N1055A Datasheet, PDF (8/19 Pages) Keysight Technologies – 35/50 GHz 2/4 Port TDR/TDT For the 86100D DCA-X Series Oscilloscope Mainframe

08 | Keysight | N1055A Remote Head Module 35/50 GHz 2/4 Port TDR/TDT - Data Sheet
Automatic Fixture Removal (AFR)
When measuring physical layer devices with non-coaxial
interfaces, test fixtures or probes are often used to connect
the device under test (DUT) to the measurement equipment.
For accurate measurements of the DUT, the fixtures or probes
need to be characterized and their effects removed from the
composite measurement of the DUT plus test fixture or probe
combination.
Modern TDR and VNA instruments have built-in de-embedding
capabilities that enable the user to remove the effects of fixtures
and probes from the measurement. Those de-embedding
capabilities depend on the user having accurate characterization
data, typically a touchstone file, for the fixture or probe to be
de-embedded.
One-port AFR
Many of the fixtures and probes used today have connectors on
one port and non-coaxial interfaces on the other port, making
them perfect candidates for characterization using one-port
AFR.
One-port AFR requires the user to measure the probe or fixture
from the connectorized port with the other port open and/or
shorted. AFR then mathematically extracts the fixture or probe
S-parameters from the open or short measurement (or both).
That S-parameter file can then be used to de-embed the fixture
using the standard TDR or VNA instrument de-embedding
capabilities.
Since these fixtures or probes typically have non-coaxial
interfaces on some ports, it is difficult to measure them directly.
Historical method for characterizing fixtures and
probes
Historically, one of the following methods have been used to
characterize a fixture or probe:
–– For probes, a calibration substrate – if available – rather than
mechanical standards or an ECal module, is used to calibrate
the TDR or VNA at the probe tips. This is often a challenge at
higher frequencies
–– For fixtures, one of two methods have been used:
–– Model the fixture using EM simulation
–– Use through-reflect-load (TRL) calibration
New method for characterizing fixtures and
probes: Automatic fixture removal
Based on simple calibration standards, time domain gating
and signal flow calculations, automatic fixture removal (AFR)
can be used to characterize fixtures and probes where a direct
measurement is not possible. This approach is much simpler than
TRL but has similar accuracy. The full suite of AFR capabilities,
in addition to in-depth analysis capability, are included with the
Keysight Technologies, Inc. Physical Layer Test System (PLTS)
software, N1930B. The following AFR capabilities from PLTS are
also available directly on the 86100D:
–– One-port AFR
–– 2x thru AFR
The details about all of the N1930B Physical Layer Test System
software capabilities are available on the Keysight Web site:
www.keysight.com/find/PLTS