Duplexer or Circulator, plz help

[henrywent]

hello there,
can anyone tell me the main difference between duplexer and circulator ? what is a typical duplexer made up of ? Someone told me that circulator is used in TDD system, can a circulator be used in a full duplex FDD system, and why not ? Any comment is welcome, thank you in advance!

 

[kspalla]

Let say both duplexer and circulator are 3 ports.
Duplexer has a common port which interface the other two ports and separate by the frequency band.
these two other ports do not have interaction with each other and are isolated by their frequency of operation.
Circulator is rotation of power in clock or counter clock mode and all work in same band. there is no band separation as in duplexer.

what is a typical duplexer made up of ?
It is made up of low pass and high pass networks.

Someone told me that circulator is used in TDD system, can a circulator be used in a full duplex FDD system, and why not ?

As circulator ports are not separated by frequency band they operate at TDD only but not in FDD.

 

[vfone]

Actually a Duplexer is made by two Band Pass Filters, when a Diplexer is made from a Low Pass Filter and a High Pass Filter.

Duplexers generally are used to separate TX and RX on the same band, when Diplexers are used for different bands.

RF Isolators permit a signal to pass in one direction while providing high isolation to reflected energy in the reverse direction.