Broadside Coupled Striplines for Galvanic Isolation in RF Devices
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Solution Overview
Problem
Existing electronic devices with external antennas face challenges in protecting against dangerous voltages without compromising performance or increasing size, as known insulation methods like optical couplers and galvanically isolated voltage converters are bulky and may attenuate signals across wide frequency bands.
Innovation Solution
The use of broadside coupled striplines for galvanic isolation between the transmission circuit and external antenna, utilizing conductive strips and a dielectric substrate to maintain signal integrity across a wide frequency range while providing insulation, with the area of facing faces and dielectric constant determining transmission performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical couplers and galvanically isolated voltage converters are used for insulation between transmission circuit and main circuit, then protection against dangerous voltages is improved, but device size and component count significantly increase
Solution Approach 1:
The patent extracts the insulation function from complex optical couplers and galvanically isolated voltage converters, implementing it through a simplified capacitive coupling structure between transmission circuit and main circuit, thereby reducing component count while maintaining protection against dangerous voltages
Solution Approach 2:
The patent changes the insulation implementation from active isolation components to a passive capacitive coupling approach, where the insulation properties are achieved through carefully selected capacitance values and physical layout, eliminating the need for bulky isolation components
2Reliability
If insulation is mounted between transmission circuit and external connection, then protection against dangerous voltages is improved, but signal transmission is attenuated across wide frequency band
Solution Approach 1:
The patent introduces a capacitive coupling structure as an intermediary between transmission circuit and main circuit, which allows RF signals to pass through while providing galvanic isolation, thus protecting against dangerous voltages without significant signal attenuation across the frequency band
Solution Approach 2:
The patent employs a composite structure combining conductive traces, dielectric layers, and capacitive elements to create an insulation solution that maintains signal integrity while providing voltage protection, avoiding the use of simple wound-wire transformers that would block wide frequency bands
3Reliability
If minimum distances are imposed between insulated parts, then protection against dangerous voltages is improved, but device size increases
Solution Approach 1:
The patent transitions from planar insulation layouts requiring large minimum distances to a three-dimensional capacitive coupling structure, where insulation is achieved through vertical layering and controlled impedance paths, thereby maintaining protection while reducing overall device area
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 isolates the antenna from dangerous voltages while allowing signal transmission across a wide frequency band, ensuring both safety and performance without significantly increasing the device's size or component count.
Implementation Method 1
The phenomenon of coupling of conductive strips by transverse electromagnetic wave is known in itself and referred to in the literature under different names such as 'broadside coupled striplines', 'broadside coupling', 'broadside coupled transmission line'... In the invention, this phenomenon is used to achieve galvanic isolation between the transmission circuit and the external connection.
Implementation Method 2
The dielectric constant of the substrate separating the conductive tracks determines the width of the coupler tracks.
Data Source
Figure 1~3
Figure 4~5
Figure 6
AI summary
An electronic device comprising a housing (1) containing a radio frequency signal transmission circuit (4) and an external connection (6) for connection to an external antenna (7). The transmission circuit is connected to the external connection by a coupler (5) comprising at least one pair of a first conductive track (8.1) and a second conductive track (8.2) extending on either side of a dielectric (9) with their principal faces at least partially facing each other to establish coupling by transverse electromagnetic waves. The first conductive track connects a first pole (11) of the transmission circuit to a second pole (12) of the transmission circuit, and the second conductive track connects a first pole (21) of the external connection to a second pole (22) of the external connection.