Coupled Transmission Line RF Switches With Lower Insertion Loss
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Solution Overview
Problem
Semiconductor switches face limitations in isolation due to capacitive coupling between the switch input and output, which cannot be effectively addressed by increasing the number of semiconductor devices in series or reducing device size without increasing insertion loss.
Innovation Solution
Incorporating a coupled transmission line that introduces inductive coupling to cancel at least a portion of the capacitive coupling, thereby improving isolation in semiconductor switches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of semiconductor devices in series is increased to improve isolation, then isolation is improved, but insertion loss increases
Solution Approach 1:
A coupled transmission line is introduced as an intermediary element between the semiconductor switch and the signal path. This transmission line provides inductive coupling that acts as a mediator to cancel the capacitive coupling between input and output, improving isolation without requiring additional series semiconductor devices that would increase insertion loss
Solution Approach 2:
The invention changes the electrical parameters of the switching circuit by introducing inductive coupling through the coupled transmission line. This parameter change (adding inductance) counteracts the capacitive coupling parameter, thereby improving isolation performance without changing the number of series semiconductor devices
2Reliability
If the semiconductor device size is reduced to improve isolation, then isolation is improved, but insertion loss increases
Solution Approach 1:
The coupled transmission line serves as an intermediary that provides the necessary inductive coupling to cancel capacitive effects. This allows the use of larger semiconductor devices (reducing insertion loss) while still achieving high isolation through the transmission line's inductive coupling mechanism
3Reliability
If a coupled transmission line is added to improve isolation, then isolation is improved, but device complexity increases
Solution Approach 1:
The coupled transmission line performs multiple functions simultaneously: it provides inductive coupling to cancel capacitive effects (improving isolation), maintains signal transmission capability, and can be integrated with existing semiconductor switch architectures. This multi-functionality justifies the added complexity by delivering multiple benefits from a single added component
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
The solution achieves ultra-high isolation in semiconductor switches while maintaining acceptable insertion loss, optimizing the performance by balancing the number of transistors in series and transmission line design.
Implementation Method 1
The coupled transmission line introduces inductive coupling, which cancels at least a part of the capacitive coupling between the switch input and the switch output
Implementation Method 2
The isolation is limited by the capacitive coupling between the switch input and the switch output
Data Source
AI summary
In semiconductor switches, the isolation can be limited by the capacitive coupling between the switch input and the switch output. Ultra-high isolation can be achieved by adding a coupled transmission line to the semiconductor switch. The coupled transmission line introduces inductive coupling, which cancels at least a part of the capacitive coupling between the switch input and the switch output.