Wideband Transmitarrays Based on Polarization- Rotating Miniaturized-Element Frequency Selective Surfaces

We present a new low-profile, wideband, transmitarray design based on polarization-rotating (PR), miniaturized-element, frequency-selective surfaces (MEFSSs). These MEFSS unit cells rotate the polarization of the transmitted wave by 90° either in the counterclockwise or in the clockwise direction. Each PR element consists of three metal layers separated by two dielectric substrates. The constituent metallic layers comprise metallic strips with specific alignments to twist the polarization of the transmitted electromagnetic wave by ±90°. We used the two rotation directions to achieve a 0°/180° phase difference in the transmission mode to achieve a 1 bit phase shifter. We also show that variations in the unit cell dimensions can be combined with polarization rotation to create an additional 90° phase shifts, which can be combined with the PR phase shift mechanism to achieve a 2 bit phase shifter. We designed, fabricated, and experimentally characterized two illustrative transmitarray prototypes with 1 and 2 bit phase-correction patterns. The measured results agree well with the simulation predictions and demonstrate wideband operation for both arrays. The measured 3 dB gain bandwidth and maximum gain are 33.4% and 24.5 dBi, respectively, for the 1 bit prototype, and 24.1% and 27.2 dBi, respectively, for the 2 bit prototype.