Ring Polyphase Filter With Balancing Resistor for Impedance Matching
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Solution Overview
Problem
Conventional RC polyphase filters have an asymmetric circuit configuration, leading to unbalanced voltages and currents at output terminals, resulting in impedance variations, amplitude errors, and phase errors.
Innovation Solution
The polyphase filter connects resistors and reactance elements in a ring shape with additional resistors between specific series connection points, ensuring balanced voltage and current relationships, which suppresses impedance variations, amplitude errors, and phase errors by achieving symmetry and impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If resistors and capacitors are alternately connected in series in a ring shape with four resistors and four capacitors, then the polyphase filter can be constructed with a compact structure, but the asymmetric circuit configuration causes unbalanced voltages and currents leading to impedance variations and amplitude/phase errors
Solution Approach 1:
The patent applies asymmetry principle by intentionally introducing a fifth resistor with a different configuration than the other resistors. This fifth resistor is connected between the series connection point of the first reactance element and second resistor, and the series connection point of the third reactance element and fourth resistor. This asymmetric addition to the otherwise symmetric ring structure creates the necessary balance in voltages and currents, resolving the impedance balance issue while maintaining the compact ring structure.
2Ease of manufacture
If the conventional asymmetric polyphase filter configuration is used, then the circuit is simpler to implement, but impedance variations and amplitude/phase errors occur at the output terminals
Solution Approach 1:
The fifth resistor acts as an intermediary element that mediates between the asymmetric voltage and current distributions in the ring structure. By connecting this fifth resistor between specific series connection points, it provides a balancing path that equalizes the voltages and currents at the output terminals, thereby improving output balance without significantly complicating the overall circuit implementation.
3Manufacturing precision
If additional resistors are added to achieve symmetry, then impedance variations and amplitude/phase errors are suppressed, but the device complexity increases
Solution Approach 1:
The patent applies local quality principle by adding the fifth resistor only at the specific location where it is most needed - between the series connection points of the reactance elements and resistors. This localized addition provides the necessary symmetry and impedance balance only where required, rather than uniformly complicating the entire circuit structure. The rest of the circuit maintains its simple alternating series connection of resistors and capacitors.
Data Source
AI summary
A first resistor to a fourth resistor and a first capacitor to a fourth capacitor are connected together in series in a ring shape. A first output terminal to a fourth output terminal are connected to series connection points between the first resistor to the fourth resistor and the first capacitor to the fourth capacitor, a first input terminal is connected to a series connection point between the fourth capacitor and the first resistor, and a second input terminal is connected to a series connection point between the second capacitor and the third resistor. Furthermore, a fifth resistor is connected between a series connection point between the first capacitor and the second resistor and a series connection point between the third capacitor and the fourth resistor.