Improvement of Radiation Efficiency for Frequency Beam-Scanning Antennas Using a Subarray Topology

In this paper, a new approach is proposed to improve the radiation efficiency of a frequency beam-scanning antenna. In this proposed approach, the entire antenna is divided into two subarrays and each subarray includes one primary slow-wave line. Parameters of these two primary slow-wave lines are identical to each other, to achieve identical progressive phase difference between elements within either subarray. Meanwhile, a secondary slow-wave line is designed and connected to the beginning of one of the two primary slow-wave lines, to introduce an additional phase difference between these two subarrays. The above setup provides more flexibility for the allocation of phase-delay units and thus enables a possibility to reduce the overall length and transmission loss of the slow-wave line utilized in a frequency beam-scanning array, which leads to a better radiation efficiency. In order to demonstrate the above topology, a novel microstrip-to-stripline power-divider and a novel broadband magneto-electric dipole element are proposed in multilayer configurations, for the realization of a 20-element prototype centered at 8.75 GHz. A reduction of 29.2% is achieved for the overall loss compared to a conventional array when achieving a scanning range of ±30°.