At 5/7/2005 10:53 AM, you wrote:
>Steve,
>
>There is nothing special about the low-pass filter that might require you
>to use a
>particular brand name. A ferrite isolator is a nonlinear device, and
>therefore it
>will generate a strong second harmonic which must be attenuated by either
>a notch
>filter or a low-pass filter.
Not always. If the isolator is driven far below it's rating, it may not go
nonlinear. We once tested an EMR Corp. 220 MHz isolator being driven with
~90 watts. The output spectrum from our RFPA was no different with the
isolator in line (no increase or decrease in harmonic content).
If you have a power attenuator handy, it might be worth actually looking at
the harmonic levels coming out of your isolator with a spectrum
analyzer. You can't use a coupler for this test because it's frequency
response will taint the measurement.
Bob NO6B
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