Naive Square Wave

Naive square wave

After introducing finite-bandwidth square waves in previous articles, I’ll now describe what happens if you follow the naive approach, and just alternate sequences of 1’s and −1’s. As you might expect after reading the previous articles, there are several problems with this. The first problem is that the naive square wave is… read more

Submitted on 27 October 2013

Finite-Bandwidth Square Wave

Square wave with harmonics 1, 3, 5, …, 19

How would you produce a square wave on a digital system? At first sight, this seems completely trivial. You might think that you could just alternate a series of +1 values with a series of −1 values and be done with it. Well, it doesn’t work like that. An ideal square wave needs infinite bandwith, so creating one is… read more

Submitted on 2 October 2013

The Perfect Camera

Airy pattern

The perfect camera is diffraction limited. This article is written strictly from an optical point of view, so don’t expect a Nikon / Canon / Leica comparison here… Optically, a camera (or telescope or other optical instrument) can be described by its point spread function (PSF), which… read more

Submitted on 21 July 2013

Impulse Response

Unit sample function

The impulse response of a system is, perhaps not entirely unexpectedly, the response of a system to an impulse. This article introduces this all important concept, and shows how knowing only the impulse response of an LTI system can be used to… read more

Submitted on 6 July 2013

Discrete-Time Signal Processing

The title of this article is Discrete-Time Signal Processing, although the term digital signal processing (with the abbreviation DSP) is much more common. Both types of signals are discrete in the time dimension, in the sense that they are sequences of numbers. The difference is that a digital signal is… read more

Submitted on 23 June 2013

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