GPS World, February 2018

COVERSTORY ANTENNA PATTERN UNIFORMITY EFFECTS ON PSEUDORANGE TRACKING ERROR MORE SATELLITES MORE CONSTELLATIONS MORE MULTI FREQUENCY RECEIVERS they all drive greater achievable accuracy But they also raise the requirements on GNSS antennas because of the stronger impact that possible imperfections might have in the overall error budget for multi frequency combinations This analysis of antenna induced errors in pseudorange code measurements for different antenna feed types helps identify the advantages and disadvantages of such technologies for precise positioning BY Stefano Caizzone Mihaela Simona Circiu Wahid Elmarissi Christoph Enneking Michael Felux and Kazeem A Yinusa German Aerospace Center DLR T he combination of signals from two frequencies and multiple constellations leads to dual frequency multi constellation DFMC capabilities which currently appear to provide improved performance due to the increased number of satellites available This leads to better available satellite geometries but also to the possibility to strongly mitigate ionosphere related errors thanks to dual frequency combination of the ranging signals In such scenarios the hardware related errors from satellite and even more from receiver side will gain a much stronger weight in the overall error budget and should be tackled accordingly This article focuses mostly on the receiver antenna contribution leaving the effects due to the satellite and to the receiver for later work We will show that the choice of the antenna technology mostly in terms of 18 GPS WORLD WWW GPSWORLD COM FEBRUARY 2018 the number of feeding points has a strong impact on the pattern uniformity and therefore on the differential group delay characteristics over the aspect angle Optimal performance is demonstrated when using more sophisticated solutions providing a ground for cost performance analysis to system engineers of specific applications GROUP DELAY PERFORMANCE Antenna performance in GNSS application is mostly evaluated in terms of antenna gain pattern noise figure and group delay for code measurement or phase center variation for carrier phase measurement Gain and noise figure impact on the signal level available at the receiver while the group delay is a measure of the delay introduced by the antenna hardware to the different spectral components of the signal The differential group delay DGD is