Phase-Agile Dual-Resonance Single Linearly Polarized Antenna Element for Reconfigurable Reflectarray Applications

A single-layer dual-resonance tunable reflectarray unit cell supporting a single linear polarization and operating at X-band is presented in this paper. The unit cell is composed of a cross element and a ring element, both capacitively loaded with varactors, enabling reconfigurability. An equivalent circuit is developed and verified to demonstrate the dual-resonant operational theory and aid in the design of the dual-resonant unit cell. The equivalent circuit is used to demonstrate the underlying physics of dual-resonant reflectarray antennas and provides a systematic design procedure. The proposed design is evaluated using both full-wave simulations and measurements. The effects of external and mutual coupling and frequency tuning range on the loss and fractional bandwidth of the unit cell are presented. A continuous phase range of 375 degrees with a peak and average loss of 4.78 and 3.09 dB at 10.0 GHz, respectively, is measured. The presented analysis provides guidelines for optimizing the unit cell performance required for high-efficiency beam-scanning reflectarray antennas.