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need suggestions from microwave experts

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Advanced Member level 3
Jan 12, 2007
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Hi friends
Do any one of you have experience in genearion of noise?
(making a noise source that is generation of noise signal at any frequency).
I am interesting in generation of white noise.
Can any one help me & suggest me

there are vendors of noise generating diodes out there... used for built in test and instrumentation applications....

You could just use the input noise of an amplifier. It may not be flat and you will need enough gain to get from ktB to the power level you want. The amplifiers will need to have a good frequency response if you need wideband noise, and the input screening needs to be perfect.
A noise diode would be the best way to get a reasonably flat power density. Some diodes give around 30dB over ktb. If you don't have a noise diode a zener works reasonably well at low frequencies, and a reverse biased base emitter junction of a microwave bipolar is OK to a few GHz. Not too flat though.

For open test setups I just use the cascaded amplifiers and some filters; usually the Mini-Circuits coaxial amps and filters. Amp stability can be a problem so you may have to pad you filters. Beware the compression point of your amplifiers. With a few GHz of noise BW that power adds up and can easily compress your last stage.

I remember using a 10V zener diode made by Motorola (>10 years ago) that created a noisy output that was flat to about 100MHz (AC coupled into 50 Ohms). You would need to set the current just right. It was a leaded part...part number started with 1n40

Thanks friends for response.
I am thinking of making an oscillator using noise source, so I want a noise source which I can Tune to any frequency I want & after getting expected frequency out I can amplify.
Can we use waveguide or any cavity to generate white noise? I want noise with high power.
Suppose I want do design 70GHz high power oscillator how should I generate noise of 70GHz with high power???
One of my thought was to make a cavity which can generate noise & make specific arrangment to take expected frequency out from that cavity.
are there any suggestion or comments on this experiment?

Has any one of you performed black body experiement?
Heat the cavity & see Plank spectrum.

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