Demodulation – From Signals Back to Numbers

The blue line is the signal template and while red is the matched filter. Notice the same magnitude on each spectral line but exactly opposite phase

Remember that in the article on correlation, we discussed that correlation of a signal with proper normalization is maximum with itself and lesser for all other signals. Since the number of possible signals is limited in a digital communication system,…
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Sampling a Continuous-Time Signal

Spectrum of a sampled signal with aliases shown

The signals of our interest — wireless communication waveforms — are continuous-time as they have to travel through a real wireless channel. To process such a signal using digital signal processing techniques, the signal must be converted into a sequence…
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Dealing with Complex Numbers

A complex number with its I and Q components

Although complex notation is not complex to understand (see Chapter 8 in Understanding Digital Signal Processing by Richard Lyons for an excellent tutorial), one of the themes of this text is to avoid complex notation altogether. A complex number is…
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What is a Signal?

A signal composed of the words "hello wireless"

A signal is any measurable quantity that varies with time (or some other independent variable). If you record the words you speak in a computer memory and plot against time, you get a speech signal. As an example, the above…
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