Single-Ended Quadrature Coupler-Based VSWR Resilient Joint mm-Wave True Power Detector and Impedance Sensor

Intelligent reconfigurable RF/millimeter-wave (mm-Wave) front ends primarily rely on built-in-self-test (BiST) circuits for real-time performance monitoring, particularly in phased arrays, where antenna elements' driving impedance varies substantially during beam steering due to the undesired element couplings. This severely degrades the power amplifier's (PA) performance. To address this problem, we propose a quadrature coupler-based voltage standing wave ratio (VSWR)-resilient mm-Wave joint impedance/true power detector integrated with a PA using the GlobalFoundries 45-nm CMOS silicon on insulator (SOI) process. A comprehensive theoretical comparison between the traditional and proposed coupler sensors is presented, including implementation details and design tradeoffs. Design guidelines for both the proposed coupler sensor and the integrated PA are presented to maximize sensing accuracy. The detailed data processing techniques are explained to accurately extract the sensor outputs and highlight hardware limitations. At 38 GHz, the proposed sensor measures the antenna impedance for VSWR = 3:1 with a maximum |Gamma| and angle Gamma error of 0.238 and 28.9 degrees respectively. The 90 degrees coupler network demonstrates a 16-dB dynamic range with an error within +/- 0.5 dB for 50-omega power sensing, as well as sensing the real power delivered to a complex antenna load for VSWR = 3:1 with less than +/- 3.35-dB power sensing error. The chip die occupies an area of 1.31 x 1.36 mm(2), while the sensor alone occupies an area of 0.47 x 0.971 mm(2).

Automated summary

This study proposes a quadrature coupler-based impedance/power detector for mm-Wave applications integrated with a power amplifier (PA). It successfully addresses the issue of driving impedance variation caused by undesired element couplings in phased arrays. The research provides design guidelines and performance evaluation based on a comprehensive comparison with traditional coupler sensors.