Research Of Phased Transmitarray Antennas Technology

In recent years,millmeter waves have been widely used in communication systems.However,to compensate the large path loss at this frequency,antennas with high gain and beam scanning ability are required for long-distance wireless communication.Phased array antennas(PAAs)and transmitarray antennas(TAAs)are common high-gain beam-scan antennas.PAAs are greatly limited in practical applications due to the high cost and excessive power consumption.TAA also has some disadvantages such as narrow scanning range and slow scanning speed,resulting in low system efficiency.This paper presents a detailed design of TAA fed by a small scale PAA,which combines the PAA beam-steering capabilities and the TAA beam-focused characteristics.The contributions and novelties of this paper are summarized as follows:Firstly,the working principle of the phased transmitarray antenna is presented and a complete design method is proposed.A divisional multiple focus phase distribution based on geometrical optics(GO)is proposed to improve the performance of beam scanning.Moreover,particle swarm optimization(PSO)is introduced to provide optimized excitations for beam scanning.The complete design of PAA-fed TAA is formed by the phase distribution of the TAA and the excitation coefficients of the PAA.Secondly,according to the proposed optimization method,two high-gain and wide-angle beam scanning PAA-fed TAAs are designed,which consist of frequency selective surface(FSS)elements and cavity backed patch antenna elements.The first one achieves a scan coverage from-30° to +30° with a gain of 30.9 dBi and the scan loss is less than 2.1 dB.The second one enables elevation beam scanning over-45° to +45° with a gain of 31.1 dBi and the scan loss below 3.1 dB.In both cases,the height-to-diameter ratio is only 0.28.Compared with other relevant works,this work has a lower profile,the higher gain and the better scanning performance.For experimental verification,the first TAA was fabricated and measured,whose results agree reasonably well with the simulated ones.Finally,a PAA-fed TAA with full power excitation is design for the application of base station.To improve the effective isotropic radiated power(EIRP)of the system,the phase distribution of the TAA adopts concentric random optimization.By controlling the excitation phases of the PAA,an antenna with the scan coverage from-15° to +15° is achieved.The measured results show that the proposed antenna has obviously improvement of the EIRP than traditional PAA.Thus,the cost of the system is significantly reduced.