JP3136834B2 - Spread spectrum communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spread spectrum communication method using direct spread modulation.

[0002]

2. Description of the Related Art Conventionally, in spread spectrum communication using direct spread modulation, a delay detection method has been used as a method that does not require a PN code (pseudo noise sequence) synchronization device on the receiving side. In this method, after transmitting data is differentially converted on the transmission side, the transmission data is multiplied with a PN code to obtain a spread spectrum signal, and the reception side spreads the reception spread spectrum signal and the reception spread spectrum signal for one cycle of the PN code The product is multiplied with the signal delayed by a minute, and the data signal is demodulated using the low-frequency component of the multiplied signal.

FIG. 4 is a block diagram of a conventional differential detection system.
FIG. 5 shows the signal waveform of each part. FIG. 4A shows a block diagram on the transmission side. In the figure, source binary data input from a signal line 500 is input to an exclusive OR gate 50. The other input of the exclusive OR gate 50 is input from the signal line 501, and the exclusive OR gate 50
, An exclusive OR operation is performed, and a so-called precoded signal is output to the signal line 502. Signal line 5
02 is input to the delay circuit 51 and the source binary data 1
The signal is delayed and output to the signal line 501.

The clock generation circuit 54 outputs a clock signal for generating a modulation PN code to a signal line 504. P
The N code generator 53 generates a modulation PN code according to the clock signal from the signal line 504 and outputs the generated PN code to the signal line 503. The multiplier 52 multiplies the signal from the signal line 502 by the signal from the signal line 503 and outputs the product to the signal line 505.

FIG. 4B shows a block diagram of the receiving side.
In the figure, a received spread spectrum signal from a signal line 507 is input to a delay circuit 55 and a multiplier 56. In the delay circuit 55, the received spread spectrum signal is delayed by one period of the PN code, that is, by one bit of the source binary data, and is output to the signal line 508. The received spread spectrum signal from signal line 507 and the signal delayed by signal line 508 are:
The multiplier 56 performs a multiplication operation and outputs the result to a signal line 509. The signal on the signal line 509 is supplied to the low-pass filter 57.
As a result, the low-frequency component is extracted and output to the signal line 510 as demodulated data.

FIG. 5 shows the signal waveform of each part. FIG. 5 (a)
5B shows the waveform of the source binary data of the signal line 500, FIG. 5B shows the precoded signal waveform of the signal line 502,
FIG. 5C shows a modulation waveform of the signal line 505 obtained by performing spread spectrum modulation on the signal of the signal line 502 using a PN code. The received spread spectrum signal on the signal line 507 has a signal waveform shown in FIG. FIG. 5D shows the signal waveform of the signal line 508 in which the received spread spectrum signal has been delayed by one period of the PN code. The multiplier 56 multiplies the signal of the signal line 507 and the signal of the delayed signal line 508 by the multiplier 56. Multiply and signal line 509
And input to the low-pass filter 57. FIG.
(E) shows the demodulated data of the signal line 510.

[0007]

In the above-mentioned conventional differential detection system, the receiving side has a P frequency in the carrier frequency band.
A delay time of one cycle of N codes is required. In order to obtain this delay time, a method using a SAW delay line and a method of synchronizing with a carrier frequency signal and converting it to a baseband signal,
There is a method in which the baseband signal is digitally generated by using a clock signal, but both methods require a complicated circuit configuration and are expensive.

[0008]

Therefore, a spread spectrum communication method according to the present invention provides a method for selectively transmitting a PN code on the transmitting side according to the polarity of source binary data to be transmitted in spread spectrum communication using direct spread modulation. And a PN code that is selectively output is multiplied by a carrier frequency signal to transmit a spread spectrum signal. On the receiving side, the selectively output PN code is output in the received spread spectrum signal. While the PN code exists, a pulse is generated for each period of the PN code, and a pulse obtained by delaying the pulse by one period of the PN code and a pulse for outputting demodulated data are output. 1 and a second signal, wherein the first signal is set to a state in which data to be demodulated is activated in preference to the second signal, and the second signal is:
The demodulated data is obtained by lowering the data to be demodulated in the activated state.

