A Differential Reflection-Type Phase Shifter Based on CPW Coupled-Line Coupler in 45nm CMOS SOI
This paper presents a mm-wave fully differential coplanar waveguide (CPW) vertically-coupled lines coupler and a reflection type phase shifter (RTPS) based on the proposed coupler. The use of grounded strip line structure for vertical coupling in CPW based coupler provides not only the improved coupling properties than the edge coupling but also provides the opportunity of using surrounding area efficiently to reduce area. The proposed coupler and phase shifter are designed and fabricated in 45nm CMOS SOI technology. Measured insertion loss of the coupler is ~ 6 dB from 18 to 43 GHz. A digitally controlled parallel LC load is used for controlling the phase of the phase shifter. Measured phase tuning range is 115 degrees, with insertion loss variation of 4.5 to 9 dB, for a frequency range of 39 GHz to 45 GHz. Total drawn area of the phase shifter is 0.214 mm2. The area of the proposed RTPS is smaller than the recently published state-of-the-art structures.