## interpolation accuracy, oversampling and fractional interpolation

Started by in comp.dsp15 years ago 30 replies

Hi all, Interpolation of a sampled signal x(n) to generate an up-sampled signal y(n) can be represented mathematically as: y(n) = x(n/L)...

Hi all, Interpolation of a sampled signal x(n) to generate an up-sampled signal y(n) can be represented mathematically as: y(n) = x(n/L) /* here L is the intrpolation factor. Regardless of the type of interpolation, if we increase the value of 'L' weather it will increase the accuracy of interpolation process? Whats about the fractional Interpolation/Decimation factors how to deal wi...

## ofdm & fft processing gain

Started by in comp.dsp18 years ago 1 reply

For 802.11a there are 64 point ifft @ 20MHz transmit signal OFDM. The carriers are spaced 312500 Hz apart [20e6/64]. Demodulated baseband...

For 802.11a there are 64 point ifft @ 20MHz transmit signal OFDM. The carriers are spaced 312500 Hz apart [20e6/64]. Demodulated baseband signal is from -10MHz to +10MHz.[48 data carriers + 4 pilot carriers + some zero channels at the highest frequencies to make up the number to 64 carriers. Now at the receiver, if we have a 80MHz oversampling ADC sampling the 20MHz wide signal, followed b...

## CAUTION! was "What is the advantage on high-sampling rate ?"

Started by in comp.dsp17 years ago 150 replies

Hi Guys, in a recent thread, mention was made of a "Sampling" paper by Dan Lavry. At the following web...

Hi Guys, in a recent thread, mention was made of a "Sampling" paper by Dan Lavry. At the following web site http://www.lavryengineering.com/pdfs/sample.pdf you can see Dan's 1997 paper: "Sampling, Oversampling, Imaging and Aliasing - a basic tutorial". I recommend caution if you decide to read that paper. In the second paragraph Dan wrote: *** Sampling theory *** ...

## Difference between CDMA pilot channel acquistion and tracking

Started by in comp.dsp12 years ago 10 replies

Hi all, Did acquisition and tracking with pilot channel sharing the same process in CDMA2000? the acquisition using xcorr find the...

Hi all, Did acquisition and tracking with pilot channel sharing the same process in CDMA2000? the acquisition using xcorr find the coarse delay,but how does tracking action? Plan to using 8x oversampling,then fed the stream to a digital matched filter to find best one from the eight. But really have no idea with the tracking process, do i need to using xcorr again when tracking? or ...

## Difference between CDMA pilot channel acquistion and tracking

Started by in comp.dsp12 years ago

Hi all, Did acquisition and tracking with pilot channel sharing the same process in CDMA2000? the acquisition using xcorr find the...

Hi all, Did acquisition and tracking with pilot channel sharing the same process in CDMA2000? the acquisition using xcorr find the coarse delay,but how does tracking action? Plan to using 8x oversampling,then fed the stream to a digital matched filter to find best one from the eight. But really have no idea with the tracking process, do i need to using xcorr again when tracking? or ...

## True Peak Measure

Started by in comp.dsp11 years ago 13 replies

Hello, I'm trying to set up a java program to make EBU R 128 measures on audio files. ( http://tech.ebu.ch/docs/r/r128.pdf ) I have an issue...

Hello, I'm trying to set up a java program to make EBU R 128 measures on audio files. ( http://tech.ebu.ch/docs/r/r128.pdf ) I have an issue with the True Peak measurement. It is basically described as four times oversampling the original signal by : padding the signal with zeros applying a low pass filter Here's a basic java source code : public class TestOversample { public stati...

## Solving DC offset problem in DSP

Started by in comp.dsp14 years ago 7 replies

Hi Experts, I am using a zero-IF system now, where the analog mixer output has a dynamic/variable DC offset. The analog mixer output is fed...

Hi Experts, I am using a zero-IF system now, where the analog mixer output has a dynamic/variable DC offset. The analog mixer output is fed into an op-amp for amplification(low amplification, no saturation) and finally into ADC. I am currently oversampling the incoming signals. My problem now is due to the variable/dynamic DC offset. This is because i am not able to find a neat way of gettin...

## Question about damping in PLL

Started by in comp.dsp10 years ago 5 replies

Hi, I am learning PLL from a web download PLLTutorialISSCC2004.pdf after I read two books on PLL. I do not understand the following...

