• Improve test throughput for
multiport devices
• 50 ohm and 75 ohm versions
• Solid-state or mechanical
switching
Easily test multiport devices
Many of today’s wireless communications, broadband, and cable-television
components have three or more
ports. These components require multiple connections for complete characterization with a two-port network
analyzer. You can simplify high-volume tuning and testing of these
devices by using a multiport test set
between the device under test (DUT)
and your network analyzer. These
test sets are useful for a variety of
multiport components such as:
• duplexers
• directional couplers
• circulators
• transmitter combiners
• receiver multicouplers
• distribution amplifiers
• cable-television multitaps and
splitters
Improve throughput
Multiport test sets dramatically
reduce overall tune and test times
because the DUT only needs to be
connected once to test multiple signal
paths. Minimizing the number of
connections also reduces operator
fatigue and lowers the chance of connection to the wrong port. In addition,
fewer connections means less wear
on cables, connectors, fixtures and
DUTs.
Wide range of measurement
solutions
Agilent Technologies multiport test
sets can be customized to your measurement application with any number
of ports, and a variety of connector
types and switching arrangements.
In their simplest configuration, they
serve as switch matrices between
your multiport device and any twoport network analyzer with an internal or external test set. Alternatively,
they can be configured with internal
couplers or bridges as well as switches. This allows consolidation of both
the signal-splitting and switching
functions into one test set for optimal
performance. These test sets are
available in both 50 ohm and 75 ohm
versions, with electromechanical or
solid-state switching. Mechanical
switches offer the lowest loss and
best isolation, while solid-state
switching provides fast and highly
repeatable measurements. All
unused test ports are terminated
internally to reduce unwanted
reflections.
Agilent 87050A/B, 87075A/B
Custom Multiport Test Sets
Product Overview
2
Wireless Communications
Applications
Fast duplexer tune and test
Duplexers are three-port filters used
to separate transmitted and received
signals that share a common antenna.
When using a duplexer test set with
only one internal switch as shown in
Figure 1A, you can simultaneously
measure the insertion loss from
transmitter to antenna ports and
antenna to receiver ports. This
allows both sides of the duplexer to
be tuned and tested at the same time.
Path interactions can also easily be
observed on the instrument display
as shown in Figure 2, eliminating the
retest and rework that occurs when
only one path at a time is measured.
A duplexer test set also allows you to
measure return loss of all three ports
of the DUT. When limit-line displays
are used with multiport test sets,
pass-fail testing of return loss, insertion loss, bandwidth, and stopband
rejection is fast and repeatable. If you
need to test the isolation between the
transmit and receive ports of the
duplexer, a full three-port test set is
required for single-connection measurements.
Full three-port testing
Transmission measurements between
all three ports of a device can be
accomplished by adding two more
switches to a duplexer test set, as
shown in Figure 1B. These measurements are often required for threeport components such as directional
couplers, and circulators. A full
three-port test set also allows you to
measure isolation between the transmitter and receiver ports of a duplexer.
Figure 1. Multiport test sets can be designed to test a variety of
multiport devices from simple passives to more complicated devices
with active components.
Figure 2. Simultaneous sweeps of the Tx-Ant and Ant-Rx paths improve
duplexer tune and test times.
Figure 1A: Duplexer Test Set
Port 1
Port 2
Test Set
Tx
Rx
ANT
Duplexer
Port 1
Figure 1B: Three-port Test Set
Port 1
Port 2
Test Set
Port 2
Port 1
Port 2
Port 3
Directional
Coupler
Network Analyzer
Ant
Port 1
Port 2
Port 1
Port 2
Port 3
Port 4
Receiver
Multicoupler
Test Set
Figure 1C: Multicoupler Test Set
CH1 S21 log MAG 10 dB/ REF 0 dB
CH2 S12 log MAG REF 0 dB10 dB/
PRm
Duplexer Test - Tx-Ant and Ant-Rx
Cor
Hld
1
PRm
Cor
Hld
CH1 START 775.000 000 MHz
CH2 START 775.000 000 MHz
1
839.470 000 MHz
1
880.435 000 MHz
1_ -1.9248 dB
1_ -1.2468 dB
PASS
PASS
STOP 925.000 000
STOP 925.000 000 MHz
MHz
2
3
Receiver multicouplers
Multicouplers are used in the receiving system of base stations to amplify
the RF signal coming from the antenna and to divide it into multiple outputs. A multiport test set and network analyzer combination (see
Figure 1C) allows a single connection
for swept-frequency linear transmission and reflection measurements,
and for nonlinear measurements such
as 1 dB gain compression.
