JPH0226902B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a secret device for preventing a third party from understanding the contents of a conversation in a communication device that transmits voice by emitting radio waves. It is related to.

Conventional technology Conventionally, as a technology of this kind, a secret speech device divides the audio spectrum into N subbands equally, and performs signal delay, amplitude determination, spectrum inversion, and frequency swapping for each frequency band of these subbands. was proposed by the present applicant in Japanese Patent Application Laid-open No. 125134/1983.

The outline of the above invention is as shown in Fig. 2. Bandpass filters BPF1 to BPF8 pass eight intermediate frequencies IF1 to IF8, for example, to equally divide the frequency of an audio signal into bands, and these bandpass filters. BPF1～BPF
8 for converting the audio frequency for each band of 8.
a first mixer M1 to M8 that transmits eight different frequencies to supply local oscillation frequencies to each of the mixers M1 to M8;
a local oscillator LOC1, eight second mixers R1 to R8 for converting each intermediate frequency IF1 to IF8 to an audio frequency different from the original audio frequency, and each of the second mixers R1 to R8. 16 different frequencies to provide local oscillator frequency (8 frequencies for spectrum inversion and 8 frequencies for non-spectrum inversion)
a second local oscillator LOC2 that oscillates a frequency), and eight delay elements D1 to D8 for temporally delaying the audio for each divided audio signal.
, eight switchers T1 to T8 for switching between signals that have passed through the delay elements D1 to D8 and signals that have not passed through the delay elements D1 to D8, and a delay element controller DC that controls each of the switchers T1 to T8; a variable gain amplifier controller VGC that controls the amplitude of the divided audio signal; eight variable gain amplifiers VA1 to VA8 controlled by the variable gain amplifier controller VGC; and a variable gain amplifier controller VGC that controls the amplitude of the divided audio signal. Low-pass filter to remove unnecessary waves such as harmonics of the filters VA1 to VA8
an LPF; an amplifier AMP for amplifying and outputting the microphone input or secret speech audio to the first mixers M1 to M8; and a power amplifier PA for amplifying the output from the low-pass filter LPF to obtain a secret speech output or secret speech reproduction output. Although a detailed explanation will be omitted, this system is characterized in that the delay and amplitude of the signal are determined for each audio frequency band, and the privacy of the audio is improved by performing spectrum inversion and frequency swapping.

Problems to be Solved by the Invention In the conventional confidential communication device shown in FIG. 2, the speech spectrum is divided into N subbands, and the spectrum is inverted and the frequency is swapped for these subbands using the known frequency inversion/swapping method. and playback method, and when outputting a secret message from the microphone input, use delay elements D1 to D8, switches T1 to T8, and delay element controller DC for each mixer output of mixers R1 to R8 to control each subband. Find the width of
The signals separated into each band are combined with the output of variable gain amplifiers VA to VA8, and then filtered to the low-pass filter.
Remove spurious components with LPF and power amplifier
It is amplified by PA and the secret message output is output to the transmission line.

When obtaining a secret playback output from a secret input, the delay elements D1 to D8, the switch T1, and the delay element controller DC are used for each of the mixer outputs of the mixers R1 to R8, and the secret input is used to reproduce the output of each subband from the secret input.
The signal of each subband is delayed so as to match the delay time of the maximum delay band, and the control output of the delay element controller DC is determined. At this point, the audio signals of each band return to their original spectra, and also return to the original audio signals that match in time. As in the case of , these signals are returned to their original amplitude by variable gain amplifiers VA1 to VA8, combined at the amplifier output, and passed through a low-pass filter.
Spurious components are removed with an LPF, amplified with a power amplifier, and the secret playback output is output to the transmission line.

As mentioned above, conventional secret speech devices selectively perform time delay operations on each band, combine well-known frequency inversion replacement and reproduction methods, give temporal changes to secret speech without using a synchronization signal, and This makes it possible to disturb the sense of rhythm in the communication system, allowing highly confidential communication. However, since the frequency reversal switching does not change during a call, there are problems such as the possibility that the secret message may be deciphered by a speaker using the same type of privacy device.

The present invention eliminates the above-mentioned drawbacks of the prior art, performs frequency inversion replacement and reproduction using a secret code that is automatically changed periodically in synchronization with a reference clock, and achieves privacy without using a periodic synchronization signal. The purpose of the present invention is to provide a new confidential communication device with improved performance.

