## Forums Search for: Interpolation

## Purpose of interpolation in DACs?

inI'd like to test my understanding of the usefulness of interpolation in a DAC: If you feed a signal to a DAC at Fc < Fclk/2 then there is a...

I'd like to test my understanding of the usefulness of interpolation in a DAC: If you feed a signal to a DAC at Fc < Fclk/2 then there is a primary image at Fc and (possibly unwanted) aliasing at Fclk +/-Fc and at harmoics of Fclk +/-Fc. Now, if you upsample (zero-stuff) the input to a higher Fclk, then the DAC runs faster, and the DAC-produced images are now at n*Fclk+/-Fc. However, th

## RRC filtering and interpolation

Hi, I'm trying to understand some Rake receiver structures for WCDMA and I'm having trouble with the interpolation stuff. Assuming down...

Hi, I'm trying to understand some Rake receiver structures for WCDMA and I'm having trouble with the interpolation stuff. Assuming down conversion to base band has been done, I think one possible way of doing a Rake is to: 1. sample at twice chip rate 2. RRC filter 3. Interpolate 4. Do timing adjust corresponding to tap delay 5. Decimate to chip rate 6. De-spread Steps 4 through 6 wo...

## machine learning vs interpolation

inGreetings. I have been using neural networks and other machine learning tools for sometime time. Yesterday the following question popped up in...

Greetings. I have been using neural networks and other machine learning tools for sometime time. Yesterday the following question popped up in my mind however: Why do we use machine learning tools when we could achive similar results with plain interpolation? Let's assume a noise free regression scenario (not classification and no measurement errors). In the case of infinite samples and...

## time domain zero padding VS fft interpolation between bins

inHi, Suppose I have N samples and I want to do one N point FFT and a 4N point FFT with zeros padding. Can do get the 4N-FFT by...

Hi, Suppose I have N samples and I want to do one N point FFT and a 4N point FFT with zeros padding. Can do get the 4N-FFT by interpolating the N-FFT? Is there a formula? Is the interpolation fast than just do a zero-padded 4N-FFT? Thanks

## FIR Interpolation question

inThis question relates to the Multirate FAQ at the dspGuru site: http://dspguru.com/info/faqs/multrate/interp.htm I have a 256 element array...

This question relates to the Multirate FAQ at the dspGuru site: http://dspguru.com/info/faqs/multrate/interp.htm I have a 256 element array that I want to interpolate at a variable density, between 4 and 10. Let's take the first case, i.e. the interpolation factor or density, L = 4. Thus, I need a 256 * 4 = 1024 tap filter. My question is this: How do I obtain the coefficients of th...

## FIR filter

inHello Everybody, I am a novice in Signal Processing field. I saw few messages on Interpolation. I have a similar doubt. I have a complex chirp...

Hello Everybody, I am a novice in Signal Processing field. I saw few messages on Interpolation. I have a similar doubt. I have a complex chirp signal. And I wanna interpolate this signal to get intermediate values.I tried to interpolate using an FIR filter with coefficients calculated using sinc interpolation but i could nt get the desired reult even with a large filter length. I dont kno...

## FFT Interpolation of complex numbers

inHi, I have been using a relatively small (256 point) FFT and some interpolation to estimate the actual input frequency when I do not have a bin...

Hi, I have been using a relatively small (256 point) FFT and some interpolation to estimate the actual input frequency when I do not have a bin at exactly that frequency. However I was wondering if any such method exists for estimating the phase at that frequency? Is it possible to interpolate the real and complex numbers of adjacent bins? If I zero pad and use a large FFT (say 2048 points...

## Correcting for DAC and analog filters

inHi, I want to identify a DT equivalent system of a transmitter. It should include the Zero-Order-Hold DAC, interpolation filter (and...

Hi, I want to identify a DT equivalent system of a transmitter. It should include the Zero-Order-Hold DAC, interpolation filter (and possibly mixer + any image rejection filters etc). I created a simple SIMULINK model which implements a 4x interpolation-DAC with the following specs: fs=200 MHz (i.e., fs_DACOUT=800Mhz), Butterworth reconstruction filter (fcut=100Mhz). Then I send BLWGN...

## SNR penalty due to Linear Interpolation

inHi All As we know that due to relative motion between TX and RX, the transmitted signal undergoes expansion/compression. And due to this symbol...

Hi All As we know that due to relative motion between TX and RX, the transmitted signal undergoes expansion/compression. And due to this symbol and phase synchronization is lost. I have simulated this perticular thing, where I am using matlab's resample function to introduce this expansion/compression. Now, at receiver I have used adaptive linear interpolation to correct this expansion/c...

## Efficient zero crossing/interpolation calculation

inI?m developing an application running on a PIC 18F.tbd that has to find (positive-going) zero crossing points on a sine input with slowly...

I?m developing an application running on a PIC 18F.tbd that has to find (positive-going) zero crossing points on a sine input with slowly varying frequency. The frequency/sampling regime is such that successive samples of the waveform are not more than 70 degrees apart. Linear interpolation between sample points therefore gives zero crossing estimates within about 2 degrees of the actual crossing ...

