Miniaturized CBCPW bandpass filter basedon thin film polyimide on lossy silicon

This letter reports a miniaturized conductor-backed coplanar waveguide (CBCPW) bandpass filter (BPF) based on a thin film polyimide layer coated on a lossy silicon. With a 20-μm-thick polyimide interface layer and back metallization, the interaction of electromagnetic fields with the lossy silicon substrate has been isolated, and as a result low-loss and low-dispersive CBCPW line has been obtained. The measured attenuation at 20GHz is below 1.2dB/cm, which is comparable with the CPW fabricated on GaAs. In addition, by using the proposed CBCPW geometry, a miniaturized Ku-band BPF was designed and its measured frequency response demonstrated excellent correlation with the predicted value which validated the performance of the proposed CBCPW geometry used for radio frequency integrated circuit interconnects and filter applications.