Dual-Band Focused Transmitarray Antenna for Microwave Measurements

A dual-band focused transmitarray antenna designed by using frequency selective surfaces (FSS) technique is proposed in this paper. Compared with the traditional transmitarray antenna, the proposed antenna has advantages of good ability to focus electromagnetic wave in the dual-band, high resistant of poor measurement environment and easy to process. The transmitarray consists of four identical metal phase shift layers, each of which is separated by an air gap. The elements distributed on metal layer are composed of a I-shaped slot at the center and four L-shaped slots with central symmetry. The change of I-shaped slot length affects the change of phase in low frequency band and the change of L-shaped slot length affects the change of phase in high frequency band. The mutual coupling between the two kinds of slots can be neglected. The proposed antenna consisting of a transmitarray and a feed has been analysed, simulated, and measured. The results show that the average focal spot diameter (SD) is 35.2 mm at 12 GHz and 24.5 mm at 18 GHz, and the dual-band focused transmitarray antenna can operate in two frequency bands 11.8-12.2 and 17.8-18.1 GHz. Simulated and measured results show that the proposed antenna has good concordance, making it possible for various microwave measurements.