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binary number system representation. The limited resolution of the binary number that corresponds
to a range of voltages creates the quantization levels and ranges.
For example, a compact disk player is built around technology that relies on the conversion of a
continuously available signal, such as music from a microphone, into a digital form. The digital
information is stored on a compact disk and later read in digital form by a laser playback system (1).
However, to serve as input to a traditional stereo amplifier, and since speakers and the human ear
are analog devices, the digital information is converted back into a continuous voltage signal for
playback.
Signal Waveforms
In addition to classifying signals as analog, discrete time, or digital, some description of the
waveform associated with a signal is useful. Signals may be characterized as either static or
dynamic. A static signal does not vary with time. The diameter of a shaft is an example. Many
physical variables change slowly enough in time, compared to the process with which they interact,
that for all practical purposes these signals may be considered static in time. For example, the
voltage across the terminals of a battery is approximately constant over its useful life. Or consider
measuring temperature by using an outdoor thermometer; since the outdoor temperature does not
change significantly in a matter of minutes, this input signal might be considered static when
compared to our time period of interest. A mathematical representation of a static signal is given by a
constant, as indicated in Table 2.1. In contrast, often we are interested in how the measured variable
changes with time. This leads us to consider time-varying signals further.
A dynamic signal is defined as a time-dependent signal. In general, dynamic signal waveforms,
y(t), may be classified as shown in Table 2.1. A deterministic signal varies in time in a predictable
manner, such as a sine wave, a step function, or a ramp function, as shown in Figure 2.5. A signal is
steady periodic if the variation of the magnitude of the signal repeats at regular intervals in time.
Examples of steady periodic behaviors are the motion of an ideal pendulum, and the temperature
variations in the cylinder of an internal combustion engine under steady operating conditions.
Periodic waveforms may be classified as simple or complex. A simple periodic waveform contains
only one frequency. A complex periodic waveform contains multiple frequencies and is represented
as a superposition of multiple simple periodic waveforms. Aperiodic is the term used to describe
deterministic signals that do not repeat at regular intervals, such as a step function.
Time
Quantization levels
(a) Digital signal
Signal
Time
(b) Digital waveform
Signal
Quantization levels
Figure 2.4 Digital signal representation and waveform.
44 Chapter 2 Static and Dynamic Characteristics of Signals
13:35:16 Page 44
binary number system representation. The limited resolution of the binary number that corresponds
to a range of voltages creates the quantization levels and ranges.
For example, a compact disk player is built around technology that relies on the conversion of a
continuously available signal, such as music from a microphone, into a digital form. The digital
information is stored on a compact disk and later read in digital form by a laser playback system (1).
However, to serve as input to a traditional stereo amplifier, and since speakers and the human ear
are analog devices, the digital information is converted back into a continuous voltage signal for
playback.
Signal Waveforms
In addition to classifying signals as analog, discrete time, or digital, some description of the
waveform associated with a signal is useful. Signals may be characterized as either static or
dynamic. A static signal does not vary with time. The diameter of a shaft is an example. Many
physical variables change slowly enough in time, compared to the process with which they interact,
that for all practical purposes these signals may be considered static in time. For example, the
voltage across the terminals of a battery is approximately constant over its useful life. Or consider
measuring temperature by using an outdoor thermometer; since the outdoor temperature does not
change significantly in a matter of minutes, this input signal might be considered static when
compared to our time period of interest. A mathematical representation of a static signal is given by a
constant, as indicated in Table 2.1. In contrast, often we are interested in how the measured variable
changes with time. This leads us to consider time-varying signals further.
A dynamic signal is defined as a time-dependent signal. In general, dynamic signal waveforms,
y(t), may be classified as shown in Table 2.1. A deterministic signal varies in time in a predictable
manner, such as a sine wave, a step function, or a ramp function, as shown in Figure 2.5. A signal is
steady periodic if the variation of the magnitude of the signal repeats at regular intervals in time.
Examples of steady periodic behaviors are the motion of an ideal pendulum, and the temperature
variations in the cylinder of an internal combustion engine under steady operating conditions.
Periodic waveforms may be classified as simple or complex. A simple periodic waveform contains
only one frequency. A complex periodic waveform contains multiple frequencies and is represented
as a superposition of multiple simple periodic waveforms. Aperiodic is the term used to describe
deterministic signals that do not repeat at regular intervals, such as a step function.
Time
Quantization levels
(a) Digital signal
Signal
Time
(b) Digital waveform
Signal
Quantization levels
Figure 2.4 Digital signal representation and waveform.
44 Chapter 2 Static and Dynamic Characteristics of Signals