Ultrabroadband Circularly Polarized Antenna Array Based on Microstrip to SIW Junction

• Published in: IEEE transactions on antennas and propagation 2022-03, Vol.70 (3), p.2346-2351
• Main Authors: Zerfaine, A., Djerafi, T.
• Format: Article
• Language: English
• Subjects: Antenna arrays; Antenna design; Antenna feeds; Antennas; Bandwidth; Circular polarization; Coupling; Delays; Gain; High gain; Hybrid structures; junction; Linear polarization; Microstrip antenna arrays; microstrip line (MSL); Microstrip transmission lines; Millimeter waves; Phase deviation; Power dividers; sequential rotation (SR); Slot antennas; substrate integrated waveguide (SIW); Substrate integrated waveguides; Transmission lines
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2021.3119098

This communication presents a circularly polarized (CP) antenna array with ultrabroadband characteristics and a high gain for millimeter-wave applications. The CP is achieved by arranging eight linearly polarized (LP) tapered slot antenna elements in a circular arrangement based on sequential rotation (SR) techniques. The hybrid structure takes advantage of microstrip line (MSL) compactness in the feeding network and the capabilities of the substrate integrated waveguide (SIW) in antenna element design. A new T-junction MSL-to-SIW transition with a wide range of coupling ratios is used to serve as a wide power divider in the compact SR-feeding network. A detailed parametric study is carried out to demonstrate the effects of the coupling mechanism between the two transmission lines and to find the optimal configuration for the elements of the proposed antenna array. A tradeoff is made between antenna coupling, phase deviation, and overall size to achieve a compact structure with robust performances. An eight-element antenna array prototype is fabricated through the PCB process with a size of 57\times 48\times96 mm 3 . Measured results show a 3 dB axial ratio bandwidth of about 49% over the entire 22.8-37.7 GHz range and a maximum gain of 18 dBi.