Forums

Power measurement

Started by vinprakash366 February 1, 2002
Hi all,

In the G.168(2000) standard, under section 6.4.1.2.1, level
measurement device, i am a little confused abt the detector-indicator
block. How should this be implemented in order to decect the power in
dBm0??. Also, is the 1-pole exponential filter mentioned in the block
a unity gain filter??

thanks in advance,
Vinod



There is an implementor's guide for G.168 available from ITU.
I don't know if your questions are addressed in that document but it's
probably worth a look.
http://www.itu.int/rec/recommendation.asp?type=folders&lang=e&parent=T-REC-G.Imp\
168 >From: "vinprakash366" <>
>Reply-To:
>To:
>Subject: [echocancel] Power measurement
>Date: Fri, 01 Feb 2002 06:26:37 -0000
>
>Hi all,
>
> In the G.168(2000) standard, under section 6.4.1.2.1, level
>measurement device, i am a little confused abt the detector-indicator
>block. How should this be implemented in order to decect the power in
>dBm0??. Also, is the 1-pole exponential filter mentioned in the block
>a unity gain filter??
>
>thanks in advance,
>Vinod

_________________________________________________________________
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http://photos.msn.com/support/worldwide.aspx


Since I wrote this section of the recommendation, let me see if I can
calrify it for you. The measurement device is a sub-paragraph of 6.4.2,
Measuring input and output levels. The paragraph tells how to make the
measuremen (RMS for example) and 6.4.2.1 tells how to make the measuring
device for this measurement. In other words, the detector and indicator
can be anything you want as long as it makes the measurement as required
by 6.4.2. The indicator is your choice as to how you want to make the
human interfece.

The exponential filter is unity gain for a sustained signal Maurice Givens
Givens Burnet, Inc.
10341 S. Prospect Ave.
Chicago, IL 60643-2824
On Fri, 01 Feb 2002 06:26:37 -0000 "vinprakash366"
<> writes:
> Hi all,
>
> In the G.168(2000) standard, under section 6.4.1.2.1, level
> measurement device, i am a little confused abt the
> detector-indicator
> block. How should this be implemented in order to decect the power
> in
> dBm0??. Also, is the 1-pole exponential filter mentioned in the
> block
> a unity gain filter??
>
> thanks in advance,
> Vinod >
> _____________________________________
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The implementor's guide does not address this since we thought the
wording was not ambiguous. This is the only question concerning this
part of the recommendation of which we are aware.

Maurice Givens
Givens Burnet, Inc.
10341 S. Prospect Ave.
Chicago, IL 60643-2824 On Fri, 01 Feb 2002 13:54:53 -0500 "mike belanger" <>
writes:
> There is an implementor's guide for G.168 available from ITU.
> I don't know if your questions are addressed in that document but
> it's
> probably worth a look.
>
http://www.itu.int/rec/recommendation.asp?type=folders&lang=e&parent=T-RE
C-G.Imp168
>
>
> >From: "vinprakash366" <>
> >Reply-To:
> >To:
> >Subject: [echocancel] Power measurement
> >Date: Fri, 01 Feb 2002 06:26:37 -0000
> >
> >Hi all,
> >
> > In the G.168(2000) standard, under section 6.4.1.2.1, level
> >measurement device, i am a little confused abt the
> detector-indicator
> >block. How should this be implemented in order to decect the power
> in
> >dBm0??. Also, is the 1-pole exponential filter mentioned in the
> block
> >a unity gain filter??
> >
> >thanks in advance,
> >Vinod
> >
> >
>
> _________________________________________________________________
> MSN Photos is the easiest way to share and print your photos:
> http://photos.msn.com/support/worldwide.aspx >
> ------------------------ Yahoo! Groups Sponsor
>
> _____________________________________
> Note: If you do a simple "reply" with your email client, only the
> author of this message will receive your answer. You need to do a
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>
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>
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>
> To Post:
>
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>
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Hello Vinod Prakash,

I hope you will get some better insight after reading my
mail..................

An exponential filter is used to sharpen spectral features; the constant is
varied to change the filter shape.
A exponential filter is of the form where is the filter constant and X is
the array (i.e., data file) whose X range is normalized between 0 and 1.
As you may note.., In Section 6.4.1.2.2, the exponential filter is
replaced by a rectangular sliding window of the same length.

The output of the Exponential Filter is then fed to a DETECTOR,( which the
G.168 Standard specifies as DETECTOR-INDICATOR ).