[0009]

According to the above method, on the transmitting side, the PN code from the PN code generator is turned on and off in accordance with the positive and negative polarities of the source binary data, and the turned on and off PN code and the carrier frequency are output. The signal is multiplied and output. On the receiving side, from the intermediate frequency spread spectrum signal obtained from the received spread spectrum signal, while the PN code exists,
A pulse is generated for each period of the PN code. This pulse is used as a first signal, and a pulse obtained by delaying the pulse by one period of the PN code is used as a second signal to generate demodulated data.

For example, when the first signal is generated, the second signal
Irrespective of the occurrence of the second signal, the demodulated data to be output is turned on prior to the second signal. When only the second signal is generated, the demodulated data to be output, which is turned on by the first signal, is turned off.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples will be described below in detail. FIG.
FIG. 3 is a block diagram showing an embodiment of a transmitting side for realizing a spectrum method for realizing the present invention. In FIG. 1A, source binary data input from a signal line 100 is input to a selection circuit 10. The other input of the selection circuit 10 is a PN code for modulation. Clock generation circuit 12
Then, the clock signal for generating the PN code for modulation is supplied to the signal line 1.
02 is output. The PN code generator 11 has a signal line 102
A PN code for modulation is generated based on the clock signal from, and is output to the signal line 101. The selection circuit 10 generates a spread spectrum signal in which the PN code from the signal line 101 is turned on and off according to the polarity of the source binary data signal from the signal line 100.

The spread spectrum signal from the signal line 103 is a PN code that is turned on and off in accordance with the polarity of the source binary data signal. The multiplication circuit 13 and the carrier frequency signal from the carrier frequency signal generation circuit 14 Multiplied. The product signal on the signal line 105 is band-limited by the band pass filter 15 and outputs a transmission spread spectrum signal to the signal line 106.

FIG. 1B shows a circuit example of the selection circuit 10 shown in FIG. In FIG. 1B, when the source binary data signal from the signal line 100 is at H (high) level, the signal line 10
The modulation PN code from 1 is output to the signal line 109, and when the source binary data signal is at the L (low) level, the modulation PN code is not output to the signal line 109 but is fixed at the L level. The PN code turned on and off by the source binary data signal from the signal line 109 is latched by the D flip-flop 19 by the clock signal from the signal line 102 and output to the signal line 103 as a spread spectrum signal.

FIG. 2 is a block diagram showing one embodiment of the receiving side for realizing the present invention. In FIG. 2A, a received spread spectrum signal input from a signal line 200 is input to a multiplier 20. The other input of the multiplier 20 is input from the signal line 201, and is multiplied by the local signal from the local oscillation frequency signal generator 21 and the received spread spectrum signal from the signal line 200, and the intermediate frequency spectrum is added to the signal line 202. Output as a spread signal.

The intermediate frequency spread spectrum signal from the signal line 202 is band-limited by the band-pass filter 22,
The signal is output to the signal line 203. The intermediate frequency spread spectrum signal from the signal line 203 is supplied to the next SAW
The signal is amplified to the optimum input level of the correlator 24. The SAW correlator 24 outputs a matched pulse signal to the signal line 205 every period of the PN code while the PN code exists.

Since the matched pulse signal contains an intermediate frequency component, the square balanced detection is performed by the double balanced modulator 25, the low-pass component is extracted by the low-pass filter 26, and output to the signal line 207. The signal-to-noise ratio of the matched pulse signal can be improved by this square detection operation and the band limitation of the low-pass filter.
Further, the receiving circuit can be realized by a configuration using a digital correlator instead of an SAW correlator which is an analog correlator.

The matched pulse signal from the signal line 207 is pulse-shaped by a matched pulse shaping circuit 27.
The signal is output to the signal line 208 as a set signal of the flip-flop circuit 29. The pulse signal of the signal line 208 is also input to the delay circuit 28, delayed by one cycle of the PN code by the delay circuit 28, and output to the signal line 209 as a reset signal of the flip-flop circuit 29.

The flip-flop circuit 29 is a set-priority set-reset flip-flop circuit.
The information data is demodulated by the set signal from the signal line 208 and the reset signal from the signal line 209 to be demodulated.
Output demodulated data.

