Reducing IIR Filter Computational Workload

Rick Lyons May 24, 2019

This blog describes a straightforward method to significantly reduce the number of necessary multiplies per input sample of traditional IIR lowpass and highpass digital filters.

Reducing IIR Filter Computations Using Dual-Path Allpass Filters

We can improve the computational speed of a lowpass or highpass IIR filter by converting that filter into a dual-path filter consisting of allpass filters as shown in Figure 1.

...

A Lesson In Engineering Humility

Rick Lyons May 20, 20196 comments

Let's assume you were given the task to design and build the 12-channel telephone transmission system shown in Figure 1.

Figure 1

At a rate of 8000 samples/second, each telephone's audio signal is sampled and converted to a 7-bit binary sequence of pulses. The analog signals at Figure 1's nodes A, B, and C are presented in Figure 2.

Figure 2

I'm convinced that some of you subscribers to this dsprelated.com web site could accomplish such a design & build task....

IIR Bandpass Filters Using Cascaded Biquads

Neil Robertson April 20, 20196 comments

In an earlier post [1], we implemented lowpass IIR filters using a cascade of second-order IIR filters, or biquads.  This post provides a Matlab function to do the same for Butterworth bandpass IIR filters.  Compared to conventional implementations, bandpass filters based on biquads are less sensitive to coefficient quantization [2].  This becomes important when designing narrowband filters.

A biquad section block diagram using the Direct Form II structure [3,4] is shown in...


A Balancing Act

Stephane Boucher April 10, 20191 comment

For the second live streaming session, I give myself a 5/10.

I felt much more comfortable and was way better prepared than when I did my first session - and that's why I went from 3/10 to 5/10 in my system of self-awarded rating - but my attempt at 'live' humor fell rather flat I think and I had some technical difficulties with the live streaming itself.   So I believe 5/10 is fair and leaves lots of room for improvement.

As far as my attempt at humor is concerned, you...


The Ice is Broken

Stephane Boucher April 1, 20196 comments

When I suggested that you lower you expectations before watching my first live session, I wasn't kidding.

Still, I was hoping I would do much better than what I had prepared you for but obviously it wasn't meant to be.

Don't get me wrong, a few things went very well, like the technical aspects for instance.  I thought the improvised studio looked pretty good, the audio sounded fine and the HD stream was nice and steady.

And my mom thinks that I looked handsome...


Controlling a DSP Network's Gain: A Note For DSP Beginners

Rick Lyons March 29, 201921 comments

This blog briefly discusses a topic well-known to experienced DSP practitioners but may not be so well-known to DSP beginners. The topic is the proper way to control a digital network's gain. Digital Network Gain Control Figure 1 shows a collection of networks I've seen, in the literature of DSP, where strict gain control is implemented.

              FIGURE 1. Examples of digital networks whose initial operations are input signal...


Lower your Expectations

Stephane Boucher March 26, 20196 comments

This Friday, I will for the first time be the person in front of the camera, the star of my own show on EmbeddedRelated.tv.  I will be experimenting with talking live to the *Related sites community, using the 'Free Goodies' prize draw as a pretext.  

This could become a very effective way to communicate with you and part of me is genuinely excited and really looking forward to go live.

But there is another part of me that is slightly...


Generating Partially Correlated Random Variables

Harry Commin March 23, 201910 comments
IntroductionIt is often useful to be able to generate two or more signals with specific cross-correlations. Or, more generally, we would like to specify an $\left(N \times N\right)$ covariance matrix, $\mathbf{R}_{xx}$, and generate $N$ signals which will produce this covariance matrix.

There are many applications in which this technique is useful. I discovered a version of this method while analysing radar systems, but the same approach can be used in a very wide range of...


Free Goodies from Embedded World - Full Inventory and Upcoming Draw Live-Streaming Date

Stephane Boucher March 22, 2019

Chances are that you already know that I went to Embedded World a few weeks ago and came back with a bag full of "goodies".  Initially, my vision was to do a single draw for one person to win it all, but I didn't expect to come back with so much stuff and so many development kits.   Based on your feedback, it seems like you guys agree that It wouldn't make sense for one person to win everything as no-one could make good use of all the boards and there would be lots of...


