The Use of Isolators in MMW Circuits

It may not always be possible to achieve a stable output at every frequency over the working range of an oscillator, as the complex impedance of the circuit to which it is being coupled will have an influence on its working point. To minimise this problem an isolator is usually placed in between the oscillator and the rest of the circuit to present a constant impedance load to the source. 

An isolator allows the transmission of MMW energy through it in the forward direction with little attenuation, typically 1 dB. A signal coming in the opposite direction, arising from a reflection or changing impedance for example, would experience a high attenuation, typically 20-26 dB. 

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