1-Bit Reconfigurable Unit Cell Based on PIN Diodes for Transmit-Array Applications in $X$ -Band

An electronically reconfigurable unit cell with 1-bit phase quantization (0°/180°) is proposed for X-band linear polarization transmit arrays. It consists of two rectangular patch antennas loaded by U- and O-slots and connected by a metallized via-hole. The transmission phase is controlled using two p-i-n diode switches integrated in the O-slot. An equivalent lumped-element circuit model is implemented and compared successfully to full-wave simulations. The numerical results are validated experimentally using an ad-hoc waveguide simulator. The prototype exhibits low insertion loss (1.8 dB) with the same level for both phase states, a broad 3-dB transmission bandwidth (14.7%), a 1-dB compression point of 13-15 dBm, and a gain of 5 dBi at 9.75 GHz. The performance and simplicity of the proposed unit cell make it attractive to build electronically steerable transmit arrays in X-band.