Reconfigurable unit-cells for beam-scanning transmitarrays in X band

Two different designs of electronically reconfigurable unit-cells with 1-bit phase quantization are studied for beam scanning transmitarrays in X band. These two unit-cells are printed on two identical Rogers RO4003 substrates and are composed of four metal layers (passive patch - ground plane - bias lines - active patch). In the first case, two p-i-n diodes are integrated on the active patch in order to control electronically the transmission phase. The experimental performances of this unit-cell are in very good agreement with the full-wave simulations. The measured insertion loss and 3-dB transmission bandwidth are equal to 2.1 dB and about 15% respectively. As the insertion loss strongly depends on the series resistance of the p-i-n diodes in the ON-state, a second unit-cell design based on RF-MEMS switches is presented. The theoretical performances of this second structure exhibit very low insertion loss (0.8 dB) and a broad 3-dB transmission bandwidth of 16%.