FERRITE DEVICES
Technical information /Technology
TECHNICAL INFORMATION
TECHNOLOGY
Y-J u n c t io n c irc u la t o r
PORT 1
PORT 2
The Y-junction circulator uses spinel ferrites or garnet ferrites
in the presence of a magnetic bias field, to provide a non-reciprocal
effect. A 3-port circulator (shown in figure 1) is the basic model,
which can be used to explain how it operates.
If a signal is applied at port # 1, it will emerge from port # 2 with a loss
characteristic called “insertion loss”. Typical values of insertion loss:
0.1 to 0.5 dB.
PORT 3
In the reverse direction, there will be leakage at port # 3 from
the incoming signal at port # 1.This leakage called isolation is typically
20 dB below incoming power at port # 1.
FIG. 1
Due to the “3rd order symmetry” of theY-junction, the behavior is the same for the other ports, with
respect to port # 1 to port # 2, port # 2 to port # 3 and port # 3 to port # 1.The circulator's role is to pass
energy, for instance, in the RF-head of a radar, assuring high isolation between the high power
transmitter and the sensitive low power receiver (figure 2).
TheY-junction exists in three main technologies:
•
•
•
Coaxial devices: these feature triplate technology with coaxial connectors.
Drop-in circulators: in triplate or microstrip technology.
Waveguide devices: it consist of three waveguides forming an H-plane junction in either a "T"
or a "Y"-symmetrical structure.
When very high power is needed, the technology uses a four-port differential phase shift duplexer.
ANTENNA
MISMATCH
POWER
SOURCE
LOAD
~
RECEIVER
TRANSMITTER
ISOLATOR
CIRCULATOR
FIG. 2
FIG. 3
15-3
Vol. 1
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