Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Ken Javor]

Yet another thing I meant to mention but forgot is that since the HDMI cable
with all conductors connected together does not represent a 50 ohm
controlled impedance transmission line, if the cable is electrically long
what you measure by connecting a 50 ohm receiver to one end is going to
depend on just how long the cable is.  Just another reason to keep things
electrically short.


And assuming that the need for cable shield SE is from 30 ­ 1000+ MHz, you
want to use the highest frequency at which the cable is electrically short.
Obviously you could use 10 kHz, but at that frequency you might not be able
to tell the difference between a pigtail and a 360 degree peripheral
termination.

If my brain were analogized to an engine, we could say it was fine but that
my transmission keeps popping out of gear...

Ken Javor
Phone: (256) 650-5261




From: Ken Javor 
Date: Fri, 20 Apr 2018 14:43:17 -0500
To: "Grasso, Charles" ,
"EMC-PSTC@LISTSERV.IEEE.ORG" 
Conversation: [PSES] Using a TDR for Shielding Effectiveness measurements
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements

One thing I should have mentioned as well is that if the cable is
electrically long, then in addition to an ugly waveform, the current
measured by the probe is probe-position dependent.  That means what you
measure as ZT isn¹t accurate if you pick any one probe position.  You need
the average. But you don¹t need accurate ZT, just repeatable. So if you pick
a probe position (must be) near the cable end connected to the receiver,
then IFF (if and only if) each cable tested is identical in length and
construction, you ought to get repeatable results. But if the cables are of
varying length and electrically long, you can only compare against identical
lengths. If you keep the cables electrically short, these problems vanish.

Ken Javor
Phone: (256) 650-5261



From: "Grasso, Charles" 
Date: Fri, 20 Apr 2018 19:36:40 +
To: Ken Javor , "EMC-PSTC@LISTSERV.IEEE.ORG"

Conversation: [PSES] Using a TDR for Shielding Effectiveness measurements
Subject: RE: [PSES] Using a TDR for Shielding Effectiveness measurements

Thank you Ken and Istvan for your insightful comments.
 
As can be seen from the minimal response set ­ the problem of evaluating
incoming inspection
is an ³ opportunity² to excel!
 
I doubt that the TDR will be the tester of choice ­ or even if there is an
easy solution to the problem.
 
 
Thanks
 
Charles Grasso
(w) 303-706-5467
 
 
 

From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Friday, April 20, 2018 12:00 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements
 
 This message originated outside of DISH and was sent by:
owner-emc-p...@listserv.ieee.org

Talk about cluelessness, I didn¹t even realize the OP was about cable shield
SE...

Totally ignorant of the standard Mr. Woodgate is citing so this post is an
addition to, not in lieu of or in contradiction to whatever that standard is
about.

I also don¹t know what HDMI cable looks like in terms of shield
configuration. I¹m assuming here that there are several conductors within an
overall shield.

If it were me, just looking for quick incoming quality check, I¹d build a
fixture that provided for proper termination of the cable connectors, and
have that mating connector bonded to a bracket that was in turn bonded to a
ground plane.  I would inject using a BCI method a signal whose spectrum was
such that the cable was electrically very short. The mating connectors would
be wired so all interior conductors were tied together, and terminated in 50
ohms on one one side and in an EMI receiver on the other. Using a current
probe to monitor injected current, and an arbitrary waveform generator
(these days) as the injection stimulus, I would select the aforementioned
frequency range (or frequency) where the cable is electrically short.  The
resultant transfer impedance measurement would be the metric of interest.
This could be considerably simplified using a spectrum analyzer with
tracking generator.

And if the cable SE isn¹t very high (high ZT) you could get by with a high
level impulse such as from a MIL-STD-461 CS115 generator (easily cobbled
together if you don¹t have one or want to buy one) and an o¹scope to read
the current coupled signal.  With CS115, you can get 5 amps on the cable and
be able to pick up say 50 mV peak, for a transfer impedance of 10 milliohms.

