 - Analog-to-digital conversion is an
electronic process in which a continuously variable (analog) signal is
changed, without altering its essential content, into a
multi-level (digital)
signal.
The input to an analog-to-digital converter
(ADC) consists of a voltage that varies among a
theoretically infinite number of values. Examples are sine waves,
the waveforms representing human speech, and the signals from a
conventional television camera. The output of the ADC, in
contrast, has defined levels or states. The number of states is
almost always a power of two -- that is, 2, 4, 8, 16, etc. The
simplest digital signals have only two states, and are called
binary.
All whole numbers can be represented in binary form as strings of
ones and zeros.
Digital signals propagate more efficiently than
analog signals, largely because digital impulses, which are
well-defined and orderly, are easier for electronic circuits to
distinguish from noise, which is chaotic. This is the chief
advantage of digital modes in communications. Computers
"talk" and "think" in terms of binary digital
data; while a microprocessor can analyze analog data, it must be
converted into digital form for the computer to make sense of it.
A typical telephone modem makes use of an
ADC to convert the incoming audio from a twisted-pair line into
signals the computer can understand. In a digital signal processing system, an ADC is required if the signal input is
analog.
| LAST UPDATED: |
24 Sep 1999
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