Switched Negative Inductance Circuit for Wideband Impedance Matching
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Solution Overview
Problem
Current circuit technologies fail to provide efficient negative inductance circuits that operate at high power levels with wideband performance, leading to inefficient power transfer and narrowband responses in compact antennas.
Innovation Solution
A switched mode negative inductance circuit using positive and negative power supplies, controlled switches, and an inductor, which operates by sensing voltage and controlling current flow through a square wave, minimizing DC power dissipation and enabling high power and broad band performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If small signal non-Foster circuits are used to match antennas, then impedance matching is achieved, but power dissipation becomes excessively high at high power levels
Solution Approach 1:
The patent employs periodic switching action where switches alternately connect and disconnect the inductor from the circuit at high frequency. This periodic switching allows the circuit to present a negative inductance impedance to the antenna while the inductor itself remains passive and does not continuously dissipate power. The switching controller modulates the switches based on the antenna current, creating the desired impedance matching effect only when needed, rather than continuously drawing DC power as in class A amplifiers.
Solution Approach 2:
The patent replaces the traditional active electronic amplification mechanism (class A, B, or C amplifiers that continuously or periodically draw DC power) with a passive inductor combined with electronic switching. The switching mechanism, controlled by a controller that senses antenna current, substitutes for the active amplification, allowing the passive inductor to achieve the negative inductance effect without the continuous DC power dissipation inherent in traditional amplifier-based non-Foster circuits.
2Loss of energy
If resonant non-Foster circuits are used, then high power efficiency is achieved at resonant frequency, but bandwidth becomes extremely narrow
Solution Approach 1:
The patent employs dynamic switching control where the switching controller continuously monitors the antenna current and adjusts the switching of the first and second switches accordingly. This dynamic adaptation allows the circuit to maintain optimal performance across a wide frequency range rather than being fixed at a single resonant frequency. The switching frequencies and duty cycles can be adjusted in real-time to match different operating conditions, providing wideband operation while maintaining high power efficiency.
Solution Approach 2:
The patent changes the operating parameters dynamically by varying the switching frequency and duty cycle of the controlled switches based on the antenna current characteristics. This allows the circuit to adapt to different frequency bands and impedance conditions, transforming the fixed resonant frequency limitation into a wideband adaptable system. The controller modifies switching parameters in response to changing operating conditions, enabling efficient operation across multiple frequencies rather than being constrained to a single resonant point.
3Reliability
If class A amplifier biasing is used in non-Foster circuits, then continuous impedance matching is maintained, but DC power dissipation increases proportionally to Q times the RF power
Solution Approach 1:
The patent replaces continuous class A amplifier operation with periodic switching action. The first and second switches are turned on and off periodically at high frequency, allowing the passive inductor to provide negative inductance only during the switching intervals when needed for impedance matching. This periodic operation eliminates the continuous DC bias current requirement of class A amplifiers, reducing DC power dissipation from being proportional to Q times RF power down to only the minimal power required for switching control.
Solution Approach 2:
The patent enables the passive inductor to serve the impedance matching function without requiring continuous active amplification. The switching controller senses the antenna current and automatically activates the switches only when impedance correction is needed, allowing the system to be self-regulating. The passive inductor combined with periodic switching provides the negative inductance effect on-demand, eliminating the need for continuous DC power consumption to maintain impedance matching.
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 achieves efficient high power and wideband performance by dissipating minimal DC power and allowing impedance matching at high power levels, overcoming the limitations of traditional non-Foster circuits.
Implementation Method 1
an inductor having a first electrode coupled to second poles of the first and second controlled switches and a second electrode coupled to the input node
Data Source
AI summary
A switched mode negative inductance circuit includes an input node responsive to a voltage signal. The circuit also includes first and second voltage sources, first and second controlled switches having first poles coupled to the first and second voltage sources, respectively and an inductor having a first electrode coupled to second poles of the first and second controlled switches and a second electrode coupled to the input node. The input node is coupled to a control electrode of the first controlled switch, and to a control electrode of the second controlled switch through a voltage inverting circuit. The disclosure also illustrates balanced negative inductance circuits and implementation approaches using NMOS transistors.