Estimation and validation of receiver antenna codephase variations for multi GNSS signals

Abstract

Besides antenna phase center corrections (PCC) for carrier phase measurements, which have to be considered for precise GNSS application, also codephase variations (CPV) exist. These are antenna dependent delays of the code which vary with azimuth and elevation. Such variations are not provided operationally in the antenna exchange format (ANTEX) at the moment. Previous studies in our working group show, that CPV should be taken into account when using code-carrier combination. Depending on the antenna type they can amount up to some dm. At Institut für Erdmessung (IfE), a concept to determine the CPV has been established. This procedure uses a robot that rotates and tilts the antenna under test precisely in the field. Real world modulated signals from the satellites are used, which is challenging in anechoic chamber procedures. Time differenced single differences are used to estimate PCC and CPV as spherical harmonics (8,8) in a post-processing approach. In this contribution we present the concept CPV of Galileo signals for several kinds of receiving antennas (mass market and high grade). In addition, we discuss the repeatability and stability of CPV for those antenna. Typical values of the CPV reaches up to 500 mm. The RMS of patterns resulting from multiple calibrations are 80 mm for Galileo C1X and 48 mm for GPS C1C.