Wideband bandpass filter design for D-band application

This paper presents the design and characterization of a wideband bandpass filter for millimetre-wave D-band application. The filter is implemented on a three-layer thin film structure using benzocyclobutene (BCB) silicon technology. Two stepped-impedance resonators are used to construct the bandpass filter, while the input/output coupling is achieved by coplanar waveguide (CPW) to stripline transition. The prototype filter is fabricated and measured. The measurement results agree with the simulation results well and exhibit a wideband bandpass filtering response with fractional bandwidth of 32.2% at 135.6 GHz. The mid-band insertion loss is only 2.94 dB.