## An intriguing story about undersampling

Started by in comp.dsp14 years ago 53 replies

Read this astonishing story at http://spazioscuola.altervista.org/UndersamplingAR/UndersamplingAR.htm Here it is an excerpt: A STORY ABOUT...

Read this astonishing story at http://spazioscuola.altervista.org/UndersamplingAR/UndersamplingAR.htm Here it is an excerpt: A STORY ABOUT UNDERSAMPLING by Angelo Ricotta - Rome, Italy a.ricotta@isac.cnr.it ITALIAN VERSION In the article "Turning Nyquist upside down by undersampling" by Bonnie Baker, EDN 12 May 2005, are reported the two formulae and to compute an allowab...

## Undersampling

Started by in comp.dsp14 years ago 7 replies

I recently read an article on undersampling, and believe that I could solve a problem I've been working on by using it. The question is whether...

I recently read an article on undersampling, and believe that I could solve a problem I've been working on by using it. The question is whether the solution makes sense, is a good way to proceed (there might be much simpler solutions), and is viable. The problem is detecting energy on a set of frequencies between 72MHz and 73MHz, spaced at 5kHz intervals. (This is an RC broadcast detector)....

Started by in comp.dsp13 years ago 1 reply

Hi, I am new to the whole DSP thing (very new) and have a question regarding the use of undersampling and quadrature mixing to demodulate a...

Hi, I am new to the whole DSP thing (very new) and have a question regarding the use of undersampling and quadrature mixing to demodulate a signal in a given range. I have been trying to research the topic but have not been getting very far. I understand how the bandpass signal can be undersampled at a rate of 2B without aliasing if the proper bandedge frequencies or chosen but have no real ...

## Undersampling IF software

Started by in comp.dsp13 years ago 1 reply

Hi, I'm looking for a software to compute the frequency sampling for undersampling an IF radio spectrum. For example, if I have a IF of 455...

Hi, I'm looking for a software to compute the frequency sampling for undersampling an IF radio spectrum. For example, if I have a IF of 455 kHz with 80 kHz bandwith, I can sample at 200 kHz and the second IF would be 55 kHz. I have try to compute with software designed for RF mixer but it doesn't work because, in my example, the second IF is : ABS ( 2=2Efreq_sampling - freq_IF ) and w...

## Undersampling to measure phase.

Started by in comp.dsp15 years ago 13 replies

I have two 70 MHz signals (one a clean reference sine wave, the other a lot less so), but wish to find the phase difference between these two...

I have two 70 MHz signals (one a clean reference sine wave, the other a lot less so), but wish to find the phase difference between these two signals. The A/D, the AD9226: http://www.analog.com/UploadedFiles/Data_Sheets/394988775AD9226_b.pdf has a maximum sampling rate of 65 MSPS, but is rated for a maximum of 200 MHz input. Hence the A/D is suitable for use in undersampling applicat...

## digital ultrasonic demodulator by undersampling

Started by in comp.dsp12 years ago

Hi! I want to make an ultrasonic leak detector. Generally, they consist mainly of an ultrasonic transducer and an analog demodulator with...

Hi! I want to make an ultrasonic leak detector. Generally, they consist mainly of an ultrasonic transducer and an analog demodulator with a carrier of 40Khz which they enable to hear and to measure an audio signal from 0 to 1.5 or 3Khz. How I can make that digitally? I'm thinking about to make it through undersampling. That is, to sample at 38.5Khz to obtain an spectra from 0 to 3Khz, from a...

Started by in comp.dsp16 years ago 25 replies

Hello, As a result of a measurement I obtain a bandlimited signal centered at 144 kHz (12kHz Bandwidth). I was planning to use undersampling...

Hello, As a result of a measurement I obtain a bandlimited signal centered at 144 kHz (12kHz Bandwidth). I was planning to use undersampling (Fs=192kHz) to fold this signal to 48kHz in the digital domain. I am having a difficulty to find an ADC for this purpose. The only ADCs I could find (I need at least 18 bit resolution) that support Fs=192kHz had too small analog bandwidth, f.ex. cirr...

## Beginner's question on undersampling and aliasing

Started by in comp.dsp12 years ago 36 replies

Hi all, I am a newbie to DSP. I have a huge number of data samples that I want to perform FFT on. But due to the enormous amount of the data...

Hi all, I am a newbie to DSP. I have a huge number of data samples that I want to perform FFT on. But due to the enormous amount of the data samples, I'd like to use only 1M samples and perform FFT. I know that this is severe undersampling and that it does not satisfy the Nyquist rate. But all I want is to prevent aliasing so that I can get correct information about the low frequency content...

## Undersampling of a clean carrier

Started by in comp.dsp14 years ago 5 replies

Hi, I have just been doing some test and I noticed a concerning problem that I may be having with the undersampling design (for FM...

Hi, I have just been doing some test and I noticed a concerning problem that I may be having with the undersampling design (for FM demod). I basically set up my board so that the adc input (which is clocked at 80MHz) feeds directly into a DAC also clocked at 80MHz. If I put a 20MHz tone (clean sine wave CW) on the input (from a signal generator) I get a clean 20MHz tone present on t...

## Is it possible to use very large undersampling factor (using 5.1kHz to sample 330MHz)?

Started by in comp.dsp7 years ago 45 replies

Hi sampling gurus, I'm thinking about undersampling a 150Hz AM signal modulated to a 330MHz carrier, thus the signal bandwidth is 300Hz. I...

