Research On Beam Manipulation And Quasi-Optical Power Combining

With the development of millimeter wave technology to the short millimeter and submillimeter wave band,high power signal source becomes the crucial component which will determine the performance of the whole MMW system.Though electronic vacuum devices with massive size can produce much higher power than solid state devices,it is difficult to apply them in the aerospace field,which requires compact size.Therefore,the high power solid state device has the advantages that cannot be replaced by the massive electronic vacuum device in aerospace field.However,due to the limitation of physical properties of the semiconductor device,the output power will decrease with the working frequency increases.Therefore,it is impossible for a single solid-state source device to generate high enough power that can satisfy the system's requirements in millimeter wave band.In order to use solid state devices,we have to utilize the power combining technology with solid-state devices to output higher power that can satisfy the MMW system's requirements.At present,there is two main methods in power combining technology: circuit power combining and space power combining.In short millimeter and submillimeter wave band,all kinds of transmission lines such as waveguide and microstrip will become smaller in size,higher in loss,lower power-handling capability and expensive cost etc.The circuit power combining technology using transmission lines cannot be applied.The millimeter wave quasioptical technology takes advantages of Gaussian beams to losslessly transfer millimeter waves in free space.Quasioptical technology can handle multiple polarizations and multiple beams.Quasioptical systems can also have considerable power-handling capability and lower manufacturing difficulties.So,quasioptical technology have obvious advantages in short millimeter wave band(above 100GHz)and Terahertz wave band.Two kinds of MMW quasi-optical power combining system are designed.In the output window of each quasi-optical power combining system,a profiled and smooth-walled matched converter is designed to realize the power concentration and transformation of the higher order beams to the fundamental Gaussian beam.With the optimal parameters' setup,the fraction of power of the whole system that is radiated out can reach to 78.42%,and the central beam occupies 95% power of the whole output beams,with a Gaussian coupling efficiency up to 97%.Finally the power combining system can efficiently transform 73.47% power into the Gaussian beam.