FMCW Radar Nonlinear Multiband Chirps for Interference-Resilient Resolution
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Solution Overview
Problem
Radar systems in autonomous vehicles face challenges such as interference from multiple unsynchronized radars operating in overlapping frequency bands, range cell migration, ambiguity between Doppler velocity and range, and high hardware complexity and cost due to linear chirp bandwidth, which affect range and velocity measurement accuracy.
Innovation Solution
The use of multiband chirps with nonlinear frequency hopping sequences and antenna multiplexing in FMCW radar systems, combined with spectral probability windowing, to improve range resolution and reduce interference, while maintaining low hardware complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear chirp bandwidth is increased to improve range resolution, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent divides the total bandwidth into multiple smaller sub-bands, each processed by separate channels with lower bandwidth requirements. This segmentation allows the system to achieve the same overall range resolution as a single wideband channel would provide, but with reduced hardware complexity in each individual channel, since each channel only needs to handle a fraction of the total bandwidth.
2Reliability
If multiple radars operate in overlapping frequency bands, then coverage and reliability improve, but interference increases
Solution Approach 1:
The patent extracts and removes interference components from the received signal through spectral analysis and filtering. By identifying frequency components that correspond to interfering radars and selectively removing or attenuating these components, the system maintains reliable detection capability while operating in crowded spectral environments with multiple radars.
3Productivity
If Doppler velocity and range are measured simultaneously, then productivity improves, but measurement precision deteriorates due to ambiguity
Solution Approach 1:
The patent segments the measurement process into separate handling for range and velocity parameters. By using multiple frequency bands with different characteristics, the system can separately optimize range measurement in some bands and velocity measurement in others, or use specific bands primarily for one parameter while relying on other bands for the other parameter, thereby reducing the ambiguity that arises when both parameters are measured simultaneously in a single band.
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 range and angular resolution, reduces interference, and minimizes hardware complexity and cost, enabling reliable detection of multiple objects in various weather conditions.
Implementation Method 1
Frequency Modulated Continuous Wave (FMCW) radar is a type of radar that offers several advantages compared to the others
Implementation Method 2
The Doppler frequency causes the frequency-time plot of the radar return signal to be shifted up or down
Implementation Method 3
The beat frequency output of a mixer in the receiver due to the range of the target
Data Source
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AI summary
A novel and useful system and method by which radar angle and range resolution are significantly improved without increasing complexity in critical hardware parts. A multi-pulse methodology is described in which each pulse contains partial angular and range information consisting of a portion of the total CPI bandwidth, termed multiband chirp. Each chirp has significantly reduced fractional bandwidth relative to monoband processing. Each chirp contains angular information that fills only a portion of the 'virtual array', while the full virtual array information is contained across the CPI. This is done using only a single transmission antenna per pulse, thus significantly simplifying MIMO hardware realization, referred to as antenna-multiplexing (AM). Techniques for generating the multiband chirps as well as receiving and generating improved fine range-Doppler data maps. A windowing technique deployed in the transmitter as opposed to the receiver is also disclosed.