RF Switch Circuit Biasing to Prevent Shunt Transistor Turn-On
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Solution Overview
Problem
Existing radio frequency switch circuits in wireless communication devices suffer from performance degradation due to deviation voltages in switching control signals, leading to increased signal loss and harmonic distortion.
Innovation Solution
A radio frequency switch circuit design incorporating a source voltage generating unit that applies a source voltage lower than the high level of the control signal and higher than the ground voltage to the common source node, ensuring accurate switching operations by preventing shunt transistors from turning on unintentionally.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a switching control signal with deviation voltage is supplied to the shunt transistor, then the circuit can operate with simple control signal generation, but the shunt transistor may turn on unintentionally causing signal loss and degraded return loss
Solution Approach 1:
A source voltage generating unit is introduced as an intermediary component between the control signal and the shunt transistor. This unit generates a source voltage by subtracting a deviation compensation voltage from the control signal voltage, thereby mediating the control signal to prevent unintentional turn-on of the shunt transistor while maintaining simple control signal generation
Solution Approach 2:
The source voltage generating unit changes the voltage parameter of the control signal by subtracting a deviation compensation voltage. This parameter modification ensures that even when the control signal has deviation voltage, the resulting source voltage remains below the turn-on threshold of the shunt transistor, preventing unintentional activation
2Reliability
If the source voltage is set too low to prevent shunt transistor turn-on, then switching accuracy improves, but the voltage margin for control signal variations decreases
Solution Approach 1:
The source voltage generating unit performs preliminary action by pre-calculating and subtracting the deviation compensation voltage from the control signal before it reaches the shunt transistor. This preliminary adjustment ensures that the source voltage remains safely below the turn-on threshold even when control signal voltage varies, maintaining both switching accuracy and adequate voltage margin
Data Source
AI summary
There is provided a radio frequency switch circuit including a first switch circuit unit connected between a first node connected to a first signal port and a common node connected to a common port, and operated according to a first control signal, a second switch circuit unit connected between a second node connected to a second signal port and the common node and operated according to a second control signal having a phase opposite to that of the first control signal, a first shunt circuit unit connected between the second node and a common source node and operated according to the first control signal, a second shunt circuit unit connected between the first node and the common source node, and a source voltage generating unit generating a source voltage, wherein the source voltage is lower than a high level of the first control signal and higher than a ground potential.