A triple-layer wideband transmitarray (TA) which works at 18.5 GHz with reduced profile is presented in this paper. The unit cell composed of three metal layers, each layer is etched on the corresponding dielectric substrate. The top layer consists of double square rings, the same as the bottom layer. The intermediate layer consists of a Jerusalem cross slot. The thickness of designed unit cell is 0.15λ, where λ is the wavelength in free-space. A large frequency range is implemented by parallel sets of phase curves generated by proposed unit cell. The magnitude of transmission coefficient is less than 1 dB and the phase shift range exceeds 360 degree across the entire frequency range. We design, fabricate and measure a TA operating at 18.5 GHz to show the validation of this paper. Through the measurement, we can obtain that the 1-dB gain bandwidth is 14.8% (17.5-20.3 GHz), and maximum gain is 22.5 dB at 18.5 GHz. The proposed transmitarray's maximum aperture efficiency is 46%.

In this paper, a novel broadband transmitarray (TA) design based on one-bit digital coding. The double-layer transmitarray element is composed of a notched square ring patches which is etched the upper layer of the dielectric substrate, and the lower layer is the same metal slit having the same shape as the notched square ring patch, but the notch direction is rotated by 180 • . By changing the physical dimensions of the notched square ring element, a phase coverage of about 360 • can be achieved. To realize the coding transmitarray, the phase compensation is fuzzified. Two kinds of elements with 0 and π phase responses to represent "0" and "1" elements for 1-bit digital coding are introduced. Theoretical rules of phase compensation fuzzified and a broadband transmitarray antenna are designed by coding unit cell. We design, manufacture and measure a digital coding transmitarray antenna by using the proposed element. The measured results show that the transmitarray has the 1-dB gain bandwidth of 25% (8.4 GHz -10.8 GHz). The proposed digital coding transmitarray antenna has a wide gain bandwidth. The measured results agree with the simulated results well, which verifies the feasibility and correctness of the proposed structure.

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In this paper, a highly efficient dual-band transmitarray antenna using cross and square rings elements is presented for X and Ku bands. The dual-band transmitarray is designed for downlink/uplink frequencies of Ku band satellite communications. The transmitarray element consists of four metal patches and two dielectric substrates. The metal patch is printed on both sides of the substrate. By optimizing the parameters, the transmitarray element can achieve a transmission phase coverage greater than 360° and work independently in both frequency bands. Then, a method to select the size of the element is proposed, so that all the elements in the array can realize the transmission phase of the two frequencies as much as possible. A 201-elements transmitarray antenna is fabricated and measured and the band ratio of the antenna is 1.13. The measured maximum gain at 11.5 GHz is 22.4 dB, corresponding to the aperture efficiency is 52.7%. The measured maximum gain at 13 GHz is 24.2 dB, corresponding to the aperture efficiency is 62.4%. The 1-dB gain bandwidths are 9.7% (10.8-11.9 GHz) at X band and 9% (12.6-13.8 GHz) at Ku band.