Radar Antenna Lens Offset Ground Plane Refractive Index
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Solution Overview
Problem
Radar antenna designs face challenges in achieving high directivity and low signal losses while maintaining a compact size and low weight, especially when detecting small targets at long distances, due to the elongated shape of the lens element and the resulting dead zones and interference issues.
Innovation Solution
An antenna assembly with axially symmetric lens element and offset feed antennas on a conductive ground plane, utilizing an electromagnetic band gap (EBG) with a refractive index lower than the lens material to converge RF beams and reduce the antenna's physical length, thereby enhancing directivity and reducing leakage and weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the lens element is made elongated to achieve high directivity and low signal losses, then the antenna gain and detection accuracy are improved, but the antenna size and weight increase
Solution Approach 1:
The patent changes the refractive index parameter of the material in the volume between the lens and ground plane to be lower than the lens material. This parameter change enables the same directivity and gain performance with a more compact lens element design, reducing both size and weight while maintaining detection accuracy
Solution Approach 2:
The patent uses composite material structure with two different materials: the lens element made of high refractive index material and the volume between lens and ground plane filled with low refractive index material. This composite approach achieves high directivity with reduced overall dimensions and weight compared to using a single elongated lens
2Measurement precision
If the lens element is made elongated to achieve high directivity, then the RF beam focusing is improved, but power leakage and interference issues worsen
Solution Approach 1:
By changing the refractive index parameter of the material between the lens and ground plane to be lower than the lens material, the patent creates an electromagnetic band gap effect that confines the RF energy more effectively, reducing power leakage while maintaining beam focusing accuracy
Solution Approach 2:
The patent converts the potential harmful effect of RF energy spreading into the beneficial electromagnetic band gap effect by using the refractive index difference, which actually improves beam confinement and reduces leakage to surrounding areas
3Measurement precision
If the feed antenna is positioned at the phase center of the lens element, then the beam pattern is optimized, but dead zones and interference issues occur
Solution Approach 1:
The patent introduces asymmetry in the material distribution around the phase center by placing low refractive index material specifically in the volume between the lens and ground plane, while keeping the lens material high refractive index. This asymmetric material placement eliminates dead zones and interference while preserving beam pattern quality
Solution Approach 2:
The low refractive index material acts as an intermediary between the lens element and the ground plane, mediating the electromagnetic field distribution to eliminate dead zones and interference issues that would otherwise occur with symmetric positioning
4Measurement precision
If the antenna aperture size is increased to detect small targets at long distances, then the detection range and resolution are improved, but the physical dimensions and weight of the antenna increase
Solution Approach 1:
The patent changes the refractive index parameter to create an electromagnetic band gap effect, which allows achieving the same effective aperture and detection resolution with a more compact physical antenna structure, reducing length while maintaining performance
Solution Approach 2:
By using composite materials with different refractive indices, the patent achieves enhanced RF beam confinement and directionality, allowing for a more compact antenna design that maintains the effective aperture needed for detecting small targets at long distances
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 configuration enables high-resolution and accurate detection of targets at various distances with improved signal-to-noise ratio and reduced size and weight, addressing the limitations of previous designs by minimizing power leakage and interference.
Implementation Method 1
a volume between the back end of the lens element and the conductive ground plane comprises material that has a refractive index that is smaller than that of the lens element for converging the outbound and inbound RF beams
Implementation Method 2
an axially symmetric lens element arranged to collimate the transmitter beam obtained via a back end of the lens element for transmission from a front end of the lens element to a monitoring direction and to focus the receiver beam received at the front end of the lens element from the monitoring direction
Data Source
Figure 1A~1B
Figure 2~4
Figure 3A~3B
AI summary
According to an example embodiment, an antenna assembly (110) for a radar apparatus (100) is provided, the antenna assembly comprising: a first feed antenna (111a) arranged to transmit outbound radio waves of a transmitter beam (113a) based on a transmitted RF signal supplied thereto and a second feed antenna (111b) arranged to capture a received RF signal based on inbound radio waves of a receiver beam (113b) received thereat; and a lens element (112) arranged to collimate the transmitter beam (113a) obtained via a back end of the lens element (112) for transmission from a front end of the lens element (112) to a monitoring direction and to focus the receiver beam (113b) received at the front end of the lens element (112) from the monitoring direction for reception via the back end of the lens element (112) at the second feed antenna (111b), wherein the first and second feed antennas (111a, 111b) are disposed on a conductive ground plane (115) that is offset from the back end of the lens element (112) by a predefined distance (k) in direction of a center axis (A) of the lens element (112), and wherein a volume between the back end of the lens element (112) and the ground plane (115) comprises material that has a refractive index that is smaller than that of the lens element (112) for converging the outbound and inbound RF beams between the back end of the lens element (112) and the first and second feed antennas (111a, 111b).