Title :
Optimum pre-emphasis for FM transmission with frequency-domain voice scrambling
Author :
Akaiwa, Yoshihiko ; Okamoto, Eiji ; Furuya, Yukitsuna
Author_Institution :
Dept. of Comput. Sci. & Electr., Kyushu Inst. of Technol., Iizuka-city, Japan
Abstract :
Optimum pre- and de-emphasis are theoretically investigated for FM and PM transmission, including frequency-domain scrambling for voice security. Using a linear system model, the optimum frequency characteristics for pre- and de-emphasis filters are given as functions of the voice signal spectrum, demodulator output noise spectrum, and the scrambling method. Comparisons of the maximum attainable SNR (signal/noise ratio) are made for various cases including plain voice (nonscrambling) and secured voice scrambled by spectrum inversion, reverberation, and DFT (discrete Fourier transform) spectrum transformation, assuming simple voice and noise spectra
Keywords :
filtering and prediction theory; frequency modulation; radiocommunication; voice communication; DFT spectrum transformation; FM transmission; PM transmission; de-emphasis filters; demodulator output noise spectrum; discrete Fourier transform; frequency-domain voice scrambling; linear system model; maximum attainable SNR; optimum de-emphasis; optimum frequency characteristics; optimum pre-emphasis; radiocommunication; reverberation; signal/noise ratio; spectrum inversion; voice security; voice signal spectrum; Bandwidth; Discrete Fourier transforms; Filters; Frequency domain analysis; Frequency modulation; Power system modeling; Privacy; Radio communication; Reverberation; Signal to noise ratio;
Conference_Titel :
Vehicular Technology Conference, 1989, IEEE 39th
Conference_Location :
San Francisco, CA
DOI :
10.1109/VETEC.1989.40075
