6-48
Calibrating for Increased Measurement Accuracy
Making Non-Coaxial Measurements
Making Non-Coaxial Measurements
Non-coaxial, on-wafer measurements present a unique set of challenges for error correction in the analyzer:
• The close spacing between the microwave probes makes it difficult to maintain a high degree of
isolation between the input and the output.
• The type of device measured on-wafer is often not always a simple two-port.
• It may be difficult to make repeatable on-wafer contacts due to the size of the device contact pads.
The capability of making non-coaxial measurements is available with TRL* (thru-reflect-line) or LRM*
(line-reflect-match) calibration. For in-depth information on TRL*/LRM* calibration, refer to
"Calibrating for
Non-Coaxial Devices (ES Analyzers Only)" on page 6-50.
Due to the simplicity of the calibration standards, TRL* or LRM* calibrations may be used for non-coaxial
applications such as on-wafer measurements. This type of calibration with time-domain gating and a variety
of probe styles can provide optimal accuracy in on-wafer measurements. At frequencies where on-wafer
calibration standards are available, short-open-load-thru (SOLT) calibrations can also be done and may be
preferred due to the better accuracy of the SOLT calibration method.
Fixtures
Fixtures are needed to interface non-coaxial devices to coaxial test instruments. It may also be necessary to
transform the characteristic impedance from standard 50 instruments to a non-standard impedance and
to apply bias if an active device is being measured.
For accurate measurements, the fixture must introduce minimum change to the test signal, not destroy the
test device, and provide a repeatable connection to the device.
For information about test fixtures for your measurement systems, ask for literature number 5962-9723E or
contact: Inter-Continental Microwave, 1515 Wyatt Drive, Santa Clara, CA 95054, USA (Web site:
http://www.icmicrowave.com).
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