A Novel Slow-Wave Structure for Millimeter-Wave Filter Application on Bulk CMOS

A novel slow-wave structure for microstrip lines is proposed. Unlike conventional slow-wave structures such as photonic bandgap (PBG) and ladder microstrip lines, which only deal with the substrate, ground plane or the signal line of a microstrip separately, the periodic patterns of this new slow-wave structure are etched in both the conductive metal strip and the ground plane of the proposed microstrip line. No extra drilling through the substrate is required. The designed slow-wave structure exhibits that size reduction and minimal loss increase can be achieved simultaneously. 2nd-order rectangular open-loop filters with and without implementing the proposed slow-wave structure have been designed and fabricated in the millimeter-wave (mm-wave) range on 65-nm bulk CMOS. Both simulations and measurements demonstrate the new design has a 52.7% size reduction with only 0.5 dB penalty in transmission loss. To author's best knowledge this compact filter is the first reported mm-wave filter using slow-wave structure on bulk CMOS.