A Wideband Bandpass Filter by Integrating a Section of High Pass HMSIW with a Microstrip Lowpass Filter

This paper presents a wideband bandpass filter based on the highpass or cutoff characteristic of the half mode substrate integrated waveguide (HMSIW) and the lowpass characteristic of a microstrip lowpass filter. The HMSIW can be seen as a highpass filter because it is inherent sharp cutoff in lower frequency. A section of HMSIW and a microstrip lowpass filter can be cascaded to form a wide-band filter. A prototype is designed and implement with the passband from 7.1-16.6 GHz, 74% bandwidth with low insertion loss and a flat good group delay in pass band are achieved.