JPH02171051A - Digital privacy call communication system - Google Patents

Abstract

PURPOSE:To make a tapping difficult by using a phase distortion generator so as to give distortion to a digital signal at a transmission side and using a phase distortion equalizer correcting the distortion at a reception side. CONSTITUTION:A voice signal inputted from a microphone 1 is converted into a digital signal by an A/D converter 2. Then in order to be a spectrum within a radio frequency allocation, a phase distortion generator 10 gives a phase distortion through a filter 3 eliminating a high frequency component. The signal is modulated, amplified by a transmitter 4 and the result is radiated from a transmission antenna 5. A reception antenna 6 at the reception side receives the radio wave, demodulated in a receiver 7, and a phase distortion equalizer 11 equalizes waveform distortion generated by the phase distortion generator 10. Then a D/A converter 8 decodes the signal into the original voice signal and the result is outputted from a speaker 9. The tapping is made difficult by adding the phase distortion generator 10 and the phase distortion equalizer 11 to a conventional digital communication equipment in such a manner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a digital communication system, for example, a digital confidential communication system such as j-sanmu.

[Conventional technology]

FIG. 3 is a block diagram showing the system of a conventional digital communication system, and in the figure, the width of the microphone is %+2) and the speaker.

I will explain the next VC@ work. The audio signal input to microphone (11) is converted into a digital signal by Z conversion 'f4+2+, passed through filter +31f, and converted to radio frequency signal 11.
Bandwidth limitation is applied to suppress the spectrum to the same bandwidth, the high iMl waves are removed, and the transmitter (modulated by 41 is applied,
It can be emitted from the transmitting antenna +61.

This magnetic wave is received by the receiving antenna on the receiving side; from 6) to the receiver 7)
It is demodulated and returned to the original audio signal by the D/H9 converter 181 VC, which is then output from the speaker (9).

[Line layer that the invention seeks to solve]

Conventional digital communication systems are structured as described above, so by demodulating with a receiver and using the required DA converter, the original audio signal can be demodulated relatively easily, making it easy to eavesdrop. There was a point.

This invention was made to solve the above-mentioned problems, and aims to provide a digital confidential communication system in which the contents of communication are difficult to be intercepted.

[Means for solving the line layer]

The digital confidential communication system according to the present invention connects a phase distortion generator, which is groove-bottomed by a phase non-linear circuit, in the front stage of the transmitter of the conventional digital communication system to apply waveform distortion, and on the receiving side, the phase non-linear circuit A phase distortion equalizer with opposite characteristics is connected.

[Effect]

In the digital confidential communication system of this invention, distortion is applied to the digital signal wave after harmonic components have been removed by a distortion generator on the transmitting side, and the phase non-linearity of the transmitting side is applied to the receiving side in order to correct the above-mentioned distortion. Since a phase distortion equalizer that corrects circuit characteristics is used, correct demodulation cannot be performed without this phase distortion equalizer, making eavesdropping difficult.

〔Example〕

Hereinafter, one embodiment gA4 of the present invention will be explained with reference to the drawings.

In FIG. 1, the symbols . . . . to (9) in the figure are exactly the same as those of the conventional Ω type, and the explanation thereof will be omitted.

:lO) is a phase distortion generator, and Uυ is a total phase equalizer.

Next, the operation will be explained.

The audio signal manually inputted from the microphone II+ is converted into a digital signal by a percentage converter 121, and a filter (2) which removes harmonic components to suppress the spectrum within the radio frequency assigned band (2) generates 1 phase distortion throughout. 0) to give phase distortion. This signal is modulated by the transmitter 4).

It is amplified and emitted from the transmitting antenna 51.

In reception/ill, this wave is received by the receiving antenna (6), demodulated in the receiver 1d device 171, and the waveform distortion generated by the phase distortion generator (10) is equalized by the phase distortion equalizer/ll+. D
/A converter (8) returns the original audio signal to the speaker (9)
Output from

In the above embodiment, the explanation was given in the case of the S-line communication system, but it can also be applied to the case of the square-wire digital communication system as shown in FIG.

This has the effect of preventing wiretapping on the line.

In Fig. 2, the output waveform of a transmitting device 1111 of a conventional square wire digital m-communication system is distorted by a phase distortion generator (0), and this distortion is removed by a phase distortion equalizer (0) on the receiving device side. Reproducing the original audio The audio cannot be reproduced, making eavesdropping difficult.

〔Effect of the invention〕

As described above, according to the present invention, wiretapping can be prevented by connecting a phase distortion generator and a phase distortion equalizer to a conventional digital communication device.

4. Drawing II? 1 is a system block diagram of a digital confidential communication system according to one embodiment of the present invention, FIG. 2 is a system block diagram of a digital square line confidential communication system according to another embodiment of the invention, and FIG.
The figure is a system block diagram of a conventional digital signal transmission system. In the figure, 111 is a microphone, 121 is a % converter, +
31 is a filter.

41 is a transmitter, 6) is a transmitting antenna, 16) is a receiving antenna, j71 is a receiver, (8) is a D/A converter, (9)
is a speaker, ! lot indicates a phase distortion generator, and Uυ indicates a phase distortion equalizer.

In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] A digital confidential communication system that is characterized by converting audio input from a radio into a digital signal, distorting the waveform, and equalizing this distortion on the receiving side.