CHENGDU JING XIN MICROWAVE TECHNOLOGY CO., LTD
An isolator is a two-port device that transmits microwave or radio frequency power in one direction only. It is used to shield equipment on its input side, from the effects of conditions on its output side; for example, to prevent a microwave source being detuned by a mismatched load.
The Waveguide Isolator can be constructed using rectangular waveguide operating in dominant mode. This is constructed by placing ferrite slab in the waveguide parallel to the narrow wall. These are places where magnetic field exhibits circular polarization which occurs usually at a/4 or 3a/4.
As we know attenuation in ferrite for negative or clockwise circular polarization is very small. It is large for positive or counter clockwise circular polarisation. This happens at resonance frequency. Due to this fact, ferrite slab is placed in such a way so that during transmission it will encounter negative circular polarisation in the reverse direction.
With this waveguide isolator, isolation of about 20 to 30 dB in the reverse direction and insertion loss of about 0.5dB in the forward direction is achieved. VSWR of about 1.1 can be obtained.
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