A 6-bit CMOS Phase Shifter with Active Balun and Three-Stage Poly-Phase Filter for Phased Arrays

A 6-bit high resolution active phase shifter using 0.18 μm CMOS process is presented for P-band phased array applications. An improved active balun converts single-ended signal to differential with high balance, wideband input/output matching and compact area. Three-stage poly-phase filter (PPF) outputs high quality broadband orthogonal signals among 300-800 MHz frequency range. Consequently, a phase shift with high phase shifting accuracy and low gain/phase errors can be obtained. Measurements show that the RMS phase error of the active phase shifter is <; 3.5° over 400-600 MHz and <; 5° in 300-800 MHz. The measured RMS magnitude error is below 1 dB and the mean gain is 4~5.5 dB in 300-800 MHz. The measured input and output return loss are both <; -12 dB at 300-800 MHz. The total power consumption is 14.7 mW under a supply of 1.8V. The chip size is 1.3×1 mm² including pads.