A High Aperture Efficiency 1-bit Reconfigurable Reflectarray Antenna with Extremely Low Power Consumption

In this communication, a 1-bit reconfigurable reflectarray antenna (RRA) providing high aperture efficiency is presented for beam scanning applications. Each element is configured as an aperture-coupled patch antenna composed of a radiating patch, a slotted ground for feed of the patch, a microstrip delay line, and a p-i-n diode switch. Unlike conventional methods, the p-i-n diode switch is not placed on the microstrip line but instead is inserted strategically at the center of the coupling slot on the ground layer. In this novel configuration, the elements of the RRA do not endure the loss through the p-i-n diode switches. The loss associated with the p-i-n diode in the proposed configuration is very small since only a small part of the RF currents flows through the diode in the ON state. Two phase states with a phase difference of 180°±20° are realized from 4.9 to 5.7 GHz. The reflection loss of each element is limited to less than 0.1 dB in both the ON and OFF states. To demonstrate the feasibility and performances of the proposed approach, a $14\times14$ -elements RRA is fabricated and measured. The measured aperture efficiency is above 18.8% in the entire band of 4.9-5.7 GHz, with a peak value of 36.5%. Furthermore, the efficiency stays almost unchanged, even when the equivalent resistor of the p-i-n diode varies from 0.9 to $9 \Omega $. This is used to lower the bias forward currents of the p-i-n diodes to lower the power consumption to merely 1.9 mW for the 196-elements RRA.