Multi-feed Plane Wave Generator for Compact OTA Multi-Target Emulation With Joint Angle-Delay-Doppler Control

Over-the-air (OTA) radar target emulation is an important method for evaluating the sensing capabilities of integrated sensing and communication (ISAC) and radar devices. Conventional single-feed compact antenna test ranges (CATRs) are generally limited to a single target direction, while multi-feed angular-synthesis methods commonly used in radar testing still require far-field illumination over the device-under-test (DUT) aperture. To overcome these limitations, this paper proposes a radar target OTA emulation framework based on multi-feed plane wave generator (PWG). The key capability is the simultaneous emulation of spatially close targets from different directions with joint angle–range–Doppler control. Target range is emulated through the corresponding delay, while Doppler and the complex echo coefficient are controlled by a channel emulator. Meanwhile, a multi-input amplitude and phase matrix (APM) maps each independent target-signal path to a dedicated PWG excitation vector that synthesizes the corresponding incident plane wave over the same test zone. This enables multiple target directions to be reproduced as local plane waves at a test distance substantially shorter than the conventional far-field requirement. The framework is experimentally validated at 3~GHz using a real $1\times 11$ phased-array DUT. The PWG–DUT separation is 1.6~m, substantially shorter than the 7.2~m Fraunhofer distance of the DUT. At this separation, the synthesized $0^{\circ }$ and ${10}^{\circ }$ incident waves each exhibit an amplitude peak-to-peak error of 1.0~dB. Across two four-target angle–delay cases and one two-target angle–velocity case, the estimated target parameters show angular deviations within $1^{\circ }$, interpolated delay errors within 2.4~ns, and velocity errors within 0.15~m/s.