A Robust Superdirective Beamforming Approach Based on Embedded Element Patterns

Superdirectivity has the potential to increase the array gain to the square of the number of antennas, pushing the spectral efficiency of wireless communications to a higher level. However, calculating the superdirective beamforming vector in the presence of strong coupling is a challenging task due to the lack of the coupling depiction. Another practical obstacle is the sensitivity problem—superdirective antenna arrays are susceptible to excitation errors, necessitating precise excitation controls. To address these problems, we first introduce the embedded element pattern (EEP), which describes the coupled radiation field. We propose an EEP-based beamforming (EEPB) method to achieve superdirectivity. To mitigate the sensitivity problem, we propose an EEP-aided orthogonal complement-based robust beamforming (EEP-OCRB) algorithm for computing a robust superdirective beamforming vector. Full-wave simulations and real-world experiments utilizing a prototype of a 5-dipole superdirective antenna array validate both the superdirectivity of the EEPB method and the robustness of the EEP-OCRB algorithm to excitation errors.