What Are The Different Types Of Spectrum Analyzers; Swept-Tuned Spectrum Analyzers - Agilent Technologies 89410A Operator's Manual

What Makes this Analyzer Different?
What are the Different Types of Spectrum
Analyzers?
There are two broad categories of spectrum analyzers: swept-tuned analyzers and
real-time analyzers. Both swept-tuned analyzers and real-time analyzers have
been around for many years. However, within the past decade or so, spectrum
analyzers have become much more sophisticated. These newer spectrum analyzers
use digital signal processing to provide additional measurement capablity—and let
you interpret measurement results much more easily.
Both swept-tuned and real-time spectrum analyzers display amplitude versus
frequency. How they process and display this information, however, varies with
the specific type of analyzer. A real-time spectrum analyzer displays the energy at
all frequency components simultaneously. A swept-tuned spectrum analyzer
displays measurement results sequentially—in other words, not in ''real time.'' This
is because a swept-tuned analyzer, in effect, uses a single narrow filter that is tuned
across a range of frequencies to produce a spectrum display.
Swept-tuned analyzers have been the traditional choice for higher frequency
applications—for example, 100 kHz and above. Real-time analyzers are generally
used for lower frequencies—for example, audio-frequency and vibration
measurements.
For an additional overview of spectrum/network measurements, see Spectrum and
Network Measurements by Robert A. Witte (Prentice Hall, Englewood Cliffs, New
Jersey, 1993).

Swept-tuned spectrum analyzers

Swept-tuned spectrum analyzers are descended from radio receivers. So it should
come as no surprise that swept-tuned analyzers are either tuned-filter analyzers
(analogous to a TRF radio) or superheterodyne analyzers. In fact, in their simplest
form, you could think of a swept-tuned spectrum analyzer as nothing more than a
frequency-selective voltmeter with a frequency range that's tuned (swept)
automatically.
Modern swept-tuned analyzers (superheterodyne analyzers, in particular) are
precision devices that can make a wide variety of measurements. However, they
are primarily used to measure steady-state signals since they can't evaluate all
frequencies in a given span simultaneously. The ability to evaluate all frequencies
simultaneously belongs exclusively to the real-time analyzer.
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