Resonant Frequency Calculations for Microstrip Cavities (Correspondence)

Microstrip circuits in metal enclosures frequently exhibit loss spikes. These spikes are sometimes shown to be related to cavity resonances whose frequency can be calculated from enclosure dimensions using known theory. These calculations are presented graphically so that resonant frequencies may be determined for a particular structure or resonances within a band avoided through judicious choice of enclosure dimensions. Comparison of experimental and calculated results are tabulated.