By R. Richard Bell and P. Rebeles, TRW Lawndale Laboratories and Semiconductor Operation
There have been several papers presented in the past dealing with nonlinear distortions in tube and transistor devices and amplifiers. Papers by Reynolds, Thomas , Akgun and Strutt discuss the various forms of distortion cancellations that can occur in devices. Nearly all of these papers have dealt with two dominant nonlinearities at the component level. Lambert has addressed the cancellation of Second order effects in CATV amplifiers and Lieberman in Systems. Because of the wide spread acceptance of amplifier hybrids we have frequently been called upon to aid in the explanation of distortion build-up behavior. What we aim to illustrate here are several unique cross-modulation and triple beat cancellations that may occur in actual systems. It will be demonstrated that these cancellations, or "poorly behaved nulls" may be extremely sensitive to any of the following operating conditions such as level, temperature, amplifier spacing, channel loading or channel spacing. Also we would like to propose a new test method which may give a better indication of a systems multi-channel capability.