# HowTo

## Getting Involved in comp.dsp

Once you have access to comp.dsp, the first thing to do is "lurk". "Lurkers" are simply people who read but don't write. Lurkers of all kinds are welcome in comp.dsp. It's best to read comp.dsp for awhile to get the flavor of it before you actually post (submit) anything. (For a heads-up on the general attitudes and expectations of the group, be sure to read about comp.dsp culture.

OK, you've lurked for awhile and you're ready to post. You'll probably want to send out a test message to see if your system is working. But please don't post that to comp.dsp. Instead, post it to the "misc.test" newsgroup, which is basically a dumping ground for test messages. If your test message appears in misc.test, your real message is very likely to appear in comp.dsp.

But having done your homework and your search having failed, you really do need to ask a real live Human Being . Well, that's why comp.dsp is there. Your newsreader probably makes posting a question to comp.dsp no harder than sending an e-mail. But as you write your question, be sure to follow the guidelines of comp.dsp culture. Think of yourself as a guest at a cocktail party: don't block the driveway; be polite; don't track mud on the carpet; put down the toilet seat when you're through.

Welcome aboard comp.dsp!

## How to Generate White Gaussian Noise

White Gaussian Noise (WGN) is needed for DSP system testing or DSP system identification. Here are two methods for generating White Gaussian Noise. Both rely on having a good uniform random number generator. We will assume that the function "uniform()" returns a random variable in the range [0, 1] and has good statistical properties.

## How to interpolate the peak location of a DFT or FFT if the frequency of interest is between bins

### Problem

If the actual frequency of a signal does not fall on the center frequency of a DFT (FFT) bin, several bins near the actual frequency will appear to have a signal component. In that case, we can use the magnitudes of the nearby bins to determine the actual signal frequency.

## How to Design Minimum-Phase FIR Filters

Like most things in DSP, there are several methods to create minimum-phase Finite Impulse Response (FIR) filters.

## How to Create Oscillators in Software

Oscillators can be created in software directly, using the "sine" function, or they can be calculated indirectly using several different iterative methods. We survey those methods here.

#### Notation:

First, let's assume that:

## How to Interpolate in the Time-Domain by Zero-Padding in the Frequency Domain

by Rick Lyons

Performing interpolation on a sequence of time-domain samples is an important (often used) process in DSP, and there are many descriptions of time-domain interpolation (a kind of curve fitting) in the literature and on the Internet. However, there’s a lesser-known scheme used for interpolation that employs the inverse discrete Fourier transform (IDFT). This little tutorial attempts to describe that technique.