FMCW Radar Altimeter Height Resolution via FFT Bin Interpolation
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Solution Overview
Problem
Conventional FMCW radar altimeters have limited range resolution and can incorrectly detect the leading edge of a target due to side lobe tracking, leading to biased altitude measurements, especially in environments with large targets.
Innovation Solution
Implementing a leading-edge-tracking algorithm and a second algorithm to determine a power ratio between the leading edge bin and adjacent bins, allowing for more accurate interpolation and reducing bias in altitude measurements by using a subset of adjacent FFT bins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If leading edge detection scheme is used, then detection speed is improved, but measurement precision deteriorates due to tracking side lobes instead of actual peak
Solution Approach 1:
The patent segments the detection process into two distinct phases: (1) leading edge detection using a threshold-based algorithm to identify the initial detection point, and (2) peak detection using a parabolic interpolation algorithm to refine the measurement. This segmentation allows the system to benefit from both the speed of leading edge detection and the precision of peak detection, resolving the contradiction between detection speed and measurement accuracy
Solution Approach 2:
The patent applies preliminary action by first using the leading edge detection algorithm to quickly identify a candidate region, then using this preliminary result as the starting point for the more computationally intensive parabolic interpolation. This preliminary detection narrows the search space for subsequent precision processing, maintaining speed while improving accuracy
2Measurement precision
If bandwidth is increased to improve range resolution, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the processing parameter from direct time-domain analysis to frequency-domain analysis using FFT, and further changes the detection parameter from leading edge threshold to parabolic peak interpolation. These parameter changes in the signal processing domain achieve improved range resolution without requiring increased hardware bandwidth, thus improving measurement precision while avoiding increased device complexity
Solution Approach 2:
The patent substitutes the physical hardware approach (increasing bandwidth) with a signal processing approach (parabolic interpolation algorithm). Instead of modifying the physical radar system to achieve better resolution, the invention uses mathematical processing of the existing signal to extract more precise measurements, replacing a mechanical/hardware solution with an algorithmic one
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 enhances the height measurement resolution of radar systems, providing more accurate distance calculations by correctly identifying the leading edge of a target and reducing the bias towards shorter altitudes.
Implementation Method 1
determining a distance to a target based on the time between transmission of the chirp signal and a reception of a reflection of the chirp signal
Implementation Method 2
generating, at a fast Fourier transform (FFT) processor, a set of FFT bins across a frequency range
Data Source
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AI summary
A method of improving height measurement resolution for a radar system is provided. The method includes periodically generating, at a FFT processor, a set of FFT bins across a frequency range based on a periodic ramping of a FMCW radar signal from a first frequency to a second frequency; selecting a subset of bins from at least one set of FFT bins by implementing a leading-edge-tracking algorithm by at least one processor; implementing a second algorithm on the selected subset of bins to determine a power ratio between the leading edge tracked bin and the remaining bins in the selected subset of bins to determine an interpolated bin number within the selected subset of bins; and determining an approximate distance to the target based on the interpolated bin number within the selected subset of bins. The sets of FFT bins are indicative of a respective plurality of distances.