Wideband MIMO Antenna Array With Low Passive Intermodulation
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Solution Overview
Problem
Distributed antenna systems face challenges in maintaining low passive intermodulation (PIM) performance, especially in high gain applications with multiple frequency bands, due to increased complexity and opportunities for spurious frequency components, which degrade signal-to-noise ratios and data rates in densely populated public venues.
Innovation Solution
A wideband antenna array design featuring co-located two-conductor arrays with capacitively coupled regions and optimized conductor configurations to minimize conductor-to-conductor interfaces, using a ground plane without direct conductor contacts, which reduces PIM and maintains constant beamwidth across multiple frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple antenna elements are arrayed together to form high gain antennas, then antenna gain is improved, but the number of connection points increases providing more opportunities for PIM to be produced
Solution Approach 1:
The patent introduces a ground plane as an intermediary reference potential that eliminates the need for direct conductor-to-conductor connections. By using capacitive coupling between antenna elements and the ground plane, the design reduces the number of physical connection points where PIM could be generated, while still achieving the desired high gain through arraying multiple elements.
Solution Approach 2:
The patent replaces direct mechanical conductor-to-conductor connections with electromagnetic field-based capacitive coupling. This substitution eliminates physical contact points that would otherwise create PIM, while maintaining the electrical functionality needed for high gain array operation through the ground plane reference.
2Reliability
If conductor-to-conductor interfaces are used in antenna arrays, then electrical connections are established, but PIM products are generated at these interfaces
Solution Approach 1:
The ground plane serves as an intermediary that enables electrical connections without direct conductor-to-conductor contact. Capacitive coupling through the ground plane provides the necessary electrical connectivity while eliminating the metal-to-metal interfaces where PIM would otherwise be generated.
Solution Approach 2:
The patent extracts and eliminates the harmful conductor-to-conductor connection points from the antenna array design. By removing these direct contact interfaces and replacing them with capacitive coupling to a ground plane, the design maintains electrical functionality while taking out the source of PIM generation.
3Shape
If full 2D arrays are implemented to achieve narrow beamwidth in both principal planes, then antenna directivity is improved, but complexity of the arraying process and PIM performance maintenance increases
Solution Approach 1:
The ground plane serves multiple functions simultaneously: it provides the reference potential for capacitive coupling, acts as a common ground for all antenna elements, and eliminates the need for complex inter-element connections. This multi-functionality simplifies the arraying process while enabling full 2D array configurations for narrow beamwidth in both planes.
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 solution effectively reduces PIM products, maintaining low noise floors and signal quality, even in high-density user environments, by eliminating conductor-to-conductor contacts and optimizing impedance matching, thereby ensuring reliable multi-band operation with consistent performance across various frequency ranges.
Implementation Method 1
A portion of the first conductor is positioned in close proximity to the ground plane to form a capacitively coupled region when placed in proximity to the ground plane
Data Source
AI summary
A wideband array capable of MIMO operation and possessing low Passive Intermodulation (PIM) characteristics is described for use in Distributed Antenna Systems (DAS) and other applications which require low PIM levels. The antenna can be configured to provide a narrow radiated beamwidth across multiple frequency bands and can support high power levels. A novel antenna design is implemented to populate the array configuration, wherein both fed and counterpoise elements are isolated from the ground plane to provide low PIM performance, while maintaining constant beamwidth across wide frequency ranges.