A Wideband Thin Transmitarray Antenna by Using L-Probe Patch Antenna With True-Time Delay

This letter presents a wideband thin transmitarray (TA) antenna by using low-profile L-probe patch antennas, which act as the receiving and transmitting antennas of the TA element. The receiving and transmitting antennas are connected by a microstrip-line phase shifter with true-time delay, so the TA element maintains low transmission loss and linear phase-shift characteristic within a wide frequency range. The continuous 360° phase shift is obtained by rotating the receiving antenna and changing the length of microstrip-line phase shifter, which is integrated with the L-probe of receiving antenna in the same substrate. Thus, the TA antenna achieves a high aperture efficiency, wide gain bandwidth with a reduced profile. For verification, a prototype of 132-element TA antenna operating at 14 GHz is fabricated and measured. The size of the element is 0.42λ0 × 0.42λ0, and the thickness of TA antenna is 0.13λ0 (λ0 is the wavelength in free space at the lowest working frequency). The measured peak gain is 22.2 dBi and the maximum aperture efficiency is 50.7%. The measured 1-dB gain bandwidth is from 12.6 to 15.2 GHz (18.7%). The measured results also show a good radiation pattern with low cross polarization of 30 dB.