High-Power Tunable Capacitor With Floating-Body Noise Isolation

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Solution Overview

Problem

Conventional high power tunable capacitors with body contacted switches experience performance degradation due to unexpected noise levels on the RF ground, which affects the negative bias supply and stability of the switches when integrated with RF power amplifiers.

Innovation Solution

A high power tunable capacitor design that incorporates a plurality of switchable capacitor branches, where each branch includes a first switch group of body contacted switches and a second switch group of non-body contacted (floating body) switches, decoupling the body bias signal from noise on the RF ground to maintain a stable negative body bias.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If body contacted switches are used in high power tunable capacitors, then power handling capability is improved, but ground noise affects the negative bias supply and degrades capacitor performance

Engineering Contradiction:

Improvepower handling capabilityVSAvoidcapacitor performance

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The switch group is segmented into multiple individual switches (first through fourth switches) arranged in a specific configuration. This segmentation allows the body terminals to be connected together to form a common node that can be biased independently, isolating the bias supply from ground noise while maintaining power handling capability through the distributed switch structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A common bias node is introduced as an intermediary element that connects the body terminals of all switches. This common node serves as an intermediate point that receives the negative bias supply and distributes it to all switches, thereby isolating the bias supply from ground noise while still providing the necessary bias to all switches for proper operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If switches are integrated with RF power amplifiers in the same package, then device integration is improved, but unexpected noise levels appear on the RF ground

Engineering Contradiction:

Improvedevice integrationVSAvoidground noise

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The body terminals of all switches are connected together to form a common equipotential node that is biased at a fixed negative voltage. This equipotential connection ensures that all switches experience the same bias condition and that the common node acts as a noise reference, isolating the switches from ground noise variations while maintaining integration with the RF power amplifier.

Inventive Principle:

Principle #12Equipotentiality

3Ease of operation

If negative bias supply is distributed to all switches, then switch control is simplified, but noise on RF ground affects all switches through the shared bias supply

Engineering Contradiction:

Improveswitch controlVSAvoidbias supply noise

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentEP2888816B1High power tunable capacitor

Publication Date: 2020.11.11 QUALCOMM INC

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AI summary

A high power tunable capacitor (500) is disclosed. In an exemplary embodiment, an apparatus includes a capacitor (508) coupled to an input signal (504), a body contacted switch (510) coupled to the capacitor, the body contacted switch coupled to a body bias signal (Bb), and a floating body switch (512) coupled between the body contacted switch and a ground, the floating body switch configured to decouple the body bias signal from the ground.