JPS63199534A - Privacy call communication equipment - Google Patents

Abstract

PURPOSE:To make the acquisition difficult by a weak radio wave by using an n-phase modulation as a 2nd order modulation so as to prevent tapping. CONSTITUTION:The n-phase modulation is used to improve the privacy call characteristic. In order to apply the demodulation of the 2nd order modulation given by a transmitter, the receiver uses an n-multiple device 18. In order to avoid a defect being weak in the nearby disturbance, a linear multiplier is selected and used for demodulation in the receiver. At the start of transmission, a transmission switch 19 of the transmitter is closed and a burst signal is sent from a speech head signal generating circuit 20. When a speech head signal decided in advance is included in the signal obtained at an output section of a frequency discriminator 8 of the receiver, a speech head signal demodulation circuit 22 demodulates it and gives an output to a switch 23.

Description

[Detailed Description of the Invention] [Summary] In an angle modulation communication device, angle modulation and n-phase phase shift are applied to the transmitted signal, and secondary modulation is performed on the n-phase phase shift to prevent eavesdropping and achieve narrowband This makes it difficult to capture radio signals by making the power weaker through angular modulation, giving it a confidential characteristic.

[Industrial application field]

The present invention relates to a wireless communication device that can be used, for example, in a simple home cordless telephone.

It is desired that such a wireless communication device consumes little power, generates a weak electric field, and is configured as a simple device.

Furthermore, since it is a wireless communication device, it is desirable that the device has a configuration that makes it difficult to eavesdrop on communication contents.

[Conventional technology]

Conventionally, a narrowband frequency modulation communication device as shown in FIG. 5 has been used to generate weak radio waves.

In the figure, an audio signal is input from a transmitter 1 to a transmitter, and is sent to a narrowband frequency modulator 3 via a transmission audio processing circuit 2 that includes a differentiation circuit 201, a low frequency amplification circuit 202, and an instantaneous amplitude limiting circuit 203. frequency modulation. The modulated audio signal is radiated from the antenna 4 as a radio frequency.

The radio waves received from the antenna 5 are frequency-converted, passed through a narrowband filter 6, an amplitude-limiting amplifier 7, and then discriminated by a frequency discriminator 8. The signal is applied to the receiver 10 via the processing circuit 9.

The communication partner is basically identified by the radio channel frequency. For example, company A is assigned a wireless channel, or a radio frequency of 150.025 MH2, and company B is assigned a radio frequency of 150.025 MH2.
If 050MH2 is assigned, the radio channels will be different, so the communication between the radios belonging to company A will not be able to be interrupted by the radio equipment belonging to company B. .

Furthermore, by using weak radio waves as radio frequencies, the receivable distance can be limited.

However, if a general FM receiver is used, reception is possible although the volume is low, but the confidentiality is not satisfactory.

In order to improve the privacy characteristic, there is a method, as shown in FIG. 6, which combines a radio channel frequency and a tone squelch, making it possible to identify only a specific communication partner even within a system using the same radio frequency.

Since there are restrictions on the use of radio frequencies, the transmitter is equipped with a tone transmitter 11 that uses a frequency below the audio band, for example 67 to 250 Hz, and the receiver is equipped with a tone transmitter 11 that uses a frequency of 67 to 250 Hz.
A tone demodulator 13 is provided.

When the tone demodulator 13 of the receiver can demodulate the tone signal, the switch 14 is closed by the output of the tone demodulator 13.

The received signal from which the tone signal has been removed by the output tone remover 12 of the frequency discriminator 8 passes through the switch 14 and is supplied to the received audio processing circuit 9, where it is converted into audio and received by the receiver 10.

When the tone signal is not demodulated, the switch 14 remains open and no audio signal can be received.

[Problem that the invention seeks to solve]

In the conventional narrowband frequency modulation method, a method for identifying a specific communicating party by combining a radio channel frequency and a tone squelch prevents eavesdropping by parties other than the specific communicating party within the same system using the same radio frequency by the tone squelch effect. However, simple FM without tone squelch, that is, without receiving switch 14
There is a problem in that radios can be easily eavesdropped on.

(Means for Solving the Problems) The above problems can be solved by the present invention, as shown in the principle diagram of the present invention in FIG. and a transmitter comprising an n-phase phase shifter BIB, a linear n-multiplier 18 that multiplies the received signal by n,
The problem is solved by the confidential communication device of the present invention, which includes a receiver including an angle demodulator 80 to which the output of the n-multiplier is supplied via a narrowband filter 6, and a received audio processing circuit 9 that processes the demodulated audio. be done.

[Effect]

In the apparatus of the present invention, the transmitter performs angular modulation of the audio signal using an angle modulator 30, and further performs secondary modulation in an n-phase phase modulator 16 to which a pulse train is supplied from a pulse oscillator 15.

In the receiver, the received wave from the antenna 5 is band-limited by a broadband filter 17, and its output is input to an n-multiplier 18, which demodulates the second-order modulated n-phase phase-changing steel by the multiplication and generates an angle-modulated wave. Restore.

Furthermore, after band-limiting with a narrowband filter 6, it is demodulated with an angular demodulator 80, and the output of the received audio processing circuit 9 is restored to an audio signal by a receiver. The n-phase phase modulated wave has privacy, and the iM amplification is realized by a simple n-multiplier, which simplifies the configuration of the device.

