12-22 Chapter 12
Theory of Operation
Source Theory Overview
Tuned Receiver Mode
In tuned receiver mode, the analyzer is a synthesized, swept, narrow-band receiver only.
The external signal source must be synthesized and reference-locked to the analyzer.
To achieve this, the analyzer’s source and phase lock circuits are completely unused. See
Figure 12-8. The fractional-N synthesizer is tuned so that one of its harmonics (1st LO)
down-converts the RF input to the samplers. (In contrast to external source mode, the
analyzer does not phase lock at all. However, the 1st LO is synthesized.)
The analyzer can function as a swept tuned receiver, similar to a spectrum analyzer, but
the samplers create spurious signals at certain frequencies, which limit the accuracy of
such measurements.
Figure 12-8 Tuned Receiver Mode
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