GPS World, January 2014

GNSS Interoperability RECEIVER DESIGN FIGURE 14 L1 C tracking on QZSS satellite FIGURE 15 Dual RF implementation of dual band front end signal simultaneously removing data transitions which can alternatively be pre stripped using the known pilot secondary code which on GPS III is 5 dB stronger than the data signal The resultant plot represents 2000 epochs each of 10 milliseconds plotted in blue with integrated result for the full 20 seconds shown in the black dashed line Assuming vehicle dynamics is taken out using carrier Doppler this allows extremely precise measurement of the code phase or analysis of any multipath in order to remove it This RF data was captured on a benign site with a static antenna so it shows little distortion The Future DYLQJ DOUHDG EXLOW LQ H WUHPH ÀH LELOLW WR WKH FRGH generators to support all known signals and generalized likely future ones the main step for the future is to support multiple frequencies starting with adding L5 DQG RU EXW DV EHIRUH HQVXULQJ WKDW HQRXJK ÀH LELOLW is built in to allow any rational user customer choice It is not viable for us to make silicon for low volume combinations nor to divide the overall market over different chips Thus our mainstream chip must also support the lower volume options We cannot however impose silicon area or power consumption penalties on the high volume customer or he will not buy our product Thus our solution to multi frequency is to make an RF that can support either band switchably with the high band integrated on the volume single chip GNSS Customers who also need the low band can then add a second RF of identical design externally connected to the expansion port on the baseband which has always existed for diagnostic purposes and was how BeiDou was demonstrated on T2 By being an RF of identical design to the internal one it incurs no extra design effort and would probably be produced anyway as a test chip during the development of the integrated singlechip version Without this approach the low volume of sales of a dual band radio or a low band radio would never repay its development costs Conclusions All four constellations have been demonstrated with live satellite signals on Teseo 2 a high volume production chip for several years and on Teseo 3 including use in combinations as a single multi constellation positioning solution With the advent of Teseo 3 with optimized BeiDou processing and hardware support for GPS 3 L1C a long term single chip solution is offered For the future dual frequency solutions are in the pipeline allowing full advantage of carrier phase and research into moving precise point postioning and UHDO WLPH NLQHPDWLF LQWR WKH DXWRPRWLYH PDUNHW IRU HOGV such as advanced driver assistance systems Acknowledgments Teseo III design and development is supported by the European Commission HIMALAYA FP 7 project This article is based on a technical paper first presented at ION GNSS 2013 in Nashville Tennessee ST GPS products chipsets and software baseband and RF are developed by a distributed team in Bristol UK system R D software R D Milan Italy Silicon LPSOHPHQWDWLRQ DOJRULWKP PRGHOOLQJ DQG YHUL FDWLRQ Naples Italy software implementation and validation Catania Sicily Italy Galileo software RF design and SURGXFWLRQ 1RLGD QGLD YHUL FDWLRQ DQG 3 The contribution of all these teams is gratefully acknowledged PHILIP G MATTOS received an external Ph D on his GPS work from Bristol University Since 1989 he has worked exclusively on GNSS implementations RF baseband and applications He is consulting on the next generation GNSS chips including one chip GPS RF digital and high sensitivity GPS and Galileo for indoor applications and combined GPS Galileo GLONASS chipsets In 2008 2009 he re implemented LORAN on the GPS CPU and in 2009 2010 led the GLONASS implementation team He is leading the team on L1C and BeiDou implementation and the creation of totally generic hardware that can handle even future unknown systems FABIO PISONI has been with the GNSS System Team at STMicroelectronics since 2009 He received a masters degree in electronics from Politecnico di Milano Italy in 1994 He was previously with the GNSS DSP and System Team in Nemerix SA and has earlier working experience in communications multi carrier receivers www gpsworld com January 2014 GPS World 63