Bandwidth Recovery in Super-Directive Antenna Arrays Leveraging the Frequency Pulling Technique
Conference
Koutinos, AG, Zekios, CL, Georgakopoulos, SV. (2025). Bandwidth Recovery in Super-Directive Antenna Arrays Leveraging the Frequency Pulling Technique
. 2015 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING, 9-12. 10.1109/AP-S/CNC-USNC-URSI55537.2025.11266840
Koutinos, AG, Zekios, CL, Georgakopoulos, SV. (2025). Bandwidth Recovery in Super-Directive Antenna Arrays Leveraging the Frequency Pulling Technique
. 2015 IEEE INTERNATIONAL SYMPOSIUM ON ANTENNAS AND PROPAGATION & USNC/URSI NATIONAL RADIO SCIENCE MEETING, 9-12. 10.1109/AP-S/CNC-USNC-URSI55537.2025.11266840
The directivity of N-element arrays with small inter-element spacing (less than 0.25 λ) can exhibit superdirective characteristics. Specifically, the directivity of an N-element end-fire array of isotropic radiators can approach N2 as the spacing between the elements tends toward zero. However, achieving such performance is extremely challenging, as the reduced interelement spacing leads to significant coupling between the elements, which diminishes the operating bandwidth and efficiency of the array. In this work, we address these challenges and we design a two-element monopole array with an inter-element spacing of 0.1 λ, leveraging the frequency pulling technique, which increases the antenna's bandwidth. As a result our array achieves a reflection coefficient of less than -10 dB across a fractional bandwidth of 19.77%, which matches the fractional bandwidth of a single-element monopole antenna over a ground plane and without sacrificing radiation efficiency. Namely, the design results in an average maximum realized gain of 6.7 dB, across its entire bandwidth of operation.
