An X-Band 7-Bit High Resolution and Ultra-Low Amplitude Variations Phase Shifter With Current Correction Technique

Abstract

In this brief, an X-band 7-bit digital-controlled vector-sum phase shifter (VSPS) with high resolution and ultra-low amplitude variations is presented. The 7-bit digital-to-analog converter (DAC) incorporating 2-bit quadrant control bits is employed to adjust the amplitude of In-phase/Quadrature (I/Q) signals, and synthesizing the desired phase, which achieves a minimum step control of 2.8125° within a full 360° range. Moreover, a current correction technique is proposed to address the challenges of degraded phase shifting accuracy caused by excessive phase stepping at quadrant intersections, as well as large amplitude variations due to the nonlinear change of transconductance with the square root of bias current. The VSPS, implemented in 130-nm CMOS technology, shows outstanding phase accuracy with the root mean square (rms) error of less than 0.93°, while the rms amplitude error is less than 0.16 dB over the frequency range of 8 to 12 GHz.