IEEE Access (Jan 2021)
Digitally Reconfigurable Transmitarray With Beam-Steering and Polarization Switching Capabilities
Abstract
In this paper, a novel digitally reconfigurable unit-cell and $4\times 4$ transmitarray operating at X-band is proposed that allows the implementation of beamforming and polarization conversion operations in a programmable way. The lower layer of transmitarray responsible for beam steering consists of two PIN diodes and a circular type patch which has two states of operations with 0 and $\pi $ phase responses which we name “State1” and “State2”. “State1” and “State2” can be represented by a digital notation as “1” and “0” elements. Similarly, the upper layer of the transmitarray responsible for polarization conversion operation consists of two states of operation which we name as “State3” and “State4”, respectively. “State3” and “State4” also can be represented by digital notations as “1” or “0” elements. By coding “0” and “1” elements for the lower side of the transmitarray in a 1-bit sequence, we can steer the beam in our desired direction. Similarly, by coding “0” and “1” elements in a 1-bit sequence element for the upper layer, we can get X-polarized and Y-polarized beams. Combining the upper layer 1-bit sequence and lower layer 1-bit sequence, we can get both polarization conversion and beam steering simultaneously. A $4\times 4$ array with our proposed unit cell was designed and fabricated. A good agreement between simulated and measured results was observed. The proposed design is a promising concept because it can be fabricated using the conventional fabrication process, it is cost-effective compared to conventional phased array antenna for satellite and radar applications. A $4\times 4$ array was taken just to check the transmission and reflection coefficients of the proposed unit cells. A very small transmitarray was manufactured and experimentally characterized just as a proof of concept, to verify that the unit cells work properly.
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