RF Front-End Switch Biasing for Leakage and Linearity Control
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Solution Overview
Problem
State-of-the-art wireless devices face non-linear distortion due to large-amplitude voltages across multiple RF switches, leading to undesirable leakage current and signal interference, which existing techniques fail to adequately address.
Innovation Solution
The implementation of a negative rectifier circuit that generates a more negative substrate bias voltage by rectifying a portion of the input voltage, coupled with a gain element to improve switch linearity, and a closed-loop technique to maintain constant substrate bias voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple RF switches are used to share antennas amongst different frequency bands and operating modes, then the device can support radio processing for multiple frequency bands and modes, but large-amplitude voltages across the switches cause non-linear distortion and undesirable leakage current
Solution Approach 1:
The patent applies different biasing strategies to different parts of the switch circuit. Specifically, the series switch and shunt switch are biased differently to optimize their respective functions. The series switch uses a bias voltage that keeps it in a linear region during transmit modes, while the shunt switch is biased to remain off during transmit and only conduct during receive modes, thereby maintaining signal linearity across multiple frequency bands and operating modes
2Reliability
If negative bias voltages are applied to switch transistors to turn them off and reduce leakage current, then leakage current is reduced, but the switch linearity is compromised due to the large-amplitude voltages
Solution Approach 1:
The patent employs dynamic biasing where the bias voltages for the series and shunt switches are adjusted based on the operating mode (transmit or receive). During transmit modes, the series switch is biased to remain linear while the shunt switch is kept off. During receive modes, the biasing is reversed. This dynamic adjustment allows the switches to maintain optimal linearity characteristics for each operating condition while minimizing leakage current
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 approach effectively reduces leakage current and enhances the linearity of RF switches, minimizing signal distortion and improving the overall performance of wireless communication devices.
Implementation Method 1
The implementation of a negative rectifier circuit that generates a more negative substrate bias voltage by rectifying a portion of the input voltage
Data Source
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AI summary
Techniques for improving the linearity of radio-frequency (RF) front-end switches. In an aspect, open-loop techniques are disclosed for superimposing the output voltage of one or more negative rectifiers on a negative substrate bias voltage to reduce the non-linearities associated with voltage-dependent substrate leakage current. In another aspect, closed-loop techniques are further disclosed for maintaining the substrate bias voltage close to a reference voltage. Exemplary embodiments of the circuit blocks are further described.