An 18-GHz 6-bit Phase Shifter for RF Beamforming With LO Quadrature Generation and Optimized Gain and Phase Accuracy

This letter presents a Ku/K-band 6-bit phase shifter designed for RF beamforming systems. The proposed design shifts quadrature signal generation to the local oscillator (LO) path, simplifying quadrature signal calibration while reducing signal loss typically introduced by RF-path quadrature generation (QG). This improvement helps preserve the signal-to-noise ratio (SNR) and enhances overall system performance. A key innovation in this work is the integration of fractional vectors into both the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> channels, enabling precise phase and gain alignment with minimal errors. Fabricated in a 90-nm CMOS process, this circuit occupies a 0.3 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> core area. Measurement results demonstrate that the proposed phase shifter achieves a root-mean-square (rms) phase error below 0.61° and an rms gain error of 0.22dB, while consuming a total of 33 mW dc power, and achieves a 3-dB bandwidth across 16.5–21.5 GHz.