A highly selective super-wide bandpass filter by cascading HMSIW with asymmetric defected ground structure

The half mode substrate integrated waveguide (HMSIW) possesses the highpass characteristic of SIW but the size is nearly half reduced. A recently proposed asymmetric defected ground structure (ADGS), composed of two square headed slots connected with a rectangular slot transversely under a microstrip line, exhibits quasi-elliptic-function band-reject characteristics around 3 GHz with high selectivity. Based on the circuit model, the structure of the ADGS is modified to perform well at about 16 GHz. By combining the HMSIW and the modified ADGS, a super-wide bandpass filter operating at about 8-16 GHz with high selectivity at both upper and lower band is proposed. Both simulated and measured results have been presented to demonstrate the validity of the proposed wideband filter.