3D Microstrip Feeding Network for Dual Polarized Patch Antenna
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Solution Overview
Problem
Conventional microstrip line feeding methods for patch antenna arrays face challenges in increasing bandwidth and reducing side lobes, leading to reduced antenna gain due to increased surface wave and spurious feed radiation, especially when constrained by physical size limitations in fixed wireless and indoor coverage applications.
Innovation Solution
A 3D microstrip line feeding network using air as a dielectric, with a reduced width and vertical matching impedance bridges, is employed to maintain impedance matching while reducing side lobes and increasing antenna gain, allowing for a compact and ultra-thin dual polarized patch antenna array.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the RF PCB substrate thickness is increased to increase bandwidth, then bandwidth is improved, but surface wave and spurious feed radiation increase causing reduced antenna gain
Solution Approach 1:
The patent transitions from a conventional 2D microstrip line feeding network etched on an RF PCB to a 3D feeding network structure. The microstrip lines are arranged in three dimensions with vertical spacing, allowing the network to achieve the required electrical length and impedance transformation without increasing the substrate thickness. This dimensional change enables bandwidth extension while avoiding the generation of surface waves and spurious radiation that occur in thick-substrate 2D configurations.
2Object-generated harmful factors
If air dielectric is used to eliminate surface wave, then radiation pattern is improved, but patch element size and strip line width increase
Solution Approach 1:
By configuring the microstrip lines in three dimensions with vertical separation, the patent achieves the required electrical path length and impedance transformation ratios without increasing the horizontal width of the strip lines or the size of patch elements. The vertical dimension provides additional space for the microstrip lines to achieve their electrical length, thereby maintaining compact horizontal dimensions while using air dielectric to eliminate surface waves.
Solution Approach 2:
The patent changes the geometric parameters of the microstrip lines, specifically the widths and spacing, to achieve the desired characteristic impedances (50 ohms, 70.7 ohms, 100 ohms) in the 3D configuration. By adjusting these parameters in the three-dimensional arrangement, the patent achieves impedance matching and transformation without requiring excessive line widths or patch element sizes, thus maintaining compact dimensions while using air dielectric.
3Reliability
If microstrip line width is increased for impedance matching, then impedance matching is improved, but insertion loss and side lobe level increase
Solution Approach 1:
The patent uses three-dimensional arrangement of microstrip lines to achieve impedance matching and transformation without requiring excessive line widths. The vertical spacing and three-dimensional path allow the microstrip lines to achieve the required electrical length and impedance transformation ratios while maintaining narrower widths, thereby reducing insertion loss and side lobe levels while preserving impedance matching performance.
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
The 3D microstrip line feeding network effectively reduces side lobes and increases antenna gain, enabling a compact and inexpensive high-gain patch antenna array that fits within physical constraints, while maintaining isolation between polarizations and improving radiation patterns.
Implementation Method 1
A plurality of patch antenna elements and a ground plane form a patch antenna array. A three-dimensional (3D) microstrip line feeding network having two layers and using air as a dielectric feeds the patch antenna elements.
Implementation Method 2
increasing the RF PCB substrate thickness to increase the bandwidth causes surface wave and spurious feed radiation to increase. This limits the bandwidth and reduces the array antenna gain because of the increase of unwanted side lobes levels.
Data Source
AI summary
An antenna assembly for transmitting or receiving radio waves, comprising: at least one patch antenna element; a three-dimensional (3D) microstrip line feeding network configured to feed the at least one patch antenna element for operation in dual polarisation, the 3D microstrip line feeding network comprising an upper layer and a lower layer; and a ground plane; wherein a first air gap is provided between the at least one patch antenna element and the ground plane, a second air gap is provided between the upper layer of the 3D microstrip line feeding network and the ground plane, and a third air gap is provided between the lower layer of the 3D microstrip line feeding network and the ground plane.