Shielded Flexible Circuits for EMI Reduction
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Solution Overview
Problem
Mobile communication devices face electromagnetic interference (EMI) issues due to high-frequency data transmissions, leading to signal distortion and loss, especially in devices with flexible conductors across rotating hinges or mechanical connectors, necessitating shielding against EMI for reliable high-data-rate transmissions.
Innovation Solution
The development of shielded flexible circuits with a first and second conductor on a flexible support member, where the conductors are electrically insulated and surrounded by co-axially disposed conductive materials to confine electromagnetic fields, effectively shielding against EMI, enabling data transmission rates up to 4 GHz without significant signal loss or distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexible conductors are used to transmit data across rotating hinges or mechanical connectors, then flexibility and adaptability are improved, but electromagnetic interference and signal distortion increase
Solution Approach 1:
The patent implements a coaxial structure where an inner conductor is nested within an outer conductor, both on the flexible circuit board. This nested arrangement creates a shielded transmission line that confines electromagnetic fields between the conductors, preventing EMI while maintaining flexibility for use in rotating hinges and mechanical connectors.
Solution Approach 2:
The outer conductor acts as an intermediary shielding element between the inner conductor and the external environment. This intermediary structure blocks electromagnetic interference from reaching the inner conductor while allowing the flexible circuit to maintain its mechanical flexibility and adaptability in challenging geometries.
2Productivity
If data transmission rates are increased to support high-quality audio and video, then productivity is improved, but electromagnetic interference and signal loss worsen
Solution Approach 1:
The coaxial nested structure enables high data transmission rates by confining electromagnetic fields between the inner and outer conductors. This shielding arrangement prevents EMI-induced signal distortion even at frequencies up to 4 GHz, supporting high-quality audio and video transmissions while maintaining signal integrity.
Solution Approach 2:
The patent employs a cost-effective flexible circuit board with integrated coaxial shielding that can be mass-produced for mobile devices. This affordable solution provides EMI protection without requiring expensive rigid shielded cables, making high-rate data transmission feasible in consumer electronics.
3Area of stationary object
If conductors are placed in close proximity to reduce space, then device compactness is improved, but electromagnetic interference between conductors increases
Solution Approach 1:
The nested coaxial structure allows conductors to be placed in close proximity while minimizing EMI. The outer conductor surrounds the inner conductor, creating a compact arrangement where electromagnetic fields are confined to the space between the conductors, preventing interference even at high frequencies and small separations.
Solution Approach 2:
The shielding structure provides localized electromagnetic protection exactly where needed - between the closely spaced conductors. The outer conductor creates a local shield that confines fields to the transmission path while allowing other components to be placed nearby without interference, optimizing space utilization.
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 shielded flexible circuits effectively prevent EMI, allowing mobile communication devices to transmit high-data-rate signals, such as streaming video, without substantial signal loss or distortion, even at close conductor spacings, enhancing the performance of flip phones and slider phones.
Implementation Method 1
A second conductive material co-axially disposed around the first conductor, the second conductive material electrically insulated from the first conductor; and a third conductive material co-axially disposed around the second conductor, the third conductive material electrically insulated from the second conductor
Data Source
AI summary
A shielded flexible cable having a plurality of shielded electronic circuits in close proximity to one another such that signals transmitted on one of said plurality of shielded electronic circuits do not substantially interfere with signals transmitted on the other of said plurality of electronic circuits comprising a polyimide support member supporting a plurality of etched copper traces on a first side of said polyimide support member and a copper layer on a second side of said polyimide support member; said polyimide support member flexible along at least one axis; said plurality of etched copper traces and said copper layer substantially as flexible as said polyimide support member; a silver based material, including, for example, silver ink or silver film, surrounding a portion of each of said plurality of copper traces along substantially the entire length of each of said plurality of copper traces; said silver based material in electrical communication with (i) said copper layer via discontinuities in said polyimide support member, and (ii) a grounded terminal; an electrically insulative material in substantial proximity to each of said plurality of copper traces so as to electrically insulate each of said plurality of copper traces from (i) the other said plurality of copper traces, and (ii) said silver based material; said electrically insulative material physically located between said silver based material and each of said plurality of copper traces; a first dielectric layer covering substantially the entire exposed surface of said silver based material; and a second dielectric layer covering substantially the entire exposed surface of said copper layer.