But the problem to watch for in a TD measurement is that if the stimulus is
fast relative to the electrical length of the cable, then the induced
current (response) will ³wash out² and you get an ugly current waveform, and
hence an ugly coupled potential, and thus difficult to take the ratio. So
the risetime and duration of a usable impulse are dependent on how long the

Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Ken Javor]

One thing I should have mentioned as well is that if the cable is
electrically long, then in addition to an ugly waveform, the current
measured by the probe is probe-position dependent.  That means what you
measure as ZT isn¹t accurate if you pick any one probe position.  You need
the average. But you don¹t need accurate ZT, just repeatable. So if you pick
a probe position (must be) near the cable end connected to the receiver,
then IFF (if and only if) each cable tested is identical in length and
construction, you ought to get repeatable results. But if the cables are of
varying length and electrically long, you can only compare against identical
lengths. If you keep the cables electrically short, these problems vanish.

Ken Javor
Phone: (256) 650-5261



From: "Grasso, Charles" 
Date: Fri, 20 Apr 2018 19:36:40 +
To: Ken Javor , "EMC-PSTC@LISTSERV.IEEE.ORG"

Conversation: [PSES] Using a TDR for Shielding Effectiveness measurements
Subject: RE: [PSES] Using a TDR for Shielding Effectiveness measurements

Thank you Ken and Istvan for your insightful comments.
 
As can be seen from the minimal response set ­ the problem of evaluating
incoming inspection
is an ³ opportunity² to excel!
 
I doubt that the TDR will be the tester of choice ­ or even if there is an
easy solution to the problem.
 
 
Thanks
 
Charles Grasso
(w) 303-706-5467
 
 
 

From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Friday, April 20, 2018 12:00 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements
 
 This message originated outside of DISH and was sent by:
owner-emc-p...@listserv.ieee.org

Talk about cluelessness, I didn¹t even realize the OP was about cable shield
SE...

Totally ignorant of the standard Mr. Woodgate is citing so this post is an
addition to, not in lieu of or in contradiction to whatever that standard is
about.

I also don¹t know what HDMI cable looks like in terms of shield
configuration. I¹m assuming here that there are several conductors within an
overall shield.

If it were me, just looking for quick incoming quality check, I¹d build a
fixture that provided for proper termination of the cable connectors, and
have that mating connector bonded to a bracket that was in turn bonded to a
ground plane.  I would inject using a BCI method a signal whose spectrum was
such that the cable was electrically very short. The mating connectors would
be wired so all interior conductors were tied together, and terminated in 50
ohms on one one side and in an EMI receiver on the other. Using a current
probe to monitor injected current, and an arbitrary waveform generator
(these days) as the injection stimulus, I would select the aforementioned
frequency range (or frequency) where the cable is electrically short.  The
resultant transfer impedance measurement would be the metric of interest.
This could be considerably simplified using a spectrum analyzer with
tracking generator.

And if the cable SE isn¹t very high (high ZT) you could get by with a high
level impulse such as from a MIL-STD-461 CS115 generator (easily cobbled
together if you don¹t have one or want to buy one) and an o¹scope to read
the current coupled signal.  With CS115, you can get 5 amps on the cable and
be able to pick up say 50 mV peak, for a transfer impedance of 10 milliohms.

But the problem to watch for in a TD measurement is that if the stimulus is
fast relative to the electrical length of the cable, then the induced
current (response) will ³wash out² and you get an ugly current waveform, and
hence an ugly coupled potential, and thus difficult to take the ratio. So
the risetime and duration of a usable impulse are dependent on how long the
cable-under-test is.

Ken Javor
Phone: (256) 650-5261



From: "Grasso, Charles" 
Reply-To: "Grasso, Charles" 
Date: Fri, 20 Apr 2018 15:48:57 +
To: 
Conversation: [PSES] Using a TDR for Shielding Effectiveness measurements
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements

Thanks John..
 

