Variable Reactance Circuit for High-Speed Impedance Matching
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Solution Overview
Problem
Existing impedance matching devices face challenges in achieving high-speed and high-voltage operations due to the limitations of rotary variable capacitors and diode-based configurations, which result in complex and large circuit designs prone to overheating and voltage issues.
Innovation Solution
A variable reactance circuit with a loosely coupled line portion and a capacity variable portion using diodes and capacitors, where the diode capacitance is changed rapidly by a variable DC power supply, allowing for high-speed reactance changes without the need for additional resistors, and a compact design by using a ground reference for the diode and power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diodes are arranged in multiple stages in series to divide voltage, then the resistor can operate within rated voltage limits, but the circuit becomes complicated and the impedance matching device becomes larger
Solution Approach 1:
The patent extracts the voltage division function from the diode stages and relocates it to the transmission line structure itself. By utilizing the inherent impedance characteristics and physical configuration of the transmission line, the voltage is naturally divided without requiring multiple diode stages, thus simplifying the circuit while maintaining resistor voltage rating compliance
Solution Approach 2:
The transmission line is given multiple functions: it serves both as the signal transmission path and as the voltage division mechanism. This multi-functionality eliminates the need for separate voltage division components (multiple diode stages), reducing circuit complexity while ensuring the resistor operates within its rated voltage limits
2Ease of operation
If rotary variable capacitors are used for impedance matching, then the capacitance can be changed mechanically, but the capacitor operating time depends on rotation speed and high-speed operation is not achieved
Solution Approach 1:
The patent replaces the mechanical rotation system with an electrical control system. Instead of mechanically rotating the capacitor to change capacitance values, the system uses electronic switching and control circuits to achieve capacitance variation, thereby eliminating the speed limitation imposed by mechanical rotation and enabling high-speed impedance matching operations
3Reliability
If resistors are inserted between the variable DC power supply and the diode to prevent high frequency components from flowing, then high frequency blocking is achieved, but the resistor generates heat when high frequency voltage is applied
Solution Approach 1:
The patent introduces an intermediary element (such as a capacitor or inductor) between the resistor and the high frequency signal path. This intermediary blocks or shunts the high frequency components away from the resistor, allowing the resistor to perform its DC bias function without being subjected to high frequency voltage that would cause excessive heat generation
Solution Approach 2:
The patent extracts the high frequency blocking function from the resistor and assigns it to a dedicated component (capacitor or inductor). This separation of functions allows the resistor to handle only DC current without generating excessive heat from high frequency voltage, while the dedicated component performs the high frequency blocking
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
Enables high-speed and high-voltage impedance matching with a compact circuit design, preventing overheating and reducing the complexity and size of the circuit by eliminating the need for multiple diode stages and additional resistors.
Implementation Method 1
the capacitance can be electrically changed at high speed by changing reverse bias voltage applied to the diode
Implementation Method 2
a loosely coupled line portion which includes a first line and a second line loosely coupled to the first line
Data Source
AI summary
An impedance matching device comprises a variable reactance circuit. The variable reactance circuit comprises a loosely coupled line portion 4 which includes a first line 2 and a second line 3 loosely coupled to the first line. One end 3a of the second line is connected to ground 5. The variable reactance circuit further comprises a capacity variable portion 6 provided between the other end 3b of the second line and ground. The capacity variable portion comprises a diode 7 connected between the other end of the second line and ground, a capacitor 8 connected in series to the diode between the other end of the second line and the diode, a variable DC power supply 11 connected between ground and a connection point 9 between the capacitor and the diode so as to apply reverse bias voltage to the diode, and a resistor 10 connected in series to the variable DC power supply between the connection point and ground.