Design and implementation of a multibeam filtering antenna array using compact 3 × 3 Nolen matrix aided by grey wolf algorithm

This paper presents a novel multibeam filtering antenna array based on a compact 3 × 3 Nolen matrix integrated with HRR filters for solar observations. The design facilitates the simultaneous recording of solar radio flux density and sky background flux density, streamlining calibration processes. The use of stub-loaded transmission line (SLTL) couplers achieves a significant 43.4% reduction in the size of the Nolen matrix, enhancing compactness. The hairpin ring resonator (HRR) filter with two transmission zeros (TZs) is employed to ensure electromagnetic compatibility (EMC). Given the limitations of conventional manual design methods, the intelligent grey wolf algorithm (GWA) is adopted to optimize the physical parameters of the Nolen matrix layout, realizing rapid and accurate achievement of the desired performance. The $-6.2\pm 0.15$ dB transmission coefficient and 0°, −120°and $+120$°of output phase differences within 2° phase error are accomplished at 2.8 GHz. Finally, the proposed multibeam filtering antenna array is fabricated and measured to confirm its ability to generate the required three beams with filtering characteristics. The measured results have a good agreement with the simulated results.