GW Instek GRF-1300A - Manual (Page 27)

An Introduction to Spectrum Analyzers
Figure B-1.
The basic
structure of a
broadband
receiver
Tunable LOs
RF Input
Detection
& Display
Unit
Mixers
BPFs
IF
Next, we are going to introduce the other basic functional
blocks that a spectrum analyzer is composed of. These blocks are
often mentioned when instructed on how to use a spectrum
analyzer.
Attenuator
An attenuator on the RF input path can increase the
dynamic range of the input signal level or provide more input
protection to the spectrum analyzer. Referring to Figure B-2, the
attenuator limits the signal level coming to the mixer (RF end) to
a certain level. If the input signal is above a reference level, it can
cause measurement errors, or cause spurious noise.
Figure B-2.
Attenuator
Attenuator
Tunable LOs
RF Input
Detection
& Display
Unit
Mixers
BPFs
IF
Resolution Bandwidth Filter
When the input signal frequency is converted to an IF, a
RBW (resolution bandwidth) filter is used to distinguish the
signals that are close to each other in frequency. Figure B-3
shows this concept.
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