I believe the implementation strategy for the DETECTOR should be based on
the
THRESHOLD of detection of the SPECTRAL PEAKS obtained from the EXPONENTIAL
FILTER......;-)

Dharmendra Lingaiah

-----Original Message-----
From: vinprakash366 [mailto:]
Sent: Friday, February 01, 2002 11:57 AM
To:
Subject: [echocancel] Power measurement Hi all,

In the G.168(2000) standard, under section 6.4.1.2.1, level
measurement device, i am a little confused abt the detector-indicator
block. How should this be implemented in order to decect the power in
dBm0??. Also, is the 1-pole exponential filter mentioned in the block
a unity gain filter??

thanks in advance,
Vinod
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Hi Maurice,

if I have understood right, the following needs to be done to
measure the power(in dBm0) of an input signal using the power
measurement device

1. pass it through the BPF specified
2. square the resulting sequence
3. pass the above , through a unity gain one pole exponential
filter ,whose difference equn is,
y(n) = a*y(n-1) + x(n)
where a = exp(-1/(8*35)) (at 8Khz sampling rate)

4. to calculate the output power(in dBm0)the following formula
is
applied the output of the above filter(say y(n)) ,
s(n) = 3.17 + 20*log(sqrt(y(n))/8159)

for the case of section 6.4.1.2.2, level measurement device for
peaks the following is done,

steps 1. and 2. are same as above
3. y(n) = sum(x(n)) from 1 to 280.
4. same as step of above.

do let me know if the interpretation is correct.

thanks and regards,
Vinod. -----Original Message-----
From: Maurice Givens [mailto:]
Sent: Monday, February 04, 2002 9:02 AM
To:
Subject: Re: [echocancel] Power measurement Since I wrote this section of the recommendation, let me see if I can
calrify it for you. The measurement device is a sub-paragraph of 6.4.2,
Measuring input and output levels. The paragraph tells how to make the
measuremen (RMS for example) and 6.4.2.1 tells how to make the measuring
device for this measurement. In other words, the detector and indicator
can be anything you want as long as it makes the measurement as required
by 6.4.2. The indicator is your choice as to how you want to make the
human interfece.

The exponential filter is unity gain for a sustained signal Maurice Givens
Givens Burnet, Inc.
10341 S. Prospect Ave.
Chicago, IL 60643-2824
On Fri, 01 Feb 2002 06:26:37 -0000 "vinprakash366"
<> writes:
> Hi all,
>
> In the G.168(2000) standard, under section 6.4.1.2.1, level
> measurement device, i am a little confused abt the
> detector-indicator
> block. How should this be implemented in order to decect the power
> in
> dBm0??. Also, is the 1-pole exponential filter mentioned in the
> block
> a unity gain filter??
>
> thanks in advance,
> Vinod >
> _____________________________________
> Note: If you do a simple "reply" with your email client, only the
> author of this message will receive your answer. You need to do a
> "reply all" if you want your answer to be distributed to the entire
> group.
>
> _____________________________________
> About this discussion group:
>
> To Join:
>
> To Post:
>
> To Leave:
>
> Archives: http://www.yahoogroups.com/group/echocancel
>
> Other DSP-Related Groups: http://www.dsprelated.com > ">http://docs.yahoo.com/info/terms/

________________________________________________________________
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_____________________________________
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You seem to have it correct.