Hi, I am learning PLL from a web download PLLTutorialISSCC2004.pdf after I read two books on PLL. I do not understand the following statements from the web pdf: ........................... Less ringing and overshoot as Zeta = 1 Severe overdamping --> ringing and overshoot Ringing at high damping due to low oversampling (large R)  Gardner limit. ............. Low damping ---> l

## Processing Time in TI eZdsp F2812

Started by in comp.dsp15 years ago 1 reply

Hi I have a question regarding the flow of my code. I am oversampling my input signal using the ADC at a rate 3.125 MHz. I have 2 inputs & am...

Hi I have a question regarding the flow of my code. I am oversampling my input signal using the ADC at a rate 3.125 MHz. I have 2 inputs & am using simultaneous sampling. I am using the adcseqovdtest code of TI as a framework. So I have 16 samples from the ADC Result registers. My question is with sampling rate of 3.125 and clock frequency of 150 MHz, I have (150/3.125) 48 instructions per samp...

## Obtaining better Fourier coefficients by oversampling

Started by in comp.dsp10 years ago 1 reply

Hi, Suppose I have a (hypothetic, real) periodic, sign alternating function: The alternations take place at rate f_nyq ("Nyquist rate") and...

Hi, Suppose I have a (hypothetic, real) periodic, sign alternating function: The alternations take place at rate f_nyq ("Nyquist rate") and the pattern repeats every, say, 200 alternations. So the function is periodic with f_nyq/200. If I want to obtain the Fourier coefficients (magnitude) I can sample the function with an oscilloscope and measure the peaks (which are spaced by f_n...

## How to design the NCO in digital timing recovery loop?

Started by in comp.dsp14 years ago 2 replies

Hi, everyone. I have a problem about the NCO design and hope to get some help from this forum. I need to design a digital timing recovery...

Hi, everyone. I have a problem about the NCO design and hope to get some help from this forum. I need to design a digital timing recovery loop. The architecture consists of a Gardner timing error detector, loop filter and NCO. (To my best knowledge, such structure is quite classical.) All three building blocks shall be implemented in digital domain. The A/D oversampling rate is 32. I have no p...

## Improving DAC Performance with Delta Sigma

Started by in comp.dsp9 years ago 13 replies

Hi Guys, Could we linearize a multi-bit DAC converter that may have nonlinearity in the lower bits by quantizing to a coarser resolution and...

Hi Guys, Could we linearize a multi-bit DAC converter that may have nonlinearity in the lower bits by quantizing to a coarser resolution and utilizing a delta sigma modulator to improve the SNR? For example, let's say our DAC is 18 bits but only has 16 "good" bits. If we design a delta sigma modulator with a 16 bit input, an oversampling ratio of four, and a modulator order of two, we co...

## Does time-domain interpolation help Manchester decoding?

Started by in comp.dsp12 years ago 4 replies

My receiver comprises the following parts: 1) a 10-bit ADC running at fs (M samples/symbol), 2) a time-domain "interpolation filter" based on...

My receiver comprises the following parts: 1) a 10-bit ADC running at fs (M samples/symbol), 2) a time-domain "interpolation filter" based on a comb-integrator stage with leaky integrator (sampling rate increase by N) does "interpolation" and acts as a dc-blocking filter as well, 3) a Manchester decoder based on a oversampling & counting algorithm decoding the interpolated signal and runni...

## ADC Vs DAC

Started by in comp.dsp18 years ago 7 replies

Hi all, I am not very familiar with ADC or DAC design or present research in these area. Popular sigma-delta,Flash or successive appoximation...

Hi all, I am not very familiar with ADC or DAC design or present research in these area. Popular sigma-delta,Flash or successive appoximation ADC design methods are matured(?). I guess same terminology(sigma delta etc.) holds good for DAC. Desiner cum researcher talk about high resolution(dynamic range), high speed DAC and ADC using oversampling techniques over low resolution ADC/DAC....

## Help me to understant sampling theory, decimation by integer factor

Started by in comp.dsp14 years ago 7 replies

Hi, everyone! I read "decimation by integer" and "interpolation by integer factors" in a DSP book. I'm just wondering why integer...

Hi, everyone! I read "decimation by integer" and "interpolation by integer factors" in a DSP book. I'm just wondering why integer factor to downsampling... Sometimes, to resample signal by rational factor, people use conversion oversampling(integer factor) -> low-passfilter -> downsampling(also integer factor). (This means "Sampling rate conversion by non-integer factors") Howe