Further investigations on the operating modes of millimeter-wave Gunn oscillators

A simple experimental system is described which permits simultaneous monitoring of all the
W
-band and
U
-band spectral components generated by a W-band GaAs transferred electron (Gunn) oscillator. By examining the voltage and mechanical tuning behavior of several such oscillators their harmonic operating mode has been confirmed. Discussion of a theoretical treatment of the fundamental and harmonic mode is presented to highlight the likely pitfalls in the interpretation of the tuning behaviour seen from a crossguide oscillator test circuit. This combination of practical and theoretical results is used to show that the recently published claim for nonharmonic operation of
W
-band GaAs TEO's is not yet proven.