RF Switch Transistor Body Connection for Harmonic Suppression

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Solution Overview

Problem

Radio frequency (RF) circuits generate unwanted harmonic signals due to nonlinear interactions, which degrade their performance and that of the overall device, despite existing techniques to mitigate these signals being incomplete.

Innovation Solution

Applying a positive body control voltage to switch transistors in RF circuits, specifically greater than 0.7 volts, improves device linearity by reducing harmonic signals and intermodulation distortion, contrasting with conventional techniques where the body bias voltage is held at zero volts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If conventional body bias voltage (zero volts) is used in switch transistors, then device simplicity is maintained, but harmonic signals and intermodulation distortion increase due to nonlinear interactions

Engineering Contradiction:

Improveharmonic signals and intermodulation distortionVSAvoidbody bias control circuitry

Core Design Contradiction:

Object-generated harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies a positive body bias voltage (e.g., +0.7V or higher) to the body terminal of the switch transistor instead of the conventional zero volts. This parameter change in the body bias voltage directly reduces the nonlinear interactions that generate harmonic signals and intermodulation distortion, improving linearity without requiring complex additional circuitry.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The body bias voltage is applied through a resistor connected to a control voltage node that is already present in the circuit. This allows the existing control signal to simultaneously serve both gate control and body bias functions, eliminating the need for separate dedicated body bias generation circuitry and reducing overall device complexity.

Inventive Principle:

Principle #25Self-service

2Object-generated harmful factors

If body bias voltage is increased to improve linearity, then harmonic signal mitigation improves, but power consumption increases

Engineering Contradiction:

Improveharmonic signalsVSAvoidpower consumption

Core Design Contradiction:

Object-generated harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent applies a moderate positive body bias voltage (e.g., +0.7V) rather than excessive voltage levels. This partial action approach achieves sufficient reduction in harmonic signals and intermodulation distortion while avoiding the excessive power consumption that would result from applying much higher body bias voltages, thus optimizing the trade-off between linearity improvement and power consumption.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS10326439B2RF circuit with switch transistor with body connection

Publication Date: 2019.06.18 QUALCOMM INC

AI summary

In some method and apparatus embodiments, an RF circuit comprises a switch transistor having a source, a drain, a gate, and a body. A gate control voltage is applied to the gate of the switch transistor. A body control voltage is applied to the body of the switch transistor. The body control voltage is a positive bias voltage when the switch transistor is in an on state. In some embodiments, an RF circuit comprises a control voltage applied to the gate of the switch transistor through a first resistance and applied to the body of the switch transistor through a second resistance. The first resistance is different from the second resistance.