Millimeter-Wave Wideband Dual-Polarized and Circularly Polarized ME-Dipole Reflectarrays With Linearly Polarized Feed

In this communication, the magneto-electric (ME) dipole structure combining the variable-length delay lines is first applied to the implementation of millimeter-wave (mmWave) wideband dual-polarized (DP) and circularly polarized (CP) reflectarray antennas (RAs). By simply adjusting the lengths of two delay lines, the phase manipulation and linearly polarized (LP)-CP conversion can be achieved simultaneously without increasing additional design difficulty. Fabrication and measurement of the proposed 16 $\times $ 16-element DP and CP RAs are carried out to verify the effectiveness of the design concept. Measured results indicate that the proposed DP RA can achieve individually controllable beams for the two polarizations at the desired directions within a wide 2-dB gain bandwidth of 29% (24.5–32.8 GHz) with a peak gain of 26.4 dBi. Besides, the proposed CP RA exhibits a wide 3-dB axial ratio (AR) bandwidth of 39.3% (23–34.25 GHz) and 3-dB gain bandwidth of 35% (23.2–33 GHz) with a peak gain of 25.2 dBic, which mitigates the underlying narrow-bandwidth problem existing in the CP RA fed by LP feed source. By virtue of wide bandwidth, stable gain response, flexible polarization conversion, relatively low profile and appropriate fabrication complexity, the proposed designs distinguish themselves as the promising candidates for diverse mmWave applications.