Hybrid RF Switch Topology for High Isolation and Low Loss
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Solution Overview
Problem
Existing RF switches face challenges in achieving low insertion loss, high isolation, and high breakdown voltage, especially at high frequencies, making them unsuitable for advanced wireless systems.
Innovation Solution
The RF switch employs a combination of III-V transistors and silicon-on-insulator (SOI) transistors, connected in a series and shunt configuration, to optimize performance by controlling the ON/OFF states of these transistors to minimize leakage and maximize breakdown voltage, thereby achieving low insertion loss and high isolation across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional RF switch designs are used, then device simplicity is maintained, but insertion loss increases and isolation decreases at high frequencies
Solution Approach 1:
The patent combines two different transistor technologies (III-V HEMT and SOI MOSFET) into a single RF switch circuit. The III-V HEMT provides low insertion loss when ON, while the SOI MOSFET provides high isolation when OFF. This merging of complementary technologies resolves the contradiction by achieving both low insertion loss and high isolation simultaneously, overcoming the limitations of conventional single-technology designs at high frequencies.
Solution Approach 2:
The invention uses a composite transistor structure where a III-V semiconductor layer (GaAs or GaN) is grown on a silicon substrate with SOI MOSFET structures. This composite material approach allows the device to leverage the high electron mobility and low loss characteristics of III-V materials while utilizing the excellent isolation properties of SOI MOSFETs, thereby achieving superior performance across both insertion loss and isolation metrics.
2Speed
If RF switch operates at high frequencies, then bandwidth is improved, but isolation and breakdown voltage deteriorate
Solution Approach 1:
The patent applies different transistor technologies to different functional requirements within the same circuit: III-V HEMT transistors are used for the series switching path where low insertion loss is critical, while SOI MOSFET transistors are used for the shunt isolation path where high isolation is critical. This local optimization of transistor type based on functional requirement allows the circuit to maintain high isolation and breakdown voltage even at high operating frequencies up to 10 GHz.
3Strength
If series transistors are used for switching, then breakdown voltage is improved, but leakage current increases
Solution Approach 1:
The patent introduces an intermediary SOI MOSFET transistor in a shunt configuration connected to ground at the node between two series III-V HEMT transistors. This intermediary transistor acts as a leakage path to ground when the main series transistors are OFF, effectively capturing and diverting leakage current away from the output. This resolves the contradiction by providing a dedicated leakage sink that maintains high breakdown voltage capability while minimizing harmful leakage current at the output.
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 enables the RF switch to operate with greater than 10 dB isolation, less than 0.4 dB insertion loss, and more than 70 volts breakdown voltage from 500 MHz to 10 GHz, making it suitable for high-power RF tuning applications.
Implementation Method 1
a first III-V transistor that is coupled between an input of the RF switch and a shunt-connection node. The first III-V transistor is controllable by a first control signal that is applied to a gate of the first III-V transistor
Data Source
AI summary
A radio frequency switch is disclosed. The RF switch uses a combination of transistor technology and a topology to create an RF switch that has a high isolation and a high voltage breakdown at frequencies including those above a gigahertz.