SOI RF Switch Charge Discharge Paths for Harmonic Suppression
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Solution Overview
Problem
Charge injection in semiconductor-on-insulator (SOI) radio frequency (RF) switches leads to performance degradation, including nonlinear response and undesirable RF harmonics, as existing technologies do not effectively address this issue.
Innovation Solution
A novel circuit and method utilizing charge injection control elements, such as resistors or transistors, to manage charge injection by conveying injected charge from resistively-isolated nodes to non-isolated nodes, with optional control signals to switch these elements between ON and OFF states, thereby minimizing performance degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SOI RF switch designs are used, then switching speed and isolation performance are achieved, but charge injection causes nonlinear response and RF harmonics that degrade performance
Solution Approach 1:
The patent extracts the harmful charge injection effect from the resistively-isolated node by introducing a dedicated charge injection control element (resistor or transistor) that provides a separate path for charge discharge. This isolates the charge injection problem from the main switching signal path, allowing the RF switch to maintain its switching performance while eliminating the nonlinear distortion and harmonics caused by charge accumulation.
Solution Approach 2:
The patent introduces a charge injection control element as an intermediary component between the resistively-isolated node and ground. This intermediary element (resistor or transistor) mediates the charge discharge process, controlling the rate at which injected charge is removed from the node. By adjusting the characteristics of this intermediary element, the patent optimizes both the removal of charge injection effects and the maintenance of switching performance.
2Reliability
If charge injection control elements are added to reduce charge injection effects, then linearity improves, but device complexity increases
Solution Approach 1:
The patent merges the charge injection control function with existing circuit elements by utilizing the body terminal of the switching transistor or integrating the control element into the switching signal path. This combining approach allows the charge injection control functionality to be implemented without adding completely separate control circuits, thereby reducing the increase in device complexity while still achieving improved linearity performance.
3Speed
If resistively-isolated nodes are used in SOI RF switches, then switching speed is improved, but charge injection occurs at these nodes causing performance degradation
Solution Approach 1:
The patent applies preliminary action by providing a charge discharge path through the charge injection control element before the injected charge can significantly accumulate and cause nonlinear distortion. The control element is configured to actively remove charge during the switching transition, preventing the build-up that would otherwise occur at the resistively-isolated node. This preliminary charge management maintains the fast switching speed benefit while preventing the harmful charge injection effects.
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 effectively reduces charge injection effects, improving the linearity and reliability of SOI RF switches by minimizing nonlinear behavior and RF harmonic generation, while maintaining switching time and isolation performance.
Implementation Method 1
Charge injection occurs when an applied voltage, such as a gate bias voltage, is connected to a 'resistively-isolated node' through a coupling capacitance
Data Source
AI summary
A circuit and method for controlling charge injection in a circuit are disclosed. In one embodiment, the circuit and method are employed in a semiconductor-on-insulator (SOI) Radio Frequency (RF) switch. In one embodiment, an SOI RF switch comprises a plurality of switching transistors coupled in series, referred to as “stacked” transistors, and implemented as a monolithic integrated circuit on an SOI substrate. Charge injection control elements are coupled to receive injected charge from resistively-isolated nodes located between the switching transistors, and to convey the injected charge to at least one node that is not resistively-isolated. In one embodiment, the charge injection control elements comprise resistors. In another embodiment, the charge injection control elements comprise transistors. A method for controlling charge injection in a switch circuit is disclosed whereby injected charge is generated at resistively-isolated nodes between series coupled switching transistors, and the injected charge is conveyed to at least one node of the switch circuit that is not resistively-isolated.