Can Any One Suggest me As i am new to ADSP and DSP about undersampling
Started by ●October 31, 2005
I want to do Sampling of a wave which is above 120KHz .But My hardware
supports only 48Khz . So I came to know that i should implement
undersampling .So kindly Explain me what is Undersampling and also
give me idea with some procedure for immplementing it.
I donot no about undersampling.
I am using VisualDSP++ 4
Reply by ●October 31, 20052005-10-31
On Mon, 31 Oct 2005, N siva kumar wrote:
> I want to do Sampling of a wave which is above 120KHz .But My hardware
> supports only 48Khz . So I came to know that i should implement
> undersampling .So kindly Explain me what is Undersampling and also
> give me idea with some procedure for immplementing it.
>
> I donot no about undersampling.
Is the information you are looking for below 24kHz? If it is, then
undersampling will work. If you need to get data at 120kHz, you need at
least 240 kHz sample rate. The idea of undersampling is that you can pick
off the DC component of a repetitive signal. "DC" means a lot slower than
your sample rate, so you average lots of data. So it depends on what you
are trying to do - the possible, or the impossible!
Patience, persistence, truth,
Dr. mike
> I want to do Sampling of a wave which is above 120KHz .But My hardware
> supports only 48Khz . So I came to know that i should implement
> undersampling .So kindly Explain me what is Undersampling and also
> give me idea with some procedure for immplementing it.
>
> I donot no about undersampling.
Is the information you are looking for below 24kHz? If it is, then
undersampling will work. If you need to get data at 120kHz, you need at
least 240 kHz sample rate. The idea of undersampling is that you can pick
off the DC component of a repetitive signal. "DC" means a lot slower than
your sample rate, so you average lots of data. So it depends on what you
are trying to do - the possible, or the impossible!
Patience, persistence, truth,
Dr. mike
Reply by ●October 31, 20052005-10-31
Since he mentions 48k specifically, I think we can assume he has a sigma
delta ADC as the converter. This means that there will be a built in
antialiasing filter with a corner somewhere near 20K. In this situation, he
cannot undersample 120k signals. The basic rule of undersampling is that
the track & hold must be fast enough to capture 120k signals but the ADC
samples at a lower rate. It also implies that the signal of interest is not
ambiguous to other signals. In this case the 120k signal would be
bandlimited (probably use a bandpass filter for antialiasing). Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
At 08:25 AM 10/31/2005, Mike Rosing wrote:
>On Mon, 31 Oct 2005, N siva kumar wrote:
>
> > I want to do Sampling of a wave which is above 120KHz .But My hardware
> > supports only 48Khz . So I came to know that i should implement
> > undersampling .So kindly Explain me what is Undersampling and also
> > give me idea with some procedure for immplementing it.
> >
> > I donot no about undersampling.
>
>Is the information you are looking for below 24kHz? If it is, then
>undersampling will work. If you need to get data at 120kHz, you need at
>least 240 kHz sample rate. The idea of undersampling is that you can pick
>off the DC component of a repetitive signal. "DC" means a lot slower than
>your sample rate, so you average lots of data. So it depends on what you
>are trying to do - the possible, or the impossible!
>
>Patience, persistence, truth,
>Dr. mike
>
delta ADC as the converter. This means that there will be a built in
antialiasing filter with a corner somewhere near 20K. In this situation, he
cannot undersample 120k signals. The basic rule of undersampling is that
the track & hold must be fast enough to capture 120k signals but the ADC
samples at a lower rate. It also implies that the signal of interest is not
ambiguous to other signals. In this case the 120k signal would be
bandlimited (probably use a bandpass filter for antialiasing). Al Clark
Danville Signal Processing, Inc.
--------------------------------
Purveyors of Fine DSP Hardware and other Cool Stuff
Available at http://www.danvillesignal.com
At 08:25 AM 10/31/2005, Mike Rosing wrote:
>On Mon, 31 Oct 2005, N siva kumar wrote:
>
> > I want to do Sampling of a wave which is above 120KHz .But My hardware
> > supports only 48Khz . So I came to know that i should implement
> > undersampling .So kindly Explain me what is Undersampling and also
> > give me idea with some procedure for immplementing it.
> >
> > I donot no about undersampling.
>
>Is the information you are looking for below 24kHz? If it is, then
>undersampling will work. If you need to get data at 120kHz, you need at
>least 240 kHz sample rate. The idea of undersampling is that you can pick
>off the DC component of a repetitive signal. "DC" means a lot slower than
>your sample rate, so you average lots of data. So it depends on what you
>are trying to do - the possible, or the impossible!
>
>Patience, persistence, truth,
>Dr. mike
>
Reply by ●November 4, 20052005-11-04
--- In adsp@adsp..., "N siva kumar" <siva18kumar@y...>
wrote:
> I want to do Sampling of a wave which is above 120KHz .But My hardware
> supports only 48Khz . So I came to know that i should implement
> undersampling .So kindly Explain me what is Undersampling and also
> give me idea with some procedure for immplementing it.
>
> I donot no about undersampling.
>
> I am using VisualDSP++ 4
>
Hi,
There is a good article in Electronic Design May 23, 1991 ediction on
"Undersampling Techniques Simplify Digital Radio"
It is concerned with sampling below the Nyquist Rate. Since your
sampling rate is 48kHz, and your signal is 120kHz, I don't know if
this method would help or not.
Here are a few links to try:
http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/mags/dt/&toc=comp/mags/dt/1999/04/d4toc.xml&DOI.1109/54.808225
http://www.sss-mag.com/pdf/ad5.pdf
(this one is very similar to the article I mentioned)
http://www.dsp-fpga.com/articles/neagoe_and_fugerer/
There are others. Some show algorithms, but you will need to determine
if the method will meet your requirements or not. (e.g. do you lose
too much information since the sampling rate is so low, etc)
I simply typed into Google:
electronic design undersampling techniques simplify digital radio
Good Luck,
Maybe others can post something of more help than just links,
But I think the answer you are looking for is out there if you google
for it for a while.
Good Luck,
John Henry
KI4JPL
> I want to do Sampling of a wave which is above 120KHz .But My hardware
> supports only 48Khz . So I came to know that i should implement
> undersampling .So kindly Explain me what is Undersampling and also
> give me idea with some procedure for immplementing it.
>
> I donot no about undersampling.
>
> I am using VisualDSP++ 4
>
Hi,
There is a good article in Electronic Design May 23, 1991 ediction on
"Undersampling Techniques Simplify Digital Radio"
It is concerned with sampling below the Nyquist Rate. Since your
sampling rate is 48kHz, and your signal is 120kHz, I don't know if
this method would help or not.
Here are a few links to try:
http://csdl2.computer.org/persagen/DLAbsToc.jsp?resourcePath=/dl/mags/dt/&toc=comp/mags/dt/1999/04/d4toc.xml&DOI.1109/54.808225
http://www.sss-mag.com/pdf/ad5.pdf
(this one is very similar to the article I mentioned)
http://www.dsp-fpga.com/articles/neagoe_and_fugerer/
There are others. Some show algorithms, but you will need to determine
if the method will meet your requirements or not. (e.g. do you lose
too much information since the sampling rate is so low, etc)
I simply typed into Google:
electronic design undersampling techniques simplify digital radio
Good Luck,
Maybe others can post something of more help than just links,
But I think the answer you are looking for is out there if you google
for it for a while.
Good Luck,
John Henry
KI4JPL
Reply by ●November 5, 20052005-11-05
