Digital PLL Tracking Filter With Jerk Correction for Signal Estimation
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Solution Overview
Problem
Conventional methods for estimating non-energy signal parameters using Phase Locked Loops (PLLs) are not adaptive to jerking motion and cannot completely eliminate dynamic measurement errors, especially in navigation systems like GPS and GLONASS.
Innovation Solution
A digital Phase Locked Loop system that includes a phase discriminator, loop filter, numerically controlled oscillator, low-pass filter, preliminary estimation block, and jerk-correction block to adaptively correct phase and frequency estimates during jerking motion, using specific recurrence equations and threshold-based corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PLL methods are used to estimate signal parameters, then the system structure is simple, but dynamic measurement errors cannot be completely eliminated during jerking motion
Solution Approach 1:
The system segments the parameter estimation process into distinct functional blocks: a preliminary estimation block that generates initial phase and frequency estimates, and a jerk-correction block that refines these estimates by compensating for dynamic errors during jerking motion. This segmentation allows each block to specialize in specific correction tasks, improving overall measurement precision without creating a monolithic complex system.
Solution Approach 2:
The preliminary estimation block performs initial parameter estimation before the jerk-correction block refines the results. By performing preliminary estimation first, the system establishes a baseline that the correction block can then improve upon, enabling adaptive correction of dynamic errors while maintaining a structured approach to complexity management.
2Adaptability or versatility
If the PLL bandwidth is expanded to adapt to jerking motion, then adaptability improves, but measurement precision deteriorates due to increased noise
Solution Approach 1:
The jerk-correction block implements feedback by taking the preliminary phase and frequency estimates, calculating corrections based on detected jerking motion conditions, and applying these corrections to produce refined estimates. This feedback mechanism allows the system to adapt to jerking motion while maintaining precision by actively compensating for errors rather than passively accepting bandwidth limitations.
Solution Approach 2:
The system dynamically adjusts its estimation behavior based on detected motion conditions. The jerk-correction block activates corrections when jerking motion is detected, allowing the system to adapt its processing approach in real-time according to the operational conditions, thereby maintaining both adaptability and precision.
3Measurement precision
If smoothing filters are used to reduce noise, then measurement precision improves, but the system cannot respond to rapid frequency changes during jerking motion
Solution Approach 1:
The system dynamically switches between different processing modes based on motion detection. During jerking motion, the jerk-correction block applies adaptive corrections that maintain responsiveness to rapid frequency changes. During normal operation, the system can apply more aggressive smoothing. This dynamic adaptation resolves the contradiction by allowing both precision and speed under different operational conditions.
Solution Approach 2:
The system changes its processing parameters based on detected conditions. The jerk-correction block modifies estimation parameters adaptively when jerking motion is detected, allowing the system to optimize its response characteristics in real-time. This parameter adaptation enables the system to maintain both precision and response speed by adjusting its behavior to match operational requirements.
Data Source
AI summary
A digital system of measuring parameters of the signal (phase, frequency and frequency derivative) received in additive mixture with Gaussian noise. The system is based on the use of variables of a PLL for calculating preliminary estimates of parameters and calculating the corrections for these estimates when there is a spurt frequency caused by a receiver motion with a jerk. A jerk is determined if the low pass filtered signal of the discriminator exceeds a certain threshold. The jerk-correction decreases the dynamic errors. Another embodiment includes a tracking filter for obtaining preliminary estimates of parameters to reduce the fluctuation errors. Estimates are taken from the tracking filter when there is no jerk and from the block of jerk-corrections when there is a jerk.