Antenna RCS minimization using load tuning

This paper synthesizes antenna RCS using load tuning, beginning with the derivation of the theoretical load impedance to achieve minimum RCS (MRCS) based on antenna radiation and conjugate-matched scattering parameters. This condition is utilized to obtain feasible MRCS zones and minimize backward RCS (BRCS) for the dipole and microstrip patch antennas. The dipole antenna exhibits a full feasible MRCS zone with a BRCS reduction of 77 dB at the resonant frequency, a 63% relative -10dB reduction bandwidth, and a full plane of reduction angles compared to the conjugate-matched condition. However, mismatching of MRCS loading significantly affects the dipole received power. Conversely, the microstrip patch antenna has a feasible MRCS zone that excludes forward directions and demonstrates a negligible mismatching level with a BRCS reduction of 35.5 dB at the resonant frequency, a 0.67% relative reduction bandwidth, a 50 degrees reduction in H-plane, and a 20 degrees reduction in E-plane compared to the conjugate-matched condition. Tuning the load reactance between conjugate-matched and MRCS loadings results in a trade-off between BRCS reduction and the received power. The calculated MRCS load for specific incident direction is applicable for nearby incidence directions, demonstrating applicability with misalignment. The findings validate the efficiency of using load-tuning method with the derived condition to minimize RCS within specific incident angles.