Angle Addition Formulas from Euler's Formula

Cedron Dawg March 16, 20198 comments
Introduction

This is an article to hopefully give a better understanding of the Discrete Fourier Transform (DFT), but only indirectly. The main intent is to get someone who is uncomfortable with complex numbers a little more used to them and relate them back to already known Trigonometric relationships done in Real values. It is essentially a followup to my first blog article "The Exponential Nature of the Complex Unit Circle".

Polar Coordinates

The more common way of...


A Fixed-Point Introduction by Example

Christopher Felton April 25, 201120 comments
Introduction

The finite-word representation of fractional numbers is known as fixed-point.  Fixed-point is an interpretation of a 2's compliment number usually signed but not limited to sign representation.  It extends our finite-word length from a finite set of integers to a finite set of rational real numbers [1].  A fixed-point representation of a number consists of integer and fractional components.  The bit length is defined...


Adventures in Signal Processing with Python

Jason Sachs June 23, 201311 comments

Author’s note: This article was originally called Adventures in Signal Processing with Python (MATLAB? We don’t need no stinkin' MATLAB!) — the allusion to The Treasure of the Sierra Madre has been removed, in deference to being a good neighbor to The MathWorks. While I don’t make it a secret of my dislike of many aspects of MATLAB — which I mention later in this article — I do hope they can improve their software and reduce the price. Please note this...


A Quadrature Signals Tutorial: Complex, But Not Complicated

Rick Lyons April 12, 201351 comments

Introduction Quadrature signals are based on the notion of complex numbers and perhaps no other topic causes more heartache for newcomers to DSP than these numbers and their strange terminology of j operator, complex, imaginary, real, and orthogonal. If you're a little unsure of the physical meaning of complex numbers and the j = √-1 operator, don't feel bad because you're in good company. Why even Karl Gauss, one the world's greatest mathematicians, called the j-operator the "shadow of...


Ten Little Algorithms, Part 2: The Single-Pole Low-Pass Filter

Jason Sachs April 27, 201513 comments

Other articles in this series:

I’m writing this article in a room with a bunch of other people talking, and while sometimes I wish they would just SHUT UP, it would be...


Understanding the 'Phasing Method' of Single Sideband Demodulation

Rick Lyons August 8, 201224 comments

There are four ways to demodulate a transmitted single sideband (SSB) signal. Those four methods are:

  • synchronous detection,
  • phasing method,
  • Weaver method, and
  • filtering method.

Here we review synchronous detection in preparation for explaining, in detail, how the phasing method works. This blog contains lots of preliminary information, so if you're already familiar with SSB signals you might want to scroll down to the 'SSB DEMODULATION BY SYNCHRONOUS DETECTION'...


An Interesting Fourier Transform - 1/f Noise

Steve Smith November 23, 200714 comments

Power law functions are common in science and engineering. A surprising property is that the Fourier transform of a power law is also a power law. But this is only the start- there are many interesting features that soon become apparent. This may even be the key to solving an 80-year mystery in physics.

It starts with the following Fourier transform:

The general form is tα ↔ ω-(α+1), where α is a constant. For example, t2 ↔...


Handling Spectral Inversion in Baseband Processing

Eric Jacobsen February 11, 20089 comments

The problem of "spectral inversion" comes up fairly frequently in the context of signal processing for communication systems. In short, "spectral inversion" is the reversal of the orientation of the signal bandwidth with respect to the carrier frequency. Rick Lyons' article on "Spectral Flipping" at http://www.dsprelated.com/showarticle/37.php discusses methods of handling the inversion (as shown in Figure 1a and 1b) at the signal center frequency. Since most communication systems process...


Understanding and Preventing Overflow (I Had Too Much to Add Last Night)

Jason Sachs December 4, 2013

Happy Thanksgiving! Maybe the memory of eating too much turkey is fresh in your mind. If so, this would be a good time to talk about overflow.

In the world of floating-point arithmetic, overflow is possible but not particularly common. You can get it when numbers become too large; IEEE double-precision floating-point numbers support a range of just under 21024, and if you go beyond that you have problems:

for k in [10, 100, 1000, 1020, 1023, 1023.9, 1023.9999, 1024]: try: ...

Free DSP Books on the Internet

Rick Lyons February 23, 200824 comments

While surfing the "net" I have occasionally encountered signal processing books whose chapters could be downloaded to my computer. I started keeping a list of those books and, over the years, that list has grown to over forty books. Perhaps the list will be of interest to you.

Please know, all of the listed books are copyrighted. The copyright holders have graciously provided their books free of charge for downloading for individual use, but multiple copies must not be made or printed. As...


