Stepwise Variable Attenuator Without Complex Logic Circuits
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Solution Overview
Problem
Existing T-type attenuators require complex logic circuits for varying attenuation amounts, leading to a complicated circuit configuration.
Innovation Solution
A variable attenuator with n attenuation resistor circuits and m adjustment resistor circuits, controlled by attenuation amount control signals, allows for stepwise attenuation changes without a logic circuit, using MOS transistors to achieve equal step widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a logic circuit is used for on-off control of shunt transistors in T-type attenuators, then attenuation amount can be varied, but circuit configuration becomes complicated
Solution Approach 1:
The attenuator is divided into multiple T-type attenuator units, each with its own shunt transistor and shunt resistor. Each unit can be independently controlled to provide different attenuation amounts (e.g., 0 dB, 3 dB, 6 dB, 9 dB), allowing the total attenuation to be varied by combining different unit outputs without requiring complex logic circuits for each attenuation step.
Solution Approach 2:
The shunt resistors are pre-configured with specific resistance values that correspond to predetermined attenuation amounts. This preliminary configuration of resistance values allows the attenuator to provide discrete attenuation steps simply by switching which shunt transistor is active, eliminating the need for complex real-time calculation logic circuits.
2Adaptability or versatility
If multiple T-type attenuators are used to vary attenuation amount, then attenuation range increases, but circuit configuration becomes complicated
Solution Approach 1:
Multiple T-type attenuator units are merged into a single integrated circuit structure with shared signal paths and ground connections. The series connection of shunt transistors and parallel connection of shunt resistors create a unified attenuator system that provides extended attenuation range (e.g., 0-9 dB in 3 dB steps) while maintaining a compact and simple overall circuit configuration.
Data Source
AI summary
A variable attenuator includes n attenuation resistor circuits and m adjustment resistor circuits connected in parallel to a signal line, the n attenuation resistor circuits are on-off controlled by corresponding attenuation amount control signals, each of the n attenuation resistor circuits being with a different attenuation amount, the adjustment resistor circuits correspond to k attenuation resistor circuits, and are on-off controlled by a signal of a logical product of k attenuation amount control signals for performing on-off control corresponding to each of the selected k attenuation resistor circuits, and when being on-controlled by a signal of a logical product of the k attenuation amount control signals, attenuation amount of the adjustment resistor circuits are made equal to a sum of attenuation amounts when the k attenuation resistor circuits controlled by the corresponding k attenuation amount control signals are independently on-controlled.