Small-Size Square Ring 1-Bit Reconfigurable Transmitarray Unit Cell for C-Band Applications

The paper presents a reconfigurable linear polarized transmitarray unit cell design with 1-bit phase quantization for C-band applications. The unit-cell structure consists of two square ring patches of reduced size, which are connected using a coupling element. Incorporating p-i-n diodes inside the coupling element allows controlling the current flow direction in the antennas and providing a 180 degrees phase difference. An analysis of the unit-cell insertion loss contributed by small-size antennas and coupling between them is discussed. The p-i-n diode parasitic parameters are taken into consideration of the unit cell performance simulation. It was shown that the insertion loss caused by the p-i-n diodes parasitic parameters can be reduced. The original biasing circuitry providing p-i-n diodes control voltage is proposed. Simulation results of the reconfigurable unit cell are validated by measurements in a waveguide. As a result of measurements, the insertion loss is -2.3 dB at 5.9 GHz, the reflection coefficient module is less than -20 dB, the phase difference error does not exceed +/- 1 degrees in the passband, while 3-dB bandwidth corresponds to 180 MHz (3.4%).