FIG. 2B shows a circuit example of the set priority flip-flop circuit 29. A set signal is input from the signal line 208 and a reset signal is input from the signal line 209. The reset signal is valid only when the set signal is at the L level, and only when the reset pulse is input. , A valid reset is applied to the signal line 213 as a negative pulse.
Output as a pulse. The set pulse signal is valid regardless of whether the reset pulse signal is at the H level or the L level. When the set pulse signal is input, the signal line 212
Is output as a negative pulse.

The set pulse signal on the signal line 212 and the reset pulse signal on the signal line 213 are input to D flip-flops 35 and 36, and are synchronized with the clock signal from the clock signal generator 30. The set pulse signal from the signal line 214 and the reset pulse signal from the signal line 215 are input to the set / reset flip-flop circuit composed of the logic gate elements 37 and 38, and the demodulated data signal is output to the signal line 216. The signal is output to the signal line 211 through the D flip-flop 39. FIG.
1 shows signal waveforms at various parts in FIGS. FIG. 3A shows a signal form of a spread spectrum signal in which the PN code of the signal line 103 in the transmission side block diagram of FIG. 1 is turned on and off by the source binary data signal. FIG. 3B shows FIG.
5 shows a signal waveform of the signal line 205 in the block diagram of the receiving side. The matched pulse signal on the signal line 205, which is the output of the SAW correlator, has phase information at the intermediate frequency. FIG. 3C shows a signal line 20 which is a square detection output.
6 shows a signal waveform of a signal line 208 obtained by shaping the signal of No. 6 and this pulse signal becomes a set signal of a set priority flip-flop circuit. FIG. 3D shows a signal waveform of the signal line 209, which is a reset signal of the set priority flip-flop circuit. FIG. 3E shows a signal waveform of the signal line 211, that is, a demodulated data signal.

[0021]

As described above, according to the spread spectrum communication method of the present invention, in the conventional delay detection demodulation method, the differential conversion circuit is not required on the transmitting side by using a simple selection circuit, and the receiving side is not required. In this case, a delay circuit for one cycle of the PN code of the matched pulse is used, and a delay circuit for one cycle of the PN code in the carrier frequency band becomes unnecessary, so that the circuit configuration can be simplified and the cost reduction effect is enormous.

[Brief description of the drawings]

FIG. 1 is a block diagram of a transmitting side in an embodiment of a spread spectrum communication method according to the present invention.

FIG. 2 is a block diagram of a receiving side in the embodiment.

FIG. 3 is a signal waveform diagram of each part on the transmission / reception side in the embodiment.

FIG. 4 is a block diagram of a conventional spread spectrum communication method.

FIG. 5 is a signal waveform diagram of each part of the method.

[Explanation of symbols]

10 selection circuit 11,53 PN code generator 12,30,54 clock signal generation circuit 13,20,52,56 multiplier 14 carrier frequency signal generator 15,22 band pass filter 16,17,31,32,34, 37, 38 and
Gate element 18, 33 OR gate element 19, 35, 36, 39 D-type flip-flop 21 Local oscillation frequency signal generator 23 Amplifier circuit 24 SAW correlator 25 Double balanced modulator 26, 57 Low-pass filter 27 Matched・ Pulse shaping circuit 28 Matched pulse delay circuit 29 Set priority flip-flop circuit 50 Exclusive OR gate element 51, 55 Delay circuit

Claims (1)

(57) [Claims] In a spread spectrum communication using direct spread modulation, a transmitting side selectively outputs a PN code and a fixed potential in accordance with the polarity of source binary data to be transmitted, and selectively outputs the PN code and the fixed potential . A PN code is multiplied by a carrier frequency signal to transmit a spread spectrum signal. On the receiving side, in the received spread spectrum signal,
While the selectively output PN code is present, PN
A pulse is generated for each cycle of the code, and a pulse obtained by delaying the pulse by one cycle of the PN code is a first signal and a second signal for outputting demodulated data, respectively. Puts the data to be demodulated in a state in which the data to be demodulated is activated in preference to the second signal, and the second signal is
A spread spectrum communication method in which the demodulated data is obtained by lowering the data to be demodulated in the activated state.