Low-profile high-gain circularly polarized antenna using high-order mode microstrip patch

<h2>Abstract</h2> This paper presents a circularly polarized (CP) square-shaped microstrip patch antenna with low profile and high gain radiation based on high-order mode. Radiated electric fields are derived from a combination of the TM₀₃ and TM₃₀ modes with equal magnitude and 90° phase difference, leading to high gain and CP operation. The patch is installed with four side-slots, which contributes to reducing the sidelobe level and antenna's dimensions as well. Further size miniaturization can be achieved by loading four crossed slots in proximity to the patch's corners. An antenna prototype with overall dimensions of 1.58 λ × 1.58 λ × 0.02 λ (λ is a free-space wavelength) is fabricated for measurements to validate the design concept. The measured data indicates that the proposed antenna can achieve good performance at 4.0 GHz with an operating bandwidth of 10 MHz and high gain of about 11.8 dBi.