From: John Woodgate [mailto:j...@woodjohn.uk]
Sent: Friday, April 20, 2018 9:40 AM
To: Grasso, Charles ; EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements

This message originated outside of DISH and was sent by: j...@woodjohn.uk

Go to:

http://www.iec.ch/dyn/www/f?p=103:22:0FSP_ORG_ID:1247

and look for publications in the 62153 series. There are several.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk 

Rayleigh, Essex UK
On 2018-04-20 16:05, Grasso, Charles wrote:
> Thanks to all that replied.  The task at hand is to devise a (relatively)
> simple measurement of the shielding
> quality at incoming inspection ­ hence the thought of 

Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Grasso, Charles]

Thank you Ken and Istvan for your insightful comments.

As can be seen from the minimal response set - the problem of evaluating 
incoming inspection
is an " opportunity" to excel!

I doubt that the TDR will be the tester of choice - or even if there is an easy 
solution to the problem.


Thanks

Charles Grasso
(w) 303-706-5467



From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Friday, April 20, 2018 12:00 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements


 This message originated outside of DISH and was sent by: 
owner-emc-p...@listserv.ieee.org
Talk about cluelessness, I didn't even realize the OP was about cable shield 
SE...

Totally ignorant of the standard Mr. Woodgate is citing so this post is an 
addition to, not in lieu of or in contradiction to whatever that standard is 
about.

I also don't know what HDMI cable looks like in terms of shield configuration. 
I'm assuming here that there are several conductors within an overall shield.

If it were me, just looking for quick incoming quality check, I'd build a 
fixture that provided for proper termination of the cable connectors, and have 
that mating connector bonded to a bracket that was in turn bonded to a ground 
plane.  I would inject using a BCI method a signal whose spectrum was such that 
the cable was electrically very short. The mating connectors would be wired so 
all interior conductors were tied together, and terminated in 50 ohms on one 
one side and in an EMI receiver on the other. Using a current probe to monitor 
injected current, and an arbitrary waveform generator (these days) as the 
injection stimulus, I would select the aforementioned frequency range (or 
frequency) where the cable is electrically short.  The resultant transfer 
impedance measurement would be the metric of interest.  This could be 
considerably simplified using a spectrum analyzer with tracking generator.

And if the cable SE isn't very high (high ZT) you could get by with a high 
level impulse such as from a MIL-STD-461 CS115 generator (easily cobbled 
together if you don't have one or want to buy one) and an o'scope to read the 
current coupled signal.  With CS115, you can get 5 amps on the cable and be 
able to pick up say 50 mV peak, for a transfer impedance of 10 milliohms.

But the problem to watch for in a TD measurement is that if the stimulus is 
fast relative to the electrical length of the cable, then the induced current 
(response) will "wash out" and you get an ugly current waveform, and hence an 
ugly coupled potential, and thus difficult to take the ratio. So the risetime 
and duration of a usable impulse are dependent on how long the cable-under-test 
is.

Ken Javor
Phone: (256) 650-5261



From: "Grasso, Charles" 
>
Reply-To: "Grasso, Charles" 
>
Date: Fri, 20 Apr 2018 15:48:57 +
To: >
Conversation: [PSES] Using a TDR for Shielding Effectiveness measurements
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements

Thanks John..


From: John Woodgate [mailto:j...@woodjohn.uk]
Sent: Friday, April 20, 2018 9:40 AM
To: Grasso, Charles >; 
EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements

This message originated outside of DISH and was sent by: 
j...@woodjohn.uk

Go to:

http://www.iec.ch/dyn/www/f?p=103:22:0FSP_ORG_ID:1247

and look for publications in the 62153 series. There are several.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk 

Rayleigh, Essex UK
On 2018-04-20 16:05, Grasso, Charles wrote:
Thanks to all that replied.  The task at hand is to devise a (relatively) 
simple measurement of the shielding
quality at incoming inspection - hence the thought of using a TDR to 
qualitatively assess (in this case) the
shielding of HDMI cables.  There would be measurements of the sample cables 
compared to
the performance of a known good cable. So I am not at specific SE number rather 
the measurement of
the construction that affects the SE. I realize now that my ask was poorly 
worded.

I am (well!) aware of the difficulties of this approach (for example :  false 
positives and false negatives) so
maybe I should restate the question: How does one measure samples of a 
manufactured lot of cables for
shielding quality? I'd be interested in suggestions!


