Radar Undersampling Aliasing Phase Analysis
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Solution Overview
Problem
Current radar sensors face challenges in accurately and unambiguously determining distances and relative velocities of objects, particularly at larger ranges, due to limitations in sampling frequency and computational requirements, which restrict their ability to detect remote objects and resolve ambiguities in velocity and distance measurements.
Innovation Solution
The method involves undersampling base band signals and using a modulation pattern with alternating sequences of ramps to allow aliasing effects, enabling detection of signals outside the frequency range and reducing computational demands by allowing larger time intervals between ramps, thereby increasing the detectable range and reducing memory and computing power needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sampling frequency is increased to improve measurement precision and extend detectable range, then the ability to detect remote objects is improved, but the memory and computing power requirements increase
Solution Approach 1:
The patent deliberately introduces aliasing effects by using a sampling frequency below the Nyquist rate, converting what is traditionally considered a harmful distortion into a beneficial feature. The aliasing folds high-frequency signals into the detectable range, enabling detection of remote objects whose baseband signals would otherwise be undetectable. The system then uses phase relationship analysis to resolve the resulting ambiguities, achieving both extended range and maintained precision without proportionally increasing computational resources.
2Productivity
If the time interval between ramps is increased to reduce computational demands, then the processing speed is improved, but the ability to resolve velocity ambiguities deteriorates
Solution Approach 1:
The patent transitions from analyzing signals in a single time dimension to analyzing phase relationships across multiple dimensions. By examining phase differences between alternating sequences and between individual ramps within sequences, the system creates additional measurement dimensions that enable velocity unambiguous determination even with larger time intervals. This multi-dimensional phase analysis compensates for the reduced temporal sampling density.
3Reliability
If conventional sampling methods are used to ensure unambiguous velocity and distance measurements, then measurement reliability is improved, but the detectable range is limited
Solution Approach 1:
The patent segments the signal analysis into multiple components: analysis of phase relationships between alternating sequences, analysis of phase relationships between individual ramps within sequences, and combination of these analyses. This segmentation allows the system to handle the aliased signals from remote objects by processing different aspects of the signal separately and then integrating the results, maintaining measurement reliability while extending detectable range.
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 allows for unambiguous and accurate measurement of distances and relative velocities, enabling detection of more remote objects and reducing the requirements for memory and computing power, while improving the separation of base band signals from stationary objects.
Implementation Method 1
the transmission signal being mixed with a received signal to form a base band signal
Implementation Method 2
the base band signals of the ramps being transformed into spectra
Data Source
AI summary
A method for determining distances and relative velocities of objects with using a radar includes transmitting a ramp-like frequency-modulated transmission signal whose modulation pattern includes multiple sequences of ramps having an identical ramp slope, which alternately follow each other, the sequences having a frequency offset and a time offset with respect to each other; Undersampling, and subjecting to a 2D Fourier transform, base band signals for the individual ramps; determining hypotheses for the distance and the relative velocity v of an object based on alternative distance-velocity relationships and based on periodic ambiguous information about velocity; ascertaining degrees of the agreements of a phase relationship between spectral values of the spectra with phase relationships expected for the hypotheses between spectral values of the sequences; and determining unambiguous estimated values for the distance and the relative velocity by selecting a hypothesis having the maximum agreement.