Reduced-Delay IIR Filters

Rick Lyons
2 comments

This document 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 Computational Workload

Rick Lyons
1 comment

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


An Experimental Multichannel Pulse Code Modulation System of Toll Quality + Electron Beam Deflection Tube For Pulse Code Modulation

L. A. Meacham and E, R. W. Sears
1 comment

See this blog post for context. Pulse Code Modulation offers attractive possibilities for multiplex telephony via such media as the microwave radio relay. The various problems involved in its use have been explored in terms of a 96-channel system designed to meet the transmission requirements commonly imposed upon commercial toll circuits. Twenty-four of the 96 channels have been fully equipped in an experimental model of the system. Coding and decoding devices are described, along with other circuit details. The coder is based upon a new electron beam tube, and is characterized by speed and simplicity as well as accuracy of coding. These qualities are matched in the decoder, which employs pulse excitation of a simple reactive network.


Stereophonic Amplitude-Panning: A Derivation of the "Tangent Law"

Rick Lyons

This article presents a derivation of the "Tangent Law"


A Brief Introduction To Romberg Integration

Rick Lyons

This article briefly describes a remarkable integration algorithm, called "Romberg integration." The algorithm is used in the field of numerical analysis but it's not so well-known in the world of DSP.


An IIR 'DC Removal' Filter

Rick Lyons
2 comments

It seems to me that DC removal filters (also called "DC blocking filters") have been of some moderate interest recently on the dsprelated.com Forum web page. With that notion in mind I thought I'd post a little information, from Chapter 13 of my "Understanding DSP" book, regarding infinite impulse response (IIR) DC removal filters.


Two Easy Ways To Test Multistage CIC Decimation Filters

Rick Lyons
1 comment

This article presents two very easy ways to test the performance of multistage cascaded integrator-comb (CIC) decimation filters. Anyone implementing CIC filters should take note of the following proposed CIC filter test methods.


FFT Interpolation Based on FFT Samples: A Detective Story With a Surprise Ending

Rick Lyons
1 comment

This blog presents several interesting things I recently learned regarding the estimation of a spectral value located at a frequency lying between previously computed FFT spectral samples. My curiosity about this FFT interpolation process was triggered by reading a spectrum analysis paper written by three astronomers.


An Efficient Linear Interpolation Scheme

Rick Lyons
3 comments

This article presents a computationally-efficient linear interpolation trick that requires at most one multiply per output sample.