Investigation of waveguide-below cutoff resonators for solid-state active devices

The use of passbands below cutoff in waveguide structures for realisation of microwave circuits using active devices is reported. Experiments were performed on waveguide structures with cutoff frequencies of 14, 17, 21, 26 and 31GHz using Gunn and avalanche diodes. Mechanical tuning ranges of nearly 10% were obtained at frequencies in the lower half of Xband.