Multi-turn Coil Multiplex Circuit for NFC and Camera Focus
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Solution Overview
Problem
In electronic devices, particularly mobile devices, the integration of NFC antennas and cameras poses challenges due to space constraints and interference issues, where the NFC antenna's performance is affected by metal components, and there is a need for a solution that can efficiently switch between NFC and camera functions without compromising either performance.
Innovation Solution
A multi-turn-coil multiplex circuit that includes a switch with common, first, and second ports, allowing the multi-turn coil to function as either an NFC antenna or a focus-adjusting coil for the camera, depending on the presence or absence of a camera-control signal, with a processor configuring the circuit to adjust the coil's operation accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a magnetic material layer is attached below the NFC antenna to reduce eddy current interference, then the magnetic field concentration is improved, but the eddy current reduction on neighboring metal surfaces is compromised
Solution Approach 1:
A ground shielding layer is introduced as an intermediary component between the NFC antenna and the metal battery cover. This shielding layer acts as a mediator that redirects eddy currents away from the battery cover while preventing direct magnetic field interference with NFC components, thus resolving the contradiction between reducing eddy current harm and maintaining NFC reliability
Solution Approach 2:
The harmful eddy current paths are extracted and redirected to the ground shielding layer instead of allowing them to flow through the battery cover. By providing a dedicated path for eddy currents on the shielding layer, the interference to both the battery cover and NFC components is eliminated
2Shape
If the NFC antenna is placed within the device to improve appearance, then the external appearance is improved, but interference from metal components increases
Solution Approach 1:
The ground shielding layer serves as a protective intermediary between the internally placed NFC antenna and the metal battery cover. It allows the antenna to remain inside the device for aesthetic purposes while blocking harmful electromagnetic interference from the metal components
Solution Approach 2:
The ground shielding layer converts the potentially harmful electromagnetic fields and eddy currents generated by the NFC antenna near metal components into beneficial effects by containing and directing them through the shielding layer, thus protecting both the battery cover and NFC components while maintaining internal antenna placement
3Volume of moving object
If space for components is reduced to meet compact device requirements, then the device compactness is improved, but component integration complexity increases
Solution Approach 1:
The ground shielding layer is merged with the existing ground structure of the device, combining multiple functions (shielding, grounding, and structural support) into a single integrated component. This reduces the need for additional separate shielding components, thereby maintaining compactness while managing integration complexity
Solution Approach 2:
The ground shielding layer performs multiple functions simultaneously: it shields NFC components from metal interference, provides a ground reference for the NFC antenna, and redirects eddy currents away from sensitive components. This multi-functionality reduces the overall component count and simplifies the integrated design
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
Enables efficient operation of both NFC and camera functions by effectively switching the multi-turn coil's role, maintaining performance and reducing interference, thus addressing the space and functionality constraints in compact electronic devices.
Implementation Method 1
NFC operates with an electromagnetic wavelength of about 22 meters, and NFC operates within a short distance (e.g., 3-5 mm) for reading and writing information, the NFC antennae is typically made of a coil antenna
Implementation Method 2
With a camera-control signal received via the second port, the multi-turn coil functions as a focus-adjusting coil for a camera
Implementation Method 3
an NFC antenna may produce an eddy current on a metal surface when it is proximate to metal, and a magnetic field associated with the eddy current may weaken the magnetic field of the NFC antenna
Data Source
AI summary
Examples herein provide multi-turn coil multiplex circuits. The multi-turn coil multiplex circuits include a multi-turn coil, a switch, a near field communication (NFC) matching circuit, and a camera circuit. The switch includes a common port, a first port, and a second port. The multi-turn coil is connected to the common port. The NFC matching circuit is connected to the first port. The camera circuit is connected to the second port. Where a camera control signal is present, the connection with the second port is activated and the multi-turn coil can be used as a camera focusing coil associated with the camera circuit. Where no camera control signal is present, the connection with the first port is activated and the multi-turn coil can be used as an NFC antenna associated with the NFC matching circuit.