A Compact Dual-Layer Antenna With Reconfigurable Polarization and Continuous Frequency Coverage

This letter presents a compact microstrip antenna with simultaneous frequency and polarization reconfigurability. The antenna employs a dual-layer coupled radiating structure, in which the top and bottom patches are excited by the same coaxial probe and redistribute the RF surface current. This configuration reduces the current flowing through the lossy p-i-n diode network, thereby suppressing diode ohmic loss and improving radiation performance. By controlling the effective radiating region through diode switching, the antenna provides continuous frequency coverage from 4.32 GHz to 6.76 GHz (44.04%) achieved by overlapping operating states. Meanwhile, the rotational symmetry of the radiating sectors enables 16 switchable linear polarization orientations. The antenna occupies a compact footprint of 0.14/λ 2 and achieves a peak gain of 6.4 dBi, corresponding to a normalized gain of 45.7 dBi/λ2. Compared with the single-layer reference, the dual-layer configuration reduces diode loss and increases the radiated power by 225% in a representative state.