Cross-Coupled Bandpass Filter with Magnetic and Capacitive Couplings
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Solution Overview
Problem
Current cross-coupled bandpass filters face challenges in generating two transmission zeros in a rejection band, particularly in high frequency bands, due to difficulties in achieving electric cross-coupling and magnetic cross-coupling in integrated passive device (IPD) fabrication processes.
Innovation Solution
A quadruplet magnetically cross-coupled bandpass filter design is implemented, featuring resonators with magnetic couplings between specific pairs and a capacitive coupling between others, using inductors and capacitors made of magnetic semiconductor or metal materials, to generate two transmission zeros in a rejection band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electric cross-coupling is used to generate transmission zeros in rejection band, then two transmission zeros can be achieved, but capacitors connected to input and output ports are too close causing short circuits in IPD fabrication process
Solution Approach 1:
The patent introduces an intermediary magnetic coupling mechanism between resonators instead of direct electric coupling through capacitors. By using magnetic coupling fields as the intermediary, the design achieves the desired transmission zero generation while physically separating the capacitors to avoid short circuits in IPD fabrication processes.
2Reliability
If magnetic cross-coupling is used to avoid short circuits, then capacitor spacing is improved, but only one transmission zero is generated in low frequency band while high frequency transmission zero is lost
Solution Approach 1:
The patent merges magnetic cross-coupling with additional capacitive coupling elements to combine the advantages of both approaches. The magnetic coupling provides reliable capacitor spacing while the additional capacitive elements restore the ability to generate transmission zeros in both low and high frequency rejection bands.
Solution Approach 2:
The patent extends the coupling mechanism from a single dimension (either electric or magnetic) to multiple dimensions by combining magnetic coupling between adjacent resonators with capacitive coupling elements connected to specific resonator terminals. This multi-dimensional coupling approach enables generation of transmission zeros in both low and high frequency bands while maintaining reliable capacitor spacing.
3Ease of manufacture
If conventional magnetic cross-coupling is implemented in IPD fabrication process, then capacitor spacing is improved, but design complexity increases and two transmission zeros in rejection band cannot be achieved
Solution Approach 1:
The patent designs a universal coupling structure that serves multiple functions: magnetic coupling for reliable capacitor spacing, additional capacitive elements for transmission zero generation, and overall compatibility with IPD fabrication processes. This multi-functional design reduces complexity by consolidating multiple requirements into a single integrated structure.
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 effectively generates two transmission zeros, including one in a high frequency rejection band, improving the selectivity and compatibility of the bandpass filter in IPD fabrication processes, meeting the requirements of portable communication devices.
Implementation Method 1
magnetic couplings are generated between the first and second resonators, between the third and fourth resonators, and between the first and fourth resonators
Implementation Method 2
a capacitive coupling is generated between the second and third resonators
Data Source
AI summary
A cross-coupled bandpass filter includes first, second, third and fourth resonators such that magnetic couplings are generated between the first and second resonators, between the third and fourth resonators and between the first and fourth resonators, a capacitive coupling is generated between the second and third resonators, and the magnetic coupling between the first and fourth resonators has a polarity opposite to that of the capacitive coupling between the second and third resonators, thereby generating two transmission zeros in a transmission rejection band.