RFDA-Based Range-Dependent Beamfocusing for Precision Electronic Warfare in Near-Field Urban Scenarios

The evolution toward large-aperture antenna systems has extended the operational environment into the radiating near-field region, not only for future 6G networks but also for modern tactical Electronic Warfare (EW) platforms operating at microwave frequencies. A critical challenge in this domain is the "depth of focus" limitation of traditional phased arrays, which creates high-intensity interference corridors along the boresight, posing severe collateral risks to friendly forces co-located with the target. To address this issue, this paper proposes a novel range-dependent beamfocusing architecture utilizing a Random Frequency Diverse Array (RFDA). By introducing random frequency offsets to a vehicle-mounted Uniform Linear Array (ULA), the proposed method effectively decouples range and angle dimensions, enabling precise energy concentration at the target while suppressing radiation at other distances. Simulation results demonstrate that the RFDA-enhanced system achieves a sharp "thumbtack-like" focal spot at the target range while synthesizing a "spatial silence" zone at the friendly unit's location. Compared to conventional beamforming, which exposes the friendly unit to nearly 85% (-0.7 dB) of the peak jamming power, the proposed approach suppresses the interference to less than 3% (-15.8 dB), providing a robust 15.1 dB isolation margin. This study confirms that RFDA-based beamfocusing is a viable solution for ensuring physical layer security and operational safety in dense, cooperative EW environments.