[Q] vector signal analyzer, dynamic signal analyzer, carrier

[Q-man]

I'd like to ask a few questions.

First of all, I am an optics person rather than electronics.

I am interested in the phase noise of carrier frequency.

I've heard that equipments such a vector signal analyzer, a dynamic
signal analyzer and a carrier noise test set can measure the phase
noise of carrier. [Q1] Is that correct?

If yes, [Q2] would you tell me a difference?

In electronic applications, [Q3] would you tell me the main purpose of
these equipments ?

 

[John Miles]

In article <1126404243.191266.162860@z14g2000cwz.googlegroups.com>,
gcsel@yahoo.com says...

I'd like to ask a few questions.

First of all, I am an optics person rather than electronics.

I am interested in the phase noise of carrier frequency.

I've heard that equipments such a vector signal analyzer, a dynamic
signal analyzer and a carrier noise test set can measure the phase
noise of carrier. [Q1] Is that correct?

If yes, [Q2] would you tell me a difference?

In electronic applications, [Q3] would you tell me the main purpose of
these equipments ?

The gear you'd need to measure phase noise depends entirely on the
amount of phase noise you're talking about. What sort of "carrier"
is being tested?

UHF/microwave sources of low to medium quality can be measured directly
on a spectrum analyzer... at which point you need to decide if you can
ignore AM noise, which will appear alongside the PM/FM noise on the
analyzer unless you use a saturating mixer or limiter between the source
and analyzer.

Higher-quality sources can be measured with the help of a frequency
multiplier. A multiplication factor of N amplifies the frequency-domain
noise by 20*log(N) dB, making it possible to 'see' noise levels on a
spectrum analyzer that would otherwise be obscured by the analyzer's own
LO.

Extremely-high quality sources (crystal oscillators and such) are
typically downconverted to DC by mixing with a known-clean source. The
noise profile beginning at 0 Hz is then observed on an LF spectrum
analyzer. This type of arrangement often requires phase-locking between
the reference source and source being measured.

Mini-Circuits has a decent app note at
http://www.minicircuits.com/appnote/vco15-15.pdf if you haven't seen it
already.

I have no experience with dynamic signal analyzers or specialized
carrier test sets, but I've recently put together a pretty nice Windows
application for spectrum analyzer-based noise measurement (
http://www.qsl.net/ke5fx/pn.html ). It was inspired by the HP 85671A
software that runs on their higher-end analyzers. It won't be
necessary or useful if you are working with dedicated noise-measurement
equipment, though.

-- jm

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