JPH08125579A - Spread spectrum communication system - Google Patents

Abstract

PURPOSE: To easily and inexpensively demodulate data by utilizing a spreading code included in a transmitted spreading signal without using data of consecutive spreading codes at the time of demodulation. CONSTITUTION: A graphic (a) shows a spectrum spreading signal for differential- BPSK-demodulating at prescribed transmitting periods and (b) shows a signal for receiving the spectrum spreading signal and delay-detecting it. In (a), 0 in original data D1 (0, 1) is converted to different data (1, 0) of the front and rear and 1 is converted to the same data (0, 0) of front and rear to be D2 (1, 0, 0) as a whole, and they are furthermore converted to a spectrum spreading signal S1 for transmitting by spreading by data of 6 bits. In (b), inputted spectrum spreading signal S1 is multiplied by a delay signal SDL1 for delaying by the period time T of the spreading code by a delay line 1 by means of a multiplier 2 to be a multiplying signal SDT1. Then, LPF3 cuts carrier frequency components into a detection signal and a data discrimination part 4 switches it to obtain a digital signal SD1.

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 system, and more particularly to a communication system for demodulating data using a spread code included in a spread signal to be transmitted.

[0002]

2. Description of the Related Art Spread spectrum communication is a communication method in which a spectrum of an information signal limited to a certain band is spread and used in a wide band.
Using a code unrelated to the information signal, for example, a PN code,
The receiving side is able to despread and demodulate based on the same spreading code sequence as the transmitting side, using its autocorrelation characteristics. Conventionally, as a demodulation method, it has been considered to demodulate using a sliding correlator, a matched filter shown in FIG. 4, and a convolver. But,
These systems have the drawbacks that an element having the same spreading code sequence data as that on the transmitting side and a spreading code generator are required, and the number of components is large and the cost is high.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems, and at the time of demodulation, a spread code sequence data transmitted by a spread code generator, a matched filter, or the like is not used, and a spread signal is transmitted. The purpose of the present invention is to demodulate data easily and inexpensively by using the spread code included in.

[0004]

In order to solve the above-mentioned problems, the present invention inputs a spread spectrum signal which is differentially BPSK (binary phased shift keying) modulated at a predetermined period and outputs the spread spectrum signal. A delay line that delays for a time equal to the spread cycle time, a multiplier that multiplies the output of the delay line and the spread spectrum signal, a low-pass filter that outputs a detection signal by removing the carrier signal from the output from the multiplier, And a data discriminating section for discriminating data from the detected signal and extracting a digital signal,
Delay detection is performed using a delay line having the same delay time as the spread code cycle.

[0005]

With the above configuration, in the spread spectrum communication system of the present invention, the input spread spectrum signal is delayed by the same time as the cycle of the spread code included in the spread spectrum signal, and the input spread spectrum signal is delayed. The data is multiplied by the spread signal and differentially detected, and the data discriminating section discriminates the data and takes it out.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A spread spectrum communication system according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a spread spectrum communication system according to the present invention. In the figure, 1 is a delay line having a delay time of the same cycle time as the spreading code. Reference numeral 2 denotes a multiplier, which multiplies the input spread spectrum signal by the delay signal passed through the delay line 1. A low-pass filter 3 cuts the carrier signal from the multiplication signal from the multiplier 2 and outputs a detection signal.
A data discriminating unit 4 discriminates whether the detection signal from the low-pass filter 3 is larger or smaller than a threshold level, and outputs it as a digital signal.

Next, the operation of the above configuration will be described. FIG. 2-a shows a differential BPS at a predetermined cycle of transmission.
FIG. 2B shows a spread spectrum signal for K (binary phased shift keying) modulation, and FIG. 2B shows a signal for delay detection by receiving the spread spectrum signal. In FIG. 2-a, the original data D1 (0,1)
0 is converted into different data (1,0) before and after, and 1 is the same data (0,0) before and after as a whole data D2.
The spread spectrum signal S1 is set to (1, 0, 0) and further spread and transmitted with 6-bit data. Figure 2
-B, a delay signal S that delays the input spread spectrum signal S1 by the delay line 1 for the period T of the spread code
DL1 is multiplied by the multiplier 2 to obtain a multiplication signal SDT1, the carrier frequency component is cut by the low pass filter 3 to be a detection signal, and the data discriminating unit 4 switches to obtain the digital signal SD1.

FIG. 3 shows a plurality of delay lines 1 having different delay times.
, a, 1b, ... Are connected in parallel and the plurality of delay lines 1
In the example in which the switch 5 is provided between the a, 1b, ... And the multiplier 3, a plurality of spread spectrum signals to be input are selected and received in which the cycle times of the spread codes match. I have to. Although the switch 5 is provided in FIG. 3 for selection, if the spread spectrum signals having different delay times are selected by changing the direction of the antenna, it is possible to operate without the switch 5.

[0009]

As described above, according to the spread spectrum communication system of the present invention, the input spread spectrum signal is delayed by the same time as the cycle of the spread code included in the spread spectrum signal and is input. Since the data is discriminated by the data discriminator after being multiplied by the spread spectrum signal for differential detection, the data is transmitted without using the spread code sequence data from the spread code generator or matched filter during demodulation. Data can be demodulated easily and inexpensively by using the spread code included in the incoming spread signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a spread spectrum communication system according to the first invention.

FIG. 2 shows a transmission waveform and a waveform of each part on the reception side.

FIG. 3 is a block diagram showing an embodiment of a spread spectrum communication system according to the second invention.

FIG. 4 is a block diagram showing an example in which a conventional spread spectrum communication SAW matched filter is used.

[Explanation of symbols]

 1 Delay Line 1a Delay Line 1b Delay Line 2 Multiplier 3 Low Pass Filter 4 Data Discriminator 5 Switch

Claims (3)

[Claims] 1. A differential BPSK (binary
Phased shift keying) A spread spectrum signal to be modulated is input, a delay line that delays by a time equal to the spread cycle time of the spread spectrum signal, a multiplier that multiplies the output of the delay line and the spread spectrum signal, A low-pass filter that outputs a detection signal by removing the carrier signal from the output from the multiplier, and a data determination unit that determines the data from the detection signal and extracts the digital signal, and has the same delay time as the cycle of the spreading code. Spread spectrum communication method characterized by differential detection with a delay line. 2. The delay line is characterized in that a plurality of delay lines having different delay times are connected in parallel and a spread spectrum signal having a different spread code period is selected and received. The spread spectrum communication method described in 1. 3. The spread line comprises a plurality of delay lines having different delay times connected in parallel, a switch provided between the plurality of delay lines and the multiplier, and spread spectrum having different spread code periods. 2. The spread spectrum communication system according to claim 1, wherein a signal is selected and received.