A Compact UWB Antenna with a Fixed WLAN Band-Notch for Low-Power Wireless Systems

This paper presents a compact, ultra-wideband (UWB) antenna designed for low-power wireless systems requiring upper WLAN (5.725–5.825 GHz) interference mitigation. The antenna integrates a tapered-slot radiator for broadband impedance matching with a dual C-shaped slot resonator on the ground plane to achieve targeted signal rejection. By leveraging the resonant properties of the slots, interference from the WLAN band is suppressed without requiring any active components, ensuring zero additional power consumption for the filtering function. The fabricated prototype, with a compact size of 31 × 40 mm2, demonstrates an operational bandwidth from 2.68 to 16 GHz (S11 < −10 dB) with a stable peak realized gain of 2–10 dB and a radiation efficiency above 80% across the passband. At the notch center frequency of 5.72 GHz, the gain decreases by 6.4 dB and the radiation efficiency falls to 0.6, there is effective signal rejection in the target notch band, and there are stable, omnidirectional H-plane radiation patterns. The reflection coefficient at the notch frequency rises to approximately −2.2 dB, effectively suppressing radiation in the WLAN band while maintaining stable gain and omnidirectional patterns in the remaining UWB spectrum. The proposed design offers a simple, low-cost, and energy-efficient solution for achieving spectral coexistence in power-constrained UWB applications.