A Microwave Feed-Forward Experiment

This paper describes an experimental microwave amplifier, designed around the Western Electric 461A traveling-wave tube, which operates with extremely low modulation products over a 20-MHz-wide microwave radio channel. The experimental results provide a fair assurance of the capability of such amplifiers for field use, with a prospect of significantly increasing the channel capacity of microwave radio systems by permitting the use of single sideband AM rather than FM transmission. This work is part of a continuing effort to explore and exploit feedforward error control techniques. Feed-forward error control was originated by Harold S. Black in 1924,1 a precursor by several years to his more famous accomplishment of feedback control. Through 1960, it was viewed, somewhat, as a curiosity, 2 and was used only in the context of a McMillan circuit 3 which fused the two Black concepts of feedback and feed-forward. Of interest in view of the present publication is U. S. Patent 2,592,716 issued in 1952 to W. D. Lewis, who extended McMillan's ideas to microwaves using traveling-wave tubes and other microwave hardware, to yield redundancy. As proposed, there are fundamental differences 2879