A Quasi-Elliptic Function Dual-Band Bandpass Filter Stacking Spiral-Shaped CPW Defected Ground Structure and Back-Side Coupled Strip Lines

A quasi-elliptic function dual-band bandpass filter (BPF) stacking spiral-shaped coplanar waveguide defected ground structure and back-side coupled strip lines is proposed, which allow two transmission paths to radio frequency signals. Each of them has quasi-elliptic characteristics and results in a respective passband. This can provide convenience to change one passband operating frequency independently of the other one. Several attenuation poles in the stopband are realized to improve the selectivity of the proposed BPF. Theoretical and experimental results with good agreement are presented