AnSem demonstrates DSP expertise in Argos satellite SoC
Argos is a satellite-based system which collects, processes and disseminates environmental data from fixed and mobile platforms worldwide. What makes Argos unique is the ability to clearly geographically locate the source of the data anywhere on the Earth utilizing the Doppler effect. Argos can track the route of a fishing vessel, large migrations of birds and other animals, or can monitor environmental sensor data (atmospheric pressure, sea temperature, animal heart rates) from animals or devices equipped with an Argos tag.
The Argos radio link operates in the 400MHz-466MHz band with all features of a modern digital communication system: digital modulation ( BPSK, QPSK and differential GMSK modulation), forward error correction and multiple datarates depending upon the application. The original ARGOS system used one way communication, send (TX) only on the tag and receive (RX) only on the satellite. Since the third generation, Argos 3, communication is two-way with the tag also being required to receive the Doppler shifted transmission from the satellite.
Under a project undertaken on behalf of the European Space Agency (ESA) AnSem has developed a small, ultra-low power, highly integrated SoC radio, "ARTIC" to be used in tiny tags weighing as low as 10 grams so as to be able to track marine animals down to 10 kg in weight. Marine animals spend most if not all of their life under water which makes tags powered by solar panels (typically used for birds) impractical. Indeed, the Argos battery operated marine tags are specified with a lifetime of 10 years. This makes it particularly difficult to meet the low weight plus long operational life required for this application.ARTIC is designed to be compatible with all Argos standards including the yet to be deployed Argos 4 satellites and provides two-way communication with the satellite. In addition to having a full RF transceiver, AnSem has integrated the full digital modem into the ARTIC SoC.
In the receive channel the digital modem integrates:
- Low IF to BB mixer
- Digital Low Pass and High pass Filtering
- Tracking of Doppler frequency shift on RX signal
- I/Q BPSK demodulator
- Manchester decoder
- Direct Sequence Spread Spectrum demodulator
- Viterbi decoder
The Transmit channel provides:
- Convolution encoder
- I/Q modulation : BPSK, QPSK, GMSK
After an analysis of the modem functions and the power budget, AnSem decided to implement and run all these PHY functions on a DSP (as opposed to a fixed hardware implementation). AnSem concluded that using a suitable DSP both increases flexibility and reduces time to market while maintaining the lowest possible power consumption. A soft solution was particularly desirable given the ARGOS 4 standard only exists so far on paper. By implementing the PHY on a DSP, the silicon hardware platform and the BSP software can be developed in parallel which speeds up the time to prototypes by several months. Additionally, AnSem has now a technology platform available that because its flexibility can be used in many more ultra low power satellite communication systems, for bird tracking, container tracking, search & rescue and many more.
The DSP was complemented with an integrated power management system to only power active blocks, minimizing both active power and leakage. Because the DSP runs from embedded memory completely internal to the SoC all high-speed datapaths are internal to ARTIC, minimizing interface power. The only active interfaces are the antenna connection on one side and the low-speed data connection to sensors on the other side.
Today the Argos 3 system is operated by ESA. The next generation Argos 4 standard is already specified but not yet launched into space. This new version or any future changes can be easily accommodated by an update of the BSP software retained in memory. Furthermore, by taking advantage of the soft modem, OEMs can use the ARTIC SoC across many applications and standards. This simplifies both supply chain management and maintenance in the field.
ARTIC, once again, shows that AnSem is a true wireless systems partner with all the in-house expertise to develop and deliver full communication systems including the RF transceiver, the analog baseband, data converters and DSP based PHY solutions.
AnSem is Europe's leading fabless analog ASIC design service company, designing and delivering state-of-the-art analog, RF and mixed-signal integrated circuits to customers worldwide. Founded in 1998 and based in Leuven, Belgium, AnSem specializes in the development of advanced integrated circuits for wired and wireless data transmission, sensor data acquisition, ultra low-power and high voltage applications. AnSem is ISO 9001 certified and is a proven and solid development partner for ambitious and visionary customers, reaching for leadership in global markets.
Phone: +32 16 38 65 00