RF Switch Cell Topology for Harmonic Suppression Under Hot Switching
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Solution Overview
Problem
Traditional RF switches with off-state linearization networks require external bias circuitry and are inefficient under hot switching conditions, leading to harmonic distortion and real estate issues.
Innovation Solution
A radio frequency switch design featuring a series of switch cells with FETs and diode stacks that intercept non-linear avalanche currents, eliminating the need for external bias circuitry and enhancing switching performance by dynamically biasing the switch cells with varactor networks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a traditional off-state linearization network is placed in parallel with the RF switch to reduce harmonic distortion, then the harmonic distortion is reduced, but the circuit real estate increases due to external bias circuitry requirements
Solution Approach 1:
The patent merges the off-state linearization function with the RF switch structure by integrating diode stacks directly into the switch cell architecture. The diode stacks are coupled to the FET bodies and operate autonomously without external bias circuitry, combining the switching and linearization functions into a unified structure that reduces circuit real estate while maintaining harmonic distortion reduction capabilities
Solution Approach 2:
The diode stacks are designed to automatically intercept non-linear avalanche currents generated by the FET bodies during off-state operation. This self-service mechanism eliminates the need for external bias circuitry to provide linearization, as the diode stacks inherently redirect the harmful currents without requiring additional control circuits or external power sources
2Reliability
If transmit signals are applied to the RF switch in off-state, then the RF switch blocks the signals, but undesirable harmonics are generated from non-linear capacitance
Solution Approach 1:
The patent converts the harmful non-linear avalanche currents generated by the FET bodies into a beneficial effect by using diode stacks to intercept and redirect these currents. The diode stacks provide a controlled path for the avalanche currents, preventing them from causing harmonic distortion while maintaining the signal blocking function. This transforms the harmful non-linear effect into a manageable current path that protects the receiver circuitry
3Adaptability or versatility
If the RF switch transitions under hot switching conditions, then the switch must handle transmit-level RF signals, but reliable switching becomes more difficult
Solution Approach 1:
The diode stacks are pre-configured and coupled to the FET bodies before switching operations begin. During hot switching transitions, the diode stacks are already in position to intercept any non-linear avalanche currents that may be generated. This preliminary configuration ensures that the switching transition can proceed reliably without the need for additional protective measures or external bias adjustments during the critical transition period
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 prevents harmonic distortion and reduces real estate requirements by allowing faster switching times and reliable operation under hot switching conditions without external bias circuitry.
Implementation Method 1
a first diode stack having a first anode coupled to the body of switch cell X and a first cathode coupled to the drain of switch cell X+1
Data Source
AI summary
A radio frequency switch having an N number of switch cells coupled in series is disclosed. Each of the switch cells includes a field-effect transistor (FET), wherein a source of switch cell 1 is coupled to a first port, a drain of switch cell N is coupled to a second port, and a drain of switch cell X is coupled to a source of switch cell X+1 for switch cell 1 through switch cell N. A first diode stack has a first anode coupled to the body of switch cell X and a first cathode coupled to a drain of switch cell X+1 for switch cell 1 through switch cell N−1, and a second diode stack has a second anode coupled to the body of switch cell X and a second cathode coupled to the source of switch cell X−1 for switch cell 2 through switch cell N.