EMC Peak measurement with HP3577A

[blisca]

Hi.,please i need some hint
forgive my simple and uncorrect use of English and my assumptions due to
lack of experience.

I have an old HP3577A network analyzer and i'm using it connected to a LISN
as a spectrum analyzer on input A in lack of a precise spectrum analyzer.
I'm trying to minimize conducted emissions of a circuit with PFC,that by
it's nature switches in a very irregular way depending by instantaneous
values of needed current and input rectified AC.Due to this i can have very
different values for the same frequency during two different sweeps.
Trying various RBW values and sweep time values is not enough to have
similar shapes of spectrum on display.
In such conditions is very difficult to appreciate if a change in a
component value or layout has a positive effect.
I think that something like "do many measurements and keep the highest ones"
would be what i need.

The question is if it is possible to have this kind of measurement with
HP3577A maybe controlling the instrument by PC and HP-Basic?

Many thanks for your attention
Diego
Milan,Italy

 

[Joerg]

Hi.,please i need some hint
forgive my simple and uncorrect use of English and my assumptions due to
lack of experience.

I have an old HP3577A network analyzer and i'm using it connected to a LISN
as a spectrum analyzer on input A in lack of a precise spectrum analyzer.
I'm trying to minimize conducted emissions of a circuit with PFC,that by
it's nature switches in a very irregular way depending by instantaneous
values of needed current and input rectified AC.Due to this i can have very
different values for the same frequency during two different sweeps.
Trying various RBW values and sweep time values is not enough to have
similar shapes of spectrum on display.
In such conditions is very difficult to appreciate if a change in a
component value or layout has a positive effect.
I think that something like "do many measurements and keep the highest ones"
would be what i need.

The question is if it is possible to have this kind of measurement with
HP3577A maybe controlling the instrument by PC and HP-Basic?

Short answer: No, it is not possible.

The 3577 is a (very good, if not the best) network analyzer but it has a
wideband amplitude/phase detector. Meaning it is not at all suited as a
spectrum analyzer. If you force it in you can see blips of spectrum show
up on the screen, of course, but those do not represent any meaningful
amplitude measurement.