Design of integrated millimetre wave microstrip interdigital bandpass filters on CMOS technology

With communication systems designed for operation in the millimeter wave frequencies it is now possible to have most of the transceiver implemented on a single CMOS die. An important system component that is required to ensure regulatory compliance is the RF bandpass filter. Unfortunately to date RF bandpass filters have been difficult to integrate on CMOS because of filter size and undesirable performance due to the conductive substrate. In this paper a six step method for the design of integrated interdigital bandpass filters on CMOS is presented. The utility of the method outlined in the paper is demonstrated for an on-chip integrated mm-wave interdigital bandpass filter designed and fabricated on 0.13 um bulk CMOS. The fabricated filter has a centre frequency of 55 GHz and exhibits an insertion loss of -4.5 dB and a return loss of better than -13 dB. This band pass filter demonstrates the feasibility of building integrated RF transmit receive bandpass filters for the front-end of wireless systems operating in the millimeter wave band on bulk CMOS.