Compact Millimeter-Wave SPDT Switches and Wilkinson Power Combiners Implemented by LC-Based Spiral Transmission Lines

This article proposes an LC-based spiral transmission line structure, which can effectively reduce the area of ON-chip transmission lines. The quarter-wavelength transmission line realized by this transmission line structure can be widely used in millimeter-wave circuits design. Based on the LC-based spiral transmission line structure, a 28-GHz single-pole double-throw (SPDT) switch and a 37-GHz Wilkinson power combiner are implemented with an area of only 0.028 mm² in 65-nm CMOS. Measurement results indicate that the SPDT switch has an insertion loss of less than 1.5 dB and an isolation better than 23.7 dB in the frequency range from 20 to 35 GHz. The insertion loss and the isolation of the Wilkinson power combiner at 36.9 GHz is 0.9 and 30.3 dB, respectively.