Constraints on Efficient Control of Tunable Impedance Matching Network Based on Barium-Strontium-Titanate Thick-Film Varactors

This paper focuses on the control of tunable lossy matching networks base on barium-strontium-titanate varactors. With the varactors´ characteristic, the existence of the optimality, i.e. maximal transducer gain, is investigated, and then compared with criteria of minimal reflection. A simple conjugate gradient method is demonstrated to achieve the global optimum. The determinative constraints from the network quality factor and resolution of digitalization are illustrated, whose limitation on the efficiency of the control is finally demonstrated by the measurement of a prototype.