Abstract
As the weak link in global navigation satellite system (GNSS) signal processing, the phase-locked loop (PLL) is easily influenced with frequent cycle slips and loss of lock as a result of higher vehicle dynamics and lower signal-to-noise ratios. With inertial navigation system (INS) aid, PLLs’ tracking performance can be improved. However, for harsh environments with high dynamics and signal attenuation, the traditional INS-aided PLL with fixed loop parameters has some limitations to improve the tracking adaptability. In this paper, an adaptive INS-aided PLL capable of adjusting its noise bandwidth and coherent integration time has been proposed. Through theoretical analysis, the relation between INS-aided PLL phase tracking error and carrier to noise density ratio (C/N0), vehicle dynamics, aiding information update time, noise bandwidth, and coherent integration time has been built. The relation formulae are used to choose the optimal integration time and bandwidth for a given application under the minimum tracking error criterion. Software and hardware simulation results verify the correctness of the theoretical analysis, and demonstrate that the adaptive tracking method can effectively improve the PLL tracking ability and integrated GNSS/INS navigation performance. For harsh environments, the tracking sensitivity is increased by 3 to 5 dB, velocity errors are decreased by 36% to 50% and position errors are decreased by 6% to 24% when compared with other INS-aided PLL methods.
Highlights
With the availability of accurate position, velocity and timing information that enables many applications we use in our daily lives, the global navigation satellite system (GNSS) has become nearly ubiquitous for both civil and military users [1,2]
This paper focuses on an inertial navigation system (INS)-aided phase-locked loop (PLL) tracking method for GNSS receiver in harsh environments with high dynamics and signal attenuation
In to verify verifythe thevalidity validityofofthe theadaptive adaptiveadjustments adjustments bandwidth integration time, simulation result of the phase tracking error of discriminator output is compared with the theoretical the simulation result of the phase tracking error of discriminator output is compared with the minimum tracking error value.error
Summary
With the availability of accurate position, velocity and timing information that enables many applications we use in our daily lives, the global navigation satellite system (GNSS) has become nearly ubiquitous for both civil and military users [1,2]. A narrower noise bandwidth and longer integration time are required to decrease the thermal noise and improve the tracking sensitivity For these two constraints, certain scenarios with high dynamic and signal attenuation will make it more difficult for GNSS signal to remain locked [4,5,6]. This paper focuses on an INS-aided PLL tracking method for GNSS receiver in harsh environments with high dynamics and signal attenuation. Based on a comprehensive theoretical analysis of the relation between INS-aided PLL tracking error and C/N0 , vehicle dynamics, aiding information update time, noise bandwidth and integration time, a method to choose the optimal integration time, noise bandwidth for a given application under the minimum tracking error criterion has been proposed. By means of the adjustments of both integration time and noise bandwidth, the adaptive ability of the INS-aided GNSS carrier tracking loop for the harsh environment can be effectively improved.
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