High-Frequency Switch Circuit Gate Network for Low Distortion
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Solution Overview
Problem
High frequency switch circuits used in mobile communication equipment face challenges in achieving low insertion loss, low distortion, and high input power simultaneously, particularly when using J-FETs, as direct connection of bidirectional diodes to the gate electrode can lead to repeated on-off switching and deterioration of distortion characteristics under high frequency signals.
Innovation Solution
A switch circuit design incorporating a transistor connected in series between input and output terminals, with a control terminal, a first resistor between the control electrode and the terminal, and a series circuit of a diode and a second resistor in parallel with the first resistor, which reduces distortion by providing an alternative current path for the gate electrode, thereby improving the high frequency switch's input power characteristics without degrading distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If bidirectional diodes are directly connected to the gate electrode of the J-FET to increase switching speed, then the response time is reduced, but the distortion characteristic deteriorates due to repeated on-off switching under high frequency signals
Solution Approach 1:
The patent introduces a resistor as an intermediary element connected between the bidirectional diode and the gate electrode of the J-FET. This resistor acts as a buffer that prevents the direct coupling of the high frequency signal from the diode to the gate, thereby eliminating the repeated on-off switching that causes distortion while still allowing the diode to provide fast switching capability. The resistor value is specifically chosen to balance the competing requirements of switching speed and distortion reduction.
2Reliability
If a resistor is connected between the gate electrode and control terminal to ensure off-state, then the transistor is reliably turned off, but the switching response time increases
Solution Approach 1:
The patent combines multiple circuit elements with different functions into a unified gate control structure. The bidirectional diode, resistor, and gate electrode are merged into a single control path where the diode provides fast switching action and the resistor ensures reliable off-state. This merging allows the circuit to simultaneously achieve both fast response time and reliable off-state without requiring separate control mechanisms.
3Power
If the switch circuit is designed for high input power handling, then the power capacity is increased, but the distortion characteristic worsens due to the non-linear effects at large voltage amplitudes
Solution Approach 1:
The resistor connected in series with the bidirectional diode serves as an intermediary that isolates the gate electrode from large voltage swings. When large voltage amplitudes are applied to the switch, the diode may conduct and generate non-linear effects, but the series resistor limits the voltage change at the gate electrode, preventing these non-linear effects from translating into signal distortion. This allows the circuit to handle high input power while maintaining low distortion.
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 proposed solution effectively reduces distortion and maintains high input power efficiency in high frequency switch circuits, allowing for faster response times and improved harmonic characteristics without deteriorating power efficiency, even under large voltage amplitudes.
Implementation Method 1
a series circuit of a diode and a second resistor, the series circuit being connected in parallel with the first resistor between the control terminal and the control electrode of the transistor
Implementation Method 2
a series circuit of a diode and a second resistor
Data Source
AI summary
There has been a problem that the distortion characteristic of a switch circuit for a high frequency is deteriorated. A switch circuit in accordance with one aspect of the present invention includes a transistor connected in series between input and output terminals, a control terminal that receives a signal to control the conductive state of the transistor, a first resistor connected between the control electrode of the transistor and the control terminal, and a series circuit of a diode and a second resistor, the series circuit being connected in parallel with the first resistor between the control terminal and the control electrode of the transistor.