## Forums Search for: Polyphase

## Polyphase decimation errors

inFolks, I understand that, based on the Nobel Identities, the output of a polyphase decimator should be identical to the output of a basic...

Folks, I understand that, based on the Nobel Identities, the output of a polyphase decimator should be identical to the output of a basic FIR decimator. This is due to the fact that even though we decimate in the full input bandwidth all the undersampled aliases will exactly cancel in the final summation. My question is, is this still the case even when we have finite sampling rate and ...

## Polyphase decimation

inHi I am implementing a polyphase decimation of a 8k signal by a factor of 20. I have designed a filter of pi/20, which means there are...

Hi I am implementing a polyphase decimation of a 8k signal by a factor of 20. I have designed a filter of pi/20, which means there are 20 subbands. In case of decimation, the input gets shifted by a sample at each time instant and then convolved with all the filters accordingly, and finally summed from all the subbands to give the output. And finally 19 out of 20 samples are thrown out....

## Fractional Resampling WCDMA gives noise

inDear all, I will be grateful if I can get some light on this. I have Tx Data upsampled from 3.84MHz to 12 MHz (@3.125X. On the Tx side I...

Dear all, I will be grateful if I can get some light on this. I have Tx Data upsampled from 3.84MHz to 12 MHz (@3.125X. On the Tx side I use a nice RRC filter to perform interpolation and upsample using Matlab inbuild polyphase filter to generate Test vectors. Problem is , on the receiver side, I do not use polyphase filter. I use RRc filter at the begining then downsample using 3,3,3...

## Sample rate conversion, Multistage and polyphase?

inHi, I'm working on a audio sample rate converter. I'm interested particularly in the conversion from 44.1 to 48kHz. I have a version that...

Hi, I'm working on a audio sample rate converter. I'm interested particularly in the conversion from 44.1 to 48kHz. I have a version that works using polyphase decomposition for a huge fir filter to convert from 44.1 to 48. I was trying to do this in a multistage cascade, but it seems to be taking up more cpu than just doing a one stage. Is there an algorithm or block diagram someone ha...

## uniform filter bank implementation.

inI have a question with regards to going from a polyphase decimation routine and adapting it to an actual filter bank to separate a...

I have a question with regards to going from a polyphase decimation routine and adapting it to an actual filter bank to separate a large bandwidth into smaller subbands. I understand how polyphase filters works, that no problem, I am just stuck on seeing how you make the transistion to a MxL (where M is the number of channels, and L is the lenght of each filter bank).... I have read previo...

## 2D image scaling using cascaded polyphase FIR filter

inHi, When looking at many of the video scalers and DSPs for consumer video, the datasheets usually list several cascaded polyphase FIR filters. ...

Hi, When looking at many of the video scalers and DSPs for consumer video, the datasheets usually list several cascaded polyphase FIR filters. They usually supply software libraries that generate the filter coefficients given a pair of numbers describing how much interpolation and decimation. In attempting to get a much better understanding of basic DSP skills, I started to build my own mod...

## Polyphase decimation filter, is it only a mathematical gimmick?

inMy decimation filter is 50 taps, and need to decimate by 10 times. First approach is by normal FIR, but latch outputs every 10th cycle. 2nd...

My decimation filter is 50 taps, and need to decimate by 10 times. First approach is by normal FIR, but latch outputs every 10th cycle. 2nd approach is by dividing them into 10 polyphase filters each with 5 taps. Is it correct to say, each decimated output I get from the two approaches comprises of multiplication and summation of the same data and coefficients?

## Polyphase interpolation on an image with real value only

inHi all, I encounter some "problem" while using polyphase filter for interpolation. I have implemented a 8 zero crossing with upsampling of...

Hi all, I encounter some "problem" while using polyphase filter for interpolation. I have implemented a 8 zero crossing with upsampling of L=32. The image I used are a simulated image with 4 sinc impulse response near the four corner. All pixels values are positive. While performing interpolation, such as for rotation operation, I found that some of the values return is negative? ...

## High pass polyphase filter

inHi all, I'm trying to design an high pass polyphase filter. The approach is to take the 5 tap high pass FIR, oversample it by a factor N...

Hi all, I'm trying to design an high pass polyphase filter. The approach is to take the 5 tap high pass FIR, oversample it by a factor N (usually 128 or 256), then subsample it again into the different phases. The oversampling was done by polynomial interpolation and by zero-padding and low-pass. I mean, the two methods were tried, not altogether. In both cases, the results are dis...

## clocks used in polyphase interpolation scheme

inGreetings, I am trying to understand how the clock domains work during interpolation using the polyphase structure. Does one use 2...

Greetings, I am trying to understand how the clock domains work during interpolation using the polyphase structure. Does one use 2 different clocks during implementation(lets say an interpolate by 2 FIR filter). One at the input and one at the output which is 2x the input clock. IS this correct? or can you just use 1 clock thru out, if the latter is true, how is this done?. Th...

