Ring-Like Magnetic Yoke for Uniform DC Field in Nonreciprocal Circuits
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Solution Overview
Problem
Existing nonreciprocal circuit devices, such as isolators and circulators, face issues with maintaining a uniform DC magnetic field and preventing electromagnetic wave leakage due to the dispersion of the DC magnetic field and deterioration of magnetic field strength caused by the magnetic yoke's design.
Innovation Solution
A nonreciprocal circuit device with a ring-like magnetic yoke surrounding the ferrite core and permanent magnets, combined with a shield conductor made of nonmagnetic metal conductive material, ensures a uniform and stable DC magnetic field application while preventing external magnetic influences and electromagnetic wave leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the magnetic yoke surrounds the ferrite core and permanent magnets from above and four sides, then the magnetic circuit is complete, but the DC magnetic field disperses on the upper surface causing non-uniform field distribution
Solution Approach 1:
The magnetic yoke is segmented into a ring-like shape with a through-hole, dividing the continuous structure into distinct regions. This segmentation allows the DC magnetic field to be confined to specific areas (ferrite core and permanent magnets) while preventing dispersion on the upper surface, thereby achieving uniform field distribution without compromising the magnetic circuit's completeness
Solution Approach 2:
The magnetic yoke structure is designed with different properties in different regions: the ring-like shape provides magnetic shielding and field confinement in the horizontal plane, while the through-hole creates a magnetic field-free zone on the upper surface. This local differentiation of magnetic properties enables uniform DC magnetic field application to the ferrite core without the adverse effects of field dispersion
2Ease of operation
If a hole is provided at the center portion of the upper surface of the magnetic yoke, then access is improved, but the magnetic field strength deteriorates and uniformity is weakened
Solution Approach 1:
A nonmagnetic metal conductive sheet is introduced as an intermediary component covering the through-hole of the magnetic yoke. This conductive sheet acts as a magnetic shield that prevents leakage of the DC magnetic field through the hole while allowing physical access to the ferrite core. The nonmagnetic property ensures it does not interfere with the magnetic circuit, and the conductive property provides electromagnetic shielding, thus maintaining both accessibility and magnetic field strength
3Ease of operation
If the hole includes the entire planar projection area of the ferrite core, then access is maximized, but high-frequency magnetic field leakage increases considerably
Solution Approach 1:
The nonmagnetic metal conductive sheet serves as an intermediary that selectively blocks different types of magnetic fields. It allows DC magnetic field lines to pass through to the ferrite core while blocking high-frequency magnetic field leakage. The conductive nature of the sheet provides electromagnetic shielding against high-frequency radiation, and its nonmagnetic property ensures it does not disrupt the DC magnetic circuit
Solution Approach 2:
The properties of the covering material are specifically selected: nonmagnetic to avoid interfering with the DC magnetic field, and conductive to provide electromagnetic shielding against high-frequency radiation. These parameter changes in material selection enable the cover to simultaneously maintain DC field strength and prevent high-frequency leakage
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 configuration maintains stable electric characteristics, reduces insertion loss, and prevents unnecessary radiation of electromagnetic waves, enabling efficient operation of the nonreciprocal circuit device.
Implementation Method 1
permanent magnets, a ferrite core to which a DC magnetic field is applied from the permanent magnets
Implementation Method 2
The magnetic yoke has a ring-like shape so as to surround the ferrite core and the permanent magnets with surfaces thereof that are substantially perpendicular to the surface of the circuit substrate
Implementation Method 3
A shield conductor made of a nonmagnetic metal conductive material is disposed directly above the ferrite core and the permanent magnets to cover an opening portion of the magnetic yoke
Implementation Method 4
since the shield conductor is made of a nonmagnetic metal conductive material, the DC magnetic field is not changed or is not deteriorated by the shield conductor
Data Source
AI summary
A nonreciprocal circuit device includes permanent magnets, a ferrite core to which a DC magnetic field is applied from the permanent magnets, center electrodes disposed on the ferrite core, a circuit substrate, a magnetic yoke, and an electromagnetic shield plate. The ferrite core and the permanent magnets are longitudinally disposed on the circuit substrate, and the yoke has a ring-like shape so as to surround side surfaces of the ferrite core and the permanent magnets. The electromagnetic shield plate includes a dielectric substrate and a shield conductor made of a nonmagnetic metal conductive film on the dielectric substrate. The shield conductor includes opening areas having slits.