Compact Slow‐Wave CMOS Wilkinson Using an Artificial Ground Structure

ABSTRACT

A compact, broadband, two‐way Wilkinson power divider/combiner is presented, created in 0.18‐ CMOS for use between 60 and 90 GHz. The suggested design uses stacked M5–M6 slow‐wave transmission lines to shorten the physical quarter‐wave length without needing extra matching capacitors, which allows for a condensed, meandering arrangement. Because of the strong broadside coupling between the stacked conductors, the suggested line has a phase constant about 43% greater than the standard structure at 75 GHz. This lets the necessary electrical length be achieved with a considerably shorter physical line. Rather than using M1 as a direct shielding ground, a recurring M1 structure is put under the signal lines as an electromagnetic field‐control layer, while the actual RF ground reference is made by the conductive ground under the substrate. Furthermore, an RC isolation network offers frequency‐shaped odd‐mode damping for wideband isolation. A back‐to‐back setup is used for precise on‐wafer characterization. The measurements show an extra insertion loss of 0.5 dB at 75 GHz, a return loss exceeding 20 dB at all ports, and an isolation greater than 34 dB from 60 to 90 GHz within a small 0.086  core area. The suggested structure works well for small mmWave CMOS front‐end uses.