FERRITE DEVICES
Technical information / Electrical features
Effect of an isolator on VSWR (Fig.7)
INPUT
LOAD
ISOLATOR
~
VWSR
SOURCE
FIG. 7
The effective input VSWR of an isolator will vary at a function of the load VSWR. If the output load
mismatch is increased, energy is reflected at the termination port, attenuated by the isolation and then
reflected back to the input.This effect increases the total input VSWR observed at the input.
Exam ple:
The load VSWR is 10: 1, the isolator has 18 dB isolation, which improves the input VSWR to 1.20: 1.
Tem perature range
The performance of a circulator or isolator is limited by ferrite and magnet material behavior in the
operating temperature range.
In this catalog, for each device the main specifications are given:
•
•
at room temperature: 25° C,
over a specified temperature range.
Power rating
The input power to a ferrite device can be supplied from a CW or a pulsed source.
For pulsed source, peak and average power should be specified, pulse duration and duty cycle are also
needed in order to determine an adequate safety margin.
Average power
For high power products, average power is limited by the dissipation in the ferrite. Adequate cooling
is necessary to insure the ferrite material does not reach excessive temperature.
There are three kinds of cooling: liquid, forced air or natural convection.
Peak power
To avoid breakdown or arcing, special ferrite materials are designed.
Frequency of operation and peak-power level determine whether the waveguide circulator should be
pressurized or unpressurized with dry air or gas (N or SF ).
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