Orthogonally Polarized Printed Dipoles for High Isolation
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Solution Overview
Problem
Closely spaced omni-directional antennas on printed circuit boards face challenges with electromagnetic coupling, common mode coupling, and random coupling, which reduce isolation and affect gain characteristics, especially when near reflecting surfaces.
Innovation Solution
The antennas are orthogonally polarized to reduce electromagnetic coupling, with a balanced configuration and non-parallel ground structures to minimize circulating currents, and a rotatable design that uses a sounding signal to provide feedback for optimal placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple omni-directional antennas are closely positioned on a PCB board, then the device size is reduced and manufacturing cost is lowered, but electromagnetic coupling between antennas increases and isolation decreases
Solution Approach 1:
The patent employs asymmetric ground structures with non-parallel edges and irregular shapes rather than symmetric circular or square grounds. This asymmetry disrupts the symmetry of electromagnetic fields and circulating currents, reducing coupling between closely spaced antennas while maintaining compact PCB footprint
Solution Approach 2:
The patent transitions from planar ground structures to three-dimensional ground structures with varying heights and elevations. By creating ground structures at different vertical levels and angles, the patent reduces electromagnetic coupling in the third dimension while maintaining compact horizontal footprint
2Adaptability or versatility
If antennas are placed close to reflecting surfaces such as walls, then installation flexibility is improved, but multi-path coupling and random coupling increase
Solution Approach 1:
The patent employs rotatable antenna configurations that can be dynamically adjusted during installation. The antennas can be rotated to different orientations and positions, allowing users to optimize performance for different installation environments including proximity to reflecting surfaces like walls
Solution Approach 2:
The asymmetric ground structures and non-parallel edge configurations create unpredictable electromagnetic field patterns that are less susceptible to regular multi-path interference from reflecting surfaces, providing better adaptability to various installation environments
3Ease of manufacture
If symmetric ground structures are used, then manufacturing is simplified, but circulating currents and ground hot spots increase causing additional radiation and coupling
Solution Approach 1:
The patent deliberately uses asymmetric ground structures with non-parallel edges and irregular shapes instead of symmetric designs. This asymmetry breaks the symmetry of circulating current paths, preventing the formation of current loops and ground hot spots that would generate additional radiation and coupling, while remaining manufacturable using standard PCB fabrication processes
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 significantly increases antenna isolation, reduces unwanted radiation, and allows for easy user adjustment to minimize interference, maintaining good gain characteristics and ease of production.
Implementation Method 1
two closely spaced antennas are orthogonally polarized to increase antenna isolation and reduce electromagnetic coupling
Implementation Method 2
The interference cause by a signal emanating from one radiating antenna into the adjacent antenna can be cancelled by establishing a polarity or orientation of the adjacent antenna having a natural tendency to cancel the signal energy
Implementation Method 3
Common mode coupling occurs due to a shared ground on a printed circuit board. Voltage perturbations on the ground plane associated with generating and transmitting a signal from one antenna circuit couple into an adjacent antenna circuit
Implementation Method 4
a ground structure having various non-parallel and non-symmetrical shapes to reduce circulating currents and ground 'hot spots' that can act as additional radiators thereby tending to increase coupling
Implementation Method 5
various printed structures that 'choke' circulating ground currents by inducing opposite polarity currents that will generate electromagnetic (EM) fields with opposite, and thus canceling, polarities
Data Source
AI summary
An antenna configuration includes two closely spaced antennas each positioned so as to be orthogonally polarized with respect to the other. The antenna configuration increases antenna isolation and reduces electromagnetic coupling between donor side antenna and repeat side antenna. The antennas include printed dipoles connected to respective transceivers through respective baluns to balance the non-symmetrical portions of the antenna feed paths to reduce unwanted radiation therein. Printed features such as chokes and non-symmetrical and non-parallel structures are preferably included in the ground plane of a multi-layer circuit board to reduce or eliminate circulating ground currents.