Techniques for Digital Array Radar Planar Near-Field Calibration by Retrofit of an Analog System

Digital arrays for radar applications are becoming more common as researchers seek to capitalize on the advantages of digital beamforming, and RF System on Chip (RFSoC) technology matures. Calibrating these digital array radars (DAR) presents new challenges. Primarily, the entire system, from the array face to the digital backend, must be tested as a single unit on these highly integrated designs. Rather than characterizing a system by comparing its analog response to an analog stimulus, engineers must now characterize system performance by comparing a digital response to an analog stimulus. In this paper we will show how a traditional analog planar near-field range (NFR) may be retrofitted to accommodate an RFSoC based DAR operating in the receive mode, address the implementation of controls, discuss clock and timing for DARs in the lab, detail a triggering technique to produce time synchronous data, illustrate post processing techniques for generating far field and hologram plots, and demonstrate the technique with a testbed DAR comprised of a Xilinx RFSoC operating at L-Band.