Amplifier Stability and Ruggedness Testing

Introduction
Automated impedance tuners are ideally suited for testing the stability and ruggedness of completed
(50Ω matched) amplifiers and completed radios. In this case, the tuner is not used to match the DUT, it
is used to stress the amplifier thereby testing its functionality under non-ideal conditions.
Typically, a series of constant VSWR circles (2:1, 3:1, 5:1…) will be presented to the completed amplifier
and its performance will be measured under each condition. Degradation testing can also be performed
by stressing an amplifier under extreme conditions (i.e. 20:1 VSWR) and seeing how it performs when
returned to 50Ω.
Stability and ruggedness testing can be implemented by using either manual or automated
impedance tuners.
Mechanical impedance tuners can be used to manually vary the VSWR presented to the amplifier. Slide-
screw tuners are ideal for this application, where adjusting the tuner’s RF probe (slug) will result in an
increased VSWR, and varying the horizontal position along the slabline will result in a phase change.
Automated impedance tuners can be used to automatically vary the VSWR presented to the amplifier.
Automated tuners controlled via USB and an associated DLL, or via TCP/IP (Ethernet) and direct ASCII
commands. Tuning is achieved at the amplifier reference plane by de-embedding losses through
interface cables or test fixtures and taking into account load terminations.
LXI-Certified Automted Impedance Tuners
An embedded LXI-certified controller allows for both TCP/IP and USB control by any personal computer or laptop. No external controller necessary.
An integrated web interface allows for easy point-and-click tuning. Simply open Internet Explorer, Firefox, Mozilla or any web browser in any operating system, and begin tuning. Capabilities include a graphic interface for de-embedded tuning at the DUT reference plane including S-Parameter blocks for test fixtures, cables, probes, adapters and terminations.
Direct ASCII commands can be sent through raw TCP/IP interface and used with any socket programming language or through any Telnet client program in any operating system. Commands include direct impedance tuning, reference-plane shifting, VSWR testing and more.
Application Notes and Data Sheets
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