Means for Solving the Problems The confidential communication device of the present invention, as shown in the block diagram of an embodiment of FIG. 2. Amplifier AMP and amplifier MAP that amplify and output the microphone input or private conversation input from switch 1
A first mixer M1 to M8 converts the output of the mixer into N (illustrated as eight in the figure) intermediate frequencies, and intermediate frequency bandpass filters BPF1 to BPF1 to pass intermediate frequencies IF1 to IF8 from the mixers M1 to M8.
BPF8, second mixer R1-R8 that returns intermediate frequencies IF1-IF8 to baseband, low-pass filter LPF that removes harmonic components, power amplifier PA that amplifies and outputs the output of low-pass filter LPF, converts baseband signals to intermediate frequency A first local oscillator circuit LOC1 that outputs eight different frequencies for spectrum non-inversion to be converted into IF1 to IF8, a second local oscillator circuit LOC2 that outputs eight different frequencies for spectrum inversion, and an intermediate frequency IF1. ~
Spectrum non-inversion to return IF8 to baseband,
gates G, each passing eight frequencies for inversion;
A controller 4 that controls the selection operation of the gate G, a start switch 5 that starts secret code calculation, a reference clock generator 6 that operates as a clock according to the specifications between the secret code devices that transmit and receive, and a basic secret code for spectrum inversion and frequency inversion. The difference between the time _T0 based on the reference clock of the secret code generator 7 and the reference clock generator 6, which generates N-bit (8-bit) code, and the time Tx when the start switch 5 is pressed (cumulative call time T= T ₀ −Tx) is converted into a bit string, the basic secret code generated by the secret code generator 6 is operated on, the secret code is periodically changed and operated, and the secret code is output to the controller 4. It is composed of a controller 8.

Function The voice spectrum is divided equally into N subbands, and the spectrum inversion and frequency swapping for each subband is performed by periodically changing the basic secret code of the secret code generator using the clock from the reference clock generator. This is performed using the secret code at the current time calculated from the secret code, and thereafter the secret code in a predetermined array is sequentially changed every 2 minutes, for example, using the reference clock, and the spectrum is inverted and By sequentially performing frequency inversion, a secret speech output and a secret speech reproduction output can be obtained, thereby providing a secret speech device with improved speech privacy.

Embodiment A more detailed explanation will be given below with reference to the embodiment shown in FIG. In order to output the audio from the microphone input as a secret speech output, first switch the switching devices 1 and 2 to microphone input and secret speech output, respectively, and turn on the activation switch 5 at the timing specified by the secret speech devices transmitting and receiving. The output of the amplifier AMP to which baseband audio is input is divided into eight equal parts by mixers M1 to M8 and intermediate frequency bandpass filters BPF1 to BPF8. The frequencies are as follows: audio input is 300Hz to 2700Hz, _S1 to _S8 for each 300Hz band, _IF is the intermediate frequency, _IL1 to _IL8 is the output of the first local oscillator LOC1, N = 1, 2...
8, _1F = _SN + _{1LN 1LN} = _IF -300N.

Next, intermediate frequency bandpass filter BPF1~
The intermediate frequencies IF1 to IF8 of BPF8 are output from the second local oscillator LOC2 and returned to baseband audio by _2L1 to _2L8 . In this case, the time Tx when the start switch 5 is turned ON and the output time of the reference clock generator 6 are used. Difference T (=T ₀ -Tx) from T ₀ The data obtained by converting the accumulated call time into a bit string is operated on the basic secret code generated by the secret code generator 7 to set the secret code. (Even if the basic secret code is the same, the secret code output will be different if the cumulative call time is different.) If this calculation process is performed every two minutes, for example,
The current secret code is determined. That is, even if a similar secret device is used, eavesdropping will not be possible unless the output time of the reference clock generator 6, the time when the activation switch is turned on, and the secret code generated by the secret code generator 7 match. If the output time of the reference clock generator is specified between the transmitting and receiving secret devices, eavesdropping becomes even more difficult.

The basic secret code from secret code generator 7 is:
It consists of a series of N-bit codes corresponding to subband spectrum inversion and frequency swapping, and in this example, N=8, so it is an 8-digit code with higher privacy than 10321920 (=8〓×2 ⁸ ) codes. secret codes are selected in a certain sequence.

Furthermore, the outputs _1L1 to _1L8 of the first local oscillator LOC1
By setting the outputs _2L1 to _2L8 of the second local oscillator LOC2 as the non-inverting frequency and the inverting frequency as the non-inverting frequency, the non-inverting frequency corresponding to the secret code at the current time determined by the secret code calculation controller 8 is determined. , the frequency for inversion and the frequency for exchange are selectively controlled by the gate G by the controller 3, and spectrum inversion and frequency exchange according to the secret code are performed.

