RF Switch Body Bias Control for Lower Harmonic Distortion
Find Innovative SolutionsGenerate Solutions
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 insufficient.
Innovation Solution
Applying a positive bias 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 or allowed to float.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional body bias voltage (zero or floating) is used, then device simplicity is maintained, but harmonic signals and intermodulation distortion increase
Solution Approach 1:
The patent applies a positive body bias voltage (e.g., +0.7V to +1.5V) to the body terminal of the RF switch transistor, changing the electrical parameter of body bias from conventional zero or floating to a controlled positive value. This parameter change reduces the on-resistance of the transistor and improves linearity, thereby reducing harmonic signals and intermodulation distortion in the RF circuit.
Solution Approach 2:
The patent introduces a body bias voltage source as an intermediary control element that independently controls the body terminal of the RF switch transistor. This intermediary allows separate optimization of the body bias from the gate control, enabling reduction of harmful nonlinear effects without affecting the primary switching function controlled by the gate.
2Reliability
If positive body bias voltage is applied, then linearity improves and harmonic signals reduce, but device complexity increases
Solution Approach 1:
The patent segments the voltage control into two independent sources: one for gate control and another for body bias control. This segmentation allows each voltage source to be optimized for its specific function - the gate control for switching and the body bias for linearity - without interfering with each other, thereby improving overall device linearity while managing complexity through functional separation.
3Object-generated harmful factors
If body bias voltage is held at zero or floating, then device complexity is low, but intermodulation distortion increases
Solution Approach 1:
The patent changes the body bias voltage parameter from zero or floating to a controlled positive value range (e.g., +0.7V to +1.5V). This parameter change modifies the transistor's operating characteristics, reducing the nonlinear effects that cause intermodulation distortion, while the body bias voltage source provides straightforward voltage application to maintain ease of operation.
Data Source
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.