A Compact Millimeter Wave Polarization Reconfigurable Double Patch Antenna

A polarization-reconfigurable single-fed patch antenna loaded with a smaller parasitic stacked bandwidth-enhancing patch are reported in this letter. The antenna system is optimized to operate at 29 GHz with three polarization modes that can be reconfigured electronically. The structure consists of two Rogers 3003 substrates of thicknesses of 0.25 and 0.50 mm for the driven antenna and the parasitic one, respectively. The main antenna's ground layer has four square loops etched out to excite the current paths on the driven patch needed for circular polarizations. These four slot loops are placed in the driven patch's four corners and are controlled with four P-I-N didoes. By shorting two diagonally placed slot loops, a circular polarization (CP) mode is created while shorting all of them will result in linearly polarized (LP) radiation. The measured gain and relative impedance bandwidth (BW) of the left-hand circular polarization (LHCP) are 3.1 dB and 5.4%, respectively. Similar results are obtained for the RHCP due to symmetry in structure and biasing conditions. The LP case reached a gain of 4.0 dB and a relative impedance BW of 5.45%. The overall size of the antenna system is 10.2×14.1×0.784 mm ³ with a radiation efficiency above 90%. Measurement results are compared and validated with simulations.