Design, Implementation and Testing of a Flexible Fully-Digital Transponder for Low-Earth Orbit Satellite Communications

Abstract

This paper presents a flexible Telemetry, Tracking & Command (TT&C) transponder for Earth Observation (EO) small satellites. The proposed device adds to the state-of-the-art EO TT&C transponders the possibility of scientific data transfer thanks to the high downlink data-rate (up to 40 Mbps) and in-flight reconfigurability via Telecomand (TC). The integration of these features in one single device represents a considerable optimization in terms of mass budget, which is important for EO small satellites. Furthermore, in-flight reconfigurability of communication parameters via TC is important for in-orbit link optimization, which is especially useful for Low-Earth Orbit (LEO) satellites where visibility can be as short as few hundreds of seconds. The proposed transponder is a digital radio unit working at 70 MHz intermediate frequency (IF). A new custom and configurable hardware accelerator was developed to cover intensive radio DSP functions at IF. The custom hardware is integrated in a single FPGA with a space-compliant processor core, for control, configuration and interface with the other satellite subsystems. All the quantization parameters were fine-tailored to reach a trade-off between hardware complexity and implementation loss (IL). The IF RX/TX ports require eight bits and seven bits, respectively. The IL is 0.5 dB at BER = 10-5 for the RX chain. A system proof-of-concept was implemented on the Xilinx Virtex 6 VLX75T-FF484 FPGA. The total device occupation is 82%. The power consumption of the design fitted in FPGA is less than 2 W. The power consumption of the whole demonstrator board is less than 9 W.

Characterization of a COTS-Based RF Receiver for Cubesat Applications

“…The term "COTS" is also related to the test facilities [10,11] and electrical ground support equipment [1,12]. Finally, the COTS-based design has been even adopted for RF systems [13][14][15][16][17][18][19][20]. They include navigation systems [13,14], transmission data systems for deep-space and remote-sensing applications [15,16], and modules for communication with the earth [2,[17][18][19][20].…”

Fully digital BPSK demodulator for satellite supressed carrier telecommand system

“…A good number of important papers on completely digital BPSK/quadrature phase shift keying demodulator is found in the literature . However, this work proposes a new BPSK demodulator architecture, detailing the adopted solutions for each functional module and presenting some original mathematical analyses in order to determine the system performance.…”