Millimeter-Wave CMOS 30/80 GHz Sharp-Rejection Dual-Band Bandstop Filters Using TFMS Open-Stepped-Impedance Resonators

In this brief, for the first time, dual-band bandstop filters (DBBSF) for millimeter-wave operation at 30/80 GHz bands are presented in 0.18 mu m CMOS process. The filter design is based on TFMS shunt open-ended stepped-impedance resonators, which exhibit dual stopband response with impedance controlled center frequencies and bandwidths. Lossless transmission line model is used for theoretical analysis, where the conditions for acquiring two stopbands and to achieve good stopband isolation are investigated using single and double resonators. Furthermore, an improved design for good passband at mid-band has been proposed, resulting in a DBBSF that could also replace a wideband bandpass filter with sharp-rejection on both sides. Two prototype filters with optimally compact geometries are fabricated and characterized to demonstrate dual-band bandstop characteristics at 30/80 GHz. The measured results are in good agreement with full-wave electromagnetic simulations.