Experiments in "SSB FM" Communication Systems

The investigation reported in this paper describes the generation and detection, with a conventional discriminator, of narrow-band SSB FM, and presents the threshold characteristics of the system. The generation and detection of wide-band SSB FM is also reported. The narrow-band signal is easily detected with a limiter discriminator and offers improved signal-to-noise ratios (SNRs) over conventional FM for modulation indexes less than approximately 0.25. The wide-band signal is generated by an exponential frequency multiplier which multiplies the frequency and modulation index of the narrow-band signal. This signal is detected as an AM signal and the detected envelope is passed through a logarithmic transfer device to recover the original signal. Since "single-sideband frequency modulation" is not an appropriate description of this special case, the authors have called it "Single-Sided Wide-band Analog Modulation" (SSWAM).