RF Blocking Filter with Capacitive Segmentation
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Solution Overview
Problem
Conventional radio-frequency blocking filters of coaxial construction require complex and lengthy connection lines, leading to large and costly filter designs, especially at low frequencies, due to the need for long signal lines to achieve high attenuation and frequency blocking.
Innovation Solution
Incorporating galvanic separation points in the signal line, which are capacitively coupled to resonators, allowing for a phase shift that effectively shortens the connection line, enabling a compact and cost-effective design by using coupling capacitors to connect resonators and reduce the length of the signal line between them.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If long signal lines are used to achieve high attenuation and frequency blocking at low frequencies, then the blocking performance is improved, but the filter size and complexity increase significantly
Solution Approach 1:
The signal line is divided into multiple segments with galvanic separations between them. Each segment is capacitively coupled to resonators, allowing the long signal line to be broken into manageable sections that can be implemented in a compact arrangement rather than requiring a single long continuous line
Solution Approach 2:
Capacitive coupling elements are introduced as intermediaries between the resonators and the signal line segments. These capacitors enable the necessary coupling and phase shift without requiring long physical connection lines, thus achieving the blocking function with reduced complexity
2Reliability
If long signal lines are used to achieve the required phase shift and attenuation, then the frequency blocking capability is improved, but the connection line length and filter dimensions increase
Solution Approach 1:
The continuous signal line is segmented into multiple sections with galvanic separations. Each segment contributes to the overall phase shift and attenuation through its capacitive coupling to resonators, eliminating the need for a single long connection line while achieving the same electrical length and blocking capability
Solution Approach 2:
The electrical characteristics of the signal path are changed by introducing capacitive couplings that provide the necessary phase shift without requiring proportional physical length. The capacitive reactance and coupling strength are adjusted to achieve the desired electrical length and attenuation in a physically compact configuration
3Reliability
If complex folded connection paths are used to achieve the required signal line length, then the blocking frequency performance is improved, but the manufacturing cost and production complexity increase
Solution Approach 1:
The signal line is divided into standardized segments that can be independently manufactured and assembled. Each segment with its capacitive coupling to resonators can be produced using simple manufacturing processes, avoiding the need for complex folded paths while maintaining the required electrical characteristics
Solution Approach 2:
Instead of extending the signal line in a single dimension through complex folding, the patent uses multiple galvanic separations arranged in a different spatial configuration. The capacitive couplings provide the necessary electrical length through vertical or lateral arrangements rather than long horizontal paths, simplifying the manufacturing layout
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 approach results in a significantly miniaturized radio-frequency blocking filter that can be produced simply and affordably, maintaining high attenuation and frequency blocking capabilities across a wide range, including frequencies like 790-862 MHz and 880-960 MHz.
Implementation Method 1
the signal line (50) additionally, in the context of the invention, being capacitively coupled to the resonators (10), in other words to the internal conductors (16), by approaching them
Implementation Method 2
The radio-frequency filter further comprises at least two coaxial resonators, which are each capacitively coupled to the connection line, in such a way that the resonators are also capacitively coupled to the input terminal and the output terminal
Implementation Method 3
The coupling points of the resonators to the connection line have to be at a distance on the connection line of a quarter of the wavelength of the average-frequency signal to be filtered by the radio-frequency filter, in such a way that the individual resonators are coupled together resonantly
Data Source
AI summary
A radio-frequency filter comprises an input terminal and an output terminal. A signal line is galvanically connected or capacitively coupled firstly to the input terminal and secondly to the output terminal. The signal line, with the formation of a capacitive inner conductor and/or resonator coupling, runs past the relevant inner conductor through the resonators of the radio-frequency blocking filter. The signal line has at least one galvanic isolation location in the form of a capacitive isolation location. The capacitive isolation location is spaced apart from the inner conductors and capacitively coupled thereto. The resonators and/or the inner conductors capacitively coupled to the signal line.