Agilent Technologies 8712ET User manual

Option 100 Fault Location and Structural
Return Loss Measurements
Agilent Technologies 8712ET/ES and 8714ET/ES
RF Network Analyzers
User’s Guide Supplement
Part No. 08714-90020
Printed in USA
Print Date: June 2000
Supersedes: October 1999
© Copyright 1998-2000 Agilent Technologies, Inc.

ii
Notice
The information contained in this document is subject to change without
notice. Agilent Technologies makes no warranty of any kind with regard
tothis material, including but not limited to, the implied warranties of
merchantability and fitness for a particular purpose. Agilent
Technologies shall not be liable for errors contained herein or for
incidental or consequential damages in connection with the furnishing,
performance, or use of this material.
Safety Information
Refer to your analyzer’s User’s Guide for safety, warranty, and assistance
information.
Key Conventions
This manual uses the following conventions:
: This represents a key physically located on the
analyzer (a “hardkey”).
: This indicates a “softkey”—a key whose label is determined
by the instrument’s firmware, and is displayed on the right side of the
instrument’s screen next to the eight unlabeled keys.
FRONT PANEL KEY
Softkey

iii
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iv
Book Overview
This book documents the use of Option 100 (fault location and structural
return loss (SRL) measurement capability) with the following network
analyzers:
• Agilent Technologies 8712ET/ES
• Agilent Technologies 8714ET/ES
Fault location and SRL measurements can help you test and
troubleshoot 50 ohm or 75 ohm transmission lines. Both fault location
and SRL measurements are used to identify damaged cables.
Fault location is best used to identify single faults greater than −40 dB.
SRL measurements are typically made before a cable has been installed
and are best used to identify many small evenly-spaced imperfections
that may be too small for a fault location measurement to detect.
The following illustration depicts a cable being measured simultaneously
in fault location and SRL modes. The upper display shows a fault
location measurement in the distance domain. The bottom display shows
a structural return loss measurement.

v
Agilent 8712ET/ES and 8714ET/ES
Network Analyzer
Documentation Map
The CDROM provides the contents of all of the documents
listed below.
The User’s Guide shows how to make measurements,
explains commonly-used features, and tells you how to get
the most performance from the analyzer.
The LAN Interface User’s Guide Supplement shows
how to use a local area network (LAN) for programming and
remote operation of the analyzer.
The Automating Measurements User’s Guide
Supplement provides information on how to configure and
control test systems for automation of test processes.
The Programmer’s Guide provides programming
information including GPIB and SCPI command references,
as well as short programming examples.
The Example Programs Guide provides a tutorial
introduction using BASIC programming examples to
demonstrate the remote operation of the analyzer.

vi
The Service Guide provides the information needed to
adjust, troubleshoot, repair, and verify analyzer conformance
to published specifications.
The HP Instrument BASIC User’s Handbook describes
programming and interfacing techniques using
HP Instrument BASIC, and includes a language reference.
The HP Instrument BASIC User’s Handbook
Supplement shows how to use HP Instrument BASIC to
program the analyzer.
The Option 100 Fault Location and Structural Return
Loss Measurements User’s Guide Supplement provides
theory and measurement examples for making fault location
and SRL measurements. (Shipped only with Option 100
analyzers.)
The CATV Quick Start Guide provides abbreviated
instructions for testing the quality of coaxial cables.
(Shipped only with Option 100 analyzers.)
The Cellular Antenna Quick Start Guide provides
abbreviated instructions for verifying the performance of
cellular antenna systems. (Shipped only with Option 100
analyzers.)

Contents
vii
1. Introduction and Measurement Theory
Fault Location Measurement Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
How the Analyzer Converts Frequency Data to Distance Data . . . . . . . . . . . . . . . . 1-4
Start/Stop Distance and Frequency Span Explanation . . . . . . . . . . . . . . . . . . . . . . . 1-5
Cable Impedance and Structural Return Loss Measurement Theory . . . . . . . . . . . . . 1-6
Cable Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
SRL and Periodic Cable Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-10
SRL and Discrete Cable Faults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
Techniques for Removing Connector Effects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14
Measurement Uncertainties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-18
2. Cable Preparation
Cable Preparation Problems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Bent Cable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
Deformed Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Contaminated Dielectric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
Damaged Outer Conductor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
Non-Flush Cut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
Recommended Tools and Cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
Recommended Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
Recommended Cables. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
3. Making Fault Location Measurements
How to Make and Interpret Fault Location Measurements . . . . . . . . . . . . . . . . . . . . . 3-3
1. Select Fault Location as the Type of Measurement . . . . . . . . . . . . . . . . . . . . . . . . 3-4
2. Enter the Measurement Parameters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
3. Calibrate the Analyzer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
4. Connect the Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
5. Interpret the Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
Example Fault Location Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14
Example 1: Identify Mismatches Expressed as Return Loss. . . . . . . . . . . . . . . . . . 3-14
Example 2: Identify Mismatches as the Magnitude of Reflection Coefficient. . . . . 3-16
Example 3: Identify Mismatches at Greater Distances . . . . . . . . . . . . . . . . . . . . . . 3-17
4. Making SRL Measurements
How to Make and Interpret SRL Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

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Contents
1. Select SRL as the Type of Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3
2. Calibrate the Analyzer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4
3. Connect the Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8
4. Determine the Connector Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8
5. Perform the SRL Cable Scan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-16
6. Interpret the SRL Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-19
5. Making Simultaneous Fault Location and SRL Measurements
How to Make Simultaneous Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-4
6. Making Impedance Measurements
How to Make Impedance Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-4
7. Characterizing and Verifying Antenna Systems
Antenna Feedline System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-3
Potential Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5
Transmission Lines/Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-5
Connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-6
Typical Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-7
Before Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-8
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-8
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-9
Installation and Maintenance Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-10
8. Key Reference
Alphabetical Key Reference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8-3
9. Characteristics
Overview of Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-2
Frequency Range Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-2
Phase Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-2
General Performance Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-3
SRL Measurement Uncertainty vs System Directivity . . . . . . . . . . . . . . . . . . . . . . . . .9-4
SRL Measurement Uncertainty vs Connector Fault . . . . . . . . . . . . . . . . . . . . . . . . . . .9-8
Minimizing Measurement Uncertainty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9-8

Contents
ix
Fault Location Distance Range and Resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12
Range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12
Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12
Typical Distance Data in Feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-13
Distance Data in Meters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16
A. Cable Loss and Velocity Factors
Cable Loss and Velocity Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-2

1-1
1 Introduction and Measurement
Theory