A 6-bit CMOS Active Phase Shifter for Ku-Band Phased Arrays

A 6-bit high-accuracy active phase shifter is developed in 0.13-mu m 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-to-analog 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 degrees at 12-18 GHz and <3 degrees 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 x 0.32 mm(2) excluding pads.