A 6-bit CMOS Active Phase Shifter for <italic>Ku</italic>-Band Phased Arrays

A 6-bit high-accuracy active phase shifter is developed in 0.13-μm CMOS technology for Ku-band phased arrays. Improved transformer balun with wriggly stub is applied to split the single input to differential and achieve high balance with reduced chip area. Two-stage polyphase filter (PPF) generates broadband I/Q signals with high accuracy. A main digital-toanalog convertor (DAC) controls the I/Q amplitude to achieve 6-bit phase resolution, while an auxiliary DAC compensates the amplitude/phase error introduced by balun and PPF. Consequently, high resolution along with low phase/gain error can be achieved. The phase shifter shows measured rms phase error of <;4° at 12-18 GHz and <;3° at 13-18 GHz. The measured mean gain is -2.5-1 dB, and the rms gain error is <;0.9 dB at 12-18 GHz. The total power consumption is 37.5 mW, and chip size is 0.75 × 0.32 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> excluding pads.