http://www.dsprelated.com en-us Copyright 2011, DSPRelated.com. http://www.dsprelated.com/new/images/logo.jpg http://www.dsprelated.com 267 48 You are invited to contribute to the content of this blog post through the magic of Google Docs' real time collaboration feature. I discovered this tool several months ago when I was looking for a way to coordinate our annual family halloween party (potluck) and avoid the very unpleasant situation of ending up with too much chips and not enough chocolate (first world problem!).  It was amu... read more]]> Thu, 30 May 2013 16:40:29 -0400 DSPRelated.com last blog entries 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: Python.scipy IIR design: Introduct... read more]]> Sun, 19 May 2013 10:58:37 -0400 DSPRelated.com last blog entries Click Here for a PDF version of this article 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, ... read more]]> Fri, 12 Apr 2013 09:19:56 -0400 DSPRelated.com last blog entries ALONG CAME POLY Polyphase filtering is a computationally efficient structure for applying resampling and filtering to a signal. Most digital filters can be applied in a polyphase format, and it is also possible to create efficient resampling filterbanks using the same theories. This post will walk through a reference implementation of both the downsampling polyphase filter and a downsampling pol... read more]]> Tue, 19 Mar 2013 22:49:55 -0400 DSPRelated.com last blog entries Some weeks ago a friend of mine, a long time radio engineer as well as a piano player, called and asked me, "When I travel in a DC-9 aircraft, and I sit back near the engines, I hear this fairly loud unpleasant whump whump whump whump sound. The frequency of that sound is, maybe, two cycles per second. I think that sound is a beat frequency because the DC-9's engines are turning at a slightly d... read more]]> Wed, 13 Mar 2013 10:25:33 -0400 DSPRelated.com last blog entries Hello! It's been a while since you've heard from me - and there are many reasons why: 1 - I've made a clown of myself (video here) 2 - I've been working on unifying the user management system.  You can now participate to the three related sites (DSPRelated, FPGARelated and EmbeddedRelated) with only one account (same login info).  3- I've been working on getting up to speed with... read more]]> Wed, 20 Feb 2013 10:56:07 -0500 DSPRelated.com last blog entries This article is also available in pdf format. I have read, in some of the literature of DSP, that when the discrete Fourier transform (DFT) is used as a filter the process of performing a DFT causes an input signal's spectrum to be frequency translated down to zero Hz (DC). I can understand why someone might say that, but I challenge that statement as being incorrect. Here are my thoughts. Usi... read more]]> Mon, 18 Feb 2013 14:11:42 -0500 DSPRelated.com last blog entries There used to be a fruit market located at 391 San Antonio Road in Mountain View, California. In the 1990's I worked part time in Mountain View and drove past this market's building, shown in Figure 1, many times, unaware of its history. What happened at that fruit market has changed the lives of almost everyone on our planet. Here's the story. William Shockley In 1948 the brilliant physicist... read more]]> Mon, 14 Jan 2013 09:19:46 -0500 DSPRelated.com last blog entries Keywords: Quantization noise; noise shaping A brief introduction to noise shaping, with firm resolve not to miss the forest for the trees. We may still stumble over some assorted roots. Matlab example code is included. Quantization Fig. 1 shows a digital signal that is reduced to a lower bit width, for example a 16 bit signal being sent to a 12 bit digital-to-analog converter. Rounding to the n... read more]]> Sun, 09 Dec 2012 10:56:03 -0500 DSPRelated.com last blog entries This blog clarifies how to obtain and interpret the z-domain transfer function of the coupled-form 2nd-order IIR resonator. The coupled-form 2nd-order IIR resonator was developed to overcome a shortcoming in the standard 2nd-order IIR resonator. With that thought in mind, let's take a brief look at a standard 2nd-order IIR resonator. Standard 2nd-Order IIR Resonator A block diagram of the stan... read more]]> Fri, 23 Nov 2012 10:49:55 -0500 DSPRelated.com last blog entries This blog discusses two ways to determine an exponential averager's weighting factor so that the averager has a given 3-dB cutoff frequency. Here we assume the reader is familiar with exponential averaging lowpass filters, also called a "leaky integrators", to reduce noise fluctuations that contaminate constant-amplitude signal measurements. Exponential averagers are useful because they allow us... read more]]> Mon, 22 Oct 2012 11:02:15 -0400 DSPRelated.com last blog entries An efficient way to implement FIR filters. Matlab / Octave example included. Keywords: Frequency masking FIR filter implementation Introduction An "upsampled" FIR filter uses multiple-sample delays between the taps, compared to the unity delays in a conventional FIR filter. The resulting frequency response has steeper edges, but contains periodic images along the frequency axis (Fig. 1). Due to... read more]]> Tue, 02 Oct 2012 11:39:03 -0400 DSPRelated.com last blog entries I have just finished implementing a new comments system for the blogs.  Do you like it? Please share your thoughts with me by adding a comment. I'll wait a few days and make sure it works properly and then I'll port it to the code snippets and papers section. Thanks! ... read more]]> Wed, 19 Sep 2012 15:29:15 -0400 DSPRelated.com last blog entries An efficient implementation of a symmetric-FIR polyphase 1:3 interpolator that doesn't follow the usual tapped delay line-paradigm. The example exploits the impulse response symmetry and avoids four multiplications out of 10. keywords: symmetric polyphase FIR filter implementation ASIC Matlab / Octave implementation Introduction An interpolating FIR filter can be implemented with a single tappe... read more]]> Wed, 12 Sep 2012 16:20:17 -0400 DSPRelated.com last blog entries Overview Octaveforge / Matlab design script. Download: here weighted numerical optimization of Laplace-domain transfer function linear-phase design, optimizes vector error (magnitude and phase) design process calculates and corrects group delay internally includes sinc() response of the sample-and-hold stage in the ADC optionally includes multiplierless FIR filter Problem Figure 1: Typ... read more]]> Sat, 18 Aug 2012 13:09:33 -0400 DSPRelated.com last blog entries