Digital Step Attenuator Diversion Circuit for RF Leakage Suppression
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Solution Overview
Problem
Conventional digital step attenuators face challenges in accurately attenuating high-frequency RF signals due to parasitic capacitors that form a high-pass path, allowing signal leakage even in attenuation mode.
Innovation Solution
The proposed digital step attenuator incorporates a diversion circuit that couples the bypass switch's control terminal to the ground terminal, utilizing a diversion capacitor, resistor, and switch in series, and an array of diversion resistors and switches to direct high-frequency signals to ground, ensuring effective attenuation by controlling the resistance and capacitance to adjust attenuation amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a bypass switch is used to allow RF signal to pass through in bypass mode, then the ease of operation is improved, but parasitic capacitors of the bypass switch create a high-pass path that allows high-frequency signal leakage in attenuation mode
Solution Approach 1:
A diversion circuit is introduced as an intermediary component between the bypass switch and ground. This diversion circuit includes a diversion switch and diversion resistor that activate when the bypass switch is open, providing a controlled path to ground that prevents high-frequency signal leakage through the bypass switch's parasitic capacitors while maintaining the bypass functionality when needed
Solution Approach 2:
The patent changes the electrical parameters (resistance and capacitance) of the diversion circuit to optimize its performance. By carefully selecting the diversion resistor value and adding a diversion capacitor, the circuit creates a low-impedance path to ground for high-frequency signals in attenuation mode, effectively suppressing signal leakage while minimizing impact on the main signal path
2Manufacturing precision
If the bypass switch is open in attenuation mode, then the signal attenuation function is achieved, but high-frequency signals can still leak through parasitic capacitors of the bypass switch
Solution Approach 1:
The patent converts the harmful effect of parasitic capacitors into a beneficial feature by using them in conjunction with the diversion circuit. The diversion circuit is designed to work with the parasitic capacitance, creating a combined effect that directs high-frequency leakage signals to ground through the diversion resistor, thereby transforming the harmful leakage path into a controlled grounding path that improves attenuation accuracy
Solution Approach 2:
The diversion circuit acts as an intermediary that intercepts high-frequency signals attempting to leak through the bypass switch's parasitic capacitors. By providing an alternative path to ground with appropriate impedance characteristics, the diversion circuit effectively blocks the harmful leakage while allowing the main attenuation function to operate correctly
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
This solution ensures accurate high-frequency signal attenuation, preventing signal leakage and allowing for tunable attenuation, thereby enhancing the digital step attenuator's performance in both attenuation and bypass modes.
Implementation Method 1
the diversion circuit (coupled to between the gate terminal of the bypass switch and the ground terminal in the attenuation mode) effectively directs the high-frequency input signal to the ground terminal
Implementation Method 2
The diversion capacitor couples the control terminal of the bypass switch to the ground terminal through the diversion resistor when the diversion switch is closed
Data Source
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AI summary
A digital step attenuator (DSA) with efficient high-frequency signal attenuation is shown. The DSA has an attenuation circuit, a bypass switch, and a diversion circuit. The attenuation circuit is coupled between an input node and an output node of the digital step attenuator. The bypass switch is controlled by a bypass control signal to provide a bypass path between the input node and the output node of the digital step attenuator. The diversion circuit couples a control terminal of the bypass switch to a ground terminal in response to the bypass control signal being in an inactive state.