This secret code is changed in a sequential sequence for each clock generated by the reference clock generator 6.

The outputs of the mixers R1 to R8 are integrated, passed through a low-pass filter LPF that removes harmonic components, are amplified by a power amplifier PA, and are output to the transmission line as a confidential output.

Next, a case will be described in which the secret speech input is reproduced to the original audio, which is the secret speech reproduction output.

The switch 1 is switched to the confidential message input, the switch 2 is switched to the confidential message reproduction output, and the start switch 5 is turned on at the timing specified by the confidential message devices transmitting and receiving.
The output of the amplifier AMP to which the secret speech signal is input is sent to mixers M1 to M8 and an intermediate frequency bandpass filter.
It is divided into 8 equal parts by BPF1 to BPF8. In this case, the frequency relationship is the same as in the case of telling a secret story above, the band from 300Hz to 600Hz is placed on IF1, and the band at 600Hz is placed on IF1.
~900Hz band is set to IF2, and the following is similarly set to 2400Hz~
2700Hz is converted to IF8. Next, the intermediate frequency of intermediate frequency band pass filters BPF1 to BPF8
IF1 to IF8 are the first and second local oscillators LOC1 to
The LOC2 and mixers R1 to R8 reproduce the spectrum of the original audio signal. In this case as well, the secret code from the secret code generator 7 is sent to the activation switch 5, as in the case of issuing the secret code mentioned above.
The time Tx based on the clock output from the reference clock generator 6 and the time based on the clock output from the reference clock generator 6 from the time Tx is turned ON.
The secret code calculation controller 8 determines the current time based on the time difference T (=To-Tx) from To. This allows for non-inversion corresponding to the secret code of the current time,
The inversion frequency and the replacement frequency are selected by the controller 3 at the gate G and reproduced.

The outputs of mixers R1 to R8 are integrated and passed through a low-pass filter LPF that removes harmonic components, and then amplified by a power amplifier PA to reproduce the original audio.

Effects As explained above, according to the present invention, there is provided a secret speech device that performs non-inversion, inversion, and frequency swapping of the audio spectrum using a series of secret codes that are changed in synchronization with the reference clock of the reference clock generator. Therefore, even if this is eavesdropped, there is no key such as a synchronization signal that can be decoded, so it has extremely high secret communication performance. Since it is also unclear from which code the secret code starts to be used, the secret speech performance is high even for speakers using the same type of secret speech device, and the configuration is also simple.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention;
FIG. 2 is a block diagram of a conventional embodiment. 1, 2...Switcher, 3...Gate, 4...Controller, 5...Start switch, 6...Reference clock generator, 7...Secret code generator, 8...Secret code calculation controller, AMP...Amplifier, PA...Power amplifier, M1-M8, R1-R8...Mixer,
BPF1 to BPF8...Intermediate frequency band pass filter, LPF...Low pass filter, LOC1...
First local oscillator, LOC2...second local oscillator.

Claims (1)

[Scope of Claims] 1. A plurality of N intermediate frequency bandpass filters that equally divide the frequency of an audio signal by band; and a plurality of N first intermediate frequency bandpass filters that convert the audio frequency for each band of the intermediate frequency bandpass filters. a first local oscillator that supplies a local oscillation frequency to each of the first mixers; and a plurality of N second mixers that convert the intermediate frequency to an audio frequency different from the original audio frequency. , a secret code generator that generates a continuous N-bit standard secret code that corresponds to spectrum inversion and frequency swapping of an audio signal; a reference clock generator that operates as a clock between the secret code devices that transmit and receive; and the above-mentioned standard. Bit conversion of the difference between the time based on the reference clock from the clock generator and the time set by the start switch, that is, the cumulative call time, arithmetic processing with the basic secret code generated by the secret code generator, and periodic a secret code arithmetic controller for changing the secret code; a start switch for activating the secret code arithmetic controller by specifying the timing of pressing between the secret code devices for transmitting and receiving; and a secret code arithmetic controller for changing the secret code; a controller for controlling the transmission of frequencies from the corresponding first and second local oscillators to each of the second mixers; A secret speech device characterized in that a secret speech output or a secret speech reproduction output is obtained by performing spectrum inversion and frequency swapping of a voice input or a secret speech voice in accordance with the secret speech code that is changed to the secret speech code.