Time-Interleaved Chirp Sequences for Radar Velocity Measurement
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Solution Overview
Problem
Radar systems face limitations in accurately measuring the velocity of objects due to maximum unambiguous velocity errors and phase rollover issues, particularly in frequency modulated continuous wave (FMCW) radar systems, which restrict the detection of higher velocities and introduce ambiguities in velocity estimation.
Innovation Solution
The implementation of time-interleaved chirp sequences, where odd-indexed and even-indexed chirps are offset, allowing for independent processing to generate direct and indirect velocity measurements, thereby increasing the maximum unambiguous velocity without reducing the frame rate, and utilizing phase differences to resolve velocity ambiguities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional FMCW radar transmits equally spaced chirps in a frame, then the frame rate is maintained, but the maximum unambiguous velocity is limited and phase rollover errors occur
Solution Approach 1:
The patent divides the chirp sequence into two interleaved subsequences: odd-indexed chirps and even-indexed chirps. Each subsequence is processed independently to generate separate velocity measurements. This segmentation allows the system to effectively double the maximum unambiguous velocity while maintaining the same frame rate, resolving the contradiction between measurement precision and velocity range adaptability.
2Adaptability or versatility
If the chirp repetition interval is increased to measure higher velocities, then the maximum unambiguous velocity increases, but the frame rate decreases
Solution Approach 1:
By segmenting the chirp sequence into two interleaved subsequences with different effective repetition intervals, the patent enables one subsequence to measure higher velocities while the other maintains higher temporal resolution. Both subsequences are processed in parallel, allowing the system to achieve extended velocity measurement range without sacrificing frame rate productivity.
Solution Approach 2:
The patent introduces a new dimension in the signal processing domain by creating two independent processing paths for odd and even chirps. This dimensional expansion in the measurement space allows simultaneous achievement of high frame rate and extended velocity range, effectively resolving the trade-off between productivity and adaptability.
3Measurement precision
If phase unwrapping is used to correct velocity ambiguities, then velocity measurement accuracy improves, but computational complexity increases
Solution Approach 1:
The patent segments the velocity measurement process into direct velocity estimation from odd chirps and indirect velocity estimation from even chirps. By comparing these two independent estimates, the system identifies and corrects phase wrapping ambiguities through logical comparison rather than complex unwrapping algorithms, reducing computational complexity while maintaining measurement precision.
Solution Approach 2:
The patent implements a feedback mechanism where the direct and indirect velocity estimates are compared to detect phase wrapping errors. When discrepancies are detected, the system uses the comparison feedback to identify the correct velocity value, providing an elegant solution that improves precision without requiring complex computational unwrapping procedures.
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 radar system's ability to detect higher velocities accurately while maintaining a high frame rate, correcting velocity ambiguities and improving the precision of velocity estimation by comparing direct and indirect measurements.
Implementation Method 1
Radar apparatuses may be used in a variety of applications. For example, automotive radar apparatuses, such as frequency modulated continuous wave (FMCW) radar apparatuses
Implementation Method 2
The reflected signal is down-converted, digitalized and processed to estimate range and velocity of objects surrounding the radar apparatus
Data Source
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Figure 2A~2C
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AI summary
Embodiments are directed to a method for determining velocity of an object. The method includes in response to two interleaved chirp sequences being sent towards the object, processing responsive chirps of each of the two interleaved chirp sequences independently from one another to produce respective Doppler-spectrum data sets, and calculating the velocity of the object based on the respective Doppler-spectrum data sets. Each of the interleaved chirp sequences being characterized by a common time spacing between respective chirps of the respective chirp sequence, and each chirp of one of the chirp sequences being offset by an amount of time that is different than the common time spacing.