Paul Lovell (@woodpecker)

I have over 40 years professional experience of analog and digital hardware and software in the following fields : a) RF communications b) Test software development for military systems. c) Signal measurement and analysis.

Update to a Narrow Bandpass Filter in Octave or Matlab

March 29, 2021

Following my earlier blog post (June 2020) featuring a Narrow Bandpass Filter, I’ve had some useful feedback and suggestions. This has inspired me to come up with an updated version, incorporating the following changes compared to the earlier one :

• Simpler code in Octave or Matlab
• Float32 precision replaces float64
• Faster processing by a factor of at least 4 times
• Easier setup of input parameters
• Normalized signal output level

A new experimental version in...

A Narrow Bandpass Filter in Octave or Matlab

The design of a very narrow bandpass FIR filter, coded in either Octave or Matlab, can prove challenging if a computationally-efficient  filter is required. This is especially true if the sampling rate is high relative to the filter's center frequency. The most obvious filter design methods, using either window-based or Remez ( Parks-McClellan ) functions, can easily result in filters with many thousands of taps.

The filter to be described reduces the computational effort (and thus...

An Efficient Lowpass Filter in Octave

November 6, 2019

This article describes an efficient linear-phase lowpass FIR filter, coded using the Octave programming language. The intention is to focus on the implementation in software, but references are provided for those who wish to undertake further study of interpolated FIR filters [1]- [3].

The input signal is processed as a vector of samples (eg from a .wav file), which are converted to a matrix format.   The complete filter is thus referred to as a Matrix IFIR or...

Re: Should work but doesn't (and vice versa)

Thanks to all for the interesting replies. Good to hear from you again, Rick.For beginners who might be rather baffled by the intricacies of recursive filters, I...

Should work but doesn't (and vice versa)

Hi everyone,  Not exclusively DSP this one, but please bear with me.I expect that most of us (especially those of more advanced years such as myself) have dealt...

Recent FFT benchmarking report

Hi Guys,I thought that some of you may be interested in the following report from the Innovative Computing Laboratory, at the University of Tennessee, Knoxville,...

Re: Real Numbers

In all my 67 years, I had never realised the importance of the number 6174.Life will never be the same again  .  .  .

Re: Multi-filter Parks McClellan algorithm

Hi all,  I'm back again,For anyone interested in designing phase/amplitude correction FIR filters, the free rePhase FIR tool on the minidsp.com website may be...

Re: Multi-filter Parks McClellan algorithm

Aha !Yes, this looks very promising Neil. Now if the h_goal parameter in the sinc_corr function could be modified to take on the inverse response of the second filter,...

Re: Multi-filter Parks McClellan algorithm

Hi kaz,I'm attempting to find a generic solution to the case where the second or subsequent filter(s) is not able to be changed, for some reason.Perhaps it is better...

Re: Multi-filter Parks McClellan algorithm

Hi Neil,Thanks for your input on this. The problem here is that the PM algorithm may not be able to handle the H2 response parameters produced by H/H1.For instance...

Re: Multi-filter Parks McClellan algorithm

Ok thanks kaz,I agree wholeheartedly that a single design is preferable ;-) I'm wondering how, from your example, we calculate h2 given that we have h and h1 parameters.Could...

Multi-filter Parks McClellan algorithm

Hi everyone,  There are of course, many situations where the design of a single linear-phase FIR filter may be accomplished using the Parks McClellan algorithm....

Re: Confusion understanding some equations in the book "Understanding Digital Signal Processing" (Indian edition).

An optimist says “The glass is half full.”A pessimist says “The glass is half empty.”A programmer says “The glass is twice as large as necessary.” ...

Re: Off-topic: Xmas gift for a techie?

Hi Neil,Sounds like a good book, but the equations do things the old fashioned way.What d'yer mean they give 100% accurate solutions ?AI (aka machine learning) is...

Re: A DSP Online Conference?

One topic I would particularly like to see covered is parallel processing in DSP.Related to techniques, algorithms, hardware, use of MPI (Message Passing Interface)...

DDSP combines DSP with a Neural Network

Hi everyone,I recently stumbled across the Differentiable DSP (DDSP) library for Python/Tensorflow. This seems to combine DSP techniques with a neural network in...

...

As easy as PI

A little gem which shows that the only involvement of mathematics in politics, should be the counting of votes (and even that is not always straightforward).   ...

Re: The Spectral Complexity of a Single Musical Note

Hi Rick,This is indeed an interesting spectral plot. However, a series of plots would be even more interesting. ie:a) Plots from microphones placed at different...

Re: Folded FIR filter in Matlab or Octave

Hi all, Thanks to all for your interesting replies. I should have said that yes, the impulse response is symmetric, and I'm interested in filter lengths from 8...

Folded FIR filter in Matlab or Octave

Most of you, I'm sure, will be familiar with the "Folded FIR" technique for reducing the computational load of FIR filters.   For instance, in the example below,...

Re: PRISM - A new type of filter ?

Hi Rick and kaz,Good to get your input on the Prism. Much of the documentation seems rather unclear and contradictory e.g. In the "bikini pdf" it states:" Each new...

PRISM - A new type of filter ?

Hi everyone,Recently I have been analyzing what is claimed to be a new type of filter, known as a Prism.However, despite studying this document and this one, I've...

Re: Hilbert-Huang Transform

Ok everyone,Here is the link to R code examples from the Hilbert-Huang Transform document.My thanks to the author Danny Bowman for this :Electronic supplement to...

Re: Hilbert-Huang Transform

Hi Tim & Gianni, I have requested a link to the code from the authors.The R code for Fig 2 (given in the document) seems to run ok, once line 5 is changed to...

Hilbert-Huang Transform

Hi Guys,Over the past month, I have been investigating possible methods of signal decomposition as an alternative to the FFT.In particular, I'm looking at signals...

Re: Off Topic: Binary Numbers

Seems like Leibniz also invented a type of mechanical calculator.Not sure if there was a binary version . . .

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