Thanks

Charles Grasso
(w) 303-706-5467




From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Thursday, April 19, 2018 11:44 PM
To: 

Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Istvan Novak]

As long as we can assume that the propagation medium and the DUT are 
linear and time invariant, the time-domain response can be easily 
transformed to frequency-response data.  This is true also in the other 
direction: vector network analyzers today can be set to operate like TDR 
instruments as far as their displayed data is concerned. The dynamic 
range limitation is likely more relevant.

Regards,
Istvan Novak



Ken Javor wrote:
Re: [PSES] Using a TDR for Shielding Effectiveness measurements Given 
the few responses to date, I’ll fess up to cluelessness and curiosity. 
Aside from the obvious dynamic range limitation working in the time 
domain, if you limit yourself to the time domain, how do you map SE 
vs. frequency?


And given the inherent wide band nature of a TDR signal, I can’t see 
it being radiated properly. I’m thinking you would have to use 
something like an ASTM 4936 coaxial test fixture in order to main 
signal integrity up to the reflection point where the sample material 
puck is installed.




Ken Javor
Phone: (256) 650-5261



*From: *"Grasso, Charles" 
*Reply-To: *"Grasso, Charles" 
*Date: *Thu, 19 Apr 2018 15:23:27 +
*To: *
*Conversation: *Using a TDR for Shielding Effectiveness measurements
*Subject: *[PSES] Using a TDR for Shielding Effectiveness measurements

Hello all,

In lieu of using shielded chambers/spectrum analyzers and such, has 
anyone used a TDR for
performing shielding effectiveness measurements?  The simplicity is 
tempting – but I am

dubious about the dynamic range?

I have poked about in the usual place – but didn’t find any definitive 
studies. (I suppose

that is a clue in and of itself!)

Thanks

Charles Grasso
(w) 303-706-5467

-


This message is from the IEEE Product Safety Engineering Society 
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emc-pstc discussion list. To post a message to the list, send your 
e-mail to >


All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html


Attachments are not permitted but the IEEE PSES Online Communities 
site at http://product-compliance.oc.ieee.org/ can be used for 
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Website: http://www.ieee-pses.org/
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List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas >
Mike Cantwell >

For policy questions, send mail to:
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David Heald >



-

This message is from the IEEE Product Safety Engineering Society emc-pstc discussion 
list. To post a message to the list, send your e-mail to 

All emc-pstc postings are archived and searchable on the web at:
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to unsubscribe)
List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas 
Mike Cantwell 

For policy questions, send mail to:
Jim Bacher:  
David Heald: 

Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Ken Javor]

Talk about cluelessness, I didn¹t even realize the OP was about cable shield
SE...

Totally ignorant of the standard Mr. Woodgate is citing so this post is an
addition to, not in lieu of or in contradiction to whatever that standard is
about.

I also don¹t know what HDMI cable looks like in terms of shield
configuration. I¹m assuming here that there are several conductors within an
overall shield.

If it were me, just looking for quick incoming quality check, I¹d build a
fixture that provided for proper termination of the cable connectors, and
have that mating connector bonded to a bracket that was in turn bonded to a
ground plane.  I would inject using a BCI method a signal whose spectrum was
such that the cable was electrically very short. The mating connectors would
be wired so all interior conductors were tied together, and terminated in 50
ohms on one one side and in an EMI receiver on the other. Using a current
probe to monitor injected current, and an arbitrary waveform generator
(these days) as the injection stimulus, I would select the aforementioned
frequency range (or frequency) where the cable is electrically short.  The
resultant transfer impedance measurement would be the metric of interest.
This could be considerably simplified using a spectrum analyzer with
tracking generator.

And if the cable SE isn¹t very high (high ZT) you could get by with a high
level impulse such as from a MIL-STD-461 CS115 generator (easily cobbled
together if you don¹t have one or want to buy one) and an o¹scope to read
the current coupled signal.  With CS115, you can get 5 amps on the cable and
be able to pick up say 50 mV peak, for a transfer impedance of 10 milliohms.

