A 6 Bit Vector-Sum Phase Shifter With a Decoder Based Control Circuit for X-Band Phased-Arrays

This letter presents a 6 bit vector-sum phase shifter with a novel control circuitry for X-band phased-arrays using a 0.25 mu m SiGe BiCMOS technology. A balanced active balun and highly accurate I/Q network are employed to generate the reference in-phase and quadrature vectors. The desired phase is synthesized by modulating and summing the generated reference vectors using current steering VGAs that are controlled by a decoder based control circuit. The phase shifter resulted in a measured RMS phase error < 2.8 degrees between 9.6-11.7 GHz and < 5.6 degrees between 8.2-12 GHz, achieving 6 bit phase resolution. The chip size is 1.87 x 0.88 mm(2), excluding pads. To the best of authors' knowledge, this is the first demonstration of a digitally controlled 6 bit vector-sum phase shifter for X-band.