Basic microwave component questions

Could anyone here tell me the basic differents between these components:

1. Limiter vs. Attenuator

2. Coupler vs. Isolator

ISOLATORS ARE USED TO ISOLATE THE PATH OF THE RECIEVED AND TRANSSMITED AND DOWNLINK THEM TO THE IF STAGE OF THE MICROWAVE TRANCIVERS,ON THE OTHER HAND,COUPLERS ARE USED TO MATCH DIFFERIENT MEDIA OR CHANEELS TO GOTHER,THE WAVE GUIED TO SPACE,OR ANY OTHER TO COMPONENTS IN A MICROWAVE DEVICE

ATTENUATORS AND LIMMITERS ARE BOATH USED TO REDUCE THE POWER OF A MICROWAVE SIGNAL.BUT ATTENUATORS ARE FREQUENCY SELECTED,SO, IT IMPACTS A CERTIN FREQUENCY COMPONENT WITHIN THE SPECTRUM OF THE SIGNAL.

RF attenuators are circuits that reduce the power level of a signal by a certain amount (gain) with little or no reflection. They reduce the output signal with respect to the input and measure the power reduction in decibels (dB). Attenuators reduce the signal level traveling along a transmission line.

Limiters are circuits that limit the amplitude or power between certain values to achieve stability. They are not used only for transmission lines. Limiters are found in power outlets.

A circulator is a piece of ferrite which, when magnetized, becomes nonreciprocal preferring progression of electromagnetic fields in one circular direction. An isolator is just a three-port circulator with one of the ports terminated in a matched load. It is used in a transmission line to pass power in one direction but not in the reverse direction.

The directional coupler is a four-port device.

Three port networks take the form of T-junctions, circulators and others, four port networs take the form of directional couplers and hybrids.


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