RF Switch Circuit With Shunt Leakage Paths for High Isolation
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Solution Overview
Problem
High performance RF and microwave communication devices face signal leakage currents and excessive impedances, resulting in high insertion losses and poor isolation, which existing technologies have not adequately addressed.
Innovation Solution
A radio frequency switch circuit with series connected transistors in two branches and shunt transistors that short leakage signals to ground, implemented in a triple well fabrication process technology with floating well structures and resistor-connected bulk bias supplies, to minimize impedance and enhance isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RF switch circuitry is used, then signal transmission is enabled, but signal leakage currents and excessive impedances occur resulting in high insertion losses and poor isolation
Solution Approach 1:
The circuit is divided into multiple independent branches (first branch with transistors Q1-Q2, second branch with transistors Q3-Q4) that can be independently controlled. Each branch contains series-connected transistors for signal transfer and shunt transistors (Q5-Q6, Q7-Q8) for leakage management. This segmentation allows independent optimization of each branch's contribution to isolation and insertion loss, resolving the contradiction by enabling selective activation of isolation mechanisms without affecting the entire circuit's signal transmission capability.
Solution Approach 2:
Shunt transistors Q5-Q8 serve as intermediary elements that provide alternative current paths. When activated, these shunt transistors create low-impedance paths to ground for leakage signals, mediating between the series transistors' signal transmission function and the isolation requirement. The body biasing circuits act as intermediaries that control the transistor operating states, enabling dynamic switching between signal transfer and leakage suppression modes without direct mechanical contact or complex switching mechanisms.
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A radio frequency (RF) switch circuit is provided. The switch includes a branch configured and arranged to transfer an RF signal coupled at an input node to an output node when a control signal is at a first logic value. A first transistor in the branch includes a first current electrode coupled at the input node and a second current electrode coupled to an intermediate node. The first transistor is formed in a first isolation well coupled to a bias voltage supply terminal. A second transistor in the branch includes a first current electrode coupled to the second current electrode of the first transistor at the intermediate node and a second current electrode coupled at the output node. The second transistor is formed in a second isolation well coupled to the bias voltage supply terminal. A third transistor includes a first current electrode coupled at the first intermediate node and a second current electrode coupled at a first supply terminal.