- Microstrip Transition Circuit Research And Applications Based On Magnetic Coupling Rectangular Waveguide

Four parts are proposed in this paper:The first part is introduction, The second part is the theoretical basis of transition, The third part is the main content of this paper-A novel millimeter-wave rectangular waveguide-microstrip transition based on the principle of magnetic field coupling, The fourth part is application proposed of based on magnetic coupling principle of a rectangular waveguide microstrip transition.As the development of millimeter wave technology, hybrid microwave integrated circuit(HMIC) and monolithic microwave integrated circuit(MMIC) are widely used in communication, radar, control-and-guide and other systems. microstrip is used in more and more areas of millimeter wave field to replace metal rectangular waveguide. However, metal rectangular waveguide has bigger power, lower loss, simple architecture and high Q, therefore it is widely used in microwave and MMwave circuits and systems. Many input and output ports of millimeter wave equipments are metal waveguide. Then how to realize low loss transition between metal waveguide and microstrip becomes the important research of microwave and millimeter wave field .Now the metal waveguide-microstrip transitions adopted in engineering, can be classified as the following:rectangular waveguide-finline-microstip transition,rectangular waveguide-ridge waveguide-microstip transition, rectangular waveguide-microstip probe transition and rectangular waveguide-coaxial probe-microstip transition. All these transitions are based on electric field excitation inside rectangular waveguide. This excitation proposed is realized with electromagnetic field transition between rectangular waveguide's dominant mode and microstrip's dominant mode so that electromagnetic wave can travel along the two different transmission lines.All these transitions have disadvantages respectively, such as big dimension, non-repeatable, necessary debugging, low bandwidth, high manufacturing precision requirement, etc.A novel rectangular waveguide-microstrip transition circuit based on rectangular waveguide's dominant magnetic field mode couling theory is presented in this paper. This paper is made use of circular metal line on E-face of rectangular waveguide and eccentric coaxial line Partial filled with medium to realize the electromagnetic field modes transition between rectangular waveguide and microstrip line. It has low insertion loss, broad bandwidth, compact architecture and there is no need debugging. Simulation and optimization were carried out by software CST at Ka band (8mm). Then a back-to-back circuit was produced and tested. The test result shows that the insertion loss S 21 of this circuit is less than 1.2dB, return loss S 11 more than 13.5dB, good bandwidth and flatness. They are compliant with the simulation results well. The innovation is that the rectangular waveguide-microstrip line transition circuit is designed based on magnetic field excitation theory which is different from traditional transition circuit based on the electric field excitati on theory.A low-noise amplifier (LNA) with rectangular waveguide-microstrip transition circuit based on magnetic field excitation theory is also presented in the article. A time sequence direct current( DC) power supply with protection circuit is made for the LNA at the same time.