If other nonlinear measurements are
needed, the test set can incorporate
additional ports to allow connection
of other instruments to the DUT. For
example, additional sources and a
spectrum analyzer could be switched
in place of the network analyzer to
perform third-order intermodulation
measurements (see Figure 3).
Another example would be the inclusion of a broadband-noise source for
measuring noise figure. In this manner, a multiport test set can greatly
improve measurement throughput by
providing a true single-connection,
multiple-measurement test system.
Broadband and Cable-TV
Applications
Distribution amplifiers
Distribution amplifiers have multiple
outputs and are used to boost television signals to make up for cable and
multitap losses. You can use a multiport test set to measure forward and
reverse frequency response and gain,
as well as return loss on all the ports.
If you need to test isolation between
all the amplifier outputs, a full N-port
test set is required.
N-port testing of multitaps and splitters
In cable-television distribution systems, multitaps are used to draw off
a portion of the feeder-line signal for
a subscriber. Splitters are used in
drop systems to provide television
signals to multiple outlets. These
components typically divide the input
signal between two and eight outputs.
A full N-port test set used in conjunction with a quick-connect fixture
allows fast and easy high-volume testing of tap or splitter frequency
response, return loss, and isolation
between all the ports.
Figure 3. An example of a single-connection multiple-measurement test system for
receiver multicouplers
Test Set
Ant
Port 1
Port 2
Port 3
Port 4
Receiver
Multicoupler
4
Test Process Improvements
Increase throughput per instrument
A multiport test set is valuable in
manufacturing applications where the
time required for device connection,
handling, and/or configuration is significantly greater than the test time.
In these situations, a dual-port test
set allows two operators or two parthandlers to share a single network
analyzer, which increases the
throughput per network analyzer.
For example, two duplexers can be
connected to the same test set, as
shown in Figure 4, allowing testing on
one device while an operator connects or disconnects cables on the
other device.
Make forward and reverse measurements
with T/R network analyzers
Network analyzers such as the 8753ET
or the 8712ET family that are based on
an internal transmission/reflection
(T/R) test set are cost-effective instruments that provide the right level of
accuracy for many applications.
However, T/R test sets are limited to
forward measurements only. By
adding an external reversing test set,
as shown in Figure 5, you get both
forward and reverse transmission
and reflection measurements with a
single connection. This eliminates
the need to disconnect the DUT, turn
it around, and reconnect it to the network analyzer. This approach is less
accurate, but more economical than
using an S-parameter network analyzer.
Figure 4. Share one network analyzer between two DUTs by using a
dual-port test set.
Figure 5. A reversing test set allows a T/R-based network analyzer to make
measurements in both the forward and reverse directions.
Tx
Rx
Port 1
ANT
Duplexer 1
Port 2
Tx
Rx
ANT
Duplexer 2
Dual 3-Port Test Set
REFLECTION
(RF OUT)
TRANSMISSION
(RF IN)
Reversing
Test Set
Port 1
Port 2
5
Remove Cable and Fixture Losses
You can reduce undesirable effects of
cables and fixtures on measurement
accuracy by calibrating the signal
paths for transmission and reflection
measurements. Combining a multiport test set with transmission/reflection or S-parameter network analyzer
allows for error-corrected measurements on any two ports at a time.
Calibration data for each signal path
can be saved in the instrument’s
internal memory, allowing for easy
retrieval when a measurement is
made using that path.
System Configuration
Compatibility
Agilent multiport test sets are compatible with the 8712 and 8753 families of RF network analyzers, and
with the 85046, and 85047 series of
standard external test sets.
Test set control
The test sets can be controlled from
the front panel of the network analyzer
or by a computer for automated
measurements.
Ordering Information
Price, delivery and relevant specifications for multiport test sets are quoted on a custom-basis by Agilent’s special handling department. The 87050
series of model numbers cover all
50 ohm test sets, while 75 ohm test
sets are covered under the 87075
series. “A” models use electromechanical switches and “B” models provide
solid-state switching.
Agilent Technologies also has several
existing test-set specials with product
numbers that are tied to specific network analyzer or test-set model
numbers.
Please consult your local Agilent sales
engineer for help in determining the
best solution for your multiport test
application.
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