Spatial-Block CDM MIMO Radar for Mixed-Doppler Resolution
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Solution Overview
Problem
Existing MIMO radar systems face issues with Doppler aliasing and inadequate coverage due to mixed Doppler intervals, especially in automotive applications where targets are moving, leading to unreliable velocity measurements and angular ambiguity.
Innovation Solution
Implementing Spatial-Block Code Division Multiplexing (CDM) in MIMO waveforms, which uses more slots than channels to account for Doppler effects by applying specific phase shifts across channels, allowing for accurate detection of mixed Doppler intervals and enabling analog beamforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MIMO techniques are used to improve angular resolution, then virtual array size increases, but Doppler aliasing and mixed Doppler intervals occur
Solution Approach 1:
The patent segments the MIMO waveform into multiple spatial blocks, where each block contains multiple slots with different phase shift codes. This segmentation allows the system to separately process different Doppler intervals by assigning unique phase shift patterns to each slot, thereby resolving the mixed Doppler interval problem while maintaining high angular resolution through the virtual array.
Solution Approach 2:
The patent changes the phase shift parameter across different slots within each spatial block. By applying different phase shift codes to different slots, the system creates distinguishable signal patterns that allow resolution of multiple Doppler intervals. This parameter variation enables the system to maintain both high angular resolution and accurate Doppler measurement by preventing signal overlap in the Doppler domain.
2Measurement precision
If phase shifts are applied to resolve Doppler ambiguity, then velocity measurement accuracy improves, but system complexity increases
Solution Approach 1:
The patent applies phase shifts to specific slots within spatial blocks rather than to all channels simultaneously. By using a partial action approach where only certain slots receive specific phase shift codes, the system achieves Doppler resolution without requiring complex phase shift management across the entire MIMO array. The excessive action is limited to only the necessary slots, reducing overall system complexity.
Solution Approach 2:
The patent segments the phase shift application into discrete codes assigned to specific slots. This segmentation allows the system to manage phase shifts in a modular manner, where each slot has a predefined phase shift code that can be independently applied. This approach simplifies the control mechanism compared to continuous phase adjustment across all channels, while still achieving accurate velocity measurements.
3Reliability
If more slots than channels are used in spatial blocks, then mixed Doppler intervals are resolved, but processing time increases
Solution Approach 1:
The patent applies preliminary phase shift codes to different slots before final signal processing. By pre-configuring the phase shifts in each slot according to a predetermined codebook, the system eliminates the need for complex real-time phase adjustment. This preliminary action allows the processor to simply compare received signals against the predefined phase shift patterns, significantly reducing processing time while maintaining reliable Doppler interval resolution.
Solution Approach 2:
The patent uses a codebook approach where phase shift patterns are copied and reused across multiple slots. Instead of generating unique complex phase patterns for each slot, the system copies predefined phase shift codes from a codebook, which simplifies the processing requirements. This copying mechanism allows rapid signal processing while maintaining the ability to resolve mixed Doppler intervals through the structured repetition of phase patterns.
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
Resolves Doppler ambiguity and provides accurate radar data with higher sensitivity and resolution, enabling reliable velocity measurements and improved angular resolution in automotive radar systems.
Implementation Method 1
multiple phase shifters configured to introduce at least one phase shift in the EM signals or the reflections
Implementation Method 2
multiple receivers configured to obtain reflections of the EM signals from one or more objects
Implementation Method 3
apply a respective Fast-Fourier Transformation to the reflections to generate complex observations at each of the channels during each of the slots
Implementation Method 4
determine, based on the complex observations, whether a Doppler phase shift between two of the slots has multiple possible values
Data Source
AI summary
Techniques and systems are described for Spatial-Block Code Division Multiplexing (CDM) for MIMO waveforms. A radar system includes multiple transmitters, receivers, and phase shifters. Electromagnetic (EM) signals are transmitted and received in a Spatial-Block CDM scheme. Each spatial block has multiple slots outnumbering the channels. In addition, each slot corresponds to a specific code of phase shifts applied across the channels by the phase shifters during that slot. Fast-Fourier Transformations are applied to reflections of the EM signals to generate complex observations at each of the channels during each slot. Based on the observations, whether a Doppler phase shift exists between two slots can be determined based in part on whether the phase shift has one or multiple possible values. The techniques allow velocities to be resolved, despite a mixed-Doppler interval detected. Analog beamforming is supported; slots can be directed at particular angles to change gain in a field of view.