Questions Regarding Circulators

Hi,

I have some questions regarding circulators.

1. What is the formula of directivity in terms of s-parameters for circulator?
2. What are the important factors like insertion loss etc. related to circulators and what are their formulas?
3. If the performance of circulators has to be checked using Network Analyzers which factors need to be measured/considered? And again their mathematical representation in terms of s-parameters?
4. Can anyone share a comprehensive article on circulators?

Thanks

Google can be your friend here.
Search for circulator design, directivity, measurements etc

Circulator has 3 ports. So the directivity you will see in a system is easily seen by measuring 3 port S parameters, AND the load impedances at the 2 other ports, and using a linear simulator to tell you the apparent "directivity".

Answer to questions:

1. Google would be your friend.
2. Insertion Loss is base on what connectors if it's a coaxial unit, what type of garnets or ferrite in your design. Frequency and bandwith is also an important factor to consider.
3. S11 is the input, S22 is the output, S12 is insertion loss, and S21 is Isolation.
4. Check out M2 Global website under the Resources tab. It has a lot of tech articles there that will answers your questions.