FMCW Radar Interleaved Scanning for Speed Ambiguity
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Solution Overview
Problem
Current FMCW radar systems require a long cycle time to scan different viewing areas, especially when locating objects in fields with large opening angles and limited ranges, which hampers efficient utilization of available time for simultaneous scanning.
Innovation Solution
The method involves interleaving measurement sequences with different time offsets between ramps within a modulation pattern, allowing for simultaneous scanning of multiple fields of view by performing two-dimensional Fourier transformations on baseband signals to determine relative speeds and angular positions of radar targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If FMCW radar measurements are carried out using transmitting antennas with different fields of view that differ in terms of aperture angle and/or range, then the radar can detect targets in different viewing areas, but the cycle time for scanning all viewing areas becomes long
Solution Approach 1:
The patent segments the measurement cycle into multiple interleaved sequences, where each sequence is assigned to a specific field of view. Instead of completing measurements for one entire field of view before moving to the next, the system divides the measurement time into sequences that alternate between different fields of view, allowing concurrent scanning of multiple viewing areas and reducing the total cycle time.
Solution Approach 2:
The patent implements periodic action by assigning different time offsets between ramps to different sequences corresponding to different fields of view. This periodic interleaving pattern allows the radar to systematically cycle through multiple viewing areas in a structured manner, ensuring each field of view receives adequate measurement attention while maintaining continuous scanning across all areas.
2Measurement precision
If the time offset between successive short ramps is reduced to allow unambiguous determination of relative speed, then the Doppler frequency measurement range is improved, but the available time for scanning multiple viewing areas is reduced
Solution Approach 1:
The patent segments the radar's time resources by assigning different time offsets between ramps to different sequences for different fields of view. This allows each sequence to have sufficient time offset for accurate speed measurement while the overall system scans multiple viewing areas in parallel through the interleaved sequence structure.
Solution Approach 2:
The patent resolves the time conflict by introducing a sequence dimension. Instead of competing for the same time resources in a single sequence, measurements for different fields of view are distributed across multiple sequences with different time offsets, effectively adding a temporal dimension to the measurement organization that allows both adequate sampling intervals and comprehensive scene coverage.
3Productivity
If larger time intervals between ramps are used, then the scanning efficiency is improved, but ambiguity in relative speed measurements increases
Solution Approach 1:
The patent segments the measurement task into multiple sequences, each with its own time offset pattern. This segmentation allows the system to use larger effective time intervals for scanning efficiency while maintaining sufficient sampling resolution within each sequence for unambiguous speed determination. The multiple sequences work together to provide both efficiency and accuracy.
Solution Approach 2:
The patent uses multiple sequences with different time offsets as intermediaries to resolve the conflict between scanning efficiency and measurement accuracy. Each sequence acts as an intermediary that maintains the necessary temporal resolution for speed measurement, while the collection of sequences together provides the overall scanning efficiency through their interleaved execution.
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 enables more precise localization of radar targets with the same hardware, allowing for larger time intervals between ramps and resolving ambiguity in relative speed measurements, thus improving the efficiency of radar scanning.
Implementation Method 1
FMCW radar sensors are used in motor vehicles to detect the traffic environment, in particular to locate other vehicles
Implementation Method 2
Due to the Doppler effect, however, the frequency difference also contains a component that is caused by the relative speed of the object
Implementation Method 3
The frequency of the baseband signal corresponds to the difference in frequency between the signal being transmitted at a given time and the signal being received at the same time. Due to the frequency modulation of the transmission signal, this frequency difference depends on the propagation time of the signal from the radar sensor to the object and back, and thus on the distance of the object
Implementation Method 4
These run length differences lead to corresponding differences in the phase of the signals that are received by the antennas and evaluated in the associated evaluation channels. By comparing the (complex) amplitudes received in the various channels with the corresponding amplitudes in an antenna diagram, the angle of incidence of the radar signal and thus the azimuth angle of the located object can then be determined
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An FMCW radar sensor and a method for locating a radar target (18), in which FMCW radar measurements are carried out with transmission antennas (12; 15) with different fields of view (p), which differ in terms of aperture angle and/or range, wherein the measurements respectively comprise time-nested sequences (22; 26; 32; 36; 40; 42; 44) of ramps (24; 28; 34; 38; 41; 43; 45) and measurements with different fields of view (p) are interwoven in time, ambiguous values for the relative speed (v) of the radar target (18) are determined from a position (k, l) of a peak in a two-dimensional spectrum (56; 57); phase relations between the spectral values of spectra (X) are monitored in respect of correspondence with phase relations (a(v,m)) expected for a plurality of the determined values of the relative speed (v), and an estimated value for the relative speed (v) of the radar target (18) is selected on the basis thereof from the specified, periodic values of the relative speed (v).