Hi sampling gurus, I'm thinking about undersampling a 150Hz AM signal modulated to a 330MHz carrier, thus the signal bandwidth is 300Hz. I found an ADC has 600MHz analogue bandwidth, and minimum Fs to be 5.1kHz. Suppose the bandpass filter is sharp enough for my my signal at 330MHz, if I use 5kHz to sample the 330MHz, will there be any problem? One of my colleagues thinks there's

## Undersampling and Quadrature Sampling ?

Started by in comp.dsp13 years ago 4 replies

Hi, I would like to undersample a 70 MHz IF signal at a sampling frequency of 55 MS/s. So this undersampling method creates a 15 MHz IF2 whith...

Hi, I would like to undersample a 70 MHz IF signal at a sampling frequency of 55 MS/s. So this undersampling method creates a 15 MHz IF2 whith 55 MS/s. Now I would like to donwconverter this 15 MHz IF2 to baseband (0 IF) with quadrature sampling, so I need to generate a sinus at 60 MS/s and a cosnius at 60 MS/s and I need to multiply theses sinus, cosinus with the 15 MHz IF2. But the...

## Undersampling Question

Started by in comp.dsp14 years ago 27 replies

Dear folks, I was wondering if you could help me with this problem. I have an accelerometer with a resonance of say 15kHz. I need to do...

Dear folks, I was wondering if you could help me with this problem. I have an accelerometer with a resonance of say 15kHz. I need to do envelope detection of this (acts a bit like AM with 15kHz as the 'carrier'). The bandwidth of this signal is lets say 4kHz so that we bandlimit from 13kHz up to 17kHz. Now suppose I sample at 8kHz - is this ok? I assume I get a spectrum that goes from 5kHz...

## Better FM demodulator

Started by in comp.dsp14 years ago 16 replies

Currently, I have a project that uses the Blackfin DSP. A 8-bit A/D will do undersampling (at 1.6384MHz) of an IF signal which is...

Currently, I have a project that uses the Blackfin DSP. A 8-bit A/D will do undersampling (at 1.6384MHz) of an IF signal which is down-converter from standard stereo FM broadcast. There are quite a few standard FM demodulators, e.g. baseband delay, phase-adapter, mixed type and PLL demodulator. It seems the mixed demodulator should have the best performance among those four. Is there any other ...

## Undersampling

Started by in comp.dsp12 years ago 7 replies

I am on a team developing a system that will record and process large (1 GHz) bandwidth pulses. Doing some research I have came across some one...

I am on a team developing a system that will record and process large (1 GHz) bandwidth pulses. Doing some research I have came across some one that suggested sampling in the 2nd nyquist zone, for two main reasons. Sampling the signal at a higher frequency makes our analog front end much better and simpler deign. It also reduces harmonics within our frequencies of interest allowing more in...

## decimation and resolution

Started by in comp.dsp5 years ago 11 replies

Hi everyone, I have an encoder which is delivering 22bit data for a 360 rotation. The rotation is accomplished in ~800ms but the serial link...

Hi everyone, I have an encoder which is delivering 22bit data for a 360 rotation. The rotation is accomplished in ~800ms but the serial link from the encoder is running such that we will sample values at 25KHz (that is a requirement). It roughly means we are grossly undersampling the amount of information the enconder is capable to provide. Would this 'decimation' have an impact o...

## Effect of OverSampling

Started by in comp.dsp13 years ago 8 replies

I'm new to DSP and also this group. My question is "what can be the negative effect of Oversamling in terms of Destortion in original signal?"....

I'm new to DSP and also this group. My question is "what can be the negative effect of Oversamling in terms of Destortion in original signal?". As in undersampling two spectrum are overlapped and we may not be able to get original signal.. is that any kind of effect in oversampling?

## Undersampling with inverted spectrum

Started by in comp.dsp4 years ago 26 replies

Hi, I undersample signal of bandwidth BW that is completely in second Nyquist zone. It ends up folded to some frequency between 0 and new fs/2....

Hi, I undersample signal of bandwidth BW that is completely in second Nyquist zone. It ends up folded to some frequency between 0 and new fs/2. This spectrum is inverted. If I now downconvert this signal to baseband by multiplying it with complex sine, I can obtain "right" spectrum by swapping I and Q axes afterwards. However, I would like to downconvert this signal by multiplying with real...

## Frequency Domain Undersampling?

Started by in comp.dsp6 years ago 6 replies

I was using matlab and switched from using the function fft to freqz. The data I was using turned out to be longer than the default freqz...

I was using matlab and switched from using the function fft to freqz. The data I was using turned out to be longer than the default freqz length of 512 but I didn't pay any attention to it at first, but now I finally caught it. So for example had x[n] of length 1024 and used matlabs function X = freqz (x). Would that be equivalent of taking an fft of length 1024 and picking off ever o...

## Undersampling: Specifying Clock Jitter?

Started by in comp.dsp12 years ago 2 replies

Hi all, I'm basically trying to design a power spectrum analyser that can capture channels with a bandwidth of 100 MHz. I select either 10...

Hi all, I'm basically trying to design a power spectrum analyser that can capture channels with a bandwidth of 100 MHz. I select either 10 MHz - 110 Mhz or 135 MHz - 235 MHz and am sampling with a 250 MHz ADC. The ADC has a full power bandwidth of 1 GHz and has 12 bits. My goal is to be able to detect a signal that is 55 dB lower than another signal that is 500 kHz away. I also want to ...

## Who attended Embedded Sys Conference in San Francisco

Started by in comp.dsp16 years ago 1 reply

Hi Guys, I'm wondering if any of you attended the Embedded Systems Conference (also called "electronicaUSA") in San Francisco last...

Hi Guys, I'm wondering if any of you attended the Embedded Systems Conference (also called "electronicaUSA") in San Francisco last month. I have a question about a paper that may be on the CD distributed at the conference. The lecture paper that interests me is titled: "Undersampling: Avoiding Misconceptions about the Nyquist Criterion", Paper# 467, by Teodor Neagoe. ...