Application of aggressive space mapping (ASM) to the efficient synthesis of stepped impedance resonators (SIRs)

In this paper, it is shown that aggressive space mapping (ASM) optimization can be applied to the synthesis of stepped impedance resonators (SIR). Specifically, the considered resonators are SIRs shunt connected to a microstrip transmission line, also known as stepped impedance shunt stubs (SISS). These resonators are thus described by means of a shunt connected series LC resonator. It will be shown in this work that the proposed ASM optimization algorithm provides convergence in few steps, being able to provide the layout corresponding to the desired inductance and capacitance value to a very good approximation. As an application example, an order-3 elliptic-function low pass filter, consisting of a SISS cascaded between two series connected inductors, is designed and fabricated. The results reveal that the agreement between the measured response and the ideal elliptic-function response is good up to frequencies beyond the transmission zero location.