CN2169954Y - Signal-noise separator for short wave data transmission equipment - Google Patents

Abstract

The utility model relates to a signal-noise separator for short wave data transmission equipment. An adjustable signal-noise separator is added on a modem receiving circuit, wherein, according to the general circuits, FSK modem chips AM7910 forms the modem receiving circuit, and the adjustable signal-noise separator is composed of a photoelectric isolation circuit (1), an active band-pass filter circuit (2), an alternating current amplifying circuit (3), a DC recovering circuit (4), an integrating circuit (5), a voltage comparing circuit (6), a switching circuit (7) and a limiting circuit (8). The signal-noise separator for short wave data transmission equipment can carry out stable and reliable transmission under 600 baud rate speed. When signal-noise is less, the highest speed of the signal-noise separator for short wave data transmission equipment can reach 1200 baud rate.

Description

Signal-noise separator for short wave data transmission equipment

The utility model belongs to the wireless data transmission technology field, specifically a kind of signal-noise separator of shortwave data transmission set.

The modulation system that is adopted in the enterprising line data transmission of short wave channel is divided into parallel system and serial system.Parallel system is with a plurality of pairs of carrier frequency simultaneously and send transmission information, also claim arrowband formula frequency multiplexing system (FDM) common have NCFSK noncoherent frequency shift keying (NCFSK), time-differential phase-shift keying (TDPSK) and frequency differential phase-shift keying (FDPSK) etc. several.It is to exchange for multipath concurrence to add long symbols with anti-multipath delay pollution, but its transmitting power dispersion is subject to the frequency selective fading influence, and frequency spectrum is more crowded, easily causes crosstalk.The serial system is the speech channel bandwidth serial transmission information with 3 kilo hertzs, and at receiving end employing (adjusting in real time) adaptive matched filter and adaptive equalizer, this serial system is to eliminate intersymbol interference with the way of isostatic compensation, compare with parallel system, it has avoided the weakness of those parallel systems, but comparatively complicated comparatively speaking.Because the advantage of serial system is remarkable, generally adopt the modulation system of serial system at present as the shortwave transfer of data.

In the serial system, in, low speed (50 to 1200 baud rate) shortwave number passes system and adopts frequency shift keying (FSK) modulation system more, and phase shift keying (PSK) since communication efficiency and bandwidth availability ratio all compare effectively, and having 3 decibels system to gain than FSK aspect the anti-white noise, so be used for higher speed (2400 baud rate) more.

The system cost of realizing the PSK mode is higher, the shortwave number of the FSK mode of existing employing low price passes system speed lower (50--150 baud rate), and it is limited to exist the transfer files type, (major part only can be transmitted text) and the transmission means incompatibility problems such as (major part are all continued to use the cable data transmission manner) that is adopted, the FSK system at a low price that makes is difficult to reach realistic scale.

AM7910 is the general FSK modem chip that U.S. AMD produces, and uses this chip to form the modulator-demodulator that satisfies CCITT or Bel's 103 agreements by a spot of peripheral cell.In short wave channel, owing to reasons such as white noise, co-channel interference and frequency dispersions, when adopting the modulator-demodulator of forming according to the mode of AMD's recommendation to carry out transfer of data, because of the demodulation level low (about 25 millivolts) of AM7910 is only very easily transferred because co-channel interference and white noise cause to misread through the signal of Filtering Processing.If the filtering output signal is sent into AM7910 again through overdamping, then can make the relative components increasing of interference signal that demodulation bit error rate is risen significantly because of incoming signal level is lower.

The purpose of this utility model is: add a kind of signal-noise separator of its shortwave data transmission set with adjustable signal/white noise separation function that makes to overcome above-mentioned deficiency in the FSK modem chip AM7910 modulator-demodulator receiving circuit that circuit constitutes routinely.

The utility model is achieved in that in the FSK modem chip AM7910 modulator-demodulator receiving circuit that circuit constitutes has routinely increased the adjustable signal noise separator of being made up of photoelectric isolating circuit, active bandwidth-limited circuit, ac amplifier circuit, DC restoration circuit, integrating circuit, voltage comparator circuit, switching circuit, amplitude limiter circuit.And the data structure that adopts custom-designed and said apparatus to adapt, make the circuit after the improvement possess stronger anti-white noise and burst interference capability, significantly rise simultaneously, be achieved thereby the modulator-demodulator that the AM7910 chip that utilizes the FSK modulation system is formed carries out the valid data transmission under short wave channel because of the level that has improved input signal makes the accuracy of demodulation.

The utlity model has following characteristics: under the speed of 600 baud rates, can carry out reliable and stable transmission, when channel noise hour, maximum speed can reach 1200 baud rates.Speed compared with more domestic like product 50 to 150 baud rates has bigger difference, has reached the purpose of the practical shortwave data transmission set of developing the FSK modulation system.

