高动态场景下GNSS信号自适应载波跟踪算法

Adaptive carrier-tracking algorithm for Global Navigation Satellite System signals in high dynamic scenarios

相对于城市应用场景,在高速飞行器上搭载的GNSS导航接收机需要承受更大的载波频率动态范围,且测量实时性要求较高,对载波环路的高精度跟踪提出了更高挑战.为此,本文提出了一种自适应载波跟踪算法,在载波跟踪环路中引入模糊控制器,随载波的频率变化自适应调整环路参数,在保证动态适应性的同时提高了测速精度.所提算法利用载波跟踪环路测量值计算模糊控制器的输入变量,采用单输入单输出的Takagi-Sugeno模糊控制模型,实时计算环路滤波器调节系数,具有结构简单且易于实现的特点.本文分别在固定多普勒频率、线性多普勒频率和正弦多普勒频率的场景下进行了分析和仿真.结果表明,所提算法能够在飞行器和接收机间径向运动速度范围±10 km/s,加速度范围±30g,输入载噪比40 dB Hz的条件下,以1 kHz的频率输出径向速度测量值,且测量误差小于3 m/s(1σ).

Compared with urban application scenarios,Global Navigation Satellite System(GNSS)navigation receivers that are mounted on high-speed aircraft must handle a higher carrier frequency dynamic and output the measured result at a higher frequency.Both these factors adversely affect the accuracy of the carrier frequency measurement.Herein,we propose an adaptive carrier-tracking algorithm to measure the radial velocity by introducing a fuzzy logic controller in the carrier-tracking loop.The proposed algorithm adaptively adjusts the loop bandwidth as the carrier frequency changes,improving the velocity measurement accuracy while ensuring dynamic adaptability.Herein,the measured result of the loop is used to calculate the input variables of the fuzzy controller,and the output of the fuzzy controller is used to adjust the loop bandwidth.The fuzzy controller adopts a single input and single output Takagi-Sugeno model,which is easy to implement.The analysis and simulation are performed under fixed-,linear-,and sine-shaped Doppler frequency scenarios.The radial velocity between the aircraft and the receiver is set in the range of±10 km/s,and the radial acceleration is set in the range of±30g.To ensure the validity of the measurement results,we output the measurement results at a frequency of 1000 points per second.Simulation results demonstrate that when the input carrier-to-noise ratio is 40 dB Hz,the velocity accuracy of the proposed algorithm is better than 0.3 m/s(1σ).