Research On Radial Beam Relativistic Back Wave Oscillator

High power microwave device is a kind of microwave source with wide application prospect,among which the relativistic back-wave oscillator(RBWO)is one of the most common devices.It has the advantages of high-power output and high electronic efficiency,and can achieve the microwave energy pulse output of GW magnitude in a period of time.In addition,the use of radial banded beam can effectively reduce the difficulty of electron focusing of such devices,and it has the characteristics of electron focusing without additional magnetic field,high electronic efficiency and small size.Therefore,radial beam RBWO is a device worthy of research.Based on the dispersion characteristics of the annular single-gate slow-wave structure,the field distribution characteristics of the coaxial single-gate structure are deeply studied in this paper.At the same time,the design of the coaxial single-gate slow wave structure is further studied by using the simulation research and the actual machining test.The research contents of this paper are as follows:(1)In order to study the influence of the introduction of annular gate on the internal field of the coaxial cavity,the field in the coaxial cavity was first analyzed and the field expression in the resonator cavity was obtained.It is found that the specific higher order modes in the coaxial cavity follow the characteristic of uniform distribution in the radius,and this rule is verified.It can be seen that the distribution of Bezier function satisfied by the radial field distribution in the coaxial line can be simplified to the form of exponential and sine function.(2)After the annular single-gate slow-wave structure is introduced into the coaxial cavity,the general dispersion equation of the structure is obtained by the field equation solution and the field matching method.And because the complexity of the two kinds of radial Bessel functions is not easy to calculate,the dispersion equation is simplified,and an approximate substitute dispersion equation is realized,which is suitable for analyzing the structure with small ratio of inner and outer diameters.(3)The antenna structure and the coaxial-circular waveguide mode transformation structure are designed to output the microwave power to the outside,and microwave absorbed by the external medium.(4)In order to further improve the output power of RBWO,the simulation study of S-band RBWO is carried out.Through constant adjustment of device parameters,the optimal power output results at two frequency points of S-band are successfully simulated.The output of 1.61 GW is obtained at 2.76 GHz,the electronic efficiency reaches 66%,and the oscillation start time is 70 ns.The output power at 3.75 GHz is1.21 GW,the electronic efficiency is 42.9%,and the oscillation start time is 46 ns.(5)To process the designed device and carry out experimental research with the pulse power supply and output antenna.However,due to practical reasons,no ideal experimental results have been obtained.We will continue to follow up in the future.