Making Return Loss Measurements; Purpose; Making The Measurement - Agilent Technologies ESA-E Series User Manual

Making Measurements

Making Return Loss Measurements

Making Return Loss Measurements

Purpose

Some of the energy incident upon a device can be reflected back towards the
source. A return loss measurement quantifies this reflected energy. Return loss is
used to determine the health of an antenna system and its associated cabling by
measuring the amount of transmitted power reflected back from the antenna
system and therefore not passed over the air interface to the mobile user.
Cables and antennae are often subjected to harsh weather conditions resulting in a
performance which deteriorates over time, leading to an eventual failure. By
monitoring return loss over time, cable and antennae performance can be
monitored and preventive action taken when required.

Making the measurement

A return loss measurement requires the use of a signal separation device such as a
directional coupler or bridge in addition to the device being tested for return loss.
The spectrum analyzer must be in spectrum analyzer mode for this measurement.
Procedure
For the following procedure, use the appropriate 50 ohm or 75 ohm cables and
accessories listed in
Table 3-2 Cables and Accessories
Cable/Accessory
Coaxial cable
RF Bridge
Coaxial load
Coaxial short (50 ohm only)
6 dB Attenuator (50 ohm only)
Adapter 75 ohm N(f) to
75 ohm BNC(f) (75 ohm only)
1. Connect the tracking generator, signal separation device, device being
22
Table 3-2.
measured and the spectrum analyzer input as shown in
Quantity 50 Ohm Setup
Part Number
2 8121-0101
1 86205A
1 909A Option 012
1 11512A
2 0955-0826
2 n/a
Figure
75 Ohm Setup
Part Number
5062-6452
86207A
909E
n/a
n/a
1250-1536
3-5.
Chapter 3