A passive mechanically tunable conformal aperture coupled phase shifter integrated with micron-sized magnetic particles for radar systems.

This work presents a conformal Micron-Sized Magnetic Particle Aperture-Coupled (µMP-AC) phase shifter for C-band (7.2-8.2 GHz) applications, implemented on a flexible Rogers RT5880 substrate. Unlike conventional phase shifters that rely on complex electrical biasing networks, the proposed design employs a purely passive tuning mechanism based on Magnetic Induction-Responsive Cavities (MIRCs). These MIRCs are embedded within the flexible substrate in concentric ring configurations in the aperture-coupled region. By mechanically moving a single small magnet, the effective permittivity of the particle-loaded substrate varies, enabling controlled linear phase shifts of 0°, 20°, and 40° on both planar and cylindrically curved surfaces (R = 100 mm). The proposed µMP-AC phase shifter is comprehensively validated through full-wave electromagnetic simulations, equivalent circuit modeling, and experimental measurements conducted in an anechoic chamber. Experimental results show close agreement with the equivalent circuit model results, demonstrating an insertion loss better than 5 dB and a return loss of 37.24 dB at 7.3 GHz. The measured phase error using Network Analyzer is approximately 1.2°, confirming stable linear phase behavior. By eliminating external DC biasing circuits, the proposed µMP-AC phase shifter offers a compact, low-complexity solution for conformal radar front ends and beam-steering systems.