FERRITE DEVICES
Technical information / Technology
A Y-junction circulator can be made into an isolator by adding an internal termination on port # 3, for example.
The device passes signals with low loss (port # 1 to port # 2) and with high loss in the opposite direction.
It is used to "isolate" one microwave device from another. It can, for example, protect expensive,
high-power RF sources from variations in loading conditions or mismatching (see
4-Port differential phase shift circulator
This four-port-device is normally used with one load, such as a high-power circulator (duplexer),
or with two dummy loads, such as a high-power isolator.
This circulator consists of three basic parts:
•
•
•
Hybrid folded magic tee
Twin parallel ferrite phase shift sections
3 dB coupler
Resonance isolator - Waveguide devices
By magnetically biasing a ferrite inside a waveguide, the non-reciprocal effect is obtained: with low
losses in one direction and high losses (isolation) in the opposite direction.
Those isolators are only used for low and medium power (see figure 4).
The ferrite material has to dissipate the return power due to mismatch.
MAGNET
WAVEGUIDE
PORT
1
PORT
3
PORT
2
Ho
FOLDED
MAGIC TEE
1/2 DIFFERENTIAL
CELLES
3 dB
HYBRID
COUPLER
PORT 4
MAGNET
FERRITE
MATERIAL
4 PORT DIFFERENTIAL PHASE SHIFT CIRCULATOR
FIG. 4
FIG. 5
Ferrite switches
These devices change the polarity of the magnetic bias (N
©
S) and the RF-signal direction
of circulation. This is made by a coil instead of a magnet. This technology is used for ferrite switches
in both product lines:
•
•
Y-junction
4-port differential phase shift device
15-4
Vol. 1
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