PMCW MIMO Radar Velocity-Labeled Multiplexing
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Solution Overview
Problem
Conventional MIMO radar sensor systems face challenges such as motion-induced phase errors, increased measurement time, velocity ambiguity, and high hardware complexity due to various multiplexing schemes like TDM, FDM, and CDM, which affect their performance in autonomous vehicles.
Innovation Solution
A phase modulated continuous wave (PMCW) MIMO radar system with velocity-labeled multiplexing (VLM) is introduced, where multiple transmitting antennas transmit simultaneously with phase shifts over a pulse repetition interval, allowing for efficient computation of range, velocity, and direction of objects, and reducing processing resources by forming a virtual receiver array and applying beamforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Time Division Multiplexing (TDM) is used to provide orthogonal transmit signals, then hardware complexity is reduced, but motion-induced phase error increases and measurement time increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the phase shift values for each transmitter in a lookup table before the radar measurement process. This allows the system to compensate for motion-induced phase errors without requiring complex real-time calculations, thus maintaining low hardware complexity while improving measurement precision.
Solution Approach 2:
The patent changes the parameter approach by transforming the phase modulation from continuous to discrete phase shift values. Each transmitter is assigned a specific discrete phase shift based on its position, which simplifies the hardware requirements while enabling precise velocity measurement through the resulting phase differences in the received signals.
2Device complexity
If Time Division Multiplexing (TDM) is used to provide orthogonal transmit signals, then hardware complexity is reduced, but velocity ambiguity increases
Solution Approach 1:
The system pre-establishes a mapping between transmitter positions and phase shift values before measurement. This preliminary configuration allows the receiver to unambiguously identify which transmitter generated each signal component, eliminating velocity ambiguity that would otherwise occur with sequential TDM operation.
Solution Approach 2:
The patent resolves velocity ambiguity by adding a spatial dimension through MIMO configuration. Multiple transmitters operate simultaneously at different positions, creating a two-dimensional virtual array that provides additional spatial information to disambiguate velocity measurements that would be ambiguous in one-dimensional TDM systems.
3Measurement precision
If Frequency Division Multiplexing (FDM) is used to provide orthogonal transmit signals, then velocity measurement precision is improved, but receiver bandwidth increases and hardware complexity increases
Solution Approach 1:
The patent changes the modulation parameter from frequency-based to phase-based multiplexing. Instead of assigning different frequency bands to transmitters (which requires wide receiver bandwidth and complex hardware), the system uses discrete phase shift values, significantly reducing hardware complexity while maintaining velocity measurement precision through phase difference analysis.
4Device complexity
If Code Division Multiplexing (CDM) is used to provide orthogonal transmit signals, then orthogonal transmit signals are achieved, but computational intensity increases and velocity spectrum sidelobe levels increase
Solution Approach 1:
The patent simplifies the multiplexing parameter from complex spreading codes to simple discrete phase shift values. This parameter change reduces the computational burden significantly, as the receiver only needs to perform simple phase difference measurements rather than computationally intensive cross-correlation operations required for CDM signal processing.
Solution Approach 2:
The patent extracts the essential orthogonality function from complex CDM spreading codes and implements it through simpler phase shift assignments. This extraction maintains the orthogonal separation of transmitter signals while eliminating the computational complexity and high sidelobe levels associated with full CDM implementation.
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 reduces processing complexity and ambiguity, enhances signal-to-noise ratio, and provides accurate velocity measurement with reduced data processing, improving the efficiency and accuracy of radar systems in autonomous vehicles.
Implementation Method 1
the transmitting antennas simultaneously transmit radar signals based on the same modulation signal. Per transmitting antenna, the transmissions are modulated with respective phase offsets on a per pulse repetition interval (PRI) basis
Implementation Method 2
Receiver channels of the radar system receive echo signals caused by the transmitted signals reflecting from objects
Implementation Method 3
the energy of the echo signal is distributed and ordered into distinguishable positions in the velocity spectrum... the energy distribution in the velocity spectrum is determined by the actual velocity of a detected object
Data Source
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AI summary
A phase modulated continuous wave (PMCW) multiple input multiple output (MIMO) radar system is described herein. The radar system is configured to compute range, velocity, and direction of arrival angle of objects relative to the radar system. The radar system includes several transmitting antennas and several receiving antennas, where selected transmitting antennas simultaneously transmit radar signals based on the same modulation signal. Per transmitting antenna, the transmissions are modulated with respective phase offsets on a per pulse repetition interval (PRI) basis. Hence, a coupling between phase shifts over PRI and transmitter positions is established. Effectively, then, each transmitting antenna is labeled with a velocity offset that corresponds to the phase rate of change assigned to the transmitting antenna. This approach is referred to herein as velocity-labeled multiplexing (VLM).