Instrumentation & Measurement Magazine 25-7 - 38

Development of Automated
Test System for Multibeam
Communication Payloads
Jatin Trivedi, Amit Nihalchandani, Devanand Panjwani, and Rakesh Vyas
D
evelopment of an Automated Test System (ATS) is
a process that involves extensive study and knowledge
of current test technologies, determination of
the requirements, and a simple design approach. Communication
payload architecture has changed from broad beam to
spot beam technology, providing more bandwidth and power.
As the number of transponders increases, the conventional
way of testing payload requires more time; this, in turn, increases
total cost, specifically thermal-vacuum test.
Multibeam payloads have multiple independent users,
hub, or user + hub configuration that caters to only forward
link (hub to user), only return link (user to hub), or both [1],
[2]. Typically configured beams, i.e., the unique path from uplink
to downlink, including redundant hardware for the single
beam, is about 300. For multibeam, it is around 2000-3000,
thus providing the opportunity to test multiple transponders
simultaneously. Therefore, a need arises to develop an ATS
system, which is modular, scalable, and low cost. Multiple
such ATS systems can be deployed parallel to reduce overall
test time and payload cost. Automated test equipment (ATE)
characterizes the performance of the payload system on-board
during various levels of satellite level tests. The setup consists
of stimuli and measurement radio frequency (RF) equipment
controlled by automation software.
Conventional ATE systems are Rack and Stack type, which
requires simultaneous access of multiple stimuli/measuring
instruments, namely the signal generators, spectrum analyzer,
two power meters, frequency counter, downconverter,
and low-frequency network analyzer. The test time plays a
significant role in overall realization, and deploying multiple
such systems is not cost-effective. Recent works and literature
in advanced ATS utilize two types of ATE systems, namely
Synthetic Measurement-based [3]-[5] and Network Analyzer
based [6], [7]. The former has a typical frequency range
of 50 MHz to 8 GHz. It can be extended up to 40 GHz by incorporating
band-specific upconverter and downconverter, while
the latter is common from UHF to Q/V band.
We have adopted Network Analyzer ATS based architecture
because of the following advantages:
38
◗ To have a standard ATE system for ground checkout
system having a frequency range extending from UHF
band (100 MHz) to Q/V band (43.5 GHz).
◗ Expertise and familiarity with the instrument as it is
widely used for s-parameter measurement of various
active and passive subsystems.
Vector Network Analyzer (VNA) based configuration allows
parallel multiband testing with multiple such ATE
systems, which results in increased test throughput. The key
features of VNA based ATE system are as follows:
◗ Capability to measure transponder parameters
⦁ Noise floor/Noise shape
⦁ Gain transfer curve
⦁ Frequency response
⦁ Group delay
⦁ 3rd order intermodulation (IMD)
⦁ Noise figure
⦁ Back-off attenuator calibration
⦁ Automatic Level Control (ALC) output power and
ALC accuracy
⦁ AM/PM conversion/transfer coefficient
⦁ Noise power ratio
⦁ Modulation parameters (Error Vector Magnitude
(EVM), magnitude and phase error, carrier suppression,
Modulation Error Ratio (MER)
⦁ Multicarrier Stability
⦁ Phase Noise
⦁ Frequency Translation Error
◗ Compact in nature and easily transportable
◗ High repeatability, accuracy and flexibility
◗ Significant reduction in test time
For DUTs with frequency converting local oscillator (LO),
VNA measures the conversion gain (SC21) and provides amplitude
and phase characteristics. Although the VNA approach
requires additional compatible accessories and a special
calibration procedure, the former provides the highest measurement
accuracy by performing full two-port calibration
(for two-port devices) to remove error terms. The developed
architecture uses a VNA, signal generator and spectrum
IEEE Instrumentation & Measurement Magazine
1094-6969/22/$25.00©2022IEEE
October 2022
Instrumentation & Measurement Magazine 25-7

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