Distributed Automotive Radar With Alternating Masters for Virtual Aperture
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Solution Overview
Problem
Existing automotive radar systems face challenges in achieving improved angular resolution without increasing physical size, due to design and integration constraints, and current solutions requiring shared local oscillator signals or complex modifications are not economically viable.
Innovation Solution
A distributed coherent radar system that combines multiple small-aperture radars without a shared local oscillator, using bi-static and MIMO techniques to form a larger virtual aperture, with signal processing to compensate for frequency and phase differences, and co-array processing to suppress spurious sidelobes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a larger aperture radar is used to improve angular resolution, then angular resolution is improved, but the physical size of the radar increases which conflicts with vehicle integration constraints
Solution Approach 1:
The system divides a large aperture radar into multiple smaller distributed radar devices positioned at different locations on the vehicle. Each device has its own independent aperture, but collectively they form a virtual large aperture through coordinated signal transmission and reception, achieving high angular resolution without requiring a single large physical radar structure.
Solution Approach 2:
The system transitions from a single-plane aperture to a three-dimensional distributed aperture configuration. By positioning multiple small radars at different spatial locations (different dimensions) on the vehicle and using time-division multiplexing, the system creates a virtual aperture that spans multiple dimensions, achieving large effective aperture without large individual components.
2Ease of manufacture
If distributed radars with independent local oscillators are used to simplify integration, then ease of manufacture is improved, but frequency and phase differences between radars cause measurement errors
Solution Approach 1:
The system uses periodic time-division multiplexing where each distributed radar is sequentially selected as a master device transmitting reference signals at regular intervals. This periodic operation allows slave radars to systematically measure and compensate frequency and phase offsets, maintaining measurement precision while using independent local oscillators that simplify integration.
Solution Approach 2:
The system implements feedback mechanisms where slave radars receive reference signals from master radars, measure frequency and phase differences, and use this feedback information to compensate their own measurements. This closed-loop approach corrects for independent oscillator variations, maintaining angular resolution accuracy without requiring synchronized local oscillators.
3Measurement precision
If complex signal processing is used to compensate for frequency and phase offsets, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system performs preliminary calibration during initialization where master radars transmit reference signals and slave radars measure frequency and phase offsets before actual measurement begins. These pre-measured offsets are stored and applied to compensate subsequent measurements, avoiding the need for complex real-time compensation processing during operational measurements.
Solution Approach 2:
The system uses reference signal copying where master radars transmit known reference signals that slave radars receive and process. By comparing the received copied reference signals with locally generated references, the system efficiently determines frequency and phase offsets using simple correlation techniques rather than complex computational methods.
4Measurement precision
If multiple distributed radars are combined to form a virtual aperture, then angular resolution is improved, but spurious sidelobes increase causing false detections
Solution Approach 1:
The system dynamically changes operating parameters including time-division multiplexing sequences, frequency offsets, and phase configurations of distributed radars. By varying these parameters across different measurement cycles and using coherent integration with parameter modulation, the system suppresses spurious sidelobes that would otherwise cause false detections while maintaining improved angular resolution from the virtual aperture.
Data Source
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AI summary
A distributed aperture bi-static radar system, apparatus, architecture, and method is provided for coherently combining physically distributed radars to jointly produce target scene information in a coherent fashion by alternately selecting first and second small aperture devices to operate as the master unit so that radar signals are sequentially transmitted from every transmit antenna in the first and second small aperture devices, thereby enabling the radar control processing unit to coherently combine mono-static and bi-static virtual array apertures from the first and second small aperture radar devices to construct an extended bi-static MIMO virtual array aperture that is larger than the bi-static MIMO virtual array apertures produced by the first and second small aperture radar devices.