JPS61174839A - Discrimination code transmission system - Google Patents

Abstract

PURPOSE:To prevent a malreception by multiplexing a modulated wave, where a subcarrier is modulated digitally with a discrimination code generated by a discrimination code generator with a frequency division to a main signal consisting of sound signal or the like and transmitting them. CONSTITUTION:A discrimination code generator 10 generates a discrimination code assigned to its own station by an ROM or the like. This discrimination code modulates the frequency of the subcarrier by a digital modulator 11, and this modulated wave is multiplexed with the main signal by a multiplexing circuit 12, and they are arranged on the frequency base. Since the subcarrier waves modulated by the discrimination code and the main signal are multiplexed in frequency division, lines are easily discriminated from one another.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an identification code transmission system used in an information transmission system that transmits audio, video, etc. using a radio frequency band, for example.

FIG. 4 shows a block diagram of an example of a line configuration of an information transmission method using a radio frequency band.

As shown in the figure, in the wireless ultra-high frequency band, for example, the transmission frequencies of transmitters 1 and 2 are set to the same frequency fo, and transmitter 1
Transmission and reception are performed between the receiver 3 and the transmitter 2 and the receiver 4.

Therefore, receiver 3 receives radio waves from transmitter 1 (hereinafter referred to as desired waves) and radio waves from transmitter 2 (hereinafter referred to as interference waves).
Therefore, the antennas 1-1 and 2-1 are arranged so that the reception level of the latter is lowered by about 1, for example, 30 dB, than that of the former.

Therefore, during normal reception, the interference waves are suppressed at receiver 3,
The effect of the interference wave is small, as the signal-to-noise ratio of the desired wave is slightly lowered, but if the desired wave is cut off, only the interference wave is received, so the content of communication from the transmitter 2 to the receiver 4 is not transmitted to the receiver. It leaks to 3. .

Therefore, there is a need for an identification code transmission system that can maintain the confidentiality of communication by cutting off the output of the receiver so that the content is not output when communication content from another route is received.

[Conventional technology]

FIG. 5 shows a block diagram of a conventional example of a video signal receiver.

In the figure, the desired wave at the standard reception level that is frequency-modulated with audio 2 video, etc., and the desired wave at the same frequency but higher than that, for example, 30
Interference waves at a dB lower level are applied to the high frequency section 5 via the antenna.

These two waves are converted into an intermediate frequency signal by a high frequency section 5, and then amplified to a predetermined level by an automatic gain control amplifier (hereinafter abbreviated as AGC amplifier) 6 and applied to a switch 8.

Here, since the reception level is higher than the specified value, the switch 8 is in the on state due to the output from the reception level detector 7.
The output of the AGC amplifier 6 is demodulated by a demodulator 9 to extract a video signal and the like.

Note that an amplitude limiter (not shown) in the demodulator 9 suppresses low-level interference waves, thereby reducing the influence of the interference waves.

However, when the reception level of the desired wave is cut off and the reception level of the interference wave is higher than the specified value above, switch 8
is in the on state, and the information contained in the interference wave is extracted by the demodulator 9.

In addition, as a method for determining the reception status, instead of using the reception level, there is a method in which a pilot signal is superimposed on the video signal and sent out, and this is detected to determine whether reception is normal or not. If the frequencies of the pilot signals that can be used are determined to be the same, it is not possible to use this to determine whether the received wave is a desired wave or an interference wave.

On the other hand, in the case of a digital signal rather than an analog signal such as an audio or video signal, an identification code is inserted into the signal and sent together with the digital signal, and the receiving side extracts this code to identify the station.

[Problem that the invention seeks to solve]

As explained in detail above, when transmitting audio, video signals, etc. on the same frequency, it is not possible to distinguish whether the received radio waves are the desired waves or not, and the receiver transmits all signals as long as they are above a predetermined reception level. Since the audio and video signals are taken out as desired waves, the confidentiality of communication is compromised.

On the other hand, in the case of digital signals, the transmission speed of the main signal is changed in order to insert the station identification signal into the main signal, but when the transmission speed of the main signal changes, a speed converter must be designed each time.・It has to be manufactured and has no versatility.

That is, in the case of analog signal transmission, the secrecy of the communication is compromised because no identification signal is inserted, and in the case of digital signals, although the secrecy of the communication is ensured, there is a problem in that the circuit lacks versatility. .

[Means for solving problems]

The above problem is that the transmitting side has an identification code generator that generates an identification code, a digital modulator that uses the output of the identification code generator to modulate a subcarrier with a frequency different from that of the cough main signal, and the digital modulator. The receiving side is composed of a combining circuit that combines the output and the cough main signal, and the receiving side includes a branching circuit that branches the received signal, an identification code detection unit that detects the identification code from the first output of the branching circuit, and a second A main signal processing circuit is provided for controlling transmission of the main signal extracted from the output, and the main signal processing circuit is controlled by a control signal from the identification code detector,
This problem can be solved by the identification code transmission system of the present invention, which transmits the main cough signal only when a specific identification code is detected.

[Effect]

The present invention provides a concealment method that sets an identification code for each line and prevents signals from being sent to the outside in the event of erroneous reception or reception interruption from another line.

