Anritsu 11410-00276 User Manual
Measurement Methods
During network deployment, maintenance, and trouble shooting phases,
insertion loss can be measured by disconnecting the antenna and connecting
an enclosed short at the end of the
transmission line. If a Tower Mounted
Amplifier (TMA) is used in the transmission feed line system, it is best to remove
the TMA and antenna from the system
configuration to perform an insertion
loss measurement. It is best to always disconnect the cable at the same location
so the measured data can be compared
to the historical data for accuracy and
repeatability.
Using Site Master, cable insertion loss
can be measured in CABLE LOSS or
RETURN LOSS mode. In Cable Loss
mode, Site Master automatically considers the signal traveling in both directions
thus making the measurement easier for
the user in the field.
The following section explains the procedure to measure insertion loss in cable
loss mode and return loss mode. The
measurement setup and equipment
required is the same for both modes.
Insertion Loss
Measurement Methods
APPLICA TION NOTE
Introduction
Transmission feed line system performance plays an important
role in wireless network coverage. Insertion loss measurement
is one of the critical measurements used to analyze transmission
feed line installation and performance quality. This application
note explains how Site Master is used to measure cable insertion
loss with different test methods and how to predict the maximum allowable cable insertion loss through manual calculations.
In wireless communication systems, the transmit and receive
antennas are connected to the radio through coaxial cable
and/or waveguide transmission lines (Figure 1).
Insertion loss measures the energy absorbed by the transmission
line in the direction of the signal path in dB/meter or dB/feet.
Transmission line losses are dependent on cable type, operating
frequency and the length of the cable run. Insertion loss of a
cable varies with frequency; the higher the frequency, the
greater the loss.
Insertion loss measurements help troubleshoot the network
by verifying the cable installation and cable performance.
High insertion loss in the feedline or jumpers can contribute
to poor system performance and loss of coverage. Measuring
insertion loss using Site Master assures accurate and repeatable
measurements.
SITE MASTER™
Verify Cable Inser tion Loss
From Ground Level
Figure 1. Typical transmission line system
Antenna
Jumper
Main Feeder
Connectors
Antenna
Jumper
2
Measuring
Insertion Loss
Using CABLE
LOSS MODE
Application Note
Required Equipment
• Site Master Model S11xx,
S33xx, or S251x
• Precision Open/Short,
Anritsu 22N50 or
Precision
Open/Short/Load, Anritsu
OSLN50LF
• Precision Load, Anritsu
SM/PL
• Test Port Extension Cable,
Anritsu 15NNF50-1.5C
• Optional 510-90 Adapter,
DC to 7.5 GHz, 50 Ω,
7/16(f)-N(m)
Figure 3. Insertion loss measurement setup when TMA
is in line.
Step 4. Connect the phase stable test
port extension cable to the
RF port.
Step 5. Calibrate the Site Master at the
end of the phase stable test port
extension cable. (See the
section entitled “Calibrating
Site Master with the Phase
Stable Test Port Extension
Cable” for details.)
Step 6. Disconnect the antenna and
connect an enclosed precision
"short" at the end of the
transmission line.
Step 7. Connect the other end of the
transmission line to the phase
stable cable of the Site Master.
A trace will be displayed on the
screen when the Site Master is
in continuous sweep mode.
Step 8. Press the
AMPLITUDE key and
set the TOP and BOTTOM
values of the display. In Figure
4, the TOP is set to 2 dB, and
the BOTTOM is set to 5 dB.
Step 9. Press the
MARKER key.
Step 10.Set
M1 to MARKER TO PEAK.
Step 11.Set M2 to MARKER TO VALLEY.
Step 12.Calculate the insertion loss by
averaging M1 (MARKER TO
PEAK) and M2 (MARKER TO
VALLEY) values as follows:
Step 13. Press
SAVE DISPLAY and name
the trace using the soft keys
and press
ENTER.Saving the
display is recommended for
historical documentation.
Saved traces can be used in
the future to compare, check
or verify changes in the transmission feedline performance.
Procedure
Step 1. Power On the Site Master and
press the
MODE key.
Step 2. Select FREQ-CABLE LOSS using
the Up/Down arrow key and
press
ENTER.
Step 3. Set the start and stop frequen-
cies F1 and F2. As an example,
F1=750 MHz and F2=850 MHz
for a typical cellular frequency
band.
Insertion Loss Measurement
Setup
The insertion loss measurement set up
for a typical transmission feed line
system is shown in Figure 2. Remove
the antenna and connect an enclosed
precision “short” at the end of the
transmission line.
If a Tower Mounted Amplifier (TMA)
is in the transmission feed line system,
remove the TMA and antenna and
connect an enclosed short at the end
of the transmission line. Insertion loss
measurement for a transmission feed
line system with a tower mounted
amplifier is shown in Figure 3.
Figure 2. An insertion loss measurement setup after antenna
is removed.
Antenna
Removed
TMA
Jumper
Antenna
Jumper
Antenna
Jumper
Precision
Short
Antenna
Removed
Test Port
Jumper Main Feeder
Cable
Site Master S251C
ESCAPE
CLEAR
1
2
START
AUTO
CAL
SCALE
3
4
SAVE
RECALL
SETUP
SETUP
56
MARKER7LIMIT
ENTER
8
SAVE
RECALL
RUN
DISPLAY
DISPLAY
HOLD
0
9
+/-
PRINT
ON
SYS
OFF
.
SWEEP
MODE
AMPLITUDE
FREQ/DIST
TMA
Removed
Test Port
Jumper Main Feeder
Cable
Site Master S251C
ESCAPE
CLEAR
1
2
START
AUTO
CAL
SCALE
3
4
SAVE
RECALL
SETUP
SETUP
56
MARKER7LIMIT
ENTER
8
SAVE
RECALL
RUN
DISPLAY
DISPLAY
HOLD
0
9
+/-
PRINT
ON
SYS
OFF
.
SWEEP
MODE
AMPLITUDE
FREQ/DIST
Tx/Rx
Precision
Short
Insertion Loss = (M1 dB + M2 dB)
2
= 3.23 + 3.95 = 3.59 dB
2
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