On the origin and characteristics of single-sided angle modulation

The invention of SSB-FM (single-sideband frequency modulation) is usually attributed to E. Bedrosian. I wish to point out, without detracting in any way from Bedrosian's significant contributions to communication theory and practice, that SSB-FM is fully covered by US Patent 3054073, which is in the name of K.H. Powers and is assigned to the Radio Corporation of America (RCA). The patent was issued about one month before Bedrosian's 1962 paper was published [E. Bedrosian, "The analytic signa] representation of modulated waveforms," Proc. IRE, vol. 50. pp. 2071-2076, October 1962]. Turning now to Glorioso's and Brazeal's paper [R.M. Glorioso and E.H. Brazeal, Jr., "Experiments in 'SSB FM' communication eyetems," ibid., vol. COM-13, pp. 109-116, March 1965], the author suggests that their Fig. 15 and the conclusions based upon it must be interpreted cautiously. Some months ago the author generated SSB-FM waves on a Fourier synthesizer and envelope-detected them amidst noise. While this work was done for another purpose, and while he did not use the postdetection logarithmic circuit employed by Glorioso and Brazeal, his records lead to conclusions different from theirs. Specifically, he questions their Fig. 15 for small values of input S/N. The difficulty here, however, may lie in definitions of, and measurement techniques for, S/N. More generally, he suggests that S/N is not a good criterion for assessing SSB-FM performance near threshold.