Distortion of SSB Transmission Due to AM-PM Conversion

It appears not to have been widely recognized that intermodulation distortion of a SSB-AM signal will be generated by AM-PM conversion effects present in amplifiers (such as traveling wave tubes), as well as by output-input nonlinearity. When the SSB-AM signal is carrying multichannel telephony this can be an important source of distortion. In the present paper, a formula is developed relating intermodulation distortion to AM-PM conversion level. The theory is also applied to two-tone testing, in order to allow comparison with experiment. The experimental results are found to be in satisfactory agreement with theoretical predictions.