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## Live Q&A with fred harris - Green FIR Filters with Large Ratio of Sample Rate to Bandwidth

fred harris - **Watch Now** - DSP Online Conference 2021 - Duration: 29:48

**fred_h**Speaker

**adam.rex**

I would be interested in the code for an M-path linear phase IIR filter bank.

**Amit**

Prof. Harris,

would it be possible to get the code for the M-Path Linear phase IIR filter bank

thanks

**adam.rex**

Can polyphase FIR filter design reduce delay compared to a non-polyphase FIR filter?

**remco_at_itsonlyaudio.com**

Boy did you bury the lead in the last few minutes!

So for a log spaced polyphase bank, do you keep the transition bandwidths equal to assure the 6 dB Nyquist overlap but scale the bandwidths by the square root multiplier? Wouldn't that lead to a varying number of coefficients for each polyphase bank?

**magarac**

thank you so much for great presentation dr harris ! I'm curious to learn more about polyphase filterbank for hearing aids which is topic of your upcoming paper, but did not catch when/where will it be published. also, some specifics about inband aliasing that might affect some processing like echo-canceller, etc...

thanks & best regards !

**Stefano**

Hi Fred,

It is always an immense pleasure listening to your talks.

Regarding RF direct sampling, what are your thoughts about one analog Hilbert transformer followed by 2 ADCs, rather than directly sampling RF with one ADC? With the first approach we would have the 2 ADCs running at half speed but never seen a system done in this way so far.

Thanks!

Stefano

13:33:31 From Emanuele Ziglioli : Happy dsp-versary Stephane! 13:36:39 From Thomas Wagner : david you are on! 13:37:07 From David Robinson : Sorry for that 13:37:16 From Thomas Wagner : No worries ;) 13:39:44 From Emanuele Ziglioli : Ric Losada? but that was zero paddin 13:51:12 From mnapier : The coefs are in a ROM. You select them. 13:52:39 From Radu Pralea : prof. harris, you've mentioned your modified remez FIR designer. I was wondering how it compares with the Least Squares method (which also provides decaying lobes 13:54:17 From kclifford : I like Least Squares as well. Also one can add e.g. time domain constraints. 14:00:33 From Radu Pralea : great, thanks! 14:00:46 From kclifford : Thanks, much appreciated! 14:01:27 From Jeff Cannon : Great information. Thanks, fred! 14:01:44 From magarac : thank you so much for great presentation dr harris ! I'm curious to learn more about polyphase filterbank for hearing aids which is topic of your upcoming paper, but did not catch when/where will it be published. also, some specifics about inband aliasing that might affect some processing like echo-canceller, etc... thanks & best regards !

adam,

The polyphase filter that implements a cascade of analysis and binary masked synthesis filter bank always has a longer delay that the direct FIR filter implementation... because you have gone through two filters between input and output....

What is interesting, there is a recursive form of the polyphase filter, one with non uniform phase and one form with linear phase (actually equal ripple approximation to linear phase) the linear phase version will present a reduced delay relative to the direct form FIR.... see my book and if interested... I can pass along the code for the M-Path Linear phase IIR filter bank...