Vehicle Radar SFCW Waveform Segmentation for Angular Resolution
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Solution Overview
Problem
Current vehicle radar systems face limitations in angular resolution, interference susceptibility, and hardware costs, particularly in achieving high-resolution azimuth and elevation measurements for autonomous driving applications.
Innovation Solution
A vehicle radar system utilizing a common frequency synthesizer, local oscillator, and mixer to generate SFCW ramps, enabling MIMO capabilities with narrowband OFDM symbols, reducing hardware costs and interference sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wideband OFDM radar is used to improve angular resolution, then measurement precision improves, but hardware cost increases due to wideband ADC requirements
Solution Approach 1:
The patent segments the wideband signal processing into multiple narrowband OFDM subcarriers. Each transmitter antenna transmits on a specific subset of subcarriers, and the receiver processes each subcarrier separately using narrowband FFT. This segmentation allows achieving wideband angular resolution through virtual antenna arrays without requiring a single wideband ADC, thereby reducing hardware complexity while maintaining measurement precision.
2Measurement precision
If MIMO is implemented with multiple transmitting antennas to improve angular resolution, then measurement precision improves, but device complexity increases due to signal separation requirements
Solution Approach 1:
The patent assigns different subsets of narrowband OFDM subcarriers to different transmitting antennas. This frequency-domain segmentation enables natural signal separation at the receiver without requiring complex time-domain switching or adjustment algorithms. Each receiver antenna receives a composite signal that can be decomposed by subcarrier frequency, simplifying the MIMO signal processing while improving angular resolution through virtual antenna array formation.
Solution Approach 2:
The patent moves the MIMO separation from the time domain to the frequency domain by assigning different frequency subsets (subcarriers) to different transmitting antennas. This dimensional change from temporal to spectral separation simplifies the receiver processing, as the virtual antenna array can be formed directly through frequency-domain decomposition without complex time-domain signal separation algorithms.
3Measurement precision
If FMCW chirp signals are used to improve range and velocity resolution, then measurement precision improves, but reliability decreases due to interference susceptibility
Solution Approach 1:
The patent employs periodic transmission of narrowband OFDM symbols with distinct subcarrier assignments for different transmitting antennas. This periodic structure with orthogonal frequency division multiplexing provides inherent immunity to interference from other radar systems, as the orthogonal subcarriers can be cleanly separated in the frequency domain. The periodic OFDM structure maintains range and velocity resolution while significantly reducing ghost target formation compared to continuous FMCW chirp signals.
Data Source
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AI summary
The present disclosure relates to vehicle radar system (3) comprising a transmitter section (7), a receiver section (8) and at least one control unit (33). The transmitter section (7) comprises a plurality of transmitter antenna devices (20a, 20b, 20c, 20d), and the vehicle radar system 3 is arranged to generate SFCW (Stepped Frequency Continuous Wave) ramps (34), each comprising a plurality of SFCW frequency steps (35). The radar system (3) is arranged to generate OFDM (Orthogonal Frequency Division Multiplexing) symbols (30) and to mix each OFDM symbol with a corresponding SFCW frequency step (35) of each SFCW ramp (34). Each OFDM symbol (30) comprises a plurality of subcarriers (31a, 31b, 31c, 31d) and each SFCW frequency step (35) comprises an OFDM symbol (30) such that a resulting stepped OFDM ramp waveform (32) is obtained, where the subcarriers (31a, 31b, 31c, 31d) of each OFDM symbol is transmitted by a corresponding transmitting antenna device (20a, 20b, 20c, 20d). The present disclosure also relates to a corresponding method.