As shown in FIG. 4, the n-phase phase modulated wave is one in which a carrier wave is phase modulated by a signal pulse a), and the modulation result is shown in b). The illustrated example is a case of a two-phase phase modulated wave. The phase modulated carrier wave is output as a high speed modulated wave having the frequency component of the signal pulse.

Due to this effect, for example, a narrowband frequency modulated wave with a bandwidth of approximately 16 kHz becomes a high-speed pulse train of several hundred Mbits to several Mbits (the repetition frequency is one half of that), and the bandwidth is approximately 10 times the frequency of the original pulse train. come to have.

Here, a general radio receiver can only receive a very small part of the emitted radio wave band, for example, about 200kHz.
Therefore, demodulation becomes impossible due to insufficient amount of information and insufficient received energy.

In this way, by using phase modulation for secondary modulation, it is possible to obtain a wireless device that prevents eavesdropping and makes capture difficult due to weak radio waves.

〔Example〕

The embodiment of the present invention will be explained according to the illustrated embodiment.

FIG. 2 is a block circuit diagram of a confidential communication device according to an embodiment of the present invention.

In the figures, functional blocks that are the same as those in other drawings are indicated by the same numbers.

According to the present invention, n-phase phase change steel is used to improve the secret characteristics. The n-phase phase modulator 16 is supplied with pulses from the pulse oscillator 15. As the pulse oscillator 15, a pulse pattern generation circuit using a multi-stage shift register can be used.

The receiver uses an n-multiplier 18 to demodulate the secondary modulation applied by the transmitter.

There are two types of multipliers: nonlinear multipliers and linear multipliers.

When the former is used, if there is an interfering wave whose amplitude is larger than the amplitude of the desired received wave in the received wave supplied to the n-multiplier 18 via the wideband filter 17, the desired wave is suppressed, resulting in reception interference. Therefore, there is a drawback that the receiver becomes susceptible to proximity interference, which must be avoided.For this reason, in the present invention, the latter linear multiplier is selected and used for demodulation.

The linear multiplier does not have the above-mentioned drawbacks, and after demodulation, the narrow band filter 6 removes the interference wave and supplies it to the limiting amplifier 7, limits the amplitude and supplies it to the frequency discriminator 8.

The n-phase phase change steel provides a distinguishing (secret speech) characteristic, but in order to provide mutual distinguishability within the same system, FIG. 2 is equipped with a circuit that inserts a burst tone at the beginning of the speech.

At the start of transmission, the transmitter closes the transmission switch 19 and sends out a burst signal from the top of the line signal generation circuit 20.

As shown in FIG. 3, at the beginning of the start of transmission of the transmission signal shown in column i), a burst signal shown in column it) is transmitted. This burst signal has a frequency f1~ as shown in column iii)
It can be given as a combination of analog frequency fn, or as a digital signal consisting of the 1st bit to the nth bit taking values of "1" and "0" shown in column iv).

In the receiver, the signal obtained at the output part of the frequency discriminator 8 is
If a predetermined head-of-talk signal is included, the head-of-talk signal demodulation circuit 22 demodulates this and provides an output to the switch 23. The received signal passes through the switch 23 and is supplied to the received audio processing circuit 9.

Although the above embodiment shows the case of frequency modulation, the present invention can also use phase modulation, and the combination of both is referred to as angle modulation.

〔Effect of the invention〕

As described above, the present invention provides a wireless communication device with excellent system privacy characteristics with a simple demodulator configuration by using n-phase phase-changing steel as secondary modulation, and its effects are as follows. Extremely large.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a block circuit diagram of a confidential communication device according to an embodiment of the present invention, Fig. 3 is a layout diagram of a burst signal at the beginning of a transmission signal, and Fig. 4 is a two-phase phase modulation diagram. FIG. 5 is a block circuit diagram of a conventional wireless communication device, and FIG. 6 is a block circuit diagram of a conventional tone squelch system. In the figure, 1 is a transmitter, 2 is a transmission audio processing circuit, 3 is a narrowband frequency modulator, and 4.5 is an antenna. 6 is a narrow band filter, 7 is a limiting amplifier, 8 is a frequency discriminator, 9 is a receiving audio processing circuit, 10 is a receiver, 11 is a tone transmitter, 12 is a tone remover, 13 is a tone demodulator, 14.23 is a 15 is a pulse oscillator, 16 is a phase modulator, 17 is a wideband filter, 18 is an n multiplier, 19 is a transmission switch, 20 is a top of the line signal generation circuit, 22 is a top of the line signal demodulation circuit, 30 is an angle modulator , 80 is an angle demodulator.

Claims (1)

[Claims] A transmitter comprising an angle modulator (30) and an n-phase phase modulator (16) that modulate the transmission signal supplied from the transmission audio processing circuit (2), and a linear n-multiplier (1) that multiplies the received signal by n.
8), an angle demodulator (80) to which the output of the multiplier is supplied via a narrowband filter (6), and a receiver comprising a received audio processing circuit (9) that processes the demodulated audio. A confidential communication device characterized in that: