Circulators

In EMIT a circulator is a passive non-reciprocal three-port device, in which a signal entering any port is transmitted to the next port in rotation (only). A signal applied to port 1 only comes out of port 2; a signal applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of port 1, so the scattering matrix for an ideal three-port circulator is

Unless otherwise specified by the Finite Isolation or Finite Bandwidth settings, EMIT assumes ideal (infinite) isolation and infinite bandwidth for circulators.

(ref: http://en.wikipedia.org/wiki/Circulator)

Noise Temperature (K): Noise power added by the circulator.

In the Type drop-down, select one of the following:

• By File
• Parametric

By File

Define the 3 port frequency characteristics of the Circulator by providing a 3-port Touchstone file containing the S-parameters for the device.

Parametric

Allows definition of the circulator characteristics by entering values for the appropriate parameters.

Insertion Loss (dB): Defines the insertion loss between circulating ports of the device. That is, the insertion loss from port 1 to 2, port 2 to 3 and port 3 to 1.

Finite Reverse Isolation: Isolation between the other, non-circulating, ports is assumed to be infinite unless Finite Reverse Isolation is enabled (True), in which case the value you provide is used.

Finite Bandwidth: By default, the bandwidth for a Circulator is considered to be infinite. When Finite Bandwidth is enabled (True) a finite bandwidth for the Circulator can be defined. The Out-of-Band Attenuation is then applied outside of the defined pass band as shown in the plot below. See Band Pass Filter for definitions of the parameters.