Current generator for 6-bit active phase shifter

A current generator for a broadband 6-bit active phase shifter (PS) with low RMS phase error and low RMS gain error using 0.18 μm BiCMOS technology is presented. The ratio of two output currents of the current generator determines the phase shift. In the proposed current generator, the two output currents are controlled independently, which makes it possible that the ratio of the two output currents can be accurately approaching the desired value. The control scheme for 6-bit phase generation is set such that the sum of the two output currents is constant for all phase states and results in a constant gain. With the proposed current generator, the 6-bit active PS obtains a RMS phase error less than 2.5° and a RMS gain error less than 0.55 dB at 5–20 GHz.