Ku Band Power Combining Reflectarray Antenna

In modern wireless communications,it is necessary to ensure efficient signal-to-noise ratio at receiver in order to guarantee the communication quality.Howerver,maintaining a certain signal-to-noise ratio will become an increasing challenge when operation carries become high or the communication distance becomes far.An important way to overcome this difficulty is to increase the output power of the transmitting antenna.However,due to the physical structure and manufacturing process,there is always a power limit for a single device,and its output power will decrease with the increase of frequency.Fortunately,power combining antenna can effectively break through the power capacity.What's more,when the output power of the transmitting antenna is greatly increased by using power combining,the transmitting antenna with high sidelobes may yield serious coupling with the surrounding electronic equipments,which will eventually make each other out-of-work.Therefore,it is important to reduce the sidelobes of the power combining antenna.Reflectarray antenna features some good characteristics including low loss,high gain,low profile,small size,light weight,conformal design,easy installation and debugging.This paper mainly studies on how to realize a power combining reflectarray antenna with high power and low sidelobes.In this thesis,a power combining antenna based on the dual-reflectarray is discussed.The principle of the power combining antenna is that the horn array antenna feeds to the sub-reflectarray,then the sub-reflectarray transmits the received energy to the main reflectarray,and makes the energy with Taylor distributions,finally the main reflectarray will radiate a high-power and low-sidelobe beam.The design is divided into three steps.Firstly,triangular-shaped array lattice is utilized in order to reduce the self-coupling of feeds,and then the structure and spatial position of the feed are designed jointly for improving the spillover efficiency of the feeding array and reducing its blockage to the sub-reflector array at the same time.Secondly,in order to make the illumination of the sub-reflectarray to be Taylor distributions,an optimization project is presented,an appropriate objective function and its gradient,as well as proper optimization algorithm are studied;two methods for initializing the reflection phase of the sub-reflectarray are also discussed.Finally,the feeding array and the sub-reflectarray are considered as a virtual feeding,and the phase compensation of the main reflectarray is achieved by using the far-field maximum gain method.Through full-wave simulations of power combining antenna based on the dual-reflectarray,it is found that the first sidelobe of the power combining antenna is about-23 dB and the rest sidelobes decrease rapidly,the aperture efficiency is 43%,the coupling between the feeding units are both less than-33 dB at the central frequency 15 GHz,and the 1dB gain bandwidth is about 8%.Finally,a prototype of the power combining antenna is built and measured.The measurement results are in good agreement with the full-wave simulation results,meaning the effectiveness of the proposed design method.