JPH0258942A - Direct spread frequency communication equipment - Google Patents

Abstract

PURPOSE:To execute a communication with a high secrecy by obtaining a random number used for a spread frequency from a natural random number. CONSTITUTION:Instead of a pseudo-random number(PN) generator, natural random number generators (natural random number memories) 15 and 17 to generate the natural random number are used. Namely, by providing the natural random number memories 15 and 17 to generate the same natural random number at transmitting and receiving both sides, a signal spread at the transmitting side can be inversely spread, and simultaneously, since the generated random number is the natural random number, a random number series is not imbalanced to a specific pattern, and a spread code is made hard to find out by a tapping person. Thus, a direct spread frequency communication equipment can be obtained in which communication contents are hardly decoded even when they are tapped by the third party.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to spread spectrum communication technology, and particularly to a device that performs communication by direct frequency spread.

[Conventional technology]

Figures 3 and 4 are, for example, from pages 18 and 6 of the document "Latest Spread Spectrum Communication System" (Jachik Publishing).
FIG. 6 is a system diagram of a conventional direct frequency spreader shown on page 6. In the figure, 1 is a carrier wave oscillator, 2 is a pseudo noise (P
N) generator, 3 converts the output of the carrier wave oscillator 1 into pseudo noise (P
N) A balanced modulator that performs direct frequency spreading with the output of the generator 2; 4 is an antenna that transmits the output of the balanced modulator 3; 5 is an antenna that receives it; 6 is a carrier wave oscillator on the receiving side; The frequency differs from 1 by the intermediate frequency. A pseudo noise (PN) generator 7 generates the same code sequence e as that of the generator 2 on the transmitting side.

8 is a balanced modulator that spreads the frequency of the carrier wave f using the output of the pseudo noise (PN) generator 7, 9 is a mixer that despreads the output d of the antenna 5 using the output of the balanced modulator 8, and 10 is a despread signal. Intermediate frequency bandpass filter (hereinafter referred to as IF) to extract
(referred to as BPF).

FIG. 4 is a system diagram of the pseudo-noise (PN) generator 2 or 7, in which 11 is a shift register consisting of registers DI""D, , and 12 is an exclusive OR circuit.

Next, the operation will be explained. Pseudo noise (PN) generator 2
The pseudorandom number sequence generated is phase modulated (PSK) by the output of the carrier oscillator 1 and the balanced modulator 3 to generate a direct frequency spread signal, which is radiated from the antenna 4.

On the other hand, the receiving side receives the spread frequency signal directly through the antenna 5. The carrier wave oscillator 6 generates a carrier wave that differs in frequency from the carrier wave oscillator l by an intermediate frequency, the pseudo noise (PN) generator 7 generates the same random number as the pseudo noise (PN) generator 2, and the balanced modulator 8 Modulation (PSK) L, generates a direct frequency spread wave. This spectrum is the same spectrum as the received signal, differing only in frequency. The output of the balanced modulator 8 is despread by the mixer 9 and the output of the antenna 5 is converted into a narrow band spectrum. The output of mixer 9 is IF
BPFIO limits the band to a narrow band and demodulates it.

Next, a pseudo-noise (PN) generator that generates pseudo-noise will be explained using FIG. 4. In the shift register 11, if all the registers D, ~D, etc. have an initial value other than "0", the rightmost value is input to the leftmost register D1, and the circuit 12 inputs the first value to the leftmost register D1. The signal is input to the (n-1)th register D□1, which is exclusive ORed with the output of the register D.

When the shift register 11 has n stages, the exclusive OR circuit 1
It is known that if the insertion position of 2 is selected well, random numbers can be generated with a period of 2''-1, and this random number sequence is called the maximum period sequence.

[Problem to be solved by the invention]

Since conventional devices use a pseudo-random number generator as shown in Figure 4, the random number sequence becomes a specific and limited pattern.
There was a risk of being intercepted.

This invention was made in order to solve the above-mentioned problems of the conventional ones, and its purpose is to obtain a direct frequency spread communication device whose communication contents are difficult to decipher even if it is intercepted by a third party. do.

