A new optoelectronic technique for microwave passive structures tuning

An optoelectronic technique useful for microwave passive structures tuning is reported. It is based on the biasing of a photoinduced plasma loading an open terminated microstrip line. Experimental results for a tapped half-wave resonator are presented. Sharp notch characteristics with a few dB insertion loss and a tunable resonant frequency with a matching better than 45 dB are obtained by varying both the optical power and the DC bias. The observed frequency shift is more than 30% below the dark resonant frequency and is carried out without altering the Q-factor. Moreover an experimental investigation on the realisation of an optoelectronically tunable bandstop filter seems to give promising results.