Hi Pete,
The lower limit on the operation of a PIN diode, is not arbitrary, it's
set by the carrier lifetime of the diode. The carrier lifetime has to
be longer than the half cycle time at the frequency of operation,
otherwise the diode stops acting like a PIN, and looks more like a
regular diode. If that happens, you will thus lose the high IP3
characteristics.
There are a few PIN diodes available with really long carrier lifetimes,
but they are not very common. It may be easier for you to use a
different mechanism for Rx protection, such as reverse biased Schottky
diodes. You need to set the reverse biasing as a compromise between
IP3, and providing adequate protection for the Rx.
73, Greg, ZL3IX
On 2012-02-02 02:16 a.m., Pete Smith N4ZR wrote:
> Quite by accident, in leafing through K9AY's new magazine I ran into a
> reference to a surface-mount PIN diode
> <http://www.skyworksinc.com/Product.aspx?ProductID=857> designed
> specifically for receiver protection. It begins to block signals at +10
> dBM, and works by quite a different mechanism than conventional diode
> limiters, resulting in pretty high IP3. The specified lower frequency
> limit is 10 MHz, but I wonder if that is arbitrary
>
> Has anyone tried this approach to receiver protection on Topband?
>
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