But the problem to watch for in a TD measurement is that if the stimulus is
fast relative to the electrical length of the cable, then the induced
current (response) will ³wash out² and you get an ugly current waveform, and
hence an ugly coupled potential, and thus difficult to take the ratio. So
the risetime and duration of a usable impulse are dependent on how long the
cable-under-test is.

Ken Javor
Phone: (256) 650-5261




From: "Grasso, Charles" 
Reply-To: "Grasso, Charles" 
Date: Fri, 20 Apr 2018 15:48:57 +
To: 
Conversation: [PSES] Using a TDR for Shielding Effectiveness measurements
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements

Thanks John..
 

From: John Woodgate [mailto:j...@woodjohn.uk]
Sent: Friday, April 20, 2018 9:40 AM
To: Grasso, Charles ; EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements
 
 This message originated outside of DISH and was sent by: j...@woodjohn.uk

Go to:

http://www.iec.ch/dyn/www/f?p=103:22:0FSP_ORG_ID:1247

and look for publications in the 62153 series. There are several.
John Woodgate OOO-Own Opinions Only
J M Woodgate and Associates www.woodjohn.uk 
Rayleigh, Essex UK
On 2018-04-20 16:05, Grasso, Charles wrote:
> Thanks to all that replied.  The task at hand is to devise a (relatively)
> simple measurement of the shielding
> quality at incoming inspection ­ hence the thought of using a TDR to
> qualitatively assess (in this case) the
> shielding of HDMI cables.  There would be measurements of the sample cables
> compared to 
> the performance of a known good cable. So I am not at specific SE number
> rather the measurement of
> the construction that affects the SE. I realize now that my ask was poorly
> worded.
>  
> I am (well!) aware of the difficulties of this approach (for example :  false
> positives and false negatives) so
> maybe I should restate the question: How does one measure samples of a
> manufactured lot of cables for
> shielding quality? I¹d be interested in suggestions!
>  
>  
> Thanks
>  
> Charles Grasso
> (w) 303-706-5467
>  
>  
>  
> 
> From: Ken Javor [mailto:ken.ja...@emccompliance.com]
> Sent: Thursday, April 19, 2018 11:44 PM
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements
>  
>  This message originated outside of DISH and was sent by:
> owner-emc-p...@listserv.ieee.org
> 
> Given the few responses to date, I¹ll fess up to cluelessness and curiosity.
> Aside from the obvious dynamic range limitation working in the time domain, if
> you limit yourself to the time domain, how do you map SE vs. frequency?
> 
> And given the inherent wide band nature of a TDR signal, I can¹t see it being
> radiated properly. I¹m thinking you would have to use something like an ASTM
> 4936 coaxial test fixture in order to main signal integrity up to the
> reflection point where the sample material puck is installed.
> 
> 
> 
> Ken Javor
> Phone: (256) 650-5261
> 
> 
> 
> From: "Grasso, Charles" 
> Reply-To: "Grasso, Charles" 
> Date: Thu, 19 Apr 2018 15:23:27 +
> To: 

Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Grasso, Charles]

Thanks John..

From: John Woodgate [mailto:j...@woodjohn.uk]
Sent: Friday, April 20, 2018 9:40 AM
To: Grasso, Charles ; EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements


 This message originated outside of DISH and was sent by: 
j...@woodjohn.uk

Go to:

http://www.iec.ch/dyn/www/f?p=103:22:0FSP_ORG_ID:1247

and look for publications in the 62153 series. There are several.

John Woodgate OOO-Own Opinions Only

J M Woodgate and Associates www.woodjohn.uk

Rayleigh, Essex UK
On 2018-04-20 16:05, Grasso, Charles wrote:
Thanks to all that replied.  The task at hand is to devise a (relatively) 
simple measurement of the shielding
quality at incoming inspection - hence the thought of using a TDR to 
qualitatively assess (in this case) the
shielding of HDMI cables.  There would be measurements of the sample cables 
compared to
the performance of a known good cable. So I am not at specific SE number rather 
the measurement of
the construction that affects the SE. I realize now that my ask was poorly 
worded.

