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Number 2310
Application Note Configuring an Optimal
Series RF/Microwave Switch System
Introduction example, mobile phone) lifetime test illustrated in Figure 1, the
DUT can be stressed at an elevated level for a specified period,
Given the explosive growth of the communications industry, a then its electrical characteristics can be measured. The DUT can
tremendous amount of testing is being performed on the various be stressed even further and the electrical characteristics can be
components that make up different communications systems. measured again. Automated switching allows this process to be
These components range from active components such as Radio performed very efficiently.
Frequency Integrated Circuits (RFICs) and Microwave Monolithic
Integrated Circuits (MMICs) to space communication systems. This note will briefly discuss several important aspects of
While the testing requirements and procedures for these compo- configuring a high frequency switch system, including the system
nents differ widely, all are tested at very high frequencies, typi- configurations and the critical switch specifications.
cally at gigahertz or higher. The main components in a typical
test system may include DC bias, DC measurement, RF power
meter, network analyzer, etc. Automating the test process and
Configuration of a Switch System
improving test efficiency demands integrating RF/ Microwave and
Switch systems can be very simple or quite elaborate. For exam-
low frequency switching systems into the test system.
ple, a Single Pole Double Throw (SPDT) switch can be used to
The purpose of a switch is to route signals from measure- route signals to two different DUTs. It can be expanded further
ment instruments to the Device Under Test (DUT). With the into a "multiplexer" configuration so that a single instrument can
help of a switch, an instrument can measure multiple DUTs with be routed to many different DUTs. Multiple instruments can be
increased efficiency. Multiple tests with different instruments routed to multiple DUTs. In this case, the switch system is known
can be run on the same DUT or multiple instruments can test either as a Multiplexer-Demultiplexer or a blocking matrix--only
multiple DUTs. With the help of a switch system, the test process one signal path is active at any given time. Figure 2 shows the
can also be automated. For example, in the typical DUT (in this application of an SPDT and a 1