Lattice BAW Filter Circuit for Multi-Band Frequency Tuning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional BAW resonator-based filtering circuits require multiple arrangements for different frequency bands, leading to increased manufacturing costs and complexity in multiband mobile telephones, as they are designed for specific frequency ranges and cannot efficiently operate at reduced frequencies like 1 GHz without significant manufacturing challenges.
Innovation Solution
A filtering circuit using a lattice structure with adjustable BAW resonators, capable of processing multiple frequency bands by controlling series and parallel impedances with common and differential mode potentials, allowing the same set of resonators to operate effectively across different frequency ranges, including 1 GHz and 2 GHz, thereby reducing manufacturing costs and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional BAW resonators are designed for specific frequency ranges (e.g., 2 GHz), then they achieve optimal performance at those frequencies, but they cannot efficiently operate at reduced frequencies (e.g., 1 GHz) without significant manufacturing challenges
Solution Approach 1:
The patent makes a single BAW resonator design serve multiple frequency bands (GSM 900, DCS 1800, WCDMA 2100) by using it in a lattice filter configuration where the resonator operates at its optimal 2 GHz frequency, but the overall filter response covers lower frequencies through the lattice structure's frequency transformation properties
Solution Approach 2:
The patent changes the operating parameters of the BAW resonator by biasing it to operate at its parallel resonant frequency (fp) rather than series resonant frequency (fs), and uses voltage-controlled capacitors to dynamically adjust the resonant frequency and impedance characteristics, enabling the same hardware to serve multiple frequency bands
2Reliability
If multiple arrangements of BAW resonators are used for different frequency bands, then each frequency band can be optimally filtered, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent uses a single set of BAW resonators to provide filtering for multiple frequency bands (GSM, DCS, WCDMA) simultaneously through the lattice filter architecture, eliminating the need for separate resonator sets for each band and reducing overall device complexity
Solution Approach 2:
The patent merges multiple filtering functions into a single lattice filter structure where the same physical resonators perform filtering across different frequency bands, combining what would traditionally require separate filter circuits into one unified structure
3Productivity
If BAW resonators operate at their optimal frequency (e.g., 2 GHz), then they achieve high Q-factor and efficiency, but they cannot process lower frequency bands (e.g., 1 GHz) effectively
Solution Approach 1:
The patent dynamically changes the electrical parameters (capacitance values) of the lattice filter using voltage-controlled capacitors, which transforms the frequency response of the filter to match different target frequency bands while keeping the BAW resonators operating at their fixed optimal frequency
Solution Approach 2:
The patent introduces voltage-controlled capacitors as intermediary elements between the fixed-frequency BAW resonators and the variable frequency requirements, allowing the capacitors to transform and adapt the frequency response to cover different bands while the resonators maintain their optimal operating point
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
Enables a single set of BAW resonators to handle multiple frequency bands, such as GSM, DCS, WCDMA, and Bluetooth, significantly reducing manufacturing costs and extending the usable frequency range of existing resonators, allowing for more efficient and cost-effective multiband mobile telephone designs.
Implementation Method 1
In BAWs, it lays inside a volume delimited between a lower electrode and a higher electrode so that the acoustic wave develops in this volume
Implementation Method 2
a BAW resonator is based on a dielectric medium arranged on a reflecting element, such as a Bragg mirror
Implementation Method 3
The second partner element is generally a capacitive type element (as illustrated by varactor 2 in FIG. 2A), which is made tunable according to an electric quantity, e.g., electric voltage Vc
Data Source
AI summary
A filtering circuit based on a lattice structure comprising a first and a second input and a first and second output. The circuit further comprises two series impedance and two parallel impedance which each comprises an acoustic resonator associated with two inductive and capacitive components which can be adjusted by a first control value. The second and fourth impedance comprise each an acoustic resonator associated to two inductive and capacitive components which are adjustable by means of a second control value. A control circuit generates the two control values which simultaneously comprise a common mode potential and a differential mode potential which allows the emergence of first and second pass bands which are usable for realizing two different bandpass filters.