BAW Tunable Filter Layout With Shared Inductors for IC Integration
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Solution Overview
Problem
The integration of tunable filter circuits in semiconductor products is challenging due to the complexity of combining BAW resonators, inductive resistors, and varactors, which requires a significant surface area and is difficult to control, especially for mobile telephony applications like WCDMA, where passive LC-type devices are delicate and SAW resonators cannot be embedded in integrated circuits.
Innovation Solution
A tunable filter circuit design that optimizes the arrangement of varactor circuits and BAW-type resonators, using only two inductive resistors to achieve effective filtering, allowing for a compact and efficient filter unit that can be embedded in semiconductor products, with the option to distribute components across different substrates for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a great number of inductive resistors are used to achieve high-performance filtering, then filtering performance is improved, but occupied surface area increases significantly
Solution Approach 1:
The patent combines multiple inductive resistors into a single shared inductive resistor that is commonly connected to multiple BAW resonators. This merging approach allows the same inductive resistor to serve multiple filtering functions simultaneously, reducing the total number of inductive resistors from four to two, and consequently reducing the occupied surface area while maintaining high-performance filtering capability.
Solution Approach 2:
The shared inductive resistor is designed to perform multiple functions by being commonly connected to different BAW resonators. This single component provides inductive functionality for multiple resonant circuits, enabling one element to fulfill the role of what would traditionally require separate dedicated inductive resistors for each resonator.
2Ease of manufacture
If BAW resonators are integrated in an integrated circuit, then embedding capability is improved, but manufacturing control becomes particularly difficult
Solution Approach 1:
The patent segments the filter circuit into distinct functional modules: BAW resonators, inductive resistors, and varactor circuits. Each module can be independently designed, optimized, and manufactured, then integrated together. This segmentation allows specialized manufacturing processes for each component type while maintaining overall system integration, thereby improving both embedding capability and manufacturing control.
3Area of stationary object
If inductive resistors are placed close together to reduce surface area, then occupied surface area is reduced, but mutual disruption between inductive resistors increases
Solution Approach 1:
Instead of placing multiple inductive resistors close together, the patent merges them into a single shared inductive resistor. This eliminates the mutual disruption problem entirely by removing the proximity issue, while still achieving surface area reduction through the consolidation of components rather than through tight packing.
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 reduces the surface area required in semiconductor products while maintaining high performance, enabling efficient filtering with fewer components and allowing for easy embedding in various substrates, such as IPAD and silicon, while ensuring high-quality passive devices and tunable frequency capabilities.
Implementation Method 1
a first BAW resonator having first and second resonant frequencies
Implementation Method 2
integrable tunable filter circuit comprising a set of BAW resonators
Implementation Method 3
comprising first and second varactor circuits, each varactor circuit comprising a capacitive adjustment element
Data Source
AI summary
A tunable filter circuit having inputs IN1-IN2 and outputs OUT1-OUT2, comprising at least a primary four-pole circuit including in cascade: a first varactor having a first electrode connected to IN1 and a second electrode; a first inductive resistor connected between the second electrode of the varactor and input IN2, a secondary four-pole circuit comprising four BAW resonators. First and second of these resonators have a first electrode connected to a first input of the secondary four-pole circuit and a second electrode connected to first and second outputs of the secondary four-pole circuit, respectively. Similarly, third and fourth of these resonators have a first electrode connected to a second input of the secondary four-pole circuit and a second electrode connected to the second and first outputs of the secondary four-pole circuit, respectively. The circuit further comprises a second inductive resistor connected in parallel to the first and second outputs of the secondary four-pole circuit and a second varactor having a first electrode connected to the first output of the secondary four-pole circuit and a second electrode for connecting a second primary four-pole circuit having the same structure. This allows realization of a particularly effective tunable filter circuit with only four inductive resistors.