Write introduction of the Article here.



Two port device:


  • It consists of a piece of circular waveguide carrying the dominant mode at both ends.
  • The ferrite rod is tapered at both the ends to reduce attenuation & also for smooth rotation of the polarized wave.


  1. When plane enters port1 its plane of polarization rotates by 90o   because of the twist.
  2. It again undergoes faraday rotation through 90o   because  of ferrite rod and wave which come out of port2 will have a phase shift of 1800compared to wave entering P1.
  3. But when the same wave enter port2, it undergoes faraday rotation through 90o in the  same anticlockwise direction.
  4. Because of twist this wave gets rotated back by 90o comes out of port1 with 0o phase shift.


  1. It is a two port device which provides very small amount of attenuation for transmission from port1 to port2 but provides maximum attenuation from port2 to port1.
  2. In most u-wave generators , the op amplitude and frequency tends to fluctuate very significantly with changes in load impedance.
  3. This is due to mismatch of generator op to the load resulting in reflected wave from load
  4. But these reflected waves should not be allowed to reach the u-wave generator which will cause amplitude and frequency instability of u-wave generator.
  5. Hence if isolator is inserted between generator & load ,the generator is coupled to load without any attenuation (zero) & reflections if any  from the load side are completely absorbed by the isolator without affecting the generator op.

Construction of Isolator:

  1. An  isolator makes use of 45o twisted rectangular W.G and 45o faraday rotation ferrite rod.
  2. A resisted card is placed along the larger dimensions of the rectangular W.G , So as to absorb any wave whose plane of polarization is parallel to the plane of resistive card.
  3. The resistive card doesn’t absorb any wave whose plane  of polarization is perpendicular to its own plane.



  • A four port u-wave device which has peculiar property that each terminal is connected only to the next clockwise terminal i.e port1 to port2 and not to port3 and port4.

Construction of Circulator:


  1. Circular can be used as a duplexer for a radar antenna system.
  2. Transmitter feed the antenna while received energy is directed to the receiver .The power full radar transmitter is isolated from sensitive receiver .
  3. And same antenna can be used for both transmission and reception.
  4. Two three-port circulators can be used in tunnel diode or parametric amplifiers as shown in fig below


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Created by Sujit Wagh on 2017/08/02 00:29