## Fractional decimation

inHello, I've been studying polyphase decomposition, decimation, interpolation and fractional decimation. I think I have a handle on what I'm...

Hello, I've been studying polyphase decomposition, decimation, interpolation and fractional decimation. I think I have a handle on what I'm doing, but there's one thing I don't understand... Do you have to have greater than an L*Mth order filter in order to use polyphase decomposition to put the compressor and expander in their most efficient places (first and last, respectively)? For exa...

## Resampling Polyphase Fir Filter

inhello, i am trying to do 12 to 1 downsampling and 1 to 12 upsampling with polyphase fir filter, I wanted to know how to design the inner...

hello, i am trying to do 12 to 1 downsampling and 1 to 12 upsampling with polyphase fir filter, I wanted to know how to design the inner filter. suppose passband frquency is 0.5, stopband freq is 0.75. input sample rate is 24 ,inband ripple is 0.1 and outband attenuation is 80db.and it is 12 path filter with filter length is equal to 348 .each path is followed by 29 taps.how to design the inner ...

## Polyphase decimating filter - not working in lab- why?

inHello... I created a polyphase filter filter based on F.Harris's book shared register design. This is a Decimation by 2, 100 tap, Fs...

Hello... I created a polyphase filter filter based on F.Harris's book shared register design. This is a Decimation by 2, 100 tap, Fs =100MHz, Low pass 20MHz - stop band 24MHz filter. Each MAC is 28-bit length, 14-bit ADC input, and the filter output is truncated. I also created a Xilinx distributed arith filter to compare using the same filter coefficients. ( For some reason I could no...

## Scaling of fir polyphase filters

inIn a FIR filter the scaling of the input in order to avoid overflow at the output can be specified by using the 1st norm of the vector...

In a FIR filter the scaling of the input in order to avoid overflow at the output can be specified by using the 1st norm of the vector of coefficients. ymax=xmax*scaling*norm_1 for xmax=ymax=1 scaling=1/norm_1 How to use this relation in a multistage interpolator with polyphase decomposition? Thanks

## Modulated Polyphase filter bank with IFIR prototype

inI have a modulated polyphase filter bank that I am trying to improve the performance and was wondering if the prototype FIR could be replaced...

I have a modulated polyphase filter bank that I am trying to improve the performance and was wondering if the prototype FIR could be replaced with an IFIR, and if that would offer any improvement. The problem I am having is trying to figure out how the cascaded filters fit together before the FFT. I am an EE with some DSP background, but mostly self taught so there are several holes in my unde...

## Polyphase decimating filter - not working - why?

inHello...I created a polyphase decimating filter based on F.Harris's book shared register design. This is a Decimation by 2, 100 tap, Fs...

Hello...I created a polyphase decimating filter based on F.Harris's book shared register design. This is a Decimation by 2, 100 tap, Fs =100MHz, Low pass 20MHz - stop band 24MHz filter. Each MAC is 28-bit length, 14-bit ADC input, and the filter output is truncated. The filter looks good at first, starts attenuating at 20MHz, and then cuts off about 23MHz.. but when I keep increasing fr...

## Intel's polyphase resampling function

inHi, All. I'm trying to use Intel's IPP polyphase resampling functions. They are part of the signal processing set and found in the manual under...

Hi, All. I'm trying to use Intel's IPP polyphase resampling functions. They are part of the signal processing set and found in the manual under Speech Recognition Functions. I've found the manual's usage description somewhat lacking. I don't understand it well enough to implement. Can anyone provide a reference that might match well with Intel's implementation? It's been a while sin...

## best method for implementing an SRC

inHi, i would like to know which is the best method for implementing a integer sample rate converter (decimation /interpolation) in terms of...

Hi, i would like to know which is the best method for implementing a integer sample rate converter (decimation /interpolation) in terms of quality. the conversion rates required are (2,4,8,16) both decimation and interpolation.i had tried with polyphase implementation and lagrange interpolation.lagrange interpolation is too spiky and polyphase resulted in flat signal without images. But i wo...

## VHDL source code for polyphase filter

inHello, Where can I find the VHDL ( or verilog) source code for polyphase filter? Is there any free implementation around? Regards

Hello, Where can I find the VHDL ( or verilog) source code for polyphase filter? Is there any free implementation around? Regards

## why do we need Polyphase decimatation filter?

inI did a decimator FIR filter simply by doing the convolution only once every M' input sample. for example M=3: feed x0,feed x1, feed x2,...

I did a decimator FIR filter simply by doing the convolution only once every M' input sample. for example M=3: feed x0,feed x1, feed x2, convolution, feed x3,feed x4, feed x5, convolution, feed x6,.... Then I find many people talk about polyphase decimation filter, I wonder if it is more efficient than what I'm doing? What is the differrence? thanks mary