Instrumentation & Measurement Magazine 25-7 - 42

To assess the impact of modified calibration methodology
on measurement parameters, the group delay of the DUT
is measured using a traditional and modified calibration approach.
Fig. 4 shows the group delay comparison of DUT with
modified calibration and traditional methods. The total calibration
time is significantly reduced to approximately 3 hours
(220 minutes) which confirms the acceptability of the modified
approach. This reduction in calibration time is about 2.5 times
as steps a-b and steps c-d are carried out in parallel. Fig. 5
shows the time distribution for traditional and proposed approaches
for different types of calibration schemes.
Fig. 4. Group delay characteristics comparison.
require absolute calibration. To ensure no phase non-linearity
in ATE system, we carry out phase calibration by mating
switch matrix uplink and downlink node through a TLT. This
will require two additional steps, namely scalar calibration using
VSG and VSA and phase calibration using TLT, making
four calibration procedures. These refer to calibration step-b
and step-d, as shown in Fig. 3b and Fig. 3d.
Calibration time plays a significant role in achieving the
required measurement accuracy. If we consider a typical
Ku-band 20 channel transponder (10 GHz to 15 GHz), approximately
73% of calibration time is required for measurement
channel calibration only, which increases with the number
of transponders. To reduce the calibration time, new steps/
approach is envisaged specific to measurement channel calibration.
We introduced two additional steps compared to
the traditional calibration approach and restricted measurement
channel calibration to network analyzer input/output.
However, to compensate for the amplitude variation due to
the uplink/downlink path from SINE input/output to transponder
uplink/downlink, step c and step d are carried out to
assess phase non-linearity impact from uplink to downlink using
a test loop translator.
ATS Software Design
As explained previously, DUT is characterized by using automated
measurement software for its various parameters in
all its possible configurations. The resulting data describes
the behavior of each configuration. The data is archived into
the database and the software processes, performs online
pass/fail criteria with expected performance and presents the
result in various formats. Fig. 6 explains the I/O interfaces between
different software package/program interfaces:
◗ Configuration Program
◗ Input Program
◗ Signal Routing Program
◗ Measurement Program
◗ Report Generation and Analysis Program
◗ Calibration Program
We utilized LabVIEWTM
based graphical user interface to
develop an automated test system. Microsoft Access (MS Access)
database separates configuration inputs and performance
data stored in various tables. The database-driven approach
provides flexible and easy configuration for varying parameters
across different instrument models and satellites. The
database is organized into configuration, performance specifications,
equipment, test and calibration, and TM/ TC data.
The primary envisaged functions of the software are as
follows:
◗ Performs all the test parameters
◗ Configurability for various instruments from different
vendors
Fig. 5. Distribution of calibration time in: (a) Traditional approach and (b) Proposed approach.
42
IEEE Instrumentation & Measurement Magazine
October 2022

Instrumentation & Measurement Magazine 25-7

Table of Contents for the Digital Edition of Instrumentation & Measurement Magazine 25-7