The Nonreciprocal Tunable Microwave Device Design And Its Lumped Equivalent Circuit Research

The magnetoelectric(ME)dual tunable microwave devices can be achieved through combining the magnetoelectric laminate material with the microwave devices,which is based on the ferromagnetic resonance effect and the ME coupling effect.The devices possess some good characteristics such as low loss,high efficiency,high tunable speed.Meanwhile,because of the magnetic anisotropy characteristics of the ferrite itself,it can be used in the nonreciprocal microwave devices' design widely.For example,the ferrite phase shifter,the isolator and the circulator.So the versatility of the microwave device is achieved.The nonreciprocal tunable microwave devices with high performance will possess huge application prospects in future electronic warfare and wireless communication system.In the design progress of the nonreciprocal microwave devices,the traditional electromagnetic(EM)field simulation and the experimental fabrication is needed.Once the device is completed,the performance will be fixed.The performance of the existed nonreciprocal microwave device is always single,the frequency always can't be tunable.Meanwhile,the design progress is time consuming and low efficient because the ME laminate is introduced.In order to improve the efficient,some scholars analysis the coupling theory between the ME laminate and microwave transmission system.They equaled the physics model to a lumped equivalent model.Then the performance is predicted effectively and the time is decreased greatly.Although there are many researches about the ME device's equivalent circuit,these researches are only focused on the reciprocal two-port filters with symmetric structure and one-port resonator.For the lumped equivalent circuit researches of the non-reciprocal tunable devices are in a blank stage.In view of the above problems,this paper mainly makes the following researches:Firstly,as for the microwave transmission system with ME double layer structure,according to the magneticstatic wave(MSW)transmission theory in the ME material,we solve the eigen frequency of the eigenmode of the ferrite device and the ferroelectric device in use of the Maxwell equation.When the ferrite phase and the ferroelectric phase are both working at the lowest mode,the maximum coupling effect occurs.So the concrete dispersion equation of the magneticstatic wave transmission in ME double layer structure is obtained.Meanwhile,the elastic Gibbs free energy is carry out for the ferroelectric material and its dielectric constant under microwave frequency is obtained in theory.Finally,put the dielectric constant into the new dispersion equation,the final dispersion equation that the MSW transferred in the ME laminate.Then use the new dispersion equation in the ME device's lumped equivalent circuit and the validity is verified.Secondly,as for the magnetoelectric nonreciprocal tunable bandpass filter,based on the converse ME effect of the ME laminate material and took the influence of the equivalent factor of the piezoelectric layer into consideration,the radiation impedance,radiation capacitance,radiation inductance and the coupling inductance are introduced to describe the reciprocal coupling part circuit.meanwhile,the T-shaped equivalent with controlled source CCVS is introduced to describe the non-reciprocal transmission characteristic.Finally the lumped equivalent circuit model based on the nonreciprocal ME tunable bandpass filter is established.The predicted results using the circuit model when the ferrite placed angle is 0 degree and 45 degree are compared with the experimental results and the model's validity is verified.Then,the electric tunable characteristic of the filter through changing the voltage of the piezoelectric phase is predicted by the lumped equivalent circuit.Compared with the EM field simulation results and the validity is verified further.Finally,the influence of the filter performance is predicted by the circuit model through changing the thickness of the ferrite slab and the width of the coupling microstrip lines.Finally,based on the anisotropic properties of the ferrite and the design theory of the rectangular waveguide isolator,put the ferrite into substrate integrated waveguide(SIW)and a half-mode SIW isolator based on the ferrite substrate is designed.This device not only achieves nonreciprocal isolated characteristic but also decreases the size of the traditional SIW.Meanwhile,the working frequency band can be adjustable through changing the external bias magnetic field.It has big application potential in microwave communication field.Next,based on the nonreciprocal transmission of the left/right hand circular polarization wave in ferrite,put the ME laminate on the periodic zigzag structure microstrip transmission line and a ME tunable isolator is realized.This isolator can only achieve a good isolated characteristic but also can achieve ME dual tunability.The above two nonreciprocal devices can provide a new thought for the designer to design a dual-function nonreciprocal devices.