DMS Filter Matching Using a Shunt Capacitive Branch
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Solution Overview
Problem
Advanced package designs with reduced static capacitances pose challenges in impedance matching, as simple re-dimensioning of external inductors is no longer effective, leading to large deviations in admittance and reflection issues.
Innovation Solution
A filter arrangement is designed with a signal path on a substrate, featuring a DMS track and a reactance element connected in series, with a shunt branch containing a capacitive element connected to ground, optimizing the capacitive element's dimensions to improve matching between the DMS track and reactance element, and utilizing a SAW resonator and interdigital structure for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If advanced package designs with reduced static capacitances are used, then device size is reduced and manufacturing is improved, but impedance matching deteriorates and reflection increases
Solution Approach 1:
An intermediary capacitive element is introduced between the DMS track and the reactance element to compensate for the reduced parasitic capacitance in advanced packages. This additional capacitance acts as a mediator to restore proper impedance matching, allowing the system to achieve good matching performance without requiring large external inductors, thus maintaining the benefits of reduced package size while solving the impedance matching problem.
Solution Approach 2:
The invention changes the capacitance parameter by adding a capacitive element with a specifically designed capacitance value (typically 0.5 pF to 2 pF) to compensate for the reduced parasitic capacitance in advanced packages. This parameter adjustment allows the filter to achieve proper impedance matching in packages with significantly lower static capacitances, resolving the contradiction between reduced package size and maintained matching performance.
2Reliability
If external inductors are used to equalize parasitic capacitances, then impedance matching is improved, but device complexity and size increase
Solution Approach 1:
The capacitive element is merged with the existing filter structure by placing it in series between the DMS track and the reactance element, utilizing the same substrate and manufacturing process. This integration approach combines the matching function with the existing components, eliminating the need for separate external inductors and reducing overall device complexity while maintaining effective impedance matching.
Solution Approach 2:
The filter structure itself provides the matching function through the integrated capacitive element, eliminating the need for external matching components. The capacitive element works together with the DMS track and reactance element to create a self-contained matching solution that is built into the filter architecture, reducing both component count and external connections.
3Reliability
If capacitive element capacitance is increased to improve matching, then matching is improved, but bandwidth is reduced
Solution Approach 1:
The capacitance value of the capacitive element is precisely optimized to a specific range (0.5 pF to 2 pF) to achieve the right balance between improving impedance matching and maintaining bandwidth. This controlled parameter change allows the system to benefit from improved matching without excessively reducing the passband width, resolving the contradiction between matching quality and bandwidth preservation.
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 achieves improved matching and reduced reflection across the entire passband, allowing for optimal power matching and increased bandwidth, potentially eliminating the need for external inductors by utilizing the capacitive element's optimized capacitance value and SAW resonator configuration.
Implementation Method 1
The reactance element can be produced on the same piezoelectric substrate using the same technology as the DMS track and, optionally, the capacitive element. It is also possible to produce the DMS track, the reactance element and the capacitive element in a single production step.
Implementation Method 2
a DMS track and a reactance element connected in series. Between the DMS track and the reactance element there is a shunt branch to the signal path in which there is an additional capacitive element that is connected to ground.
Implementation Method 3
A capacitive element with a relatively high capacitance can be implemented as an interdigital structure. It could also be constructed as metallization on the piezoelectric substrate using the same technology as the DMS track
Data Source
AI summary
For improving the matching of a DMS track that is connected in series with a reactance element, it is proposed to connect a shunt branch to ground between the DMS track and reactance element parallel to the signal-carrying conductor section, where a capacitive element is arranged in this shunt branch.