Realization of Extremely High and Low Impedance Transforming Ratios Using Cross-Shaped Impedance Transformer

Abstract

In this brief, the design methodology of microstrip impedance transformers with extreme (i.e., extremely high and extremely low) impedance transforming ratios is proposed by deploying the cross-shaped structure (CSS) configuration. The proposed impedance transformer can significantly eliminate the line width limitation of traditional quarter-wave impedance transformer and hence an extremely wide range of impedance transformation can be easily realized. At the same time, the impedance transformer provides a good frequency selectivity, especially in the narrowband regime. To demonstrate the outstanding performance of proposed CSS impedance transformer, two examples, with the load-to-source impedances of 2000-to-50 $\Omega $ and 5-to- $50~\Omega $ , respectively, are presented and prototyped. The measurement results are in good agreement with the simulated counterparts and hence, the outstanding performance of extreme impedance transforming ratios is validated.