MIMO Radar Angle-Doppler Ambiguity via Sinusoidal Phase Center Motion
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Solution Overview
Problem
Existing radar systems face challenges in unambiguous discrimination of angle and Doppler signatures due to angle-Doppler coupling, leading to ghost targets and limited angular resolution, especially when multiple targets with different Doppler shifts are present.
Innovation Solution
The method employs a MIMO radar system with a non-linear phase center motion (PCM) using amplitude modulation (AM) for transmit signals, allowing for orthogonal angle-Doppler coding and reducing ambiguity by using sinusoidal phase center motion trajectories, which are processed using a filter bank to derive Doppler signatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If linear phase center motion is used for angle coding in MIMO radar, then angular resolution is improved, but angle-Doppler coupling occurs causing ghost targets
Solution Approach 1:
The patent applies sinusoidal (curved) phase center motion trajectories instead of linear trajectories. The phase center position is modulated sinusoidally in both in-phase and quadrature components, creating a curved motion path that enables orthogonal encoding of angle and Doppler information, thereby resolving the angle-Doppler coupling problem while maintaining angular resolution
Solution Approach 2:
The patent introduces a second dimension of phase center motion by independently modulating both in-phase and quadrature components of the phase center position. This two-dimensional sinusoidal modulation creates orthogonal trajectories that simultaneously encode angle and Doppler information without coupling, adding a degree of freedom to the traditional single-dimensional linear PCM approach
2Adaptability or versatility
If multiple targets with different Doppler shifts are present, then radar coverage is improved, but ghost targets appear due to angle-Doppler coupling
Solution Approach 1:
The patent applies different sinusoidal modulation parameters (frequency, amplitude, phase) to different transmit antenna elements, creating locally distinct phase center trajectories. This local differentiation ensures that each antenna element contributes uniquely to the overall signal, enabling the system to resolve and identify multiple targets with different Doppler shifts without generating ghost targets
3Measurement precision
If more antenna elements are used to improve angular resolution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces dynamic phase center motion through sinusoidal modulation of antenna element activation. Instead of using a large static antenna array, the system dynamically switches between antenna elements according to sinusoidal patterns, creating virtual phase center trajectories that achieve fine angular resolution with fewer physical antenna elements, thereby reducing system complexity
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 effectively reduces angle-Doppler ambiguity, improves target discrimination, and allows for the use of fewer antenna elements, enabling better separation of targets within the same range-Doppler bin.
Implementation Method 1
The method employs a MIMO radar system with a non-linear phase center motion (PCM) using amplitude modulation (AM) for transmit signals
Implementation Method 2
Analysis of this approach leads to the understanding that the TDM MIMO concept is effectively a linear phase center motion within the antenna structure. Due to the linear phase center motion (PCM), the target angle is coded into frequency. However, if there is an additional target motion which distorts the PCM, a strong angle-Doppler coupling appears
Data Source
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AI summary
A method for obtaining an angle-Doppler signature for a target using sparse arrays in multiple-input-multiple-output (MIMO) radar, the MIMO radar including a transmit antenna array, the transmit antenna array being at least one-dimensional (e.g. 2-D, 3-D or 4-D) and having a plurality of antenna elements. The method comprises generating transmit signals for transmission by the transmit antenna array, the transmit signals defining at least a first transmit trajectory (e.g. circular) of a phase center within the transmit antenna array, and transmitting the transmit signals using Amplitude Modulation on the transmit antenna array. The method further comprises receiving receive signals from the target, the receive signals resulting from the incidence of the transmit signals upon the target, and determining the angle-Doppler signature from the receive signals. The first transmit trajectory is such that, in operation, the phase center undergoes non-linear motion within the transmit antenna array.