Resistive Directional Coupler Circuit for Low-Frequency Chip Integration
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Solution Overview
Problem
Conventional directional couplers with inductors become physically large when handling low frequency signals, making them unsuitable for applications where miniaturization is essential.
Innovation Solution
A directional coupler configuration incorporating a resistive element and amplifier circuits that output currents proportional to voltages and voltage differences, with adder circuits to sum these currents, allowing for efficient signal transmission without the need for large inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inductors are used in directional coupler to achieve signal transmission, then signal transmission is enabled, but physical size becomes large at low frequency bands
Solution Approach 1:
The patent replaces the conventional inductor-based directional coupler structure with an operational amplifier-based circuit implementation. This substitution transforms the mechanical/physical inductor system into an electronic circuit system using operational amplifiers, resistors, and capacitors, thereby achieving the same directional coupling function without the large physical size associated with low-frequency inductors
Solution Approach 2:
The patent changes the fundamental operating parameters from inductor-based impedance transformation to operational amplifier-based voltage/current amplification and subtraction. By using operational amplifiers with high gain and virtual ground concepts, the circuit achieves directional coupling through parameter manipulation rather than physical inductor dimensions, enabling compact low-frequency operation
Data Source
AI summary
A directional coupler is configured so as to include: a resistive element in which one end thereof is connected to a first terminal and the other end is connected to a second terminal; a first amplifier circuit for outputting either a current directly proportional to a first voltage applied to the one end of the resistive element or a current directly proportional to a second voltage applied to the other end of the resistive element; a second amplifier circuit for outputting a first current which is directly proportional to the voltage difference between the first voltage applied to the one end of the resistive element and the second voltage applied to the other end of the resistive element and whose polarity is different from that of the current outputted from the first amplifier circuit when a signal is flowing from the first terminal to the second terminal, and for outputting a second current which is directly proportional to the voltage difference between the first voltage and the second voltage and whose polarity is identical to that of the current outputted from the first amplifier circuit when a signal is flowing from the second terminal to the first terminal; and a first adder circuit for outputting either a signal having a voltage value directly proportional to a current which is the sum total of the current outputted from the first amplifier circuit and the first current or a signal having a voltage value directly proportional to a current which is the sum total of the current outputted from the first amplifier circuit and the second current to a third terminal.