Measuring Return-Loss Resonances to Estimate RF Wall Loss in MM-Wave Coupled-Cavity Circuits

Wall losses in millimeter-wave coupled-cavity circuits are found from return-loss resonance measurements without consideration of resonance coupling conditions. Changes in the circuit resonator length for a fixed coupling geometry can alter the resonator input impedance and the resonance curves for a given resonance mode. Calculations of the unloaded Q's for both overcoupled and undercoupled conditions for a set of resonance curves show that one result of each pair of calculations is near the correct value.