A new nonlinear Type3-PLL with noise rejection and fast locking performance in tracking telemetry and command systems

• Published in: Acta astronautica 2019-04, Vol.157, p.397-403
• Main Authors: Zhu, Congying, Li, Xiaoping, Shi, Lei, Liu, Yanming, Yao, Bo, Si, Dongyu
• Format: Article
• Language: English
• Subjects: Acceptable noise levels; Control stability; Control theory; Error reduction; Fast locking; Locking; Loss threshold; Low pass filters; Noise; Noise rejection; Nonlinear control; Nonlinear element; Parameters; Phase error; Phase locked systems; Synchronism; Telemetry; Tracking; Type3-PLL
• ISSN: 0094-5765; 1879-2030
• DOI: 10.1016/j.actaastro.2019.01.006

Type3-PLLs are widely used for carrier synchronization in tracking telemetry and command (TT&C) systems. A major challenge with the traditional Type3-PLL is how to further improve their acquisition and tracking speed without compromising the noise suppression ability and stability. In this article, drawn lessons from the nonlinear control theory, a new structural Type3-PLL is presented. The idea of the proposed Type3-PLL, which can be denoted by N-Type3-PLL, is to couple with a designed nonlinear element in the traditional Type3-PLL. The loop noise bandwidth is adaptively adjusted by the designed nonlinear element on the basis of the loop filter output, which is determined by the frequency-phase error. The output noise of the nonlinear element is then suppressed by the consequent low-pass filter. The influence of the nonlinear element parameters on the N-Type3-PLL is quantitatively analyzed and discussed. Simulation results indicate that the N-Type3-PLLs under various parameters can achieve locking faster than the traditional Type3-PLL in response to a step change in frequency. The nonlinear element parameters constraint the comprehensive performance of the N-Type3-PLL. The optimal parameters of the nonlinear element are solved via a suggested iterative feedback method. Compared with the traditional Type3-PLL, the output frequency of the N-Type3-PLL under the optimal parameters jitters much less and the standard deviation of frequency-phase error is reduced from 0.6198 (rad/s) 2 to 0.2264 (rad/s) 2 when the input SNR equals −15 dB. The lock time after the step is extended from 0.22 s to 0.24 s, which is within an acceptable range. The loss threshold of the proposed N-Type3-PLL is reduced from −20 dB to −23 dB. •A new structural Type3-PLL coupled with a designed nonlinear element is proposed.•The loop noise bandwidth of the proposed Type3-PLL can be adaptively adjusted.•Optimal parameters of the N-Type3-PLL are solved via a iterative feedback method.•The loss threshold of the proposed N-Type3-PLL is reduced from −20 dB to −23 dB.