Stacked SOI RF Switch Circuit for Isolated-Node Charge Injection
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Solution Overview
Problem
Charge injection issues in semiconductor-on-insulator (SOI) radio frequency (RF) switches lead to performance degradation, including nonlinear response and undesirable RF harmonics, as existing technologies do not effectively address the problem of charge accumulation at resistively-isolated nodes during switching.
Innovation Solution
A novel circuit and method using charge injection control elements, such as resistors or transistors, connected between switching transistors to convey injected charge to non-resistively-isolated nodes, allowing controlled switching between ON and OFF states to mitigate charge injection effects, thereby improving RF switch performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RF switch designs are used, then basic switching function is achieved, but charge injection causes nonlinear response and harmonic generation that degrades performance
Solution Approach 1:
A charge injection control element is introduced as an intermediary component connected between the gate and source/drain of the switching transistor. This element mediates the charge injection process by providing a controlled path for charge flow, preventing excessive charge accumulation at the resistively-isolated node while maintaining the switching function. The control element acts as a buffer that decouples the gate control signal from the charge injection effect on the channel node.
Solution Approach 2:
The invention changes the electrical parameters of the switching circuit by introducing a control element that dynamically adjusts the charge distribution. By modifying the resistance or conductance parameters of the control element, the system can control the rate and amount of charge injection, thereby adjusting the nonlinear response and harmonic generation characteristics of the RF switch to achieve better performance.
2Object-generated harmful factors
If charge injection control elements are added, then charge injection is reduced, but device complexity increases
Solution Approach 1:
The charge injection control element is designed to perform multiple functions simultaneously: it controls charge injection, maintains gate voltage stability, and preserves the RF switching function. By integrating these functions into a single element, the circuit complexity increase is minimized while achieving comprehensive charge injection control. The control element can be implemented using standard transistor or resistor components that are already part of the RF switch architecture.
Solution Approach 2:
The invention merges the charge injection control function with the existing gate control structure of the RF switch. Instead of adding a completely separate control system, the control element is integrated into the gate circuitry, combining the charge control capability with the voltage control function. This merging approach reduces the overall complexity compared to adding entirely separate control circuits.
3Productivity
If resistively-isolated nodes are used in switching transistors, then switching performance is improved, but charge accumulation occurs at these nodes during switching
Solution Approach 1:
The invention extracts the excess charge from the resistively-isolated node by providing a dedicated charge removal path through the control element. The control element actively removes accumulated charge during the switching process, preventing charge buildup that would otherwise degrade performance. This extraction mechanism allows the resistively-isolated node to maintain its high-speed switching capability while avoiding the harmful effects of charge accumulation.
Solution Approach 2:
The control element operates continuously during the switching process to maintain proper charge levels at the resistively-isolated node. Rather than allowing charge to accumulate and then correcting it later, the control element provides continuous charge management throughout the switching cycle, ensuring that the node maintains optimal charge conditions for high-speed operation without interruption or performance degradation.
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-related nonlinearities and harmonic generation, enhancing the reliability and linearity of SOI RF switches by strategically managing charge injection, thus improving switching performance and maintaining RF isolation.
Implementation Method 1
The coupling capacitance through which charge injection occurs may be either a parasitic capacitance of a circuit element (e.g., gate-to-source capacitance in a transistor), or a capacitance associated with a capacitor.
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.