Space-wave Isolator Based On Remanence At Microwave Frequencies

Ferrite isolator is an indispensable microwave component,which is widely used in microwave communication.It plays the role of stage isolation and crosstalk prevention in the system.The traditional isolator adds an absorption load on the basis of the isolation port to achieve the purpose of reverse isolation.In practice,there are manufacturing difficulties and the drawbacks of complicated components,which can no longer meet the needs of miniaturization and integration.Ferrite remanence remains magnetic even when the external magnetic field is removed.The remaining magnetic field destroys the time-reversal symmetry of the YIG material,so there is an asymmetry in the permeability of the diagonal element,which leads to the remanence.The SMPs supported by the surface has different dispersion curves in the forward and backward propagation directions,the unidirectional propagation band is between the reverse asymptotic frequency and the cut-off frequency of the bulk mode region.We theoretically analyze the dispersion properties of SMPs at the interface of ferrite remanence-air,also numerically calculated the transmission properties at the interface.Based on this,we proposed a unidirectional physical waveguide model of ferrite remanence-air-ferrite remanence.Through numerical analysis,we found that there are three transmission modes in the unidirectional waveguide structure.One is the surface mode with odd symmetry distribution,second is the conventional mode with odd symmetry distribution,and the third is the surface mode with even symmetry distribution.Using the regular mode with odd symmetry distribution in the unidirectional waveguide,we designed a space wave isolator.The designed space wave isolator has the characteristics of simple structure,small size,and easy control.It is free from the device that requires an external magnetic field.The influence of the thickness of the YIG remanent magnetic layer and the thickness of the dielectric layer on the performance of the isolator is analyzed.The transmission spectrum and reflection spectrum of the isolator of YIG remanence under different loss conditions are simulated and analyzed.The results show that as the thickness of the YIG remnant layer increases,the operating frequency of the device gradually decreases.As the thickness of the dielectric layer increases,the operating frequency and half bandwidth of the device gradually decrease,and the isolation gradually increases.In addition,the transmission spectrum and the reflection spectrum of the two cases when the dielectric layer is air and glass are numerically calculated and compared,and both achieve a good isolation.