Fig. 1 is the circuit block diagram of the utility model signal noise separator

Fig. 2 is the circuit diagram of the utility model signal noise separator

Embodiment, in with the FSK modem chip AM7910 modulator-demodulator receiving circuit that circuit constitutes routinely, increased the signal noise separator, as shown in Figure 1 and Figure 2, the adjustable signal noise separator of forming by photoelectric isolating circuit 1, active bandwidth-limited circuit 2, ac amplifier circuit 3, DC restoration circuit 4, integrating circuit 5, voltage comparator circuit 6, switching circuit 7, amplitude limiter circuit 8.By operational amplifier UA741, the output of the photoelectric isolating circuit 1 that photoelectronic coupler 4N25 is formed is coupled to the input of the active bandwidth-limited circuit 2 that is made of LM324, the output of band pass filter is coupled to the input of the ac amplifier circuit of being made up of MC1458 3, the output one tunnel of ac amplifier circuit directly is coupled to the input of the switching circuit of being made up of MC4066 7, another road is connected to the dc retorater circuit 4 that is made of MC1458 and carries out DC converting, the output that direct current recovers is linked the corresponding DC level of signal (or noise) to be converted to and to import in the integrating circuit of being made up of RC 5, the output of integrating circuit directly enters the voltage comparator circuit 6 that is made of LM311 and makes it and comparing with reference to level by the adjustable resistance decision, when the level that obtains is higher than this with reference to level by input signal (or noise), the output of comparator is high level by the low level upset, this output level is directly used in the control end of control switch circuit 7, when this level when being high, switch connection, signal by AC amplifier output is delivered to the amplitude limiter circuit of being made up of MC1458 and 1N4,148 8 by the output of switching circuit, and the output of amplitude limiter is sent into AM7910 and carried out demodulation.

Input signal is through behind the photoelectric isolating circuit, the power-supply system of transceiver and the power-supply system of modulator-demodulator are isolated, on the other hand, 1 volt of audio signal of transceiver output is carried out the signal noise constant amplitude decay first time, noise and signal are all decayed to below 200 millivolts.Send into bandwidth-limited circuit filtering through the signal of attenuation of the first kind and carry out the frequency-selecting amplification, amplify the useful signal in the passband.After amplifying through frequency-selecting, the active constituent that is superimposed upon through the interference signal on the signal that has amplified significantly weakens.The signal of this process filtering is delivered to the input of switching circuit, and it is that the driving voltage that changes switching circuit into is prepared to produce enough energy that the signal of another road process filtering enters ac amplifier circuit.The signal that comes out from ac amplifier circuit enters DC restoration circuit again, and through after the DC restoration circuit, AC signal changes the direct current signal of pulsation into, the direct current signal of this pulsation is sent into integrating circuit make it to change into direct voltage.Integration circuit time constant has determined the response sensitivity to the co-channel interference signal, and the amplitude of this direct voltage changes with the variation of power, time and the frequency of input signal.Experimental results show that, even interference signal or white noise that amplitude is equal to or greater than data-signal occur in channel, thereby corresponding with it direct current amplitude has also reached the purpose of effective mask data signal and interference signal well below the pairing direct current amplitude of data-signal.The direct voltage of DC restoration circuit output is directly sent into voltage comparator circuit as control switch connecting and disconnecting of the circuit whether control voltage.The reference voltage that changes voltage comparator circuit is the threshold voltage of this device of may command, to determine the connecting and disconnecting of input signal.The output signal of switching circuit is cut and is directly sent into AM7910 behind the top and carry out demodulation through falling into width of cloth circuit.

After increasing this device, make equipment greatly strengthen anti-white noise and burst interference capability, equipment can still can be accomplished accurately synchronously under the situation of strong white noise and burst interference.Simultaneously, owing to improved incoming level, the relative amplitude of interference signal significantly weakens, and greatly improves to understand and transfers accuracy.

Claims (9)

1, a kind of signal-noise separator of shortwave data transmission set, it is characterized in that in the FSK modem chip AM7910 modulator-demodulator receiving circuit that circuit constitutes routinely, having increased by photoelectric isolating circuit (1), active bandwidth-limited circuit (2), ac amplifier circuit (3), DC restoration circuit (4), integrating circuit (5), voltage comparator circuit (6), switching circuit (7), the adjustable signal noise separator that amplitude limiter circuit (8) is formed, (1) output is coupled to the input of (2), (2) output is coupled to the input of (3), (3) output one tunnel directly is coupled to the input of (7), another road connects (4), (4) output is connected with the input of (5), (5) output is connected with (6), (6) output is connected with the control end of (7), and the output of (7) is received the input of (8), and the output of (8) is sent into AM7910 and carried out demodulation.

2, signal-noise separator according to claim 1 is characterized in that photoelectric isolating circuit is made up of operational amplifier UA741, photoelectronic coupler 4N25.

3, signal-noise separator according to claim 1 is characterized in that active bandwidth-limited circuit is made of LM324.

4, signal-noise separator according to claim 1 is characterized in that ac amplifier circuit is made up of MC1458.

5, signal-noise separator according to claim 1 is characterized in that switching circuit is made of MC4066.

6, signal-noise separator according to claim 1 is characterized in that DC restoration circuit is made of MC1458.

7, signal-noise separator according to claim 1 is characterized in that integrating circuit is made up of RC.

8, signal-noise separator according to claim 1 is characterized in that voltage comparator circuit is made of LM311.

9, signal-noise separator according to claim 1 is characterized in that amplitude limiter circuit is made up of MC1458 and 1N4148.

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