Cavity Filter PCB Cover for Intermodulation Reduction
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Solution Overview
Problem
Conventional high-frequency cavity filters face intermodulation problems due to inadequate mechanical and electrical connections between the cover and housing, and they are costly to produce, especially when using separate plastic covers.
Innovation Solution
A cavity filter design utilizing a printed circuit board cover with an electrically conductive copper layer, which is softer and more flexible than traditional metal covers, ensuring a 100% high-frequency-proof connection and allowing for cost savings by eliminating the need for separate plastic covers. The printed circuit board cover is fixed to the housing with screws, providing a reproducible and secure electrical connection, and a tuning sleeve with an inner thread is inserted into the board to adjust the resonant frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal housing cover is used for the cavity filter, then good electrical contact and high-frequency-proof fitting are achieved, but intermodulation problems occur due to inadequate mechanical and electrical connections
Solution Approach 1:
The patent applies composite materials by combining a plastic housing cover with a metallic coating layer. The plastic base provides mechanical flexibility and damping properties, while the metallic coating (such as aluminum or silver) provides electrical conductivity and high-frequency shielding. This composite structure eliminates intermodulation problems by ensuring reliable mechanical and electrical connections without the harmful effects of pure metal constructions.
2Ease of manufacture
If a plastic housing cover is used for the cavity filter, then cost is reduced and mechanical flexibility is improved, but electrical conductivity and high-frequency-proof connection are insufficient
Solution Approach 1:
The patent uses a composite material structure where a plastic housing cover is coated with a metallic layer. The plastic provides cost-effectiveness and mechanical flexibility, while the metallic coating (aluminum, silver, or other conductive materials) ensures adequate electrical conductivity and high-frequency-proof connection. This combination resolves the contradiction by integrating the advantages of both materials.
Solution Approach 2:
The patent changes the electrical parameter of the plastic housing cover by applying a conductive coating layer. This transformation modifies the surface properties of the plastic to achieve the required electrical conductivity and high-frequency shielding performance, while maintaining the cost and mechanical advantages of the plastic base material.
3Strength
If screws are used to fix the housing cover, then a firm mechanical connection is achieved, but electrical connection reproducibility is insufficient
Solution Approach 1:
The patent combines the mechanical fastening capability of screws with the electrical conductivity of the metallic coating on the plastic housing cover. The screws provide firm mechanical connection, while the continuous metallic coating ensures reproducible electrical connection across the entire contact surface, eliminating dependence on point-contact reliability.
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 design significantly improves passive intermodulation properties and electrical connections while reducing costs, ensuring a reliable and tunable high-frequency filter with improved mechanical and electrical performance.
Implementation Method 1
On the inside of the printed circuit board cover, facing the housing interior, there is provided an electrically conductive layer, preferably in the form of a copper layer
Implementation Method 2
ensuring a 100% high-frequency-proof connection
Implementation Method 3
a tuning sleeve with an inner thread is inserted into the board to adjust the resonant frequency
Data Source
AI summary
The invention relates to an improved HF cavity filter characterized by the following features: the housing cover (17) is made of a circuit board (21); the at least one additional hole (29) is made in the circuit board (21), in which a tuning bushing soldered at the outer circumference to an electrically conductive layer (25) on the circuit board is inserted; the tuning element (37) can be threaded to a varying depth into the tuning bushing (31); at least one electrically conductive structure is implemented on the circuit board (21); and the dielectric conductive structure comprises at least one conductor and/or at least one SMT component and/or at least one HF overcoupling device.