I am (well!) aware of the difficulties of this approach (for example :  false 
positives and false negatives) so
maybe I should restate the question: How does one measure samples of a 
manufactured lot of cables for
shielding quality? I'd be interested in suggestions!


Thanks

Charles Grasso
(w) 303-706-5467



From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Thursday, April 19, 2018 11:44 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements


 This message originated outside of DISH and was sent by: 
owner-emc-p...@listserv.ieee.org
Given the few responses to date, I'll fess up to cluelessness and curiosity. 
Aside from the obvious dynamic range limitation working in the time domain, if 
you limit yourself to the time domain, how do you map SE vs. frequency?

And given the inherent wide band nature of a TDR signal, I can't see it being 
radiated properly. I'm thinking you would have to use something like an ASTM 
4936 coaxial test fixture in order to main signal integrity up to the 
reflection point where the sample material puck is installed.



Ken Javor
Phone: (256) 650-5261



From: "Grasso, Charles" 
>
Reply-To: "Grasso, Charles" 
>
Date: Thu, 19 Apr 2018 15:23:27 +
To: >
Conversation: Using a TDR for Shielding Effectiveness measurements
Subject: [PSES] Using a TDR for Shielding Effectiveness measurements

Hello all,

In lieu of using shielded chambers/spectrum analyzers and such, has anyone used 
a TDR for
performing shielding effectiveness measurements?  The simplicity is tempting - 
but I am
dubious about the dynamic range?

I have poked about in the usual place - but didn't find any definitive studies. 
(I suppose
that is a clue in and of itself!)

Thanks

Charles Grasso
(w) 303-706-5467

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
>

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website:  http://www.ieee-pses.org/
Instructions:  http://www.ieee-pses.org/list.html (including how to 
unsubscribe) 

List rules: http://www.ieee-pses.org/listrules.html

For help, send mail to the list administrators:
Scott Douglas >
Mike Cantwell >

For policy questions, send mail to:
Jim Bacher  >
David Heald >
-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
>

All emc-pstc postings are archived and searchable on the web at: 
http://www.ieee-pses.org/emc-pstc.html

Attachments are not permitted but the IEEE PSES Online Communities site at 
http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
formats), large files, etc.

Website: http://www.ieee-pses.org/
Instructions: http://www.ieee-pses.org/list.html (including how 

Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Istvan Novak]

Ken,
Actually what I was referring to: we can transmit a pulse (or rather a 
step, if it is a TDR), measure the response with an oscilloscope in the 
time domain and as long as the DUT is linear and time invariant, we can 
take the time-domain data from the oscilloscope, transform it into the 
frequency domain with Fourier transform, and if we do it properly, the 
result will be exactly the same that we would get with a vector-network 
analyzer, minus the dynamic range.

Best regards,
Istvan Novak



On 4/20/2018 11:00 AM, Ken Javor wrote:

My response was predicated on a purely time domain measurement.  If we are
going to transmit a pulse but measure in the frequency domain, then there is
no dynamic range limitation, assuming we have a pre-selected front end to
our receiver.  And if we are making a frequency domain measurement, then any
set of suitable transmit antennas will do, as we are only looking at some
fraction of the pulse spectrum at any one time; no need to transmit the
entire pulse spectrum simultaneously.

But if those are the ground rules, then any impulse generator laying around
the lab, from the old days when they were used to calibrate EMI receivers,
would suffice.

Ken Javor
Phone: (256) 650-5261




From: Istvan Novak 
Date: Fri, 20 Apr 2018 08:28:09 -0400
To: Ken Javor , 
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements

As long as we can assume that the propagation medium and the DUT are
linear and time invariant, the time-domain response can be easily
transformed to frequency-response data.  This is true also in the other
direction: vector network analyzers today can be set to operate like TDR
instruments as far as their displayed data is concerned. The dynamic
range limitation is likely more relevant.
Regards,
Istvan Novak



Ken Javor wrote:

Re: [PSES] Using a TDR for Shielding Effectiveness measurements Given
the few responses to date, I¹ll fess up to cluelessness and curiosity.
Aside from the obvious dynamic range limitation working in the time
domain, if you limit yourself to the time domain, how do you map SE
vs. frequency?

