In order to realize the miniaturization of quasi-Yagi antenna array, an antenna array with split-ring resonators (SRRs) based on two 7 units quasi-Yagi elements is designed in this paper. The radiation performance of the quasi-Yagi antenna array degrades significantly when array element spacing is reduced. After embedding SRRs on both sides of the miniaturized dielectric substrate surface, the S parameters and gain of array are significantly better than the array without SRRs, and the adjustable wave beam energy is also enhanced effectively. It indicates that the proposed antenna array with SRRs has good directional radiation performance under the miniaturize process at the operation frequency of 2.45 GHz, which could be widely applied in the fields of smart rail transportation and wireless power transfer.

Deep learning (DL) approaches have been increasingly adopted to design antenna autonomously. For obtaining geometry of the broadband quasi-Yagi antenna from its physic response images directly, we propose an inverse design approach based on the optimized bidirectional symmetry GoogLeNet, which can extract the required bandwidth information to redesign the geometric parameters of antenna without changing its physical structure. It demonstrates that the bandwidth of a reference quasi-Yagi antenna is improved from 0.6 GHz to 1.15 GHz through the proposed inverse design DL approach, and the measured bandwidth value of this redesigned quasi-Yagi antenna achieves 1.16 GHz, which is improved 93% actually. The numerical and measured results indicate that the proposed DL approach could significantly improve the performance of the existed quasi-Yagi antenna and present a new attempt to apply the image processing techniques in resolving physical problem.

A compact quasi-Yagi antenna with bent arms and split-ring resonators (SRRs) is proposed. Compared with traditional quasi-Yagi antennas employing straight arms, the resonant frequency of the proposed antenna could be always consistent with its center frequency, and there is no obvious frequency shift under the process of its miniaturization. The SRRs are adopted in the proposed compact antenna for a high gain of 6.58 dBi. The reliability verification of the proposed antenna radiation characteristics is further experimentally proved with the prototype measurement. The proposed quasi-Yagi antenna has an adjustable compact structure and low frequency offset and could be used in the precise point-to-point wireless communication environment.

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