A New Technique for Multimode Power Measurement

A new and simple technique for measuring total power flow to within ± 1 db in an overmoded waveguide has been developed. A set of fixed probes (typically, 40 probes) samples the electric fields normal to the surface of an enlarged waveguide section. The enlarged waveguide and a dispersive line stretcher permit quick determinations of power delivered to a matched load when the power is propagating in a large number of modes. Extension to the case of a mismatched load is also discussed. This technique is useful for measuring spurious emissions of microwave transmitters and power flow in millimeter and submillimeter waveguides.