RF Switch Circuit With Dynamic Bulk Bias for High Linearity
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Solution Overview
Problem
Existing RF switch circuits face challenges in achieving high voltage withstanding and linearity, particularly in high-band 5G applications, due to uneven voltage distribution and increased nonlinearity.
Innovation Solution
The RF switch circuit design includes multiple stages of switch transistor units connected in series, with each stage comprising a switch transistor, gate bias resistor, bulk bias resistor, path resistor, mirror resistor, and a dynamic adjustment unit. The dynamic adjustment unit connects the bulk of each switch transistor to its intermediate terminal and balances voltage across the mirror resistor chain, improving voltage distribution and reducing nonlinearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple stages of switch transistor units are connected in series to improve voltage withstanding capability, then the voltage withstanding capability is improved, but the linearity deteriorates due to uneven voltage distribution
Solution Approach 1:
The patent introduces a dynamic adjustment unit connected to the bulk terminal of each switch transistor that can dynamically adjust the bulk bias voltage based on the instantaneous voltage distribution across the series-connected transistors. This dynamic adjustment compensates for the uneven voltage distribution that occurs in series-connected transistor stacks, thereby maintaining linearity while preserving the high voltage withstanding capability provided by the series configuration.
Solution Approach 2:
The patent changes the bulk bias voltage parameter of each switch transistor dynamically through the adjustment unit. By monitoring and adjusting the bulk voltage of each transistor in the series stack, the system optimizes the voltage distribution across all transistors, preventing any single transistor from experiencing excessive voltage stress and thereby maintaining both voltage withstanding capability and linearity.
2Strength
If more switch transistors are added in series to handle higher voltages, then the voltage withstanding capability is improved, but the device complexity increases
Solution Approach 1:
The dynamic adjustment unit serves multiple functions simultaneously: it monitors the voltage distribution across the series-connected transistors, adjusts the bulk bias voltage to optimize voltage distribution, and protects the transistors from excessive voltage stress. This multi-functional approach allows the system to handle high voltages without proportionally increasing circuit complexity, as a single adjustment unit can manage multiple transistors in the series stack.
Solution Approach 2:
The bulk terminal and bulk bias resistor act as intermediary elements between the series-connected switch transistors. The dynamic adjustment unit modifies the bulk voltage to mediate the voltage distribution across the transistor stack, effectively decoupling the direct voltage stress from each transistor and thereby reducing the complexity of individual transistor design while maintaining overall high voltage capability.
3Stability of the object's composition
If the bulk bias resistor is increased to improve voltage distribution, then the voltage distribution is improved, but the linearity deteriorates due to increased nonlinearity
Solution Approach 1:
Instead of using a fixed bulk bias resistor value, the patent implements a dynamic adjustment mechanism that actively modifies the bulk bias voltage based on real-time voltage distribution conditions. This dynamic approach allows the system to optimize voltage distribution uniformity while maintaining linearity, as the adjustment unit can respond to changing conditions and prevent the nonlinear effects that would result from a fixed, overly large bulk bias resistor.
Data Source
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Figure 3(a)~3(c)
AI summary
A high-linearity radio frequency switch circuit, a chip and an electronic device having same, which can relieve the nonlinear problem of radio frequency switch circuits, and improve the withstand power and the voltage withstanding capability of same. The radio frequency switch circuit consists of multiple stages of switching transistor units connected in series, wherein of each switching transistor (Mi), a gate is connected to a corresponding gate bias resistor (RAi), a drain and a source are separately connected to a corresponding via resistor (Rdsi), and a body is connected to a corresponding body bias resistor (RBi); the gate bias resistor (RAi) and the body bias resistor (RBi) in a switching transistor unit of each stage are connected in series; mirror resistors (Rci) are successively connected in series to form a mirror resistor chain; and the body of each switching transistor (Mi) is connected to an intermediate wiring end (C1) of a corresponding dynamic adjustment unit (DAi), and a first side wiring end (C2) and a second side wiring end (C3) of each dynamic adjustment unit (DAi) are respectively connected across to two ends in symmetric correspondence of at least one series resistor in the mirror resistor chain.