RF Switch Branch Linearity via Body Node Biasing
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Solution Overview
Problem
Conventional RF switch branches face challenges in achieving high linearity due to parasitic conduction layers in silicon-on-insulator technologies, which hinder effective isolation of the body node, leading to nonlinearity and harmonic distortion in high-frequency signal transmission.
Innovation Solution
The implementation of small MOS devices between the source and body, and another small MOS device between the body and drain of a transistor, ensures the body node is continuously biased to the median voltage between the input and output, reducing AC impedance and improving input/output symmetry and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional stacked switch branch with isolated body nodes is used, then high power transmission capability is achieved, but linearity deteriorates due to parasitic conduction layer
Solution Approach 1:
A parasitic conduction layer (PCL) is intentionally formed at the interface between the base oxide layer and substrate to serve as an intermediary that provides a controlled conduction path. This PCL acts as a mediator between the body node and substrate, enabling the body node to track the midpoint between drain and source voltages while maintaining high power transmission capability through stacked transistor configuration.
2Ease of operation
If body node isolation is attempted in SOI technology, then transistor control is improved, but parasitic conduction layer formation degrades linearity
Solution Approach 1:
The parasitic conduction layer, which was originally a harmful defect in SOI technology that degraded linearity, is converted into a beneficial element. By intentionally forming and controlling the PCL, it becomes a useful mechanism that enables the body node to naturally track the midpoint voltage, thereby improving linearity without requiring expensive polysilicon passivated substrates or complex isolation techniques.
3Manufacturing precision
If expensive polysilicon passivated substrates are used, then body node isolation is improved, but manufacturing cost increases
Solution Approach 1:
The invention replaces expensive polysilicon passivated substrates with a simpler, more cost-effective approach using standard SOI technology. The parasitic conduction layer is formed through conventional processing steps rather than requiring expensive specialized substrates, making the solution economically viable for mass production while achieving superior linearity performance.
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 approach significantly attenuates even-order harmonics, enhancing the linearity of the RF switch branch without requiring expensive SOI manufacturing techniques, thereby reducing RF interference and improving end-system performance.
Implementation Method 1
This reduction in AC impedance may allow the transistor's body node voltage to more closely track the midpoint between the drain voltage and the source voltage
Data Source
AI summary
Disclosed is a radio frequency (RF) switch branch having a reduced nonlinearity and an associated method for reducing nonlinearity in a RF switch branch. The RF switch branch includes a primary transistor, a first transistor having power terminals electrically connected between a drain node and a body node of the primary transistor, and a second transistor having power terminals electrically connected between the body node and a source node of the primary transistor. The RF switch may further include a body resistor electrically connected between the body node of the primary transistor and ground, and a gate resistor electrically connected between a gate of the primary transistor and a gate voltage source. A gate of each of the first transistor and the second transistor is electrically connected to the gate voltage source such that the first transistor and the second transistor are ON only when the primary transistor is ON.