Dual-Band Lowpass-Bandpass Filter with Three Element Resonator Configuration

This paper presents a new type of the lumped element dual-band lowpass-bandpass filter network and its numerical synthesis method based on the objective function. Two synthesized examples with the different passband widths illustrate the effectiveness of the synthesis method. As a prototype circuit it provides a good candidate for the design of the dual-band lowpass-bandpass filter up to microwave frequency band since it can be easily transformed into a distributed circuit of physically realizable configuration. The measured results of the fabricated filter up to 2700MHz validates experimentally the prototype filter.