Chapter 12 12-3
Theory of Operation
How the Analyzer Works
How the Analyzer Works
Network analyzers measure the reflection and transmission characteristics of devices and
networks. A network analyzer test system consists of the following:
• source
• signal-separation devices
• receiver
•display
The analyzer applies a signal that is either transmitted through the device under test, or
reflected from its input, and then compares it with the incident signal generated by the
swept RF source. The signals are then applied to a receiver for measurement, signal
processing, and display.
The analyzer consists of a high resolution synthesized RF source, test set, and a dual
channel three-input receiver to measure and display magnitude, phase, and group delay of
transmitted and reflected power. Analyzers with Option 010 provide the additional
capability of transforming measured data from the frequency domain to the time domain.
Figure 12-1 is a simplified block diagram of the network analyzer system. A detailed block
diagram of the analyzer is located at the end of Chapter 4 , “Start Troubleshooting Here.”
Figure 12-1 Simplified Block Diagram of the Network Analyzer System
The Built-In Synthesized Source
The analyzer's built-in synthesized source produces a swept RF signal in the range of
30 kHz to 3.0 GHz. The Agilent 8753ET/ES Option 006 is able to generate signals up to
6 GHz. The source output power is leveled by an internal ALC (automatic leveling control)
circuit. To achieve frequency accuracy and phase measuring capability, the analyzer is
phase locked to a highly stable crystal oscillator.
For this purpose, a portion of the transmitted signal is routed to the R channel input of the
receiver, where it is sampled by the phase detection loop and fed back to the source.
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