Radar Distance Measurement Using Adaptive FFT Decimation
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Solution Overview
Problem
Current radar systems face challenges in accurately determining radar-ground distance measurements due to frequency ambiguities caused by limited computation capabilities and the need for increased sampling frequencies, which degrade distance resolution and require more complex FFT calculations.
Innovation Solution
A radar system and method that involve transmitting and receiving two radiofrequency signals, sampling the frequential quantity, and applying a fast Fourier transform with decimation based on distance measurement accuracy to adapt frequential resolution without increasing the number of FFT measurements, allowing for improved distance resolution and maintaining constant accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sampling frequency is increased to avoid frequency ambiguities, then measurement precision is improved, but distance resolution degrades
Solution Approach 1:
The patent applies dynamics by making the FFT calculation adaptive based on the measured distance. The system dynamically adjusts the number of FFT measurements and decimation ratio according to the current distance range, allowing optimal frequency resolution for each measurement scenario rather than using a fixed high sampling rate that degrades distance resolution.
Solution Approach 2:
The patent changes the parameter of FFT measurement count and decimation ratio based on distance. By varying these parameters according to the measured distance, the system maintains appropriate frequency resolution while avoiding the degradation of distance resolution that would result from consistently high sampling frequencies.
2Manufacturing precision
If the number of FFT measurements is increased to improve distance resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system dynamically adjusts the number of FFT measurements based on the measured distance. For closer distances, fewer FFT measurements are required, while farther distances require more measurements. This dynamic adaptation reduces overall computational complexity compared to consistently performing maximum FFT measurements.
Solution Approach 2:
The patent applies partial action by performing only the necessary number of FFT measurements required for accurate distance measurement at each range, rather than always performing the maximum possible number of measurements. This reduces unnecessary computational complexity while maintaining sufficient resolution.
3Measurement precision
If the frequential resolution is increased to maintain constant measurement accuracy, then measurement precision is improved, but computational load increases
Solution Approach 1:
The system dynamically adjusts the decimation ratio and number of FFT measurements based on the current distance measurement. This allows the system to maintain constant measurement accuracy across different ranges while reducing computational load by avoiding excessive frequency resolution requirements at closer distances.
Solution Approach 2:
The patent changes the decimation ratio and FFT measurement parameters according to distance. By adjusting these parameters dynamically, the system maintains appropriate frequency resolution for accurate measurement while reducing the computational load that would result from consistently high frequency resolution settings.
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 distance resolution adaptability based on measured distances, maintaining constant measurement accuracy and reducing computational load by adjusting frequential steps through decimation, thereby overcoming frequency ambiguities and improving measurement precision.
Implementation Method 1
the reception of signals obtained by the reflection of the two transmitted signals by the ground
Implementation Method 2
a frequency shift denoted fD due to the Doppler effect generated by the movement of the carrier
Data Source
AI summary
A radar system configured to determine radar-ground distance measurements. The radar system includes transmission and reception means configured to transmit two radiofrequency signals towards the ground and to receive the signals obtained by the reflection of the two transmitted signals by the ground and computation means configured to determine the frequential representations of the transmitted signals and of the received signals and determine a frequential quantity as a function of the frequential representations. The radar system is wherein the computation means are configured to sample the frequential quantity over a determined number of samples, which provides a sampled signal; determine a number of frequency measurements as a function of a constant distance measurement accuracy value; determine frequency measurements by applying to the sampled signal a spectral decomposition by fast Fourier transform using a decimation of the sampled signal in a ratio dependent on the distance measurement accuracy value, and determine a distance measurement corresponding to each frequency measurement.