Design Techniques for L-C-L T-Type Wideband CMOS Phase Shifter with Suppressed Phase Error

Abstract

In this study, we designed a K-band CMOS switch-type phase shifter. Equivalent circuits of shift and pass modes were analyzed to minimize phase errors in a wide frequency range. In particular, the impedance inside the equivalent circuit of the pass mode was analyzed to derive a frequency region in which the equivalent circuit of the pass mode becomes an L-C-L structure. Based on the fact that equivalent circuits in shift and pass modes can be regarded as L-C-L structures beyond a specific frequency, a design methodology of the wideband phase shifter was proposed through slope adjustment of the phase according to the frequency of each of the two modes. To verify the feasibility of the proposed design methodology, a 20°-bit phase shifter was designed through a 65 nm RFCMOS process. As a result of the measurement at 21.5 GHz to 40.0 GHz, the phase error was within 0.87°.