$W$ -Band Low-Profile Transmitarray Antenna Using Different Types of FSS Units

A low-profile transmitarray (TA) antenna consisted of three different types of frequency-selective surface (FSS) unit cells and a “short” feed horn is proposed. The FSS unit cells, which have different magnitude and phase responses, are properly arranged on one layer of a substrate to enhance the phase-shift range. The proposed TA with a thickness of 0.127 mm (0.042 λ0 at 100 GHz) is placed near the feed aperture to achieve a low-profile TA antenna. The full TA prototype is fabricated and measured. The maximum gain measured at 100 GHz is 23.8 dBi, which has an 8 dB improvement compared to the feed without increasing the radiation aperture size. A relative bandwidth of 15% is obtained within 3 dB gain variations. The cross-polarization level is -43.4 and -47.9 dB for E- and H-planes, respectively. A maximum gain of 24.5 dBi with an aperture efficiency of 46.1% is achieved at 97.7 GHz. This method considerably reduces the complexity of TA and achieves a much more compact structure.