Ah, good question. The case is a simple single tone, x MHz in produces
an amplified output of x MHz at plus some level and a series of odd
harmonics, 3 times x. The 3rd harmonic is down 10 db from the original
signal.
Some additional follow up information:
1. the bias is set near the high end, increasing its value does not
significantly add to overall gain.
2. I suspect an output impedance mismatch, if that were the case could
it cause harmonics?
Dan
On 11/18/2010 10:39 PM, Fuqua, Bill L wrote:
> Another question.
> Are you saying if you put in, as an example, 10 MHz you are getting a 30 MHz
> signal only 10 db down from the 10 MHz.
> Or is this a two-tone measurement and you are looking at the intermodulation
> products?
> And if you are how do you have your instrumentation set up? Sometimes
> there are errors produced in the instrumentation.
> 73
> Bill
>
> kind of late. I must get some sleep. Check in the morning.
>
> ________________________________________
> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of
> Dan Sawyer [dansawyer@earthlink.net]
> Sent: Friday, November 19, 2010 12:31 AM
> To: Amps
> Subject: [Amps] source of '3rd harmonic'
>
> All,
>
> I am trying to add bias to a commercial class B NPN RF module. The input
> and outputs are 4:1 and 1:4 'binocular' transformers, feedback is a
> simple CR network. The output has a significant 3rd harmonic, about -10db.
>
> I have done research on the source of odd harmonics, however I can't
> find specific references. What is the root cause of odd harmonics, what
> would affect the level of harmonic?
>
> Thanks for your help,
>
> Dan
> kb0qil
>
>
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>
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