Because the ferrite has anisotropy, so under the constant magnetic field hi, the left and right circularly polarized rotating magnetic field with hi direction to left and right helix have different permeability (respectively set to μ-and μ+). A point on a microwave transmission line containing a ferrite material, along the +z direction of the transfer of the left magnetic field, the direction of the transfer of the right rotating magnetic field, the two transmission of the same distance, but the corresponding permeability is different, so the left and right rotating magnetic field phase velocity is different, the resulting phase shift is different, this is the ferrite phase shift irreversibility.
On the other hand, ferrite has resonance absorption effect of ferromagnetic resonance and circularly polarized magnetic field. The ferromagnetic resonance effect of the so-called ferrite is that when the working frequency of the magnetic field is equal to the resonant angular frequency of the ferrite, Ω 0 o'clock, the absorption of the microwave energy by the ferrite reaches its maximum value.
For the circularly polarized magnetic field, the magnetic field of the left and right polarization has different permeability, so the two have different absorption characteristics. For the reverse transfer of the right rotation polarization magnetic field, the permeability is μ+, it has ferromagnetic resonance effect, but to forward transmission of the left polarization magnetic field, permeability is μ-, it does not exist ferromagnetic resonance characteristics, which is the resonant effect of circularly polarized magnetic field. Ferrite resonator Isolator is made of this characteristic of ferrite.