Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

Brent DeWitt Fri, 10 May 2013 22:51:41 -0700

Title: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

The small chamber with the lights was the work of Mike Hatfield, then of NSWC Dahlgren.

Brent DeWitt

-----Original Message-----
From: Luke Turnbull
Sent: May 10, 2013 7:07 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

I’ve seen this on a video related to Frank Leferink’s reverb tents, where the modes are stirred by shaking the side wall of the tent. The fabric is think enough to see the tube inside.

Luke Turnbull

From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ken Javor
Sent: 09 May 2013 18:17
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

There is a nice little demo that one can usually see at the EMC Symposium where someone (don’t recall who) has a small reverb chamber with some fluorescent lamps that come on and go off as the paddle is stirred.

Ken Javor
Phone: (256) 650-5261

From: Ed Price <edpr...@cox.net>
Date: Thu, 9 May 2013 10:04:56 -0700
To: <EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: RE: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

I view the power density concentrations as varying density little clouds, chimera, moving regularly in 3 dimensions, and continuously changing their dimensions as they move. The presence of the ground plane, stirrer supports, antenna and EUT would have the motions not always linear. The motions wouldn’t be “darting” but more gracefully oscillating; it would make for one heck of an animation.

One thing we haven’t talked about is knowing the response time of your EUT. Most times, I was fortunate enough to be testing systems which had the courtesy of crashing rather quickly and completely, so a “response” was obvious. But when your definition of a “response” is “any degradation of operation, any unintentional responses and nor any failure of intentional responses”, then you have a formidable task before your testing just to learn how your EUT degrades.

Ed Price
WB6WSN
Chula Vista, CA USA

From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Thursday, May 09, 2013 8:10 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

Well, an area of constructive or destructive interference is going to have dimensions on the order of a half-wavelength. That sets the upper bound on the illumination spot-size. Clearly, the spot size decrease with increasing frequency.

Ken Javor
Phone: (256) 650-5261

From: Luke Turnbull <luke.turnb...@trw.com>
Date: Thu, 9 May 2013 09:53:35 +0000
To: Ken Javor <ken.ja...@emccompliance.com>, "EMC-PSTC@LISTSERV.IEEE.ORG" <EMC-PSTC@LISTSERV.IEEE.ORG>
Conversation: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?
Subject: RE: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

The picture I have in my mind is that there’s a (or several) relatively small hot spot(s) – you could say will-o’-the-wisp(s) – that dart around the test chamber as the paddles move. Therefore my understanding is that a large system isn’t simultaneously illuminated by the reverb method.

Luke Turnbull

From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ken Javor
Sent: 04 May 2013 17:52
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

Let me recode that – sorry for the typos:

The paddle must spin slow enough – or stop and dwell - so that the test sample has time to respond to the peak field intensity. Since one doesn’t know where in the chamber the peak is, only its amplitude, the rotation rate or dwell time must be such that the test sample response time is accommodated at every paddle position. This makes reverb testing take much longer than anechoic testing.

Ken Javor
Phone: (256) 650-5261

From: Ken Javor <ken.ja...@emccompliance.com>
Date: Sat, 04 May 2013 11:49:23 -0500
To: <EMC-PSTC@LISTSERV.IEEE.ORG>
Conversation: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?
Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

He paddle must spin slow enough – or stop and dwell, so that the test sample has time to respond to the peak fed intensity. Since one doesn’t know where in the chamber the peak is, only its amplitude, the rotation rate or dwell time must be such that the test sample response time is accommodated at every paddle position. This makes reverb testing much longer than anechoic testing.

Ken Javor
Phone: (256) 650-5261

From: Pat Lawler <plawl...@gmail.com>
Date: Sat, 4 May 2013 08:36:58 -0700
To: <owner-emc-p...@listserv.ieee.org>
Cc: <EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

The issue of waiting to get the peak field intensity could be shortened by spinning the paddles at a higher speed. However, I wouldn't want to be inside a metal chamber with a 4'x8' metal plate spinning at 300 RPM. Sounds like an Edgar Allen Poe story -- 'The Plate In The Reverb Chamber'.

Thanks to all who replied. This is a corner of EMC testing I've never been involved with.
If EMC is called black magic by some, mode-tuned/stirred/stepped chambers sound like black magic^2.

Pat

On Mon, Apr 29, 2013 at 9:23 AM, Luke Turnbull <luke.turnb...@trw.com> wrote:
Hi all,

Our experience is that you get pretty much the same levels with either a reverberation chamber, or with high gain antennas in a regular anechoic chamber. It is possible to increase the antenna gain by 3 or 4 dB compared to “traditional methods”, and get up to the same levels achieved in a reverberation chamber. Our methods achieve a minimum 3000 V/m, 1-18 GHz in a regular anechoic chamber.

Luke Turnbull

Dr Luke Turnbull
EMC Technical Manager
TRW Conekt
Stratford Road
Solihull
West Midlands B90 4GW
United Kingdom

Tel:        +44 (0)121.627.3966 <tel:%2B44%20%280%29121.627.3966>

email: luke.turnb...@trw.com
web:     www.conekt.co.uk <http://www.conekt.co.uk> <http://www.conekt.co.uk> <http://www.conekt.co.uk/>

From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ed Price
Sent: 28 April 2013 17:53
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: RE: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

<snip>

You can take advantage of the multiple reflections in a chamber (actually enhancing the reflections through the use of the moving mechanical structures) to achieve higher E-fields. This allows you to get higher E-fields for a test like RS103 than you could get using traditional methods.

<snip>

Ed Price
WB6WSN
Chula Vista, CA USA

From: Pat Lawler [mailto:pat.law...@verizon.net]
Sent: Sunday, April 28, 2013 7:38 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

All,

Over the years, I've come across pictures of test chambers with descriptions such as mode-stirred, mode-turned, and reverberation. They seem to look similar, with metal walls and rotating metal paddles.

Do these names reference the same basic design, or are they different animals? Which ones are used for which type of RF immunity test?

Thanks,

Pat Lawler

Teset engineer

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Re: [PSES] Mode-stirred, Mode-tuned, Reverb - what's the difference?

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