Miniature 2×2 Rectangular Patch Array Antenna for Ka-band Application with the CP Characteristics

This article presents a miniaturized 2 × 2 microstrip patch array antenna designed for circular polarization. The patch elements are strategically oriented at 0°, 90°, 180°, and 270° to achieve the desired polarization. Each patch is individually fed by microstrip lines connected through a matching network featuring resistive power dividers and two λ/4 transformers. The antenna size is 22mm x 17mm x 0.9mm with an FR-4 (dielectric constant, ε<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> = 4.3) substrate and operates in the Ka-band, making it suitable for satellite links, terrestrial microwave communication, radar, and vehicle speed detection. Simulations conducted using CST Microwave Studio reveal a resonant frequency of 26.988 GHz with an impedance bandwidth of 1.949 GHz and a return loss of -61.46 dB, indicating excellent matching. The antenna demonstrates a gain of 5.71 dBi and a directivity of 8.94 dBi, alongside an axial ratio bandwidth of 1.271 GHz, confirming its effective circular polarization capabilities.