[Means to solve the problem]

The direct frequency spreading device according to the present invention has a pseudo-random number (PN
) generator is replaced with a natural random number generator that generates natural random numbers.

[Effect]

In this invention, since generators that generate the same natural random numbers are provided on both the transmitting and receiving sides, it is possible to despread the signal spread on the transmitting side, and the generated random numbers are natural random numbers. Therefore, the random number sequence does not follow a specific pattern, making it difficult for eavesdroppers to find the spreading code.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a direct frequency spread communication device according to an embodiment of the present invention. In the figure, 1 is a carrier wave oscillator, 16 is a counter, 15 is a natural random number memory, and 3 is the output of the carrier wave oscillator l. A balanced modulator that performs direct frequency spreading on its output; 4 is an antenna for transmitting the output of the balanced modulator 3; 5 is an antenna for receiving; 6 is a carrier wave oscillator, and its oscillation frequency differs from carrier wave oscillator 1 by an intermediate frequency. . 18 is a counter, and 17 is a natural random number memory, which generates the same code sequence as the memory 15. 8 is a balanced modulator that spreads the frequency of the carrier wave 6 using the output of the natural random number memory 17, 9 is a mixer that despreads the output of the antenna 5 using the output of the balanced modulator 8, and 10 is an IF that extracts the despread signal.
It is BPF.

FIG. 2 shows a memory writing device for writing natural random numbers into memories 15 and 17, 20 is a noise generator such as thermal noise, 21 is a sampler, and 22 is a memory writing device.

Next, the operation will be explained. First, counter 16 on the sending side
A natural random number is called from the natural random number memory 15 according to the address specified by , and is phase modulated (PSK) with the output of the carrier oscillator 1 by the balanced modulator 3 to generate a direct frequency spread signal and radiated from the antenna 4.

On the other hand, the receiving side directly receives the frequency signal through the antenna 5. The carrier wave oscillator 6 oscillates a carrier wave that differs in frequency from the carrier wave oscillator 1 by an intermediate frequency, and the natural random number memory 17 generates the same random number as the natural random number memory 15 according to the address specified by the counter 18. modulation(
PSK)L, generates direct frequency spreading. This spectrum is the same spectrum as the received signal but has a different frequency. The output of the balanced modulator 8 is despread by the mixer 9 and the output of the antenna 5 is converted into a narrow band spectrum. The output of mixer 9 is demodulated by limiting the band to a narrow band using IF BPFIO.

Next, we will explain how to record natural random numbers. In FIG. 2, the noise generated from the noise generator 20 is transmitted to the sampler 21.
is digitally counted and written into the natural random number memory 15 or 17 by the memory writer 21.

In the above embodiment, the natural random number output is directly PSKed, but as shown in FIG. 5, a D/A converter 23 is provided between the balanced modulator 3 and the natural random number memory 15, Also, D/ is connected between the balanced modulator 8 and the natural random number memory 17.
The analog value may be balanced-modulated by installing the A converter 24, and the same effect as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the direct frequency spread communication device according to the present invention, since the random numbers used for frequency spreading are obtained from natural random numbers, there is an effect that highly confidential communication is possible.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a direct frequency spread communication device according to an embodiment of the present invention, Fig. 2 is a diagram showing a natural random number recorder used in the embodiment of Fig. 1, and Fig. 3 is a diagram showing a conventional direct frequency spread communication device. FIG. 4 is a diagram showing a spreading communication device, FIG. 4 is a diagram showing a pseudo-random number generation circuit, and FIG. 5 is a diagram showing another embodiment of the present invention. In the figure, 3.8 is a balanced modulator, 15.17 is a natural random number memory, 23.24 is a D/A converter, 20 is a noise generator, 21 is a sampler, and 22 is a memory writer.

Claims (1)

[Claims] (1) In a direct frequency spread communication device that performs communication by spreading digital data with a code sequence faster than the data rate, the transmitting and receiving sides are provided with means for storing and generating the same natural random number; A direct frequency spread communication device that performs direct frequency spreading on the transmitting side and despreading on the receiving side using random numbers.