Digitally Reconfigurable BAW Filter Without Analog Varactors
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Solution Overview
Problem
Existing filtering circuits with Bulk Acoustic Wave (BAW) resonators require complex analog circuitry for configuration, which is costly and difficult to implement, and lacks easy digital control.
Innovation Solution
A filtering circuit with BAW resonators that includes cascaded quadripoles with series and parallel branches, where the branches are controlled by switching transistors connected to a digital control bus, allowing full digital control of the filtering characteristics without the need for varactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If varactors connected in series or parallel with resonators are used for configuration, then filtering characteristics can be adjusted, but the control circuit becomes complex and costly
Solution Approach 1:
The patent replaces the mechanical/electrical analog control system (varactors requiring analog voltage control) with a digital control system. Switching transistors are controlled by digital control signals to achieve the same filtering characteristic adjustment, substituting complex analog circuitry with simpler digital logic control.
Solution Approach 2:
The patent changes the control parameter from analog voltage (continuous) to digital control signals (discrete states). By using switching transistors controlled by digital signals, the system adjusts filtering characteristics through discrete parameter changes rather than continuous analog adjustment, simplifying the control circuit.
2Adaptability or versatility
If varactors are used for resonator control, then frequency adjustment is possible, but implementation becomes difficult and costly
Solution Approach 1:
The patent substitutes varactors (which require precise analog control and are difficult to manufacture) with switching transistors controlled by digital signals. This replacement makes the device easier to manufacture using standard digital CMOS processes while maintaining frequency adjustment capability through digital control of the switching elements.
Solution Approach 2:
The patent uses simple switching transistors that can be easily manufactured and replaced compared to varactors. The switching transistors are integrated into the standard CMOS process, making them cheaper and easier to manufacture than the specialized varactor components.
3Adaptability or versatility
If analog circuitry is used for resonator control, then filtering adjustment is achievable, but cost increases
Solution Approach 1:
The patent replaces expensive analog control circuitry with digital control logic. The switching transistors are controlled by digital signals generated by standard digital logic circuits, eliminating the need for specialized analog components and reducing manufacturing costs while maintaining filtering adjustment capability.
Solution Approach 2:
The patent uses a universal digital control interface that can control multiple switching transistors connected to different resonators. This digital control approach is more versatile and can be integrated with standard digital processors, making the system more universally applicable and easier to manufacture across different applications.
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 cost-effective, simplified digital control of filtering circuits, reducing interference and improving selectivity, particularly in mobile telephony applications by allowing configuration of filtering characteristics through digital processing.
Implementation Method 1
a first switching transistor controlled by a first control voltage for performing a short circuit of that capacitance
Implementation Method 2
the acoustic resonator is located on the surface of a semiconductor product while 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 3
BAW (Bulk Acoustic Wave Resonator)
Data Source
AI summary
A filtering circuit with BAW type acoustic resonators having at least a first quadripole and a second quadripole connected in cascade, each quadripole having a branch series with a first acoustic resonator of type BAW and a branch parallel with each branch having an acoustic resonator of type BAW, the first acoustic resonator having a frequency of resonance series approximately equal to the frequency of parallel resonance of the second acoustic resonator, the branch parallel of the first quadripole having a first capacitance connected in series with the second resonator and, in parallel with the capacitance, a first switching transistor to short circuit the capacitance.