UHF Switch Circuit Using Resonance to Improve Isolation
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Solution Overview
Problem
Transistor switches face challenges in disconnecting terminals at ultra-high frequency bands due to capacitance, leading to signal leakage, making it difficult to maintain electrical isolation effectively.
Innovation Solution
A switch circuit design incorporating a transistor with an inductor in parallel, a variable gate driver, and input resistors, which adjusts the gate input voltage based on capacitance to control the turn-on and turn-off states, ensuring effective electrical connection and disconnection of ultra-high frequency signals by matching the center frequency of a resonance circuit with the input signal frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transistor switch is used to disconnect terminals, then electrical isolation is achieved at low frequencies, but signal leakage occurs at ultra-high frequencies due to capacitance
Solution Approach 1:
An inductor is introduced as an intermediary component connected in parallel with the transistor switch. This inductor forms a resonance circuit with the inherent capacitance between terminals, creating a band-stop filter that blocks ultra-high frequency signals while maintaining electrical isolation at lower frequencies. The inductor mediates between the transistor's switching function and the capacitance-induced signal leakage.
Solution Approach 2:
The invention dynamically changes the operating parameters of the transistor by applying different gate voltages. A first gate voltage turns on the transistor for low-frequency signal transmission, while a second gate voltage turns off the transistor to block low-frequency signals. This parameter change allows the switch to adapt its behavior based on the frequency characteristics of the input signal, effectively preventing both signal leakage and maintaining isolation as needed.
2Ease of operation
If a transistor switch is used for switching, then electrical connection and disconnection is achieved, but frequency response control is insufficient for ultra-high frequency signals
Solution Approach 1:
The transistor switch is enhanced to perform multiple functions: it acts as both a simple on/off switch for low-frequency signals and as part of a frequency-selective resonance circuit for ultra-high frequency signals. The same transistor structure achieves both switching control and frequency response adaptation, eliminating the need for separate frequency-selective components.
Solution Approach 2:
The invention makes the switch circuit dynamic by allowing real-time adjustment of the gate voltage to different levels. This dynamic control enables the circuit to adapt its frequency response characteristics based on operating conditions, transforming a static switch into a dynamically adjustable frequency-selective device that can optimize performance across different frequency ranges.
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 enables precise control over the switch's frequency response, enhancing isolation characteristics across a wide frequency range, particularly at ultra-high frequencies, by dynamically adjusting the gate input voltage in response to capacitance variations.
Implementation Method 1
an inductor connected to the transistor in parallel, between the input stage and the output stage... a center frequency of a resonance circuit formed by the transistor and the inductor connected to the transistor in parallel
Implementation Method 2
When a turn-on voltage is applied to the gate terminal of the transistor switch, a channel is formed between the first terminal and the second terminal... When a turn-off voltage is applied to the gate terminal of the transistor switch, the channel is not formed
Data Source
AI summary
Disclosed is a switch circuit for an ultra-high frequency band, which includes a transistor including a first terminal connected to an input stage, a second terminal connected to an output stage, and a gate terminal, an inductor connected to the transistor in parallel, between the input stage and the output stage, a variable gate driver to apply a gate input voltage to the gate terminal and, an input resistor connected between the variable gate driver and the gate terminal. The variable gate driver adjusts the gate input voltage to be in one of a first voltage level for turning on the transistor and a second voltage level for turning off the transistor. The second voltage level varies depending on a capacitance between the first terminal and the second terminal, when the transistor is in a turn-off state.