And given the inherent wide band nature of a TDR signal, I can¹t see
it being radiated properly. I¹m thinking you would have to use
something like an ASTM 4936 coaxial test fixture in order to main
signal integrity up to the reflection point where the sample material
puck is installed.



Ken Javor
Phone: (256) 650-5261



*From: *"Grasso, Charles" 
*Reply-To: *"Grasso, Charles" 
*Date: *Thu, 19 Apr 2018 15:23:27 +
*To: *
*Conversation: *Using a TDR for Shielding Effectiveness measurements
*Subject: *[PSES] Using a TDR for Shielding Effectiveness measurements

Hello all,

In lieu of using shielded chambers/spectrum analyzers and such, has
anyone used a TDR for
performing shielding effectiveness measurements?  The simplicity is
tempting ­ but I am
dubious about the dynamic range?

I have poked about in the usual place ­ but didn¹t find any definitive
studies. (I suppose
that is a clue in and of itself!)

Thanks

Charles Grasso
(w) 303-706-5467

-


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Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Grasso, Charles]

Thanks to all that replied.  The task at hand is to devise a (relatively) 
simple measurement of the shielding
quality at incoming inspection - hence the thought of using a TDR to 
qualitatively assess (in this case) the
shielding of HDMI cables.  There would be measurements of the sample cables 
compared to
the performance of a known good cable. So I am not at specific SE number rather 
the measurement of
the construction that affects the SE. I realize now that my ask was poorly 
worded.

I am (well!) aware of the difficulties of this approach (for example :  false 
positives and false negatives) so
maybe I should restate the question: How does one measure samples of a 
manufactured lot of cables for
shielding quality? I'd be interested in suggestions!


Thanks

Charles Grasso
(w) 303-706-5467



From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: Thursday, April 19, 2018 11:44 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements


 This message originated outside of DISH and was sent by: 
owner-emc-p...@listserv.ieee.org
Given the few responses to date, I'll fess up to cluelessness and curiosity. 
Aside from the obvious dynamic range limitation working in the time domain, if 
you limit yourself to the time domain, how do you map SE vs. frequency?

And given the inherent wide band nature of a TDR signal, I can't see it being 
radiated properly. I'm thinking you would have to use something like an ASTM 
4936 coaxial test fixture in order to main signal integrity up to the 
reflection point where the sample material puck is installed.



Ken Javor
Phone: (256) 650-5261


From: "Grasso, Charles" 
>
Reply-To: "Grasso, Charles" 
>
Date: Thu, 19 Apr 2018 15:23:27 +
To: >
Conversation: Using a TDR for Shielding Effectiveness measurements
Subject: [PSES] Using a TDR for Shielding Effectiveness measurements

Hello all,

In lieu of using shielded chambers/spectrum analyzers and such, has anyone used 
a TDR for
performing shielding effectiveness measurements?  The simplicity is tempting - 
but I am
dubious about the dynamic range?

I have poked about in the usual place - but didn't find any definitive studies. 
(I suppose
that is a clue in and of itself!)

Thanks

Charles Grasso
(w) 303-706-5467

-


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
>

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http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used 
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>

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This message is from the IEEE Product Safety Engineering Society emc-pstc 
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Re: [PSES] Using a TDR for Shielding Effectiveness measurements

[Ken Javor]

My response was predicated on a purely time domain measurement.  If we are
going to transmit a pulse but measure in the frequency domain, then there is
no dynamic range limitation, assuming we have a pre-selected front end to
our receiver.  And if we are making a frequency domain measurement, then any
set of suitable transmit antennas will do, as we are only looking at some
fraction of the pulse spectrum at any one time; no need to transmit the
entire pulse spectrum simultaneously.

But if those are the ground rules, then any impulse generator laying around
the lab, from the old days when they were used to calibrate EMI receivers,
would suffice.

