Variable Inductance Circuit for Acoustic Resonator Capacitance Offset

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Solution Overview

Problem

Existing wireless devices face challenges in achieving optimal performance in high-frequency communication applications due to the complexity of filtering demands and the inherent capacitance of acoustic resonators, which affects signal rejection and impedance matching.

Innovation Solution

A variable inductance circuit is introduced, comprising an impedance inverter circuit and a variable capacitance circuit, which can be configured to present a variable inductance within a target frequency range. This circuit can be coupled in parallel to an acoustic resonator in an acoustic ladder network to offset the inherent capacitance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If acoustic resonators are used in filter networks for high-frequency communication applications, then signal filtering performance is improved, but inherent capacitance of the resonators degrades signal rejection and impedance matching

Engineering Contradiction:

Improvesignal filtering performanceVSAvoidinherent capacitance effects

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful inherent capacitance of acoustic resonators into a beneficial feature by introducing a variable inductance circuit that can dynamically compensate for the capacitance. The inductance circuit is designed to resonate at the same frequency as the resonator's capacitance, transforming the harmful capacitive effect into a useful resonant characteristic that improves signal rejection and impedance matching.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent employs parameter changes by making the inductance value variable through a varactor diode. The inductance circuit's resonant frequency and inductance value can be dynamically adjusted by changing the bias voltage applied to the varactor diode, allowing the system to adapt to different operating conditions and frequency ranges to optimize performance.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If filter network complexity is increased to meet challenging filtering demands, then signal rejection is improved, but device footprint increases

Engineering Contradiction:

Improvesignal rejectionVSAvoiddevice footprint

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The variable inductance circuit serves multiple functions simultaneously: it provides impedance matching, enhances signal rejection, and enables frequency tuning. By integrating these functions into a single circuit block rather than using separate components for each function, the patent achieves improved signal rejection without proportionally increasing the device footprint.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The inductance circuit is nested within the existing filter network architecture, with the variable inductance element integrated into the resonator structure. This nesting approach allows the additional functionality to be incorporated into the existing layout without requiring separate dedicated space for each function, thereby minimizing the overall footprint increase.

Inventive Principle:

Principle #7Nested doll (Nesting)

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 variable inductance circuit improves signal rejection and impedance matching without increasing the footprint of the wireless device, thereby enhancing the overall performance of wireless devices in high-frequency communication applications.

Implementation Method 1

The impedance inverter circuit includes an input node coupled to the first terminal, an output node coupled to the second terminal, and an intermediate node coupled to a selected one of the first terminal and the second terminal. The variable capacitance circuit is coupled between the impedance inverter circuit and the selected one of the first terminal and the second terminal and further to the intermediate node.

Methodology Applied

Scientific EffectImpedance inversion:

Implementation Method 2

The variable capacitance circuit is configured to cause the variable inductance circuit to present a variable inductance within a target frequency range between the first terminal and the second terminal

Methodology Applied

Scientific EffectCapacitance to inductance transformation:

Implementation Method 3

The variable inductance circuit can be coupled in parallel to an acoustic resonator in an acoustic ladder network to help offset an inherent capacitance of the acoustic resonator

Methodology Applied

Scientific EffectCapacitance offset:

Data Source

PatentUS20250167764A1Variable inductance circuit

Publication Date: 2025.05.22 QORVO US INC

AI summary

A variable inductance circuit is provided. Notably, the variable inductance circuit can be provided in a wireless device in places where a variable inductance and/or capacitance is deemed desirable for specific types of operating scenarios. Herein, the variable inductance circuit includes an impedance inverter circuit and a variable capacitance circuit that can be provided in various topologies between a first terminal and a second terminal. The variable capacitance circuit is configured to cause the variable inductance circuit to present a variable inductance within a target frequency range between the first terminal and the second terminal. By configuring the variable inductance circuit to provide a desired inductance(s) at a place(s) as needed, it is possible to improve performance (e.g., signal rejection, impedance matching, etc.) without increasing a footprint of the wireless device.