A Ka-Band 360° Digitally-Controlled Passive Phase Shifter in 65-nm CMOS

Abstract

A digitally-controlled 360° passive phase shifter is presented. The phase shifter is developed from coplanar waveguide with ground shield (CPWG). The propagation constant is shifted by switching between two sets of ground lines while the characteristic impedance is kept constant by placing additional switched capacitors. MOS switches are optimized to achieve a flat insertion loss with accurate phase shift. The phase shifter is fabricated in 65-nm CMOS and occupies a core area of 0.24 mm2. Measurement results show that the phase shifter operates with 6.7° steps and an RMS phase error of 1.3° across 360° range at 35 GHz. The average insertion loss is 14 dB at 35 GHz with an RMS gain error of 1.3 dB. In addition, the phase shifter operates with 5.2° steps and an RMS phase error of 1.0° across 290° range at 28 GHz. The average insertion loss is 10.7 dB and the RMS gain error is 0.4 dB at 28 GHz.