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 0.42λ
₀
× 0.42λ
₀
, and the thickness of TA antenna is 0.13λ
₀
(λ
₀
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.