5-11
Figure 5-8C.—Time versus frequencies.
FREQUENCY-DOMAIN DISPLAY CAPABILITIES
The frequency domain contains information not found in the time domain. The spectrum analyzer
can display signals composed of more than one frequency (complex signals). It can also discriminate
between the components of the signal and measure the power level at each one. It is more sensitive to
low-level distortion than an oscilloscope. Its sensitivity and wide, dynamic range are also useful for
measuring low-level modulation, as illustrated in views A and B of figure 5-9. The spectrum analyzer is
useful in the measurement of long- and short-term stability such as noise sidebands of an oscillator,
residual fm of a signal generator, or frequency drift of a device during warm-up, as shown in views A, B,
and C of figure 5-10.
Figure 5-9A.—Examples of time-domain (left) and frequency-domain (right) low-level signals.
