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Microwave Circulators/Isolators

Microwave circulators and isolators are used primarily in radar and communication systems.  These devices typically consist of a ground plane, microwave ferrite and a permanent magnet.  These devices are critical in the switching and routing of microwave energy.  An isolator is analogous to a diode in a dc circuit.  A circulator adds a third port and is used primarily to isolate a transmitter and a receiver from a single port.

Dexter_Circulator_Assembly

Click on the image to enlarge and see the following pieces labeled:

  • Magnets: Sm-Co
  • Pole Piece: Carbon steel
  • Microwave Ferrite: Ceramic (Hard ferrite)
  • Waveguide: Copper

Additionally, Dexter offers the ability to calibrate magnets for circulators and/or prestabilize them for high temperature environments.

When working with our engineering group, you might be asked:

  1. What is the highest temperature the assembly will experience?

  2. What is the minimum magnetic strength and how large of a volume is required?

  3. Various magnetic materials respond differently to temperature changes. How much of a variation can your assembly tolerate?

  4. Are there any harsh environmental conditions (such as water, corrosive gases, etc)?

Samarium Cobalt magnet material is frequently used in circulators due to high temperature stability and relatively high field strength.  Some other materials that are also frequently used include:

  1. How do I select the best magnet material for my device?
  2. What considerations should I take when designing a device for a harsh environment?
  3. Do I need plating or coating to protect the magnets?
  1. You must determine the minimum magnetic field necessary to magnetize the ferrite.
  2. Samarium Cobalt or  Alnico are usually the materials of choice for harsh environments.  Although they are not as strong as Neodymium Iron Boron, they have superior corrosion resistance properties
  3. For Samarium Cobalt or Alnico, generally no.  For Neodymium Iron Boron, definitely yes.

Models of the initial design can usually be completed within 2 weeks.  Sometimes samples of various sizes and magnetic strengths are necessary and can be produced within 4 weeks.