Ultrashort Wave Communication Mute Key Technology Research And Validation

Ultrashort wave radios are widely used in the field of operations command of thearmy. The quality of speech communication has a direct impact on the remote commandsystem of the army scheduled and orders accurately issued. Under normal circumstances,the wired telephone almost has no background noise. But in the complex environmentof ultrashort wave communication, the speech will be polluted by all kinds of noise, thenoise level、the received signal level、 the communication distance and dopplermotionhas a great influence on the quality of the speech.When making a call by ultrashort wave radio,we have an experience that while thereceived signal level is high, the noise level is low or no noise, and the speech is veryclean; on the other side, the noise level is high, especially the noise is very loudly whenthere are no speech. The squelch function of ultrashort wave radio is to solve theproblem of speech quality and to reduce noise, to turn off the audio circuit when thereare no speech, and to denoise the polluted speech, ultimately to get the quality of speechsignal improved.We design a squelch system on the ultrashort wave communication hardwareplatform. This system can detect the speech signals in the received signals, turning offaudio circuit when there are no speech signals in the received sigals, and suppressingthe nosie if the speech signal is in the low SNR cases.First, the thesis discusses present technology of squelch of ultrashort wavecommunication. The key technology of squelch is consist of speech detection an noisesuppression.Secondly, according to the the squelch needs and conditions of ultrashort wavecommunication hardware platform, we design the squelch program of ultrashort wavecommunication, and accomplish the digital squelch technology on the ultrashort wavecommunication platform hardware which core is TMS320C6748chip.Finally, we build a testical platform to verify the function and performance of squelchsystem of ultrashort wave communication. The test results show that the squelchfunction of ultrashort wave communication is good, and the system can suppress thenosie if the speech is in the low SNR cases, so the SNR of noisy speech is improved.In this paper, the designed squelch program of ultrashort wave communication notonly can have the the ability to detect the speech signal, but also can suppress noisewhen the speech signal is in the low SNR cases, the SNR of noisy speech signal beingincreased5.1dB. It has a good application prospect in the next generation of newultrashort wave radio.