Experimental performance of harmonic suppressed Bandpass Filter

In this paper, the experimental performance of a fabricated single grooved broadband parallel coupled microstrip bandpass filter (PCMBF) with improved passband response and first harmonic suppression is presented. The suppression of the first harmonic spurious response is possible through transmission zero frequency realignment method. A single groove of specific dimensions located at the center of the parallel coupled line has been employed for the realignment of the transmission zero and first harmonic frequencies. An implemented single-stage bandpass filter with various coupling gaps showed harmonics suppressions with optimized groove. Then, two-stage bandpass filters of different operating bandwidth were designed for optimized groove. It was then implemented and tested. The measured results validate real harmonics suppression performance with controllable single groove parameters.