FERRITE DEVICES
Technical information / Electrical features
Load VSWR
Power rating of a ferrite device depends on the mismatch at the output port (load VSWR); for instance,
for an isolator, if load VSWR is 2: 1, more than 10% of the input power is reflected inside the ferrite
device to the internal load.
In case of short-circuit (infinite load VSWR), the ferrite device has to handle the equivalent of twice
the input CW-power, and the equivalent of a peak power equal to 4 times the input power, based on
the higher internal voltage levels.
Therefore, the time-duration of short circuit or high load VSWR is needed in order to determine an
adequate safety margin.
Third order interm odulation products (IMP
)
32
Harmonics and third order intermodulation products appear when non-linear elements are used such
as ferrite materials, metal welds, surface finish, etc.
When two tones - F and F - are applied to a ferrite device, the relative amplitudes of 2F - F and
1
2
1
2
2F -F are critical in some communication systems and should be specified when ordering (see Fig. 8).
2
1
POWER
P1
IMP32
P2
PIM3
2F1 - F2
2F2 - F1
F1
F2
FREQUENCY
∆ F
FIG. 8
•
•
Test conditions (to be specified)
-
-
F and F
1 2,
P and P in W or dBm.
1
2
Third order intermodulation products
-
-
P
in dBm or,
IM3
IMP = P
- P in dBc.
1
32
IM3
15-7
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