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Frequency-Diverse Metasurface Antenna With Hybrid Bunching Methods for Coincidence Imaging

A frequency-diverse metasurface antenna with hybrid bunching methods for coincidence imaging is proposed in this paper. The hybrid frequency-diverse bunching metasurface antenna contains an excitation system, a frequency-diverse metasurface and a double-layer-metal-plate bunching system. Firstly, the excitation system of the metasurface antenna is divided into two parts, the bunching-excitation module and the random-excitation module. The bunching-excitation module includes a seven-element coherent antenna array that can generate bunching beams with 80 degree beamwidth from 32GHz to 36GHz; and the random-excitation module includes eight antenna elements distributed evenly to excite the frequency-diverse metasurface in the same working bandwidth. A multilayer feed system is also designed utilizing the stripline structure to feed both the bunching-excitation module and the random-excitation module. Secondly, six kinds of metamaterial elements possessing disparate transmitted phases are selected to constitute the frequency-diverse metasurface. The frequency-diverse metasurface is loaded to the excitation system to generate the frequency-diverse radiation patterns. Then, in order to achieve a narrower bunching angle, a double-layer-metal-plate bunching system is designed. Furthermore, the performances of the proposed bunching metasurface antenna, including the radiation efficiency, the reflection coefficient and the correlation coefficients of radiation patterns at different frequencies are evaluated. Finally, the coincidence imaging experiment is carried out using the proposed hybrid bunching metasurface antenna and the image of the target is reconstructed successfully. The designed is verified by both simulations and measurements.