[time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[Bob Camp]

HI

It sort of depends on what offset frequency you are looking at. If you are after very wide band stuff at very low levels, 
the notch filter / spectrum analyzer approach has always been a good one. You may or may not need a low noise 
amp after the notch depending on the analyzer. Your notch may need to be more deep with some analyzers. It’s 
been used since at least the 1960’s. I would not be surprised to find it goes back a bit further than that. 

One basic assumption with the notch approach:

You are measuring total noise. Both the AM noise and PM noise go past the notch and into the analyzer. The fundamental
assumption is that out there the noise is equally distributed between AM and PM. There would be a paper in it if you
can prove that’s not the case. 

Lots of fun !!

Bob

> On Jun 18, 2016, at 6:11 PM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 6/18/16 12:05 PM, Bob Camp wrote:
>> Hi
>> 
>> The Symmetricom Time Pod is pretty much the lowest cost commercial / newl “low phase noise” measurement instrument. You can find all sorts
>> of older stuff on auction sites in who knows what shape. The HP 3048 is the granddaddy of them all.
>> 
> 
> the time pod is about 8-9k (I just got a quote on one).
> 
> I don't think the 4406 is inherently very quiet, if they're making close in measurements, they may have another quiet source to drive it from, or they are beating the unit under test against a quiet reference, and just using the 4406 to look at the IF.
> 
> 
> 
> 
>> Bob
>> 
>>> On Jun 18, 2016, at 12:11 PM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
>>> 
>>> I was looking at some high end commercial low noise oscillators and see
>>> they use instrument like the Agilent E5052B signal source analyzer for
>>> phase noise measurements. When I looked for them on eBay, it soon because
>>> apparently they were very expensive.
>>> 
>>> Then I see this oscillator that locks to GPS
>>> 
>>> http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=234
>>> 
>>> and looked at what was used to make the phase noise measurements. It was an
>>> Agilent E4406A. The noise floor is nowhere near as low as the more
>>> expensive instruments, but the E4406A is available for under $500, which is
>>> more than two orders of magnitudes cheaper than an E5052B.
>>> 
>>> I'm wondering if there are other more suitable commercial instruments
>>> around that don't cost a fortune, yet would allow lower levels of phase
>>> noise to be measured. I tend to preference HP/Agilent kit, as it is better
>>> supported, both by the manufacturer and places like the HP/Agilent Yahoo
>>> group.
>>> 
>>> Dave
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