Reconfigurable Modular Antenna System With Null Steering and Circular Polarization

The design and analysis of a modular antenna system that can achieve both multidimensional null steering and dual-sense circular polarization (CP) is presented. The system is built using compact elementary units, each comprising a wideband tunable phase shifter and a printed dipole, allowing a modular assembly for various operational modes. The tunable phase shifter, designed with a broadside coupling structure and varactor-tuned stubs, provides a 145° tuning range with ±2° phase imbalance and less than 1 dB insertion loss across the band 5–7 GHz. Reconfiguration is achieved by tuning the phase shifters, enabling both 1-D and 2-D null steering as well as dual-sense CP. In its 1-D configuration, the system achieves a null steering range of ±40° from the broadside with more than 15 dB null depth. The 2-D configuration extends this steering capability to two planes. A different configuration of modules enables left-hand and right-hand CPs with high purity, maintaining an axial ratio below 2.3 dB across the operation band. Experimental results align closely with simulations, underscoring the potential of compact, tunable phase shifters for versatile reconfigurable antenna systems.