Ken Javor
Phone: (256) 650-5261



> From: Istvan Novak 
> Date: Fri, 20 Apr 2018 08:28:09 -0400
> To: Ken Javor , 
> Subject: Re: [PSES] Using a TDR for Shielding Effectiveness measurements
> 
> As long as we can assume that the propagation medium and the DUT are
> linear and time invariant, the time-domain response can be easily
> transformed to frequency-response data.  This is true also in the other
> direction: vector network analyzers today can be set to operate like TDR
> instruments as far as their displayed data is concerned. The dynamic
> range limitation is likely more relevant.
> Regards,
> Istvan Novak
> 
> 
> 
> Ken Javor wrote:
>> Re: [PSES] Using a TDR for Shielding Effectiveness measurements Given
>> the few responses to date, I¹ll fess up to cluelessness and curiosity.
>> Aside from the obvious dynamic range limitation working in the time
>> domain, if you limit yourself to the time domain, how do you map SE
>> vs. frequency?
>> 
>> And given the inherent wide band nature of a TDR signal, I can¹t see
>> it being radiated properly. I¹m thinking you would have to use
>> something like an ASTM 4936 coaxial test fixture in order to main
>> signal integrity up to the reflection point where the sample material
>> puck is installed.
>> 
>> 
>> 
>> Ken Javor
>> Phone: (256) 650-5261
>> 
>> 
>> 
>> *From: *"Grasso, Charles" 
>> *Reply-To: *"Grasso, Charles" 
>> *Date: *Thu, 19 Apr 2018 15:23:27 +
>> *To: *
>> *Conversation: *Using a TDR for Shielding Effectiveness measurements
>> *Subject: *[PSES] Using a TDR for Shielding Effectiveness measurements
>> 
>> Hello all,
>> 
>> In lieu of using shielded chambers/spectrum analyzers and such, has
>> anyone used a TDR for
>> performing shielding effectiveness measurements?  The simplicity is
>> tempting ­ but I am
>> dubious about the dynamic range?
>> 
>> I have poked about in the usual place ­ but didn¹t find any definitive
>> studies. (I suppose
>> that is a clue in and of itself!)
>> 
>> Thanks
>> 
>> Charles Grasso
>> (w) 303-706-5467
>> 
>> -
>> 
>> 
>> This message is from the IEEE Product Safety Engineering Society
>> emc-pstc discussion list. To post a message to the list, send your
>> e-mail to 
>> 
>> All emc-pstc postings are archived and searchable on the web at:
>> http://www.ieee-pses.org/emc-pstc.html
>> 
>> Attachments are not permitted but the IEEE PSES Online Communities
>> site at http://product-compliance.oc.ieee.org/ can be used for
>> graphics (in well-used formats), large files, etc.
>> 
>> Website: http://www.ieee-pses.org/
>> Instructions: http://www.ieee-pses.org/list.html (including how to
>> unsubscribe) 
>> 
>> List rules: http://www.ieee-pses.org/listrules.html
>> 
>> For help, send mail to the list administrators:
>> Scott Douglas 
>> Mike Cantwell 
>> 
>> For policy questions, send mail to:
>> Jim Bacher  
>> David Heald 
>> 
>> -
>> 
>> 
>> This message is from the IEEE Product Safety Engineering Society
>> emc-pstc discussion list. To post a message to the list, send your
>> e-mail to >
>> 
>> All emc-pstc postings are archived and searchable on the web at:
>> http://www.ieee-pses.org/emc-pstc.html
>> 
>> Attachments are not permitted but the IEEE PSES Online Communities
>> site at http://product-compliance.oc.ieee.org/ can be used for
>> graphics (in well-used formats), large files, etc.
>> 
>> Website: http://www.ieee-pses.org/
>> Instructions: http://www.ieee-pses.org/list.html (including how to
>> unsubscribe)
>> List rules: http://www.ieee-pses.org/listrules.html
>> 
>> For help, send mail to the list administrators:
>> Scott Douglas >
>> Mike Cantwell >
>> 
>> For policy questions, send mail to:
>> Jim Bacher