Hardware-in-the-loop experimental assessment of SDR-based phase-conjugating cross-eye jamming arrays

Phase-conjugating (PC) cross-eye jamming has been proposed as an electronic countermeasure (ECM) capable of inducing systematic bias in monopulse angle estimates. While prior work established an analytical framework and tolerance analysis, the experimental evidence under realistic hardware constraints remains limited. This paper presents a hardware-in-the-loop (HIL) experimental assessment of PC cross-eye jamming implemented with software-defined radio (SDR) hardware in a controlled guided-wave environment. The jammer is realized with a dual-channel USRP B210 performing digital phase conjugation and enforcing a 175° phase offset on one channel, while a monopulse receiver is implemented using a second B210 SDR. A calibration procedure is used to compensate static inter-channel offsets, and a GPS-disciplined reference clock is used on the jammer to improve LO stability and reduce phase errors. Antenna pattern effects are emulated numerically prior to applying the monopulse processing. Experimental results confirm that the measured monopulse responses follow the trends predicted by the analytical framework under the tested phase and amplitude conditions, which confirms the robustness of the proposed framework.