Switchable FBAR Shunt Filter for Multi-Band Frequency Control
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Solution Overview
Problem
The increasing number of filters required to support multiple communication bands in wireless terminals complicates signal processing, increases manufacturing costs, and enlarges the filter module size due to the need for subminiature, high-quality factor filters like film bulk acoustic resonators (FBARs).
Innovation Solution
A filter design incorporating a series unit and a shunt unit with selectively operable shunt resonators and switches, where the shunt unit includes a first and second shunt resonator with different anti-resonant frequencies, and a transistor that varies its equivalent impedance between resistor and capacitor states to adjust the frequency band, allowing for flexible operation and reduced interference between adjacent frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple filters are used to control multiple communication bands, then the frequency band coverage is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent implements a variable frequency filter where the cutoff frequency can be dynamically adjusted by changing the impedance of the shunt arm circuit. This is achieved by using reactive elements (inductors and capacitors) whose values can be modified through switching networks, allowing a single filter to adapt to multiple frequency bands rather than requiring multiple fixed-frequency filters
Solution Approach 2:
The filter design enables a single filter structure to perform multiple functions by covering multiple communication bands through frequency adjustment. The shunt arm circuit with switchable reactive elements allows the filter to be universally applicable across different bands (e.g., LTE bands), replacing the need for multiple dedicated filters
2Adaptability or versatility
If multiple filters are used to control multiple communication bands, then the frequency band coverage is improved, but the manufacturing cost increases
Solution Approach 1:
The patent merges the functionality of multiple filters into a single variable frequency filter unit. By combining multiple reactive elements (inductors L1, L2, L3 and capacitors C1, C2, C3) with switching networks in one integrated circuit, it achieves multi-band coverage without the need to manufacture and assemble multiple separate filter components
Solution Approach 2:
A single filter module is designed to universally support multiple communication bands through electronic frequency adjustment, reducing manufacturing complexity and cost compared to producing multiple specialized filters for different bands
3Adaptability or versatility
If multiple filters are used to control multiple communication bands, then the frequency band coverage is improved, but the filter module size increases
Solution Approach 1:
The patent integrates multiple filter functions into a single compact module by combining reactive elements and switching networks. This merging approach reduces the overall footprint compared to housing multiple separate filters, making it suitable for space-constrained wireless terminals
Solution Approach 2:
The filter design employs a nested structure where switching networks are integrated within the filter circuitry, and reactive elements are arranged in compact configurations. The shunt arm circuit with embedded switches and reactive components creates a space-efficient layout that minimizes the filter module size
4Area of stationary object
If the number of filters is reduced to minimize module size, then the filter module size is reduced, but the interference between adjacent frequency bands increases
Solution Approach 1:
The variable frequency filter dynamically adjusts its cutoff frequency to precisely match the edges of communication bands, creating effective frequency separation. By electronically tuning the cutoff frequency rather than using fixed-frequency filters, the design prevents adjacent band interference while maintaining compact size
Solution Approach 2:
The filter uses switchable reactive elements that change the impedance parameters of the shunt arm circuit. By altering the values of inductors and capacitors through switching networks, the cutoff frequency is adjusted to create proper attenuation between adjacent bands, preventing interference without requiring multiple physical filters
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 design allows for the reduction of the number of filters needed to control overlapping bands, minimizing module size and manufacturing costs while preventing interference between frequency bands, thereby enhancing the efficiency and miniaturization of wireless terminal filters.
Implementation Method 1
a film bulk acoustic resonator. Such FBAR may be mass-produced at a minimal cost to have subminiature size. In addition, the FBAR may have a high quality factor (Q) value, a main characteristic of a filter.
Implementation Method 2
each of the shunt resonators includes a film bulk acoustic resonator
Data Source
AI summary
A filter comprises a series unit, and a shunt unit disposed between the series unit and a ground. The shunt unit includes resonators that are selectively operated, and each of the shunt resonators includes a film bulk acoustic resonator.