Maurice Givens
Givens Burnet, Inc.
10341 S. Prospect Ave.
Chicago, IL 60643-2824
On Mon, 4 Feb 2002 19:44:34 +0530 "Vinod Prakash"
<> writes:
> Hi Maurice,
>
> if I have understood right, the following needs to be done
> to
> measure the power(in dBm0) of an input signal using the
> power
> measurement device
>
> 1. pass it through the BPF specified
> 2. square the resulting sequence
> 3. pass the above , through a unity gain one pole
> exponential
> filter ,whose difference equn is,
> y(n) = a*y(n-1) + x(n)
> where a = exp(-1/(8*35)) (at 8Khz sampling rate)
>
> 4. to calculate the output power(in dBm0)the following
> formula
> is
> applied the output of the above filter(say y(n)) ,
> s(n) = 3.17 + 20*log(sqrt(y(n))/8159)
>
> for the case of section 6.4.1.2.2, level measurement device
> for
> peaks the following is done,
>
> steps 1. and 2. are same as above
> 3. y(n) = sum(x(n)) from 1 to 280.
> 4. same as step of above.
>
> do let me know if the interpretation is correct.
>
> thanks and regards,
> Vinod. > -----Original Message-----
> From: Maurice Givens [mailto:]
> Sent: Monday, February 04, 2002 9:02 AM
> To:
> Subject: Re: [echocancel] Power measurement > Since I wrote this section of the recommendation, let me see if I
> can
> calrify it for you. The measurement device is a sub-paragraph of
> 6.4.2,
> Measuring input and output levels. The paragraph tells how to make
> the
> measuremen (RMS for example) and 6.4.2.1 tells how to make the
> measuring
> device for this measurement. In other words, the detector and
> indicator
> can be anything you want as long as it makes the measurement as
> required
> by 6.4.2. The indicator is your choice as to how you want to make
> the
> human interfece.
>
> The exponential filter is unity gain for a sustained signal > Maurice Givens
> Givens Burnet, Inc.
> 10341 S. Prospect Ave.
> Chicago, IL 60643-2824 >
> On Fri, 01 Feb 2002 06:26:37 -0000 "vinprakash366"
> <> writes:
> > Hi all,
> >
> > In the G.168(2000) standard, under section 6.4.1.2.1, level
> > measurement device, i am a little confused abt the
> > detector-indicator
> > block. How should this be implemented in order to decect the power
>
> > in
> > dBm0??. Also, is the 1-pole exponential filter mentioned in the
> > block
> > a unity gain filter??
> >
> > thanks in advance,
> > Vinod
> >
> >
> >
> > _____________________________________
> > Note: If you do a simple "reply" with your email client, only the
> > author of this message will receive your answer. You need to do a
>
> > "reply all" if you want your answer to be distributed to the
> entire
> > group.
> >
> > _____________________________________
> > About this discussion group:
> >
> > To Join:
> >
> > To Post:
> >
> > To Leave:
> >
> > Archives: http://www.yahoogroups.com/group/echocancel
> >
> > Other DSP-Related Groups: http://www.dsprelated.com
> >
> >
> > ">http://docs.yahoo.com/info/terms/
> >
> >
>
> ________________________________________________________________
> GET INTERNET ACCESS FROM JUNO!
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Hi maurice , vinod and members of the group,

It is regarding "acoustic" echo cancellation in hands free mobile.
singal power estimation algorithm, you stated is valid for network echo
cancellationl. because there you have signal in A-law or Mu-law formet. What
if the signal is in raw PCM format. will this formula still hold true.

Thanks and Regards,
Shiv

-----Original Message-----
From: Vinod Prakash [mailto:]
Sent: Monday, February 04, 2002 7:45 PM
To:
Cc:
Subject: RE: [echocancel] Power measurement Hi Maurice,

if I have understood right, the following needs to be done to
measure the power(in dBm0) of an input signal using the power
measurement device

1. pass it through the BPF specified
2. square the resulting sequence
3. pass the above , through a unity gain one pole exponential
filter ,whose difference equn is,
y(n) = a*y(n-1) + x(n)
where a = exp(-1/(8*35)) (at 8Khz sampling rate)

4. to calculate the output power(in dBm0)the following formula
is
applied the output of the above filter(say y(n)) ,
s(n) = 3.17 + 20*log(sqrt(y(n))/8159)

for the case of section 6.4.1.2.2, level measurement device for
peaks the following is done,

steps 1. and 2. are same as above
3. y(n) = sum(x(n)) from 1 to 280.
4. same as step of above.

do let me know if the interpretation is correct.

thanks and regards,
Vinod. -----Original Message-----
From: Maurice Givens [mailto:]
Sent: Monday, February 04, 2002 9:02 AM
To:
Subject: Re: [echocancel] Power measurement Since I wrote this section of the recommendation, let me see if I can
calrify it for you. The measurement device is a sub-paragraph of 6.4.2,
Measuring input and output levels. The paragraph tells how to make the
measuremen (RMS for example) and 6.4.2.1 tells how to make the measuring
device for this measurement. In other words, the detector and indicator
can be anything you want as long as it makes the measurement as required
by 6.4.2. The indicator is your choice as to how you want to make the
human interfece.

The exponential filter is unity gain for a sustained signal Maurice Givens
Givens Burnet, Inc.
10341 S. Prospect Ave.
Chicago, IL 60643-2824
On Fri, 01 Feb 2002 06:26:37 -0000 "vinprakash366"
<> writes:
> Hi all,
>
> In the G.168(2000) standard, under section 6.4.1.2.1, level
> measurement device, i am a little confused abt the
> detector-indicator
> block. How should this be implemented in order to decect the power
> in
> dBm0??. Also, is the 1-pole exponential filter mentioned in the
> block
> a unity gain filter??
>
> thanks in advance,
> Vinod >
> _____________________________________
> Note: If you do a simple "reply" with your email client, only the
> author of this message will receive your answer. You need to do a
> "reply all" if you want your answer to be distributed to the entire
> group.
>
> _____________________________________
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>
> To Join:
>
> To Post:
>
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>
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