MIMO Radar Antenna Array Doppler Ambiguity Resolution
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Solution Overview
Problem
MIMO radar systems face challenges in accurately determining relative velocities and location angles with high uniqueness and resolution due to ambiguity in Doppler measurements, especially when operating below the Nyquist limit.
Innovation Solution
The system employs a transmitter and receiver array configuration where the antenna distances are above the Nyquist limit for unambiguous angle measurements, with a control and evaluation unit that transmits signals in varying multiplex schemes across measuring blocks, performs Doppler estimation and correction, and refines angle and Doppler estimations using phase information from multiple antennas, extending the multiplex cycle duration for improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If antenna distances are increased to improve angle resolution, then angle measurement precision is improved, but Doppler measurement ambiguity increases due to operating below the Nyquist limit
Solution Approach 1:
The measurement process is segmented into multiple measuring blocks within a multiplex cycle, with different antenna subsets or configurations used in each block. This segmentation allows the system to collect diverse phase information that can be combined to resolve Doppler ambiguities while maintaining the large antenna distances needed for high angle resolution.
Solution Approach 2:
The system employs periodic multiplex cycles that repeat after a defined period, with each cycle containing multiple measuring blocks. This periodic structure enables the system to accumulate phase information over time and use the known periodicity to disambiguate Doppler measurements while maintaining the antenna geometry required for high angle resolution.
2Device complexity
If antenna distances are increased to reduce the number of antennas needed for high angle resolution, then device complexity is reduced, but measurement time increases due to the need for multiple measuring blocks
Solution Approach 1:
The system maintains continuous measurement activity by overlapping or back-to-back arranging multiple measuring blocks within the multiplex cycle. This continuous operation minimizes idle time between measurements while still collecting the necessary phase information from different antenna configurations to resolve Doppler ambiguities.
Solution Approach 2:
The system uses a partial set of antennas in each measuring block rather than all antennas simultaneously, allowing for simpler per-block processing. By strategically selecting which antennas to use in each block and combining the results, the system achieves the required measurement accuracy without requiring the full antenna array to be active at once, reducing overall measurement time.
3Reliability
If multiple measuring blocks are used to resolve Doppler ambiguity, then reliability of velocity measurement is improved, but computing time increases due to refined estimation across blocks
Solution Approach 1:
The system performs preliminary Doppler estimation in each measuring block before the final refinement stage. These preliminary estimates are used to guide the subsequent refinement process, allowing the system to focus computational resources on resolving ambiguities around the most likely velocity values rather than performing exhaustive searches across the entire velocity range.
Solution Approach 2:
The system uses feedback from the phase information and intermediate estimation results of previous measuring blocks to guide the refinement process in subsequent blocks. This feedback mechanism allows the system to iteratively improve velocity estimates with each block, converging on the correct unambiguous value more efficiently than independent processing of each block would allow.
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 allows for high-resolution and unambiguous Doppler measurements, enhancing the accuracy of relative velocity determination and signal quality, while maintaining a given complexity and computing time, thereby improving the overall accuracy of measured results.
Implementation Method 1
Radar systems are used to an increasing extent in motor vehicles for detecting the vehicle surroundings and provide pieces of information about distances, relative velocities and direction angles of located objects
Implementation Method 2
the results of the relative velocity measurements, though in fact high resolution, are ambiguous. To resolve this ambiguity, the provided method capitalizes on the fact that the demultiplex methods, with which signals that are able to be unambiguously assigned to the individual transmitting antennas of the transmitter array are reconstructed again from the received signals, provide results of high quality only if the phase offset caused by the Doppler effect is appropriately corrected
Data Source
AI summary
A MIMO radar system. The system includes a transmitter array, a receiver array, the antenna distances in one of the transmitter and receiver arrays being below the Nyquist limit for unambiguous angle measurements, but the antenna distances in the combination of the transmitter and receiver arrays being above this Nyquist limit. The system further includes a control and evaluation unit, which is designed to transmit via the transmitter array a sequence of transmit signals, which are subdivided into multiple measuring blocks, in each of multiple repeatedly implemented measuring cycles, a uniform multiplex scheme being applied within each measuring block and the multiplex schemes varying from measuring block to measuring block, carry out a Doppler estimation and an angle estimation based on the receiver array, carry out a Doppler correction of the received signals based on the Doppler estimations, demultiplex the Doppler-corrected signals, and refine the Doppler estimations and angle estimations.