Digital Quieting Tone Design Based On Dsp

With the rapid development of wireless communication technology, communication equipment surrounding electromagnetic environment is also more and more complex, the impact of noise and interference on the communications equipment is also growing, requirements of wireless radio communication with speech communication function to quieting tone technology is becoming more and more high. The in-depth study of the IF digital processing technology, based on SNR estimation techniques and speech feature extraction techniques, combined with high cost performance of DSP chip TMS320C6748, puts forward a digital quieting tone design method based on DSP. The main research work are as follows:(1) Study the background and significance of the quieting tone technology, analyzed about the present situation of the quieting tone technology at home and abroad, summarized, and based on the carrier and speech combined quieting tone method, proposed the quieting tone method based on SNR and speech characteristics.(2)Study the differential drive chip, A/D converter and DSP, FPGA, such as main chip, the use of the method, And on this basis, combined with this topic research goal, completes the digital quieting tone circuit hardware circuit design.(3) In order to get good quality of speech signal, a AM IF digital demodulation method is presented, and detailed introduces the AGC and bandpass sampling, anti aliasing filter and the AM demodulation design method of DSP.(4) In order to distinguish the signal quality, and to distinguish between different levels of quieting tone, proposed the quieting tone method based on SNR. By COSTAS PLL design to solve the problem of the extraction of the signal-to-noise ratio parameter inaccurate; By filter transform design to solve the problem of carrier frequency offset range and filtering effect can not meet the requirements at the same time; By self-recovery phase-locked loop fast design to solve the problem of phase-locked loop can not track larger frequency offset; By modulation recognition design to solve the problem of difficult to determine the quieting tone threshold modulation changes; By several statistical decision design to solve the problem of signal-to-noise ratio quieting tone door unstable.(5) In order to distinguish between speech and noise, proposed the quieting tone method based on speech characteristics. By sliding window design to solve the problem of quieting tone processing delay larger; By extracting autocorrelation characteristics of speech signal to solve the problem of noise and interference effect larger; By several statistical decision design to solve the problem of speech feature quieting tone door unstable; By timer closing quieting tone door design to solve the problem of speech pauses caused headphones or speaker issue "Kacha Kacha harshness;(6) The use of the state of the signal-to-noise ratio and speech characteristics quieting tone door, through a joint decision type, we get the ultimate state of quieting tone gate. Thus, not only make quieting tone function stronger anti-jamming and anti-noise performance, and can according to different equipment working environment, the real-time adjust quieting tone level, to meet the needs of the users of the equipment.(7) Proposed a set of effective, feasible test scheme, and the scheme of test. Tests show that this article describes the design method to achieve the requirements of the research objectives.