Experimental investigation of single groove parallel coupled microstrip line bandpass filter with harmonic suppressed

Abstract

This paper describes, the experimental performance of a fabricated single grooved Parallel Coupled Microstrip Bandpass Filter (PCMBF) on a low cost laminate board, with improved passband response and first harmonic suppression for various operating bandwidth. 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, on a low cost laminate board, showed excellent harmonics suppressions with optimized groove. Then, two-stage bandpass filters of different operating bandwidth were designed for optimized groove. It was then implemented on a low cost laminate board and tested. The measured results validate real harmonics suppression performance with controllable single groove parameters.