Narrowband Ranging Using Coarse and Fine Delay Estimation
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Solution Overview
Problem
Conventional ranging systems face challenges in achieving both accuracy and precision in distance estimation due to noise-induced ambiguity and cycle slips, with low-pass filtering providing accuracy but not precision, and band-pass filtering providing precision but not accuracy.
Innovation Solution
The method combines coarse and fine delay estimation by applying low-pass filtering for accurate but ambiguous results and band-pass filtering for precise but potentially inaccurate results, using correlations to optimize both accuracy and precision, and reducing the probability of cycle slips by windowing low-pass signals to lower side lobe ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-pass filtering is applied to the reference and reflected signals, then measurement accuracy is improved, but measurement precision deteriorates due to noise-induced ambiguity
Solution Approach 1:
The patent segments the distance estimation process into two distinct stages: coarse delay estimation using low-pass filtered signals for accuracy, and fine delay estimation using band-pass filtered signals for precision. This segmentation allows each stage to optimize for its specific goal without being constrained by the weaknesses of the other approach.
Solution Approach 2:
The patent merges the results of coarse delay estimation (accurate but ambiguous) and fine delay estimation (precise but potentially inaccurate) through a combining process. The coarse estimate provides a reliable range, and the fine estimate refines this within that range, achieving both accuracy and precision in the final distance measurement.
2Measurement precision
If band-pass filtering is applied to the reference and reflected signals, then measurement precision is improved, but measurement accuracy deteriorates due to cycle slips
Solution Approach 1:
The patent segments the processing into two filtering paths: low-pass filtering for coarse estimation that ensures accuracy by avoiding cycle slips, and band-pass filtering for fine estimation that provides precision. Each filtering type is applied in the appropriate segment of the overall process.
Solution Approach 2:
The patent performs preliminary coarse delay estimation using low-pass filtered signals before performing the fine delay estimation using band-pass filtered signals. This preliminary action establishes an accurate baseline that prevents subsequent fine estimation from producing inaccurate results due to cycle slips.
3Use of energy by moving object
If signal transmission power is reduced, then energy consumption is lowered, but range error standard deviation increases
Solution Approach 1:
The patent implements continuous processing of both coarse and fine delay estimates, ensuring that the full information content of the received signal is utilized. This continuous dual-processing approach maintains measurement precision even when transmission power is reduced, as it extracts maximum information from the available signal.
Solution Approach 2:
The patent changes the processing parameters by applying different filtering characteristics (low-pass and band-pass) to different aspects of the signal analysis. This parameter differentiation allows the system to maintain precision at lower power levels by optimally processing the signal characteristics that remain detectable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces range error standard deviation by 18% and allows for a 20% reduction in signal transmission power without affecting range error standard deviation, enhancing the overall accuracy and precision of distance estimation.
Implementation Method 1
a transducer to receive a reference signal and a reflected signal
Implementation Method 2
a filter to generate a band-pass reference signal and a band-pass reflected signal by filtering (A) reference signal samples associated with the reference signal and (B) reflected signal samples associated with the reflected signal
Implementation Method 3
a correlator to generate a first correlation by correlating the band-pass reference signal with the band-pass reflected signal and a second correlation by correlating the reference signal samples with the reflected signal samples
Implementation Method 4
a delay estimator to determine a distance to the target based on the first correlation and the second correlation
Implementation Method 5
The transmitted signal is reflected off the target and back to the ranging system
Data Source
AI summary
Methods and apparatus to determine a distance to a target using coarse and fine delay estimation based on a narrowband transmit signal are disclosed. An example apparatus includes a transducer to receive a reference signal and a reflected signal, the reflected signal being the reference signal after being reflected of a target; a filter to generate a band-pass reference signal and a band-pass reflected signal by filtering (A) reference signal samples associated with the reference signal and (B) reflected signal samples associated with the reflected signal; a correlator to generate a first correlation by correlating the reference signal samples with the reflected signal samples and a second correlation by correlating the band-pass reference signal with the band-pass reflected signal; and a delay estimator to determine a distance to the target based on the first correlation (coarse delay) and the second correlation (fine delay) and output a signal including the distance to the target.