Simulation-Driven Design for a Dual-Band Impedance Transformer with Improved Bandwidth

In this paper, a dual-band impedance transformer (DBIT) with improved bandwidth performance is presented, of which matching phase and impedance bandwidths' properties are demonstrated by using the image parameter theory. It is discovered that the introduced odd-even mode resonant frequency ratio is the core parameter to ensure the second passband enlargement and the structural miniaturization simultaneously. Aggressive space mapping (ASM) technique is adopted as the simulation-driven design strategy. Key ASM steps are detailed for synthesizing a specified planar microstrip DBIT operative at 2.4/5.8 GHz, testifying the relatively high efficiency and robustness of the proposed synthesis technique.