Planar PCB Inductors for RF Heating Impedance Matching Networks
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Solution Overview
Problem
Conventional capacitive food heating systems using large helical inductors are costly, difficult to manufacture, and susceptible to changes in electrical characteristics due to vibration and temperature, leading to reduced efficiency and increased system size.
Innovation Solution
The use of a solid-state heating apparatus with a variable impedance matching network incorporating planar inductors, which can be adjusted during operation to improve matching between the amplifier arrangement and the cavity, reducing costs, manufacturing complexity, and enhancing robustness against vibration and temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large helical inductors are used in capacitive food heating systems, then the system can provide sufficient RF power, but the system becomes costly, difficult to manufacture, and susceptible to changes in electrical characteristics due to vibration and temperature
Solution Approach 1:
The patent replaces mechanical helical inductors with solid-state planar inductors implemented as PCB traces. This substitution eliminates the mechanical structure that is susceptible to vibration and temperature changes, providing a more reliable solution that maintains stable electrical characteristics while delivering the required RF power output
Solution Approach 2:
The patent changes the physical form and material parameters of the inductor from large-scale mechanical helical structures to planar conductive traces on PCB substrates. This parameter change reduces sensitivity to environmental factors while maintaining the necessary inductance values for RF power generation
2Power
If large helical inductors are used in capacitive food heating systems, then the system can provide sufficient RF power, but the manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent replaces complex mechanical inductor assemblies with planar inductors fabricated using standard PCB manufacturing processes. This substitution dramatically simplifies manufacturing by eliminating precision mechanical assembly while maintaining the required RF power output capability
Solution Approach 2:
The patent merges the inductor function directly into the PCB structure itself, eliminating separate inductor components and their associated mounting and wiring. This integration reduces manufacturing steps and assembly complexity while preserving the necessary electrical performance
3Power
If large helical inductors are used in capacitive food heating systems, then the system can provide sufficient RF power, but the system size increases
Solution Approach 1:
The patent transitions the inductor design from three-dimensional helical structures to two-dimensional planar traces on a PCB substrate. This dimensional change dramatically reduces the volume occupied by the inductor while maintaining the necessary inductance for RF power generation
Solution Approach 2:
The patent embeds the inductor function within the PCB structure itself, nesting the inductive elements within the existing circuit board layers and substrate. This nesting approach eliminates the need for separate inductor components and reduces overall system volume while maintaining RF power output
4Ease of operation
If conventional capacitive electrodes are used for food heating, then gentle warming can be provided, but the system lacks adaptability to changing load impedance
Solution Approach 1:
The patent introduces a variable impedance matching network that can dynamically adjust its parameters to match changing load impedance conditions. This dynamic adaptation allows the system to maintain optimal power transfer and gentle warming capability across varying food load conditions
Solution Approach 2:
The patent implements an impedance sensing and matching system that monitors load conditions and adjusts the matching network parameters accordingly. This feedback mechanism enables the system to adapt to changing load impedance while maintaining gentle and efficient heating operation
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 enables more efficient and robust heating systems by maintaining optimal RF power absorption despite changes in load impedance, reducing system size, and improving reliability.
Implementation Method 1
an impedance matching network that includes a first planar inductor, the first electrode being electrically coupled to the RF signal source through the planar inductor
Implementation Method 2
a radio frequency (RF) signal source that can produce an RF signal
Implementation Method 3
low power electromagnetic energy is supplied to the electrodes to provide gentle warming of the food load
Data Source
AI summary
A solid-state heating apparatus may be incorporated into stand-alone appliances or other systems. The heating apparatus may include an impedance matching network coupled between an electrode and a radio-frequency (RF) source. The impedance matching network may be a variable impedance matching network that can be adjusted during the heating operation. The impedance matching network may include planar inductors formed from patterned conductive layers disposed either side of a substrate.