Coaxial Feed Cable Grounding for PIM Suppression
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Solution Overview
Problem
Wireless communication systems face interference due to passive intermodulation products (PIM) generated by non-linear interactions between RF signals and coaxial feed cables, which degrade signal quality and data rates in Wi-Fi and cellular networks.
Innovation Solution
The implementation of antenna systems with coaxial feed cables that include direct galvanic connections between the outer conductor and the RF ground plane, specifically through openings in the cable jacket located at quarter-wavelength distances from the ends of the feed cables, to suppress intermodulation products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coaxial feed cables are used to connect radiating elements, then RF signal transmission is enabled, but passive intermodulation products are generated that degrade signal quality
Solution Approach 1:
The patent applies equipotentiality by connecting the outer conductor of the coaxial feed cable to the RF ground plane through direct galvanic connections at multiple points along the cable length. This ensures the outer conductor remains at RF ground potential, eliminating voltage differences that cause non-linear interactions and intermodulation product generation between RF signals and the cable structure.
Solution Approach 2:
The patent segments the grounding connection by providing multiple separate galvanic connection points along the length of the coaxial feed cable rather than a single ground connection. This segmentation ensures that the entire outer conductor is maintained at RF ground potential, preventing localized non-linear interactions that would generate intermodulation products.
2Object-generated harmful factors
If direct galvanic connections are added between outer conductor and RF ground plane, then intermodulation products are suppressed, but device complexity increases
Solution Approach 1:
The patent merges the grounding function with the existing coaxial cable structure by integrating direct galvanic connections into the cable assembly. The grounding connections are combined with the cable jacket openings and outer conductor structure, creating a unified solution that suppresses PIM without requiring separate external grounding components or complex additional structures.
Solution Approach 2:
The coaxial feed cable structure is modified to provide its own grounding connections through openings in the cable jacket that expose the outer conductor for direct galvanic connection to the RF ground plane. The cable itself serves the dual function of RF signal transmission and PIM suppression through its modified structure, eliminating the need for separate grounding systems.
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 solution effectively reduces PIM distortion and RF noise, enhancing the performance of wireless radio units by setting the potential of the outer conductors at RF ground, thereby improving signal quality and compliance with network standards.
Implementation Method 1
The cable jacket includes a first opening that exposes a first portion of the outer conductor, and the first portion of the outer conductor is galvanically connected to the RF ground plane
Data Source
AI summary
Antenna systems for access points and other wireless radio units include an RF ground plane, a radiating element mounted in front of the RF ground plane, and a coaxial feed cable coupled to the radiating element. The cable jacket includes a first opening that exposes a first portion of an outer conductor of the coaxial feed cable so that the cable jacket is on either side of the first opening along a longitudinal direction of the coaxial feed cable. The first portion of the outer conductor is galvanically connected to the RF ground plane via a first direct galvanic connection.