Noncontacting measurement of power in microstrip circuits

This paper describes the use of a loop coupler probe for noncontacting measurement of power in microstrip circuits. The additional uncertainties, compared to contacting measurements, are investigated. The sensitivity of the coupling to positioning errors gives an uncertainty contribution in the same order as when using galvanically contacting techniques. The uncertainty due to probe directivity is comparable to the uncertainty when galvanically contacting internal parts of the circuit board. The impact of the probe on the waves on the circuit board is also investigated. In addition to the laboratory investigation of a probe, noncontacting measurements on a series produced microwave system are included. They agree well with contacting measurements.