal with a signal received one period before the PM code.

Example FIG. 1 is a block diagram showing an embodiment of the present invention.

Reference numeral 18 denotes a transmitter, which outputs the spread signal generated by the PN code generating means 19, having its phase inverted by a correlator 21 by 1180' according to the data 2o rl'' and rj. Here, it is assumed that one bit of data corresponds to one cycle of the PN code. 22 is a receiver, which transmits the received signal 23 to delay means 2;
4, a correlator 26 takes the correlation between the signal 25 delayed by one period of the PN code and the received signal 23. The delay means 24 consists of a delay line if the signal is an analog signal, or a shift register if the signal is a digital signal. Further, a delay element such as a BBD (packet brigade device) or a COD (charge coupled device) may be used. When the output of the correlator 26 is passed through a low-pass filter 27, data 28 is demodulated. However, the data 27 demodulated here is 1 bit earlier and r
Since it is information whether lJ and rOJ are reversed or the same,
When transmitting, the start bit is set to ``0'' or ``1'', and the actual data is sent starting from the second bit.

A time chart is shown in FIG. 2, and the operation of the embodiment shown in FIG. 1 will be explained. Data 2o is the start bit tro
It is assumed that the signal is "011".

When spread with PN code 29, the output of correlator 21, that is, the received signal, becomes PN when the data is rOJ as shown in 23.
When the code and data are "1", it becomes an inverted signal of the PM code. - The resulting signal 28 correlated with the bit-delayed signal 25 indicates whether it is the same as the previous bit or is inverted. Since the start bit is "0", the first bit of the data matches the start bit, so it is "0".
, since the second bit of the data is inverted from the first bit, the output of the correlator 21 is "1" because it does not match over one bit, and the third bit of the data matches the second bit, so it is "1". As with 2 bits, it can be demodulated to be "1". As shown in FIG. 3, the normal received signal 23 has a waveform different from the PN code 3o in the transmitted signal due to distortion in the signal transmission path. When correlating with the PN code 29, the correlation output 31 has a period of disagreement, but when correlating with the output 26 of the delay means 24, the previous bit is similarly distorted, so the output 32 of the correlator 21 There can be no disagreement. Note that when one bit is sent for two periods of the PN code, similar demodulation can be achieved by delaying the signal for two periods of the PM code using the delay means 24 of the receiver. Conversely, when 2 bits of data are sent during one period of the PM code, it can be determined from the demodulated data whether the bits are inverted compared to 2 bits before. Although two-phase balanced modulation has been described above, if a four-phase correlator is used, four-phase balanced modulation can be similarly demodulated.

4 and 5 show another embodiment. Here, PN code-cycle transmission is defined as "1", and PN code-cycle transmission after a pause of one cycle is defined as "0". FIG. 4 is a block diagram of the receiving circuit. Delaying means 34 for delaying the received signal 33
The signal is delayed by one period of the PM code to obtain an output 35, and further delayed by another period by the delay means 3e to obtain an output 37. Correlators 38 and 39 calculate the correlation between each output and the received signal 33.
After taking it with a reduced pass filter 40.41? After passing, data 42.43 is obtained. FIG. 6 shows a time chart of the signals. Here, () represents one period's worth of PN code. Data 44 is rljt as start bit 45
- Send information after sending. The received signal 33 is correlated with the signal 35° delayed by one period and the signal 3 completed delayed by two periods, and when data 42.43 can be demodulated, "↑"
is marked. Here, when the output is output to data 42, “
1", and when the output is output to the data 43, it becomes "0".

However, when an output is output to both 42 and 43, the transmitted information is obtained by setting it to "1".

Effects of the Invention As described above, according to the device of the present invention, data can be demodulated instantly with a simple circuit and a start signal for one cycle of the PN code. Furthermore, waveform distortion caused by the transmission line is corrected and faithfully demodulated, eliminating the conventional problems.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the device of the present invention, and FIG.
The figure is a time chart of the device shown in Fig. 1, Fig. 3 is a time chart explaining transmission distortion correction, Fig. 4 is a block diagram showing another embodiment, Fig. 5 is its time chart, and Fig. 6 is a time chart for explaining the correction of transmission distortion. Block diagram of a conventional spread spectrum receiver, No. 7
The figure is a time chart explaining the principle, and FIG. 8 is a time chart when the waveform is distorted. 23...Received signal, 24,34.36...
...delay means, 26,38.39...correlator. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 18 - Transmitter n - Receiver 0 -4- 1 -a-1 d""] Figure 3 8 Maada Sword Figure 4 #I 5 Figure 6 Figure 7 TI!J (A) Figure 8

Claims (1)

[Claims] 1. A spread spectrum communication receiving device characterized in that a signal obtained by delaying a received signal by one cycle of a pseudo-noise signal sequence or a multiple of one cycle is correlated with the received signal and demodulated.