Calibration of the Cylindrical Polarimetric Phased Array Radar via GPS-Disciplined Bistatic Pattern Measurement

The cylindrical polarimetric phased array radar (CPPAR) project acts as a case study in cylindrical array design for applications in dual-polarized weather radar, allowing fundamental research such as beamformer optimization and weather measurement verification to be conducted. Developed at the University of Oklahoma’s Advanced Radar Research Center (ARRC), the CPPAR system relies on GPS-disciplined reference clocks for its transceivers and nearly synchronous triggering to transmit and receive bistatically from an isolated measurement horn located in the main array’s far-field, allowing the array’s element and beam patterns to be measured. This measurement scheme introduces phase distortion resulting from time-varying differences between the two reference clocks’ frequencies, a phenomenon which adds a time-varying bias to baseband phase measurements, rendering them unusable without significant post-processing. In this article, our approach to managing this and other measurement-specific challenges is detailed. To provide appropriate background information, the CPPAR’s relevant high-level system design, control systems, and theory is also discussed. Lastly, our method for deriving array bias terms from measured element patterns is detailed. The procedures outlined in this article were successfully deployed to measure element patterns and in turn derive power and phase calibration weights for the system, which ultimately allowed for the completion of two major experiments using the platform.