MIMO Antenna Elevation Detection via Vertical Offset
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Solution Overview
Problem
Current automotive radar systems can only determine horizontal or azimuth angles to a target, lacking elevation angle detection, which is crucial for avoiding elevated objects, and increasing the number of antennas to improve elevation resolution increases system cost and introduces grating lobes.
Innovation Solution
A multiple input multiple output (MIMO) antenna configuration with vertically offset transmit antennas and a receive antenna formed of paired vertical arrays, allowing for elevation angle detection without increasing the number of antennas, and achieving half-wavelength spacing to minimize grating lobes through virtual synthetic arrays and digital beam-forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of transmit and receive antennas is increased to improve elevation resolution, then elevation angle detection capability is improved, but system cost increases
Solution Approach 1:
The patent applies dimensionality change by vertically offsetting the second transmit antenna from the first transmit antenna in the elevation dimension. This vertical separation creates a baseline for interferometric elevation measurement without requiring additional antenna arrays in the horizontal plane, thereby achieving elevation detection capability while avoiding the cost increase associated with adding more antennas.
Solution Approach 2:
The patent makes the existing transmit antennas serve multiple functions: the first transmit antenna transmits signals for both azimuth and elevation measurement, while the second transmit antenna (vertically offset) provides additional elevation measurement capability. This multi-functionality allows the system to achieve 3D spatial resolution using the same number of antennas, avoiding the cost increase that would result from adding more dedicated elevation measurement antennas.
2Reliability
If parallel arrays are used to increase antenna gain, then receive sensitivity is improved, but grating lobes are introduced causing variation in receive sensitivity
Solution Approach 1:
The patent changes the spacing parameter between antenna elements to be less than half a wavelength (specifically, the vertical offset between transmit antennas and the spacing between receive elements are both controlled to be < λ/2). This parameter change eliminates grating lobes while maintaining high receive sensitivity, as the sub-array spacing is optimized to prevent the formation of unwanted lobes that would cause sensitivity variations.
3Object-affected harmful factors
If sub-arrays are overlapped to reduce phase-center spacing, then grating lobe effects are reduced, but complex multi-layer feed structure is required
Solution Approach 1:
The patent extracts the elevation measurement function from the receive antenna array configuration and implements it instead through the vertical offset between transmit antennas. By taking out the elevation detection requirement from the receive side and placing it on the transmit side through vertical separation, the patent avoids the need for complex multi-layer feed structures that would be required to achieve sub-array overlap on the receive side.
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
Enables accurate elevation angle measurement and improved spatial resolution while maintaining cost-effectiveness by doubling the size of transmit and receive antennas with 50% overlap of sub-arrays, eliminating grating lobes and enhancing detection range without the need for additional channels or complex feed structures.
Implementation Method 1
a multiple input multiple output (MIMO) antenna for a radar system is provided. The antenna includes a receive antenna, a first transmit antenna, and a second transmit antenna. The receive antenna is configured to detect radar signals reflected by a target toward the receive antenna
Implementation Method 2
The second transmit antenna is vertically offset from the first transmit antenna by a vertical offset distance selected so an elevation angle to the target can be determined
Data Source
AI summary
A multiple input multiple output (MIMO) antenna for a radar system that includes a receive antenna, a first transmit antenna, and a second transmit antenna. The receive antenna is configured to detect radar signals reflected by a target toward the receive antenna. The first transmit antenna is formed of a first vertical array of radiator elements. The second transmit antenna is formed of a second vertical array of radiator elements distinct from the first vertical array. The second transmit antenna is vertically offset from the first transmit antenna by a vertical offset distance selected so an elevation angle to the target can be determined.