风云三号D卫星GPS信号功率调整及干扰分析

全球定位系统(global positioning system，GPS)卫星的IIR和IIF卫星能够在各个信号分量之间重新分配其发送信号的功率，一个或多个GPS信号可以在指定区域根据需要进行功率调整或者关闭。分析GPS信号的变化特征对于地面和空间应用有重要的意义。风云三号D（FengYun-3D，FY-3D）卫星是中国极轨气象卫星之一，利用FY-3D卫星实际测量数据可以帮助GPS用户全面了解GPS功率调整的特点。首先，利用FY-3D运行轨道全球覆盖的特点分析GPS信号的强度，特别是GPS信号功率调整时间段信号变化的特点；然后，使用在轨数据研究了全球范围L波段信号干扰的特征，得到了干扰对全球导航卫星系统掩星探测仪掩星天线的自动增益控制和基底噪声的影响。结果表明:从2020-02-14开始的GPS功率调整以35°N，37°E]和35°N，69°E]为中心，覆盖半径约为7 500 km，在该区域内GPS P(Y)码功率增加约10 dB；GPS L1和L2频段在中东地区持续受干扰的影响，该区域的基底噪声比其他区域增加约3~10倍；干扰区域中心点和GPS功率调整区域中心点大致在同一位置。GPS卫星的功率调整和信号干扰对GPS用户，特别是低轨卫星的定位有明显的影响，在GNSS接收机设计时应引起重视。

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.