RF Switch Coupling Circuit for Intermodulation Distortion
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Solution Overview
Problem
Radio-frequency (RF) switches face challenges in achieving improved intermodulation distortion (IMD) performance, power handling, and isolation due to limitations in existing transistor biasing and coupling circuits, which affect the switching performance and linearity in multi-band and multi-mode wireless communication systems.
Innovation Solution
The implementation of a radio-frequency switch using field-effect transistors (FETs) with a coupling circuit configured between the body and gate of each FET, including a capacitor in series with a resistor, to discharge interface charge and enhance IMD performance, along with gate and body bias resistors to improve switching characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional RF switch design is used, then the device can perform basic switching functions, but the intermodulation distortion performance deteriorates due to non-linearity issues
Solution Approach 1:
The patent extracts and removes the harmful interface charge from the body of the FET through a dedicated discharge path. The body is connected to ground through a resistor and capacitor network that actively discharges accumulated interface charge, separating the charge discharge function from the normal switching operation to eliminate non-linearity effects.
Solution Approach 2:
The patent introduces an intermediary discharge circuit consisting of resistors and capacitors connected between the body and ground. This intermediary network acts as a mediator to safely discharge interface charge without interfering with the primary switching function, thereby improving linearity and IMD performance.
2Reliability
If the coupling circuit components are optimized for IMD performance, then the IMD performance improves, but the device complexity increases
Solution Approach 1:
The body connection network serves multiple functions simultaneously: it provides a discharge path for interface charge, establishes proper biasing conditions, and sets appropriate time constants for charge removal. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while achieving improved IMD 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 configuration enhances the IMD performance, power handling capability, and isolation of the RF switch, leading to improved linearity and reduced interference susceptibility, particularly beneficial for multi-band and multi-mode wireless communication systems.
Implementation Method 1
The coupling circuit is configured to allow discharge of interface charge from the respective body
Data Source
AI summary
Radio-frequency (RF) switch circuits are disclosed providing improved switching performance. An RF switch system includes at least one field-effect transistor (FET) disposed between a first node and a second node, each having a respective source, drain, gate, and body. The system includes a coupling circuit including a first path and a second path, the first path being between the respective source or the respective drain and the respective gate of the at least one FET, the second path being between the respective source or the respective drain and the respective body of the at least one FET. The coupling circuit may be configured to allow discharge of interface charge from either or both of the coupled gate and body.