High-Frequency Attenuator Layout With Fewer Switches and Lower Parasitics
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Solution Overview
Problem
Conventional high frequency variable attenuation circuits require a large circuit surface area due to the increasing number of resistors and switching elements, leading to increased parasitic capacitance and impedance matching issues.
Innovation Solution
A high frequency variable attenuation circuit configuration with a π-type attenuator topology, where the first switching circuit is only connected to the output side, reducing the number of switching elements and minimizing parasitic capacitance, and incorporating a bypass switching element for attenuation control, while maintaining impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of selection variations of the attenuation amount increases, then the attenuation control flexibility is improved, but the circuit surface area increases
Solution Approach 1:
The patent divides the attenuation control function into two independent parts: a fixed π-type attenuator for impedance matching and a variable attenuator for attenuation control. This segmentation allows the variable attenuator to use fewer switching elements since the impedance matching function is already provided by the fixed π-type attenuator, thereby reducing the circuit surface area while maintaining attenuation control flexibility.
Solution Approach 2:
The π-type attenuator serves dual functions: it provides both impedance matching and a baseline attenuation level. This multi-functionality reduces the burden on the variable attenuator, allowing it to achieve multiple attenuation variations with fewer switching elements, thus reducing the overall circuit surface area while maintaining adaptability.
2Adaptability or versatility
If the number of resistors and switching elements increases, then the attenuation control flexibility is improved, but the parasitic capacitance increases
Solution Approach 1:
By segmenting the attenuation function into a fixed π-type attenuator and a variable attenuator, the patent reduces the number of switching elements needed in the variable portion. Fewer switching elements directly reduce the total parasitic capacitance while maintaining the ability to provide multiple attenuation levels through the combined operation of both attenuators.
3Adaptability or versatility
If switching circuits are added on both input and output sides, then the attenuation control flexibility is improved, but the device complexity increases
Solution Approach 1:
The patent extracts the impedance matching function from the variable attenuator and assigns it to a separate fixed π-type attenuator. This extraction allows the variable attenuator to focus solely on attenuation control with fewer switching elements, reducing device complexity while maintaining the flexibility to control attenuation levels through the combination of both circuits.
Data Source
AI summary
A high frequency variable attenuation circuit includes an input terminal, an output terminal, a first resistor, a second resistor, a third resistor, and a first switching circuit. The first switching circuit has an output side resistor and an output side switching element that are connected in series to each other. The first switching circuit has a first circuit end connected to the second end of the second resistor and the output terminal, and a second circuit end connected to the ground.