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Rf isolator symbol8/15/2023 ![]() ![]() In addition, there are no standing wave patterns in the magnitude plot of the electric field. This is a good value for circulator designs.Įlectric field norm and power flow in the microwave circulator.Īs you can see from the power flow arrows in the plot above, the microwave energy flows in one direction from port to port, as desired. You can use this value to find a reflection coefficient of around -35 dB. In the next plot, take closer look at the eps_r value of 1.29. This result shows that a minimum reflection is achieved at around eps_r = 1.29. The graph below compares the relative permittivity of the dielectric matching elements ( eps_r) with the S 11 parameter, which relates to the reflection coefficient at Port 1 (the input arm). Using the RF Module, you can run an S-parameter analysis of the circulator device. Does This Ferrite Circulator Design Function Properly? You can do so by finding the S-parameters (which measure the transmittance and reflectance of the circulator) in relation to the tuning element permittivity for the fundamental TE 10 mode. To match the junction, it’s necessary to determine how well the TE 10 wave propagates between the three ports for various tuning element materials. One design goal for circulators is to reduce reflections at the input port by matching the junction. ![]() Since a TE 10 waveguide mode has no variations in the transverse direction, it’s possible to simplify the analysis with a 2D model.ĢD circulator geometry with dielectric tuning elements. The model analyzes the transmission of a 10-GHz TE 10 wave through the circulator. Three-port microwave circulator geometry. A ferrite post is placed at the center of the joint and is magnetized by a H 0 bias field along the axis. Within each branch, identical dielectric tuning elements are used to match the junction. The lossless three-port ferrite circulator example shown below is made from three rectangular waveguide sections joined at 120° angles. Modeling a Three-Port Ferrite Circulator with the COMSOL® Software In this example, we use the RF Module, an add-on to the COMSOL Multiphysics® software, to accurately analyze both the ferrite material and the inner workings of the circulator. However, the choice of material can affect how a wave propagates between the circulator’s ports. To build a circulator, engineers often use anisotropic materials like ferrites due to their high electrical resistance and high magnetic permeability. One common application of microwave circulators is a duplexer, where a circulator enables a transmitter and receiver in a radio communication system or radar unit to share a common antenna while still isolating the receiver from the transmitter. Licensed under CC BY-SA 3.0, via Wikimedia Commons. Due to this functionality, electrical engineers use circulators to isolate microwave components.Ī simple schematic of a circulator. In a circulator, a wave incident originating in one port can only be coupled to the next port. Microwave circulators are nonreciprocal multiport devices that often contain three ports in a “Y” shape. To ensure that circulators function successfully, electrical engineers can study their designs with electromagnetics simulation.Ī Quick Introduction to Microwave Circulators This characteristic makes circulators useful for applications that involve coupling transmitters and receivers to common antennas. In a circulator, however, the microwave signal always exits at the next available port. Circulators are a bit like traffic circles (also known as rotaries or roundabouts), where motion occurs in one direction only and each pathway doubles as an entrance and exit. ![]()
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