Microwave bandpass filters with multiple couplings, designed using electromagnetic simulations and linear circuit optimization

In this paper a bandpass planar filter, with cross-couplings and with a pair of attenuation poles, is investigated. The equi-ripple in-band response and the location of the poles on the frequency axis can be precisely controlled by using a new technique which combines accurate electromagnetic field simulations and fast linear circuit optimization, allowing the design of bandpass filters with improved performances. To illustrate the procedure, a microstrip bandpass filter was designed, verified by em-field simulation, fabricated and tested. The response of the designed filter is in good agreement with the specification, confirming the possibilities of realizing microwave bandpass filters with rigorously controlled characteristics, with reduced design time and non-prohibitive computational effort.