An adaptive biasing method for SRD comb generators

This paper presents an adaptive biasing method for step recovery diode based comb generators which are controlled by a software routine. The aim is to provide the maximum possible harmonic output power for a given configuration and different input frequencies during input power variation. This increases the usefulness of comb generators as harmonic phase reference sources for non-linear VNA measurements in the millimeter wave range. The effects are studied on a SRD comb generator which is able to generate -30...-20 dBm harmonics in the 50 to 60 GHz range when wideband terminated. It is shown that depending on the combination of input power and frequency, different bias level behaviors for maximum harmonic output power over frequency exist. Data for maximum power level bias is provided for output frequencies up to 60 GHz. Additionally the effect of subharmonic comb frequency generation is demonstrated.