Assystem France, a leading European aerospace engineering firm, has extensive experience in test bench and microwave subsystem design and manufacturing. We built the RF Rack upon CNES (Centre National d’Études Spatiales - National Centre for Space Studies) specifications.
Complete Test Bench Description
We integrated the RF rack in a complete test bench specifically designed for testing high data rate telemetry (HDRT) that we plan to use on future Earth observation satellites. Our goal with the test bench is to emulate a complete telemetry chain from an on-board modulator to a receiving ground subsystem. To this end, the system features these subassemblies :
- A high data rate L band modem implementing specific signal processing algorithms (equalization)
- Upconverter and downconverter racks to ensure the RF conversion from/to L band to/from X band
- The Assystem France RF rack to amplify a low-level RF signal with a representative TWTA
- A specific rack to simulate a representative RF environment at receiving part level
- The goal of the system is to characterize new telecommunication standards by testing signals in an environment as close as possible to space reality.
RF Rack Architecture
We integrated the TWTA, EPC, and CompactDAQ system in a five-rack chassis. We directly connected the input of the TWTA to the front panel of the rack. We connected the output of the TWTA, which can reach up to 46 dBm to a 30 dB waveguide coupler. The coupled path connects on the front panel of the rack while the direct path of the coupler goes to a 50 W load cooled by two fans. The components connect with waveguides specifically designed for the rack with a 3D study.
The Pleiades TWTA connects to its high-voltage power supply (EPC), which is also the interface that drives the TWTA. We connected the CompactDAQ to the EPC so we could send the commands and retrieve all the telemetries from the TWTA. A current-monitored power supply source powers the EPC.
The CompactDAQ system has the following configuration :
- The NI 9472 digital output module connects to a 24 V DC supply. We use this module in pulse mode to handle the EPC and TWTA on/off commands
- The NI 9201 analog acquisition module retrieves the on/off status and acquires specific TWTA parameters such as TWTA helix current and TWTA high voltage values. We use those two parameters as the input for LabVIEW software to compute TWTA consumption
- The NI 9217 temperature acquisition module monitors many elements, including the EPC and RF load temperatures
LabVIEW software performs the following functions:
- Monitors TWTA parameters in real time
- Acquires launch and on/off actions
- Acquires five temperatures
- Records and visualizes data
- Features an event logbook.
Considering its form factor, CompactDAQ was the right product for us to integrate in a limited space environment. Paired with LabVIEW software, CompactDAQ helped us deliver the best solution at both the technical and financial levels. With experience learned on CompactDAQ during this project, we are now integrating this system for new products.
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