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

fYear

1989

fDate

1-3 May 1989

Firstpage

206

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;

fLanguage

English

Publisher

ieee

Conference_Titel

Vehicular Technology Conference, 1989, IEEE 39th

Conference_Location

San Francisco, CA

ISSN

1090-3038

Type

conf

DOI

10.1109/VETEC.1989.40075

Filename

40075