Digital Signal Processing Reference
In-Depth Information
1
Introduction
to Digital Signal Processing
1.1
Brief Theory of DSP Concepts
Digital Signal Processing (DSP) primarily deals with commonly occurring
signals such as speech, music, video, EKG or ECG (heart), and EEE (brain).
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These signals occur naturally in analog continuous-time form, as shown in
Figure 1.1
, which depicts a typical speech signal, representing the phrase
“She sells sea shells” said over a time span of about 1.8 seconds.
1.1.1
Applications of DSP
Given an analog signal (see Figure 1.1), the following applications are possible:
•
Preparing the analog signal for communication through a communication
channel.
Years of study and research have shown that one efficient
means of communicating the signal across a channel is as shown in
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The signal is first converted from analog to digital (A/
D), then modulated with a high frequency carrier and transmitted
from an antenna. Likewise, at the receiver, the modulated signal is
received by an antenna, demodulated, and then converted back from
digital to analog format (D/A). In DSP, we are primarily focused on
baseband signals, i.e., the A/D and D/A conversion stages.
•
Analyzing the analog signal for use in a voice recognition telephone system.
Today, it is common to encounter voice recognition systems when
we call businesses, railway and airline reservation lines, banks, and a
host of other places. In these systems, the analog signal is sampled
and then analyzed, using a Fast Fourier Transform (FFT), as shown
in
Figure 1.3
.
The analyzed frequency spectrum data is input into a
microprocessor, which matches the latter spectrum with a stored
signal spectrum. If a good match is determined between the two
signal spectra, then a particular operation is initiated.
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