High Dynamic Carrier Tracking Using Kalman Filter

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  • Topic: Kalman filter, Signal processing, Phase-locked loop
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High Dynamic Carrier Tracking Using Kalman Filter
Aided Phase-Lock Loop

Weibin Li†,‡, Shanjian Liu†,‡, Chunhui Zhou‡, Shidong Zhou‡, Tingchang Wang†
† Institute of Communication Engineering PLAUST
Nanjing P, R China
Email: liwb@wireless.mdc.tsinghua.edu.cn

Abstract—Tracking dynamics on the GPS signal is still a big challenge to the receiver designer as the operating conditions are becoming more volatile. Usually, the Phase-locked loop (PLL) is used in GPS receivers to track an incoming signal and to provide accurate carrier phase measurements. However, in high dynamic situations, the conflict between improvingPLL tracking

performance and the ability to track the signal necessitates some compromises in PLL design. Optimizing the stand-alone system for dynamics, generally, degrades the accuracy of measurements. Theadvanced signal processing techniques as maximum

likelihood (ML) and extended Kalman filter (EKF) can be used to track a common trajectory exhibiting high dynamics. However, the estimated values of these algorithms can not be used directly to demodulate the signals. A combination of both inertial

measurement unit (IMU) and GPS is an attractive method to deal with the problem of high dynamic tracking. Unfortunately, these units of IMU are often very expensive. In this paper, a new Kalman filter aided phase-lock loop is proposed to address this issue. Doppler derived from EKF is used to aid the carrier

tracking loop for improving the performance under dynamic
conditions. While the cost is significantly reduced compare with the IMU method. Simulations show that the method is feasible.

Keywords-high dynamic; Kalman filter; Phase-lock loop;
signal processing
I.INTRODUCTION
Tracking dynamics on the GPS signal is still a big challenge to the receiver designer as the operating conditions are
becoming more volatile. In GPS receivers, the Phase-locked
loop (PLL) is used to track an incoming signal and to provide accurate carrier phase measurements [1][2][3]. However, High noise and high platform dynamics scenarios present a difficult problem for most GPS receivers. In a high noise environment, a simple solution is to decrease the closed-loop bandwidth of the tracking loops since the amount of noise present in the system is directly proportional to the bandwidth. However, as the receiver platform experiences high dynamics, a Doppler

shift is induced on the received RF signal. In order to track this shift without error, the bandwidth of the tracking loops must increase. Given these two constraints, there are certain scenarios that will prohibit signal lock from being maintained [3]. In some applications, a loss-of-lock condition is

unacceptable, and a backup system must be implemented.
Typically, this backup system is a high grade inertial
measurement unit (IMU)[4][5]. Unfortunately, these units are

This work was supported by China’s 863 Project-No.2006AA01Z274 and Tsinghua-Qualcomm.Project

‡ National Laboratory for Information Science and
Technology, Tsinghua University, Beijing, P. R. China

often very expensive. Less expensive IMU’s generally have large output errors which degrade the estimate of the
platform’s position and velocity. A desirable approach would be a combination of both IMU and GPS that is robust to the
stresses posed by high dynamics and high noise while
accounting for errors in the inertial measurements. Contrary to use IMU, some advanced signal processing techniques were
proposed to directly estimate the carrier frequency for high dynamic trajectories. Hurd etc. [6] compare four different
estimation techniques applied to the problem of continuously estimating the rapidly varying parameters of sinusoidal signal. Thesetechniques include an approximate maximum
likelihood (ML) estimator, an extended Kalman filter (EKF), a cross-product automatic frequency control loop and a
phase-locked loop....
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