That is, on the transmitting side, a modulated wave in which a subcarrier is digitally modulated with an identification code generated by an identification code generator is multiplexed by frequency division onto a main signal composed of audio, video, and/or digital signals, and then transmitted.

On the receiving side, when the detected identification code is not a specified code or when reception is interrupted, the output of the received signal is cut off to prevent erroneous reception from being sent to the outside.

In this way, the confidentiality of communication is maintained, and since the main signal and identification code are multiplexed by frequency division, if the main signal is a digital signal, the transmission speed of this signal is irrelevant, and this superimposition circuit can be used for general purpose. There is sex.

〔Example〕

The contents of the present invention will be specifically explained below with reference to illustrated embodiments. Note that the same reference numerals indicate the same objects throughout the figures.

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
The frequency spectrum of the figure is shown.

On the transmitting side in FIG. 1, an identification code generator 10 generates an identification code assigned to its own station using, for example, a read-only memory (hereinafter abbreviated as ROM), and can easily be used for other identification codes by replacing the ROM. It is possible to generate a code.

This identification code is subjected to frequency, phase, or amplitude shift keying modulation on the subcarrier in the digital modulator 11, and this modulated wave is synthesized with the main signal in the synthesis circuit 12, and is synthesized with the main signal in the synthesis circuit 12.
Or they are arranged on the frequency axis as shown in (b).

FIG. 2(a) shows a composite signal in which subcarriers modulated with an identification code are arranged on the frequency axis in a main signal composed of a video signal and an audio subcarrier modulated with an audio signal,
FIG. 2(b) shows a case where subcarriers modulated with identification signals are arranged in the main signal, for example, a frequency division multiplexed signal or digital signal of 1800 channels.

The signal in FIG. 2 (al or ('b)) is sent to the transmitter 13
Sent via .

On the receiving side, the above composite signal is extracted in the receiving section 14 and
The branch circuit 15 divides the signal into a main signal and a modulated subcarrier, and the former is applied to the main signal processing circuit 17 and the latter to the identification code detection section 16.

The latter reproduces a clock from the identification code demodulated by the digital demodulator 16-1 in the clock generating section 16-2, and uses the recovered clock to generate a demodulated signal whose waveform is shaped and the self-signal in the identification code detector 16-3. The station identification code is compared, and if they match, the main signal processing circuit 17 becomes normal with the sent control signal. Therefore, only the main signal of the composite signal is outputted through the low-pass filter 18, but if there is a mismatch, the main signal processing circuit 17 becomes abnormal (no words are outputted).

The main signal processing circuit is composed of, for example, a switch circuit,
If no identification code is detected, the main signal output is set to 1. Alternatively, it may be configured with a two-manpower changeover switch so that a test pattern or the like is output when no identification code is detected.

FIG. 3 shows a block diagram of another embodiment of the invention.

On the transmitting side, after converting the transmission speed of the identification code and digital signal from the identification code generator 10 using the speed converter 19,
A multiplexing unit 20 performs time division multiplexing. Then, the digital modulator 11 modulates the subcarrier using this multiplexed digital signal.

The following operations are the same as those on the transmitting side in FIG.

On the receiving side, the above multiplexed digital signal is obtained by the digital demodulator 16-1.

Therefore, as in FIG. 1, the clock regenerator 16-5 and the identification code detector 16-6 determine whether or not the own station identification code has been detected, and then send out a control signal. Furthermore, using the clock obtained by the clock regenerator 16-5.

The clock signal generators 16 to 7 generate a clock for the digital signal before speed conversion, and the separator 16-4 extracts the original digital signal using this clock.

Although FIG. 1 shows an example of use in a wireless device, it can also be used in a wired system such as coaxial.

〔Effect of the invention〕

As explained in detail above, subcarriers modulated with identification codes and the main signal are multiplexed by frequency division, making it easy to identify between lines, and if the main signal is a digital signal, the main signal The identification code can be superimposed regardless of the transmission speed.

That is, the confidentiality of communication is maintained, and in the case of digital signals, the circuit configuration has the advantage of being versatile.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
3 is another block diagram of the present invention, FIG. 4 is a block diagram of an example of a line configuration, and FIG. 5 is a block diagram of a conventional example of a video signal receiver. In the figure, 0 is an identification code generator, 11 is a digital modulator, and 12 is an identification code generator.
is a synthesis circuit, 13 is a transmitter, 14 is a receiver,
15 is a branch circuit, 16 is an identification code detection section, 17 is a main signal processing circuit, and 1 is a low-pass type wave transmitter. Difference (S side receiving μ side year 3rd

Claims (1)

[Claims] In an information transmission system that transmits a main signal, the transmitting side includes an identification code generator that generates an identification code, a digital modulator that uses the output of the identification code generator to modulate a subcarrier having a frequency different from that of the main signal, and It consists of a combining circuit that combines the output of the digital modulator and the main signal, and the receiving side includes a branching circuit that branches the received signal, an identification code detection unit that detects the identification code from the first output of the branching circuit, and A main signal processing circuit is provided to control transmission of the main signal taken out from the second output, and the main signal processing circuit is controlled by a control signal from the identification code detector to detect a specific identification signal. An identification code transmission system characterized in that the main signal is transmitted only when the main signal is present.