Mahmud, R H; Skaik, T; Shang, X; Wang, Y (2025) A highly selective circularly polarized filtering slot antenna based on stub-loaded resonators. IEEE Antennas and Wireless Propagation Letters, 24 (7). pp. 1645-1649.

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Abstract

This article presents a novel approach for designing highly selective circularly polarized (CP) filtering antennas. It is based on rectangular waveguide cavity resonators that are directly coupled with each other. Capacitive stubs are loaded to the cavity ends without increasing the circuit size to create adjustable transmission nulls. Two orthogonal radiating slots are opened onto the side-wall of the last coupled resonator to achieve end-fire CP radiation. An equivalent circuit model is presented to represent the cavities integrated with capacitive-stubs, and the model results are numerically analyzed. This approach is demonstrated by designing, simulating, and fabricating a fourth-order bandpass filter (BPF) and a fourth-order CP filtering antenna operating at X-band. The measured and simulated results are in excellent agreement, showing a quasi-elliptic response it is with an insertion loss of 0.18 dB over the passband, and a gain value of 7.0 ± 0.1 dBic. The 10-dB reflection coefficient (S11) and 3-dB axial ratio (AR) bandwidths are 7.5% and 5.5%, respectively. The competitive performance and compactness of the proposed devices make them promising candidates for communications and radar applications with stringent frequency selectivity requirements.

Item Type:	Article
Subjects:	Electromagnetics > RF and Microwave
Divisions:	Electromagnetic & Electrochemical Technologies
Identification number/DOI:	10.1109/LAWP.2025.3543757
Last Modified:	06 Oct 2025 09:17
URI:	https://eprintspublications.npl.co.uk/id/eprint/10179