A Compact-Size and High Isolation Dual-Band Coplanar-Waveguide Bandpass Filter

A compact and high isolation CPW dual-band bandpass filter using the interdigital resonator structures (IDTRS) is presented for application in GPS and IEEE 802.11 b WLANs. Since the two passbands can be tuned individually, the filter has more design freedoms. IDTRS are used to generate and control the second passband frequency. Two transmission zeros in the stopband are realized to improve the selectivity of the filter, and to achieve a high isolation higher than 30 dB between two passbands. Good agreements between the simulated and measured results demonstrate our proposed structure.