Performance Improvement for a Varactor-Loaded Reflectarray Element

The application of varactor diodes as phase-shifting devices in reflectarrays has received considerable attention because it represents a low-cost and low-complexity solution for the creation of scanning antennas with continuous phase tuning. The main issues related to the design of varactor-loaded reflectarrays are the difficulty in the correct characterization of the unit cell, and the limited phase range achievable by changing the polarization voltage of the device. The contribution presented in this communication attempts to cover both these aspects. In particular, a simple model for the analysis of a varactor-loaded microstrip reflectarray cell is presented, and then employed to increase the patch´s phase response to 360^?? . The result is then validated experimentally, with the results showing good agreement between simulated and measured data.