## polyphase, interpolation, timing error

inI've been following a number of threads over the past couple of weeks regarding fractional timing delays and interpolation, but none of...

I've been following a number of threads over the past couple of weeks regarding fractional timing delays and interpolation, but none of them really address my problem, so here goes.... I have a sampled received signal taken at r(kTs), Ts = sample rate and k is integer. The sampled signal is then fed into a bank of matched filters (MFs) (my system has a min number of 2 MFs and a max of 16 M...

## Polynomial interpolation and Gardner TED

inHello everybody, I am trying to built a model in Matlab for symbol timing recovery by using the Gardner TED that feeds a polynomial...

Hello everybody, I am trying to built a model in Matlab for symbol timing recovery by using the Gardner TED that feeds a polynomial interpolator. Does anyone know how can I go from the error signal output of the GAD TED to the fractional delay '=B5n'. Do I have to use a loop filter and a interpolation controller? What are the functions of the the interpolattion controller and of the loop fil...

## Implementing this MATLAB function as a filter (Lagrange interpolation)

inBelow is some code I wrote that uses peicewise barycentric lagrange interpolation to change the sampling rate of a signal from 9Hz to 30Hz....

Below is some code I wrote that uses peicewise barycentric lagrange interpolation to change the sampling rate of a signal from 9Hz to 30Hz. My numerical implementation below works far better than any Farrow or variable fractional delay filter built in MATLAB. How can implement my function below as a filter? Or how can I build it from blocks in Simulink? ------------- clear, clc fun = in...

## Sinc interpolation

inHi all, I am modelling sampling jitter in matlab using sinc interpolation. The input is a vector of 256 complex data(16QAM symbols). Have...

Hi all, I am modelling sampling jitter in matlab using sinc interpolation. The input is a vector of 256 complex data(16QAM symbols). Have introduced jitter in sampling time as t=k/Fs+k*err where Fs is sampling frequency, k is the symbol index, t is the new sampling instant. I have assumed ideal sampling when err is 0. But, when err is non zero and the product k*err exceeds Ts/2 (i.e k*er...

## Interpolation w/ cubic convolution kernel - boundary treatment?

inMy problem is not dsp related, but the method is closely related to methods in dsp, so I am hoping to get some help here. I am using the...

My problem is not dsp related, but the method is closely related to methods in dsp, so I am hoping to get some help here. I am using the symmetric cubic convolution kernel ("Catmull-Rom splines") to interpolate data over a limited range in a variable x. For the interpolation I am using typically 10 nodes which are equidistant in x. Example: The interpolated function between nodes 4 and 5 i...

## FIR interpolator border effects

inHi, i'm trying to implement an interpolator filter on a finite sequence and i'm faced to a quite anoying problem, the border effects. The...

Hi, i'm trying to implement an interpolator filter on a finite sequence and i'm faced to a quite anoying problem, the border effects. The problem is that more the filter is long more the effects on the borders a re huge and so the interpolation has a lot of errors. I've seen once that someone use different sets of coefficients for the interpolation near the borders but i dont find any litera...

## How to interpolation in frequency domain will not affect time domain signal?

inHi, everyone! I am new in this group. a N-point spectrum was obtained after FFT to N-point sampled sine signal. But the sampling frequency is...

Hi, everyone! I am new in this group. a N-point spectrum was obtained after FFT to N-point sampled sine signal. But the sampling frequency is not big enough to distinguish close peaks, I try to interpolate in the N-point spectrum to achieve a 2N-point spectrum which will increase resolution. the interpolation goes on like zooming out vector graphics. My problem is that when I iFFT the interpola...

## PLESIOCHROUNOUS re-sampling of audio using D/A > A/D

inI have a question about PLESIOCHROUNOUS re-sampling of audio. It was mentioned in another thread that simply deleting or repeating a sample...

I have a question about PLESIOCHROUNOUS re-sampling of audio. It was mentioned in another thread that simply deleting or repeating a sample now and then is a poor solution because it adds clicks. It was mentioned that linear interpolation is not ideal. Why? Because it adds noise? or distortion? I presume the "ideal" digital solution is to use a higher order interpolation algo...

## Lagrange multipliers and other higher-order interpolation methods

inI am wondering if there are any applications for higher-order Lagrange approximating polynomials in digital signal processing or image...

I am wondering if there are any applications for higher-order Lagrange approximating polynomials in digital signal processing or image re-sampling. I know that Lagrange multipliers are used to some extent in the construction of FIR filters, and are also used in bicubic interpolation. However, is there an application involving higher order Lagrange polynomials? Does anyone know of a ...

## How to calculate interpolation error?

inI want to calculate the interpolation error occured when I resampled regularly the irregularly sampled data. Infact there exists the...

I want to calculate the interpolation error occured when I resampled regularly the irregularly sampled data. Infact there exists the resampled points corresponding to whos time of existance there are no sample points lies in original irregularly sampled data. Thnks in advance for your ideas. This message was sent using the Comp.DSP web interface on www.DSPRelated.com