Agilent Technologies 8753ES Option 011 Service Manual page 358

Theory of Operation
How the Analyzer Works
Test Sets
Signal separation for the analyzer can be accomplished using any one of the following
HP/Agilent accessories:
• 85044A/B Transmission/Reflection Test Set
• 85046A/B S-Parameter Test Set
• 85047A S-Parameter Test Set
• HP/Agilent Made Special Option Transmission/Reflection or S-Parameter Test Set
• 86205A/86207A RF Bridge
• 11667A Two-Way Power Splitter and 86205A RF Bridge
Signal separation devices are needed to separate the incident signal from the
transmitted/reflected signal. The incident signal, which comes from the analyzer's source
RF output, is applied to the R channel receiver input. Meanwhile, the
transmitted/reflected signal is applied to the A or B channel receiver input via a test port
coupler (in a test set) or an RF bridge.
The HP/Agilent 85046A/B and 85047A S-parameter test sets contain the hardware
required to make simultaneous transmission and reflection measurements in both the
forward and reverse directions. An RF path switch in the test set allows reverse
measurements to be made without changing the connections to the device under test.
Test Set Step Attenuator
The 70 dB step attenuator contained in the test set is used to adjust the power level to the
DUT without changing the level of the incident power in the reference path. The
attenuator in the 85046A/B or 85047A test set is controlled from the front panel of the
analyzer using the or softkeys located
ATTENUATOR PORT 1 ATTENUATOR PORT 2
in the power menu.
The Receiver Block
The receiver block contains three sampler/mixers for the R, A and B inputs. The signals
are sampled, and down-converted to produce a 4 kHz IF (intermediate frequency). A
multiplexer sequentially directs each of the three IF signals to the ADC (analog to digital
converter) where it is converted from an analog to a digital signal to be measured and
processed for viewing on the display. Both amplitude and phase information are measured
simultaneously, regardless of what is displayed on the analyzer.
The Microprocessor
A microprocessor takes the raw data and performs all the required error correction, trace
math, formatting, scaling, averaging, and marker operations, according to the instructions
from the front panel or over GPIB. The formatted data is then displayed.
Required Peripheral Equipment
In addition to the analyzer, a system requires calibration standards for vector accuracy
enhancement, and cables for interconnections.
12-4 Chapter 12