Microstrip bandpass filters: Using novel dual-mode resonators

New challenges are constantly faced in the development of RF and microwave filters, which have not only sustained but fuelled microwave filter research over the many years. These developments have encouraged new solutions for the realization of compact, low loss, highly selective RF and microwave filters. This text presents a novel distributed dual-mode resonator configuration which allows the realisation of tunable, highly compact microwave bandpass filters. Many interesting and attractive characteristics of the resonator are explored in detail. Application of this resonator in bandpass filter design is discussed with examples illustrating the design process with theoretical and experimental results to showcase filter performance. All-pole, generalised Chebyshev and dual-bandpass filters are shown to be easily developed with the novel resonator while achieveing a highly miniature footprint and a wide stopband. Finally, by employing a novel non-linear distortion enhancement technique readily applicable to this resonator, the design of highly linear tunable filter is discussed.