Python scipy.signal IIR Filtering: An Example

Christopher Felton May 19, 2013
Introduction

In the last posts I reviewed how to use the Python scipy.signal package to design digital infinite impulse response (IIR) filters, specifically, using the iirdesign function (IIR design I and IIR design II ).  In this post I am going to conclude the IIR filter design review with an example.

Previous posts:


A Balancing Act

Stephane Boucher April 10, 20191 comment

For the second live streaming session, I give myself a 5/10.

I felt much more comfortable and was way better prepared than when I did my first session - and that's why I went from 3/10 to 5/10 in my system of self-awarded rating - but my attempt at 'live' humor fell rather flat I think and I had some technical difficulties with the live streaming itself.   So I believe 5/10 is fair and leaves lots of room for improvement.

As far as my attempt at humor is concerned, you...


The Ice is Broken

Stephane Boucher April 1, 20196 comments

When I suggested that you lower you expectations before watching my first live session, I wasn't kidding.

Still, I was hoping I would do much better than what I had prepared you for but obviously it wasn't meant to be.

Don't get me wrong, a few things went very well, like the technical aspects for instance.  I thought the improvised studio looked pretty good, the audio sounded fine and the HD stream was nice and steady.

And my mom thinks that I looked handsome...


Lower your Expectations

Stephane Boucher March 26, 20196 comments

This Friday, I will for the first time be the person in front of the camera, the star of my own show on EmbeddedRelated.tv.  I will be experimenting with talking live to the *Related sites community, using the 'Free Goodies' prize draw as a pretext.  

This could become a very effective way to communicate with you and part of me is genuinely excited and really looking forward to go live.

But there is another part of me that is slightly...


Free Goodies from Embedded World - Full Inventory and Upcoming Draw Live-Streaming Date

Stephane Boucher March 22, 2019

Chances are that you already know that I went to Embedded World a few weeks ago and came back with a bag full of "goodies".  Initially, my vision was to do a single draw for one person to win it all, but I didn't expect to come back with so much stuff and so many development kits.   Based on your feedback, it seems like you guys agree that It wouldn't make sense for one person to win everything as no-one could make good use of all the boards and there would be lots of...


Free Goodies from Embedded World - What to Do Next?

Stephane Boucher March 6, 20193 comments

I told you I would go on a hunt for free stuff at Embedded World in order to build a bundle for someone to win.


Back from Embedded World 2019 - Funny Stories and Live-Streaming Woes

Stephane Boucher March 1, 20191 comment

When the idea of live-streaming parts of Embedded World came to me,  I got so excited that I knew I had to make it happen.  I perceived the opportunity as a win-win-win-win.  

  • win #1 - Engineers who could not make it to Embedded World would be able to sample the huge event, 
  • win #2 - The organisation behind EW would benefit from the extra exposure
  • win #3 - Lecturers and vendors who would be live-streamed would reach a (much) larger audience
  • win #4 - I would get...

Spread the Word and Run a Chance to Win a Bundle of Goodies from Embedded World

Stephane Boucher February 21, 2019

Do you have a Twitter and/or Linkedin account?

If you do, please consider paying close attention for the next few days to the EmbeddedRelated Twitter account and to my personal Linkedin account (feel free to connect).  This is where I will be posting lots of updates about how the EmbeddedRelated.tv live streaming experience is going at Embedded World.

The most successful this live broadcasting experience will be, the better the chances that I will be able to do it...


Launch of EmbeddedRelated.tv

Stephane Boucher February 21, 2019

With the upcoming Embedded Word just around the corner, I am very excited to launch the EmbeddedRelated.tv platform.  

This is where you will find the schedule for all the live broadcasts that I will be doing from Embedded World next week.  Please note that the schedule will be evolving constantly, even during the show, so I suggest your refresh the page often.  For instance, I am still unsure if I will be able to do the 'opening of the doors' broadcast as...


Live Streaming from Embedded World!

Stephane Boucher February 12, 2019

For those of you who won't be attending Embedded World this year, I will try to be your eyes and ears by video streaming live from the show floor.   

I am not talking improvised streaming from a phone, but real, high quality HD streaming with a high-end camera and a device that will bond three internet connections (one wifi and two cellular) to ensure a steady, and hopefully reliable, stream. All this to hopefully give those of you who cannot be there in person a virtual...