Before Installation; Installation; Maintenance - Agilent Technologies ENA Series User Manual Supplement

Characterizing and Verifying Antenna Systems
Typical Measurements
NOTE To reduce interference when performing return loss and fault location
measurements, reduce the system IF bandwidth . To further reduce interference
when performing fault location measurements, use the bandpass mode.

Before Installation

Before installation, ensuring specified performance with incoming inspection can
save hours of needless disassembly and reassembly of the cell site's antenna system.
Important characteristics at this stage include cable return loss, characteristic
impedance, and velocity factor.

Installation

At installation, it is necessary to do a complete set of tests on the antenna feedline
system in order to fully characterize its initial performance. During assembly, return
loss is usually measured after the addition of each component. Once assembly is
complete, tests such as insertion loss, feedline system return loss, fault location and
length are done. For characterization of the antenna, independent of the
contributions made by the feed system, an important parameter is antenna return
loss.
A significant property of an antenna is the propagation characteristics that result in
antenna patterns. Many of the measured properties of the overall antenna system
(which are determined at installation) are good indicators of whether or not the
antenna pattern has been altered. Typically, this condition is confirmed from data
collected by drive tests that define the cell site "foot print."
The ability to save the measurement data taken at installation for a baseline is very
important. This allows you to compare the original data with future measurement
results, making problem detection and troubleshooting much easier.

Maintenance

Routine maintenance allows early detection of problems or trends, thus avoiding
costly system shutdowns. However, when service must be interrupted, the outage
can be minimized with rapid diagnostic procedures. The frequency with which
routine maintenance is performed varies widely. But on average, it is done every six
months. This is often done by the service provider, or may be contracted out to an
independent group. Maintenance tests are typically limited to return loss and fault
location, the two key indicators of the antenna feedline's integrity.
82 Chapter 6