High Performance Microstrip Bandpass Filters with Nonsymmetrical Parallel Coupled Lines

A new improved technique for the design of bandpass microstrip filters based on the image parameter concept is presented. Realizability is guaranteed by manufacturing constraints being incorporated into the design procedure. Passband limitations associated with a previous technique are circumvented by the use of nonsymmetrical parallel-coupled sections. Both computed and experimental results demonstrate excellent filter performance in terms of bandpass attenuation, associated with a reduced number of elements.