Capacitively Grounded Cable Bracket for Low PIM Antennas

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Solution Overview

Problem

Designing omnidirectional broadband antennas with low Passive Intermodulation (PIM) levels is challenging, especially in the frequency range of 380 MHz to 520 MHz, where achieving reasonable PIM levels is difficult due to galvanic contact issues and high compression contact limitations.

Innovation Solution

The use of capacitively grounded cable brackets with non-ferromagnetic materials, proximity coupled grounding through dielectric adhesive tape, and a parasitic ring element to reduce PIM, avoiding direct galvanic contact and improving bandwidth and VSWR margins.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional galvanic contact grounding is used, then electrical connection is achieved, but PIM levels increase and bandwidth is limited

Engineering Contradiction:

ImprovePIM levelVSAvoidbandwidth

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

A dielectric adhesive tape is introduced as an intermediary between the cable bracket and ground plane, replacing direct galvanic contact with capacitive coupling. This mediator eliminates PIM-generating metal-to-metal contacts while maintaining electrical connection through capacitance, thereby reducing PIM levels and enabling broader frequency operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The grounding mechanism transitions from galvanic contact (zero impedance) to capacitive coupling (frequency-dependent impedance). This parameter change in the electrical connection characteristics allows the antenna to operate effectively across a wider bandwidth while maintaining low PIM performance, as the capacitive impedance increases with frequency rather than creating PIM at contact points.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If compression contact is increased to improve grounding, then electrical connection improves, but PIM levels increase due to high compression contact

Engineering Contradiction:

Improvegrounding connectionVSAvoidPIM

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The dielectric adhesive tape serves as a mediator that eliminates the need for high compression contact between metal surfaces. By providing capacitive coupling through the dielectric layer, the system achieves reliable grounding connection without the PIM-generating high compression metal-to-metal contacts.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical compression contact system is replaced with an electric field-based capacitive coupling system. Instead of relying on mechanical pressure to maintain electrical contact, the system uses the electric field across the dielectric adhesive tape to achieve grounding, thereby eliminating PIM generated by mechanical contact.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If direct galvanic contact is used for grounding, then electrical connection is established, but PIM is generated at contact points

Engineering Contradiction:

Improveelectrical connectionVSAvoidPIM at contact points

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The dielectric adhesive tape is positioned between the cable bracket and ground plane as an intermediary that prevents direct galvanic contact. It maintains electrical connection through capacitive coupling while eliminating the PIM-generating metal-to-metal contact points.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful galvanic contact interface is extracted and removed from the system. By eliminating the direct metal-to-metal contact between the cable bracket and ground plane, the source of PIM generation is removed, while the desired grounding function is preserved through capacitive coupling.

Inventive Principle:

Principle #2Taking out (Extraction)

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 achieves low PIM levels, improved bandwidth, and stable performance across the frequency range, particularly at lower frequencies, with enhanced radiation patterns and compact antenna design.

Implementation Method 1

capacitively grounded cable brackets

Methodology Applied

Scientific EffectCapacitive coupling: Capacitance

Implementation Method 2

proximity coupled grounding through dielectric adhesive tape

Methodology Applied

Scientific EffectDielectric insulation: Dielectric

Implementation Method 3

a parasitic ring element to reduce PIM, avoiding direct galvanic contact and improving bandwidth and VSWR margins

Methodology Applied

Scientific EffectParasitic element coupling: Electromagnetic Induction

Data Source

PatentUS9680215B2Omnidirectional broadband antennas including capacitively grounded cable brackets

Publication Date: 2017.06.13 TE CONNECTIVITY SOLUTIONS GMBH

AI summary

Disclosed are exemplary embodiments of omnidirectional broadband antennas and capacitively grounded cable brackets. In an exemplary embodiment, an omnidirectional broadband antenna generally includes a ground element, an antenna element, an annular element, and a cable bracket capacitively grounded to the ground element. The cable bracket is configured to allow soldering of a cable braid to the cable bracket for feeding the antenna element without direct galvanic contact between the cable braid and the ground element.