GPS World, December 2014
RECEIVER DESIGN Consumer OEM FIGURE 3 Full power sportwatch left and ultra low power chip right in more accuracy testing wearable ultra low power GNSS chip produces a comparable GNSS track to existing devices using repurposed full power sportwatch chips while using only a fraction of the power Speed Accuracy Not only does the ultra low power solution produce a comparable GNSS track it actually outperforms FIGURE 4 Position accuracy on reacqusition emerging from overpass existing solutions when it comes to speed and distance thanks to close integration with sensors and dynamic power saving features FIGURES 2 and 3 GNSS Reacquisition GNSS only wearable devices face a design challenge to provide complete coverage and to avoid outliers This is seen most clearly when the user runs or walks under an overpass FIGURE 4 Familiar to urban joggers everywhere the underpass allows the user to cross a busy road without needing to check for traffic but requires the GNSS to reacquire the signals on the tunnel exit See the GNSS track in FIGURE 5 when the device reacquires the signals the position and speed accuracy suffers Using the filtered GNSS and sensors however FIGURE 6 enables smooth tracking of speed and distance through the disturbance Urban Multipath The pace analysis in FIGURE 7 shows a user instructed to run at a constant 8 minute mile pace stopping to cross the street where necessary The red line on each plot shows the true pace profile The commercial GNSS only sportwatch on top shows frequent multipath artifacts missing some of the stops and worse for a runner incorrectly showing erroneously high pace The ultra low power chip captures all the stops and shows a constant running pace when not stopped WIRELESS INNOVATIONS COMPANY GPS L1 L2 ANTENNAS BUILT ON ADVANCED HELICORE TECHNOLOGY Maxtena designs and builds high performance multiband antennas for GNSS GPS GLONASS Galileo Beidou Iridium Inmarsat and Thuraya Satellites and M2M MSS LTE applications 33 x 132mm GPS GLONASS 417 x 193mm GPS L1 243 x 129mm GPS L1 38 x 185mm GPS L1 48 x 185mm GPS GLONASS 509 x 30mm GPS L1 L2 GLONASS Tel 1 844 505 7053 Email contact@ maxtena com www maxtena com GPS World December 2014 www gpsworld com 48
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