Design and measurements of circularly polarized millimeter-wave phased array antenna using time delay transmission lines

This paper proposes a cost-effective millimeter-wave (mmWave) phased array antenna incorporating circular polarization (CP) capabilities for beam scanning applications. An initial evaluation involves the examination of an open single-loop antenna. Subsequently, the phased array design is presented, featuring a 4-element circular loop phased array antenna designed to operate at a frequency of 27.5 GHz. The precise control of the main beam steering is achieved through the implementation of a corporate feed network and four-phase shifters employing transmission line time delay techniques. To expand the CP bandwidth, the design incorporates concentric parasitic open-loop antennas. Experimental findings confirm the configuration’s ability to facilitate left-hand circular polarization (LHCP) radiation over a scanning angle span of 50°, specifically ranging from −25° to +25°. This accomplishment aligns with the stringent criteria for maintaining a radiation pattern with an axial ratio (AR) of less than 3 dB across a broad frequency spectrum. Additionally, the design achieves a peak gain of approximately 11 dBic in combination of a total efficiency surpassing 85% throughout the CP bandwidth. In addition, the proposed design offers the advantages of compact size and low cost. Prototypes were fabricated and measured, with results closely matching simulations. Owing to the achieved radiation properties, the proposed design demonstrates a potential for practical applications in satellite and wireless communications systems.