A unidirectional device is an irreversible attenuator. That is to say, if the attenuation of the forward wave is small, then the attenuation of the reverse wave is large. When a unidirectional device is placed in a waveguide circuit, the electromagnetic field will only pass along the direction indicated by the arrow on the unidirectional device housing. That is to say, for unidirectional equipment, its main function is to act as an isolation device, which can improve the standing wave ratio, ensure that all components and units do not affect each other, and can work stably.
A unidirectional device, like a circulator, operates by utilizing the magnetic field of electromagnetic waves and the interaction between ferrite elements and a constant magnetic field. A ferrite plate is placed perpendicular to the wide edge of the waveguide, and a layer of resistance film is applied to its surface. A magnet is used to generate a constant magnetic field perpendicular to the wide edge of the waveguide outside the waveguide. If a constant magnetic field changes direction, the direction in which it passes will be opposite.
The principle of a unidirectional device: The microwave ferrite device in a unidirectional device is made by utilizing the rotational magnetic effect of ferrite. It is a nonlinear anisotropic magnetic material. Its magnetic permeability will also vary with the applied magnetic field, exhibiting nonlinearity; When a constant magnetic field is applied, the magnetic permeability of the microwave magnetic field varies greatly in all directions, indicating anisotropy. Due to these characteristics, when electromagnetic waves pass through ferrite from different directions, they exhibit a non reciprocal behavior, resulting in the production of various non reciprocal ferrite components.
The definition of a unidirectional filter: A unidirectional filter, also known as a unidirectional isolator, is a device that can transmit electromagnetic waves in one direction. As a non reciprocal dual port microwave ferrite device, it actually developed from the principle of microwave devices - circulators. Later, it will be specifically designed for wireless paging transmitters, with the ability to absorb the energy of interference signals entering the transmitter through the antenna feedback system from the outside, as well as to protect the transmitter and reduce the failure rate.