Use of low dielectric constant substrates for microstrip time-delay triggered TRAPATT oscillators

Our experimentation with microstrip trapatt oscillators of the type described by Davies et al.1 has indicated that the feasibility of such a design is dependent on the ratio of strip width to dielectric height (W/h) for the substrate used for a given microstrip-line impedance. For example, realisation on a polyguide substrate (¿r = 2.32) of 1.58 mm height failed to give coherent oscillation due to unexpected transient voltage variations shown up by time-domain-reflectometry tests. However, simple modifications to the microstrip design to remove the transient voltage variations led to considerable improvement in the performance of the oscillator, and coherent behaviour was then obtained.