Miniaturization Design of Ultra‐Wideband Circularly Polarized Antenna Based on Vivaldi Structure

ABSTRACT This letter presents an innovative design of a miniaturized ultra‐wideband circularly polarized (CP) antenna based on a Vivaldi structure. The design employs four identical Vivaldi antenna elements arranged in a spatially rotated configuration on a dielectric substrate to achieve broadband circular polarization characteristics. A feeding network system incorporating three‐stage second‐order Wilkinson power dividers is specifically designed for phase control, delivering equal amplitude and a precise phase progression of 0°, 90°, 180°, and 270° across the 1.5–5.5 GHz frequency range. Prototype testing confirms an ultra‐compact geometry of 0.21 λ l × 0.21 λ l × 0.19 λ l ( λ l is the free space wavelength at 1.6 GHz), while demonstrating a 114.3% impedance bandwidth (IBW) and a 98.4% axial ratio bandwidth (ARBW). Measured results reveal stable radiation patterns and a peak circular polarization gain of 8.1 dBic. Combining broadband performance with spatial efficiency, this design proves particularly suitable for modern wireless communication scenarios with stringent requirements on antenna dimensions and frequency bands, such as satellite communications (SatCom) and 6G millimeter‐wave systems.