Adjustment of GPS Flex Power and Its Interference Analysis Based on FY-3D Satellite

  Objectives  Global positioning system (GPS) block IIR and block IIF satellites have the capability to redistribute the power of their transmitted signals between individual signal components. One or more GPS signals upon designated area can be adjusted or even shut off as needed. The analysis of GPS signals is of great importance for both ground and space uses. FengYun-3D (FY-3D) satellite is one of China's polar orbiting meteorological satellites. We try to help GPS users comprehensively understand the characteristic of GPS flex power based on real measurement data of FY-3D satellite.

  Methods  The global coverage of FY-3D satellite is used to analyze the strength of GPS signals, especially the characteristics of the signal change during GPS flex power period. The characteristics of global interference of L band is also researched by using the in-orbit data. And the interference on the automatic gain control and base noise of occultation antenna of global navigation satellite system occultation sounder is reported.

  Results  The results show that the GPS flex power, which started on February 14, 2020, is centered on 35°N, 37°E and 35°N, 69°E, and its radius is about 7 500 km. The GPS P(Y) code is increased by about 10 dB in this region. The interference of GPS L1 band and L2 band are continuously affected by interference in the Middle East. The base noise in this region is increased about 3—10 times compared with other areas. The centre point of interference and the centre point of GPS flex power is roughly in the same place.

  Conclusions  GPS flex power and interference have a significant impact on GPS users, especially on the positioning of low earth orbit satellites, which should be taken into account in the design of GNSS receivers.