Jim:
I'll thread my comment into your last post. I'm still making the
assumption that you want to stay with the cheapest reasonable solution, and
not throw tens of kilobucks at the problem. That means a used sweeper and SA
(maybe from a rental house or even from a surplus dealer).
-----Original Message-----
From: Jim Eichner [SMTP:jeich...@statpower.com]
Sent: Wednesday, September 15, 1999 3:53 PM
To: 'EMC-PSTC - forum'
Subject: Re: Sweeping components and filters
Thanks, Robert and Ed, for your replies. I have included them
below,
along with my original request.
I'm guessing by the low number of responses, that not many people do
this, which I guess isn't that surprising considering I too have
been
getting by without. Still, I'd appreciate any further input people
have, particularly regarding methods that extend up into the 10's or
100's of MHz.
Ed's suggestion to use a sweeper with our SA is an interesting one.
It
hadn't occurred to me that I don't need to synch up the two
instruments,
but can just let the display fill in.
This works best if you have a stable sweeper and a digital storage
SA. Just connect the sweeper to a 6dB pad, then to another 6dB pad, and then
to the SA. Set both sweeper and SA running, with the SA on peak hold.
Depending on the frequency range, the range will fill in anywhere from a few
seconds to several minutes.
This will give you your reference level. Store it in Trace 1. Now,
put your unknown between the pads, and run again. Store as Trace 2. Now,
subtract T2 from T1, and there's your response curve.
The worst time I have had was when I characterized some High Pass
filters which have Fc's of 750 MHz and 3 GHz. Looking at these out to 18 GHz
is tedious, and takes all day. Still, once set up, you don't have to stand
there to watch it.
If Ed or anyone else can add a
catalogue number or two to the list of mfr's (Wiltron, Wavetek, and
HP)
that would save me reinventing the wheel.
I use a Rohde & Schwarz SMG (about $7K used, 30Hz-1GHz) and an
HP-8350B/HP-83592A (about $8K used, 10MHz-18GHz). I'm not too familiar with
the other manufacturer's numbers, but even the old HP-8390 series would work
(but they are getting really old to rely on). The SA can be an HP-141T with
8566 (30Hz-300KHz with tracking gen built-in) or 8553 (1KHz-110MHz) or 8554
(100KHz-1250MHz) or 8555 (10MHz-18GHz). The mainframe is about $300 now, and
each plug-in goes from about $350 to $900 now. Unfortunately, it's NOT
digital, so you have to visually take your data or photograph the traces.
Next level SA up might be an Anritsu or Hameg, etc. New, and
digital.
I use an HP-8562A (from 1987, but it still goes for about $20K ). I
also use an HP-8566B sometimes. BTW, for the 8562, I recently bought HP's
Benchlink software for $300. It's a nice simple tool for moving data from
the SA to a PC, and saves in formats importable into Word and Excel.
Also, Ed, is this method
useable over a wide frequency range, into the 100-200 MHz
neighbourhood?
I characterize current probes, coax cables, filters, LISN's and
couplers from 30Hz to 18 GHz. Very good quality coax and connectors are
necessary above a few GHz. At 200 MHz, you can be using RG-223 with BNC
connectors and still get great results. (I buy my coax in bulk, and make all
my cables. You have to be able to trust you cables. BTW, I tag my cables
with colored Ty-Wraps to identify them easily.)
Robert: You say you sweep the components, then model the filter,
then
sweep the filter and compare to the simulation. How good is the
correlation between the model and the network analyzer sweep? How
good
is the correlation between either and the real-life performance of
the
filter when you drop it into your noisy circuit?
You can refine your measurements by changing the pads I described
above to resistive matching networks. For instance, design T or Pi pads with
50 ohms to 600 ohms (if you application is a 600 ohm system). The pad loss
is not a factor in the above described substitution method.
Finally, the idea of upgrading my SA to add in the tracking
generator is
still kicking around my head. Any input people have regarding the
usefulness of the SA/TG combo for sweeping filters would be
appreciated,
along with any other things that people use the combo for.
My experiences with tracking generators has been mixed. They sure
can be convenient, but I have also been zapped when I didn't watch closely
to see if they were really tracking.
Thanks for your help,
I am a river unto my people! <grin>
Ed
Jim Eichner
> Senior Regulatory Compliance Engineer
Statpower Technologies Corporation
jeich...@statpower.com
http://www.statpower.com
> phone: (604) 420-4820 ext. 2162
> fax: (604) 420-1591
Any opinions expressed are those of my invisible friend, who really
exists. Honest.
-----Original Message-----
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Price, Ed
Sent: Friday, September 10 1999 02:21
To: 'Jim Eichner'; 'EMC-PSTC - forum'
Subject: RE: Sweeping components and filters
Jim:
OK, here's my 2 Euro's opinion!
If you are starting from scratch, then buy a used HP-141T mainframe
with
an
8552 and 8556 plug-ins. This will give you a spectrum analyzer with
analog
memory, covering 20Hz to 300 KHz. And it has a tracking generator to
provide
the excitation. Later you can buy some other plug-ins which will
give
you a
pre-compliance tester for CE & RE. Here in the USA, you can get this
for
under $1000.
OR
If you have a spectrum analyzer with a memory, you can use a sweeper
as
the
source. Wiltron and Wavetek and HP sweepers can be obtained on the
surplus
market for several hundred dollars. No need for any sync between the
two.
Set the sweep ranges for both, and let them run for a while until
you
fill
in the spectrum of interest.
(SNIP)
Regards,
Ed
> -----Original Message-----
> From: Jim Eichner [SMTP:jeich...@statpower.com]
> Sent: Thursday, September 09, 1999 4:03 PM
> To: 'EMC-PSTC - forum'
> Subject: Sweeping components and filters
>
>
> Greetings all:
>
> I have long wished that I had an instrument for sweeping filters
and
> components that I am working on, to determine where I can expect
the
> usefulness to start rolling off, where and if there are
resonances,
> etc.
(SNIP)
> Thanks
>
> Jim Eichner
> > Senior Regulatory Compliance Engineer
> Statpower Technologies Corporation
> jeich...@statpower.com
> http://www.statpower.com
> Any opinions expressed are those of my invisible friend, who
really
> exists. Honest.
>
:-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-)
Ed Price
ed.pr...@cubic.com
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA. USA
619-505-2780 (Voice)
619-505-1502 (Fax)
Military & Avionics EMC Services Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis
:-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-):-)
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