Symmetric Polyphase Filter Circuit for Impedance and Phase Balance
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Solution Overview
Problem
Conventional 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 is designed with a ring-shaped circuit configuration where four resistors and four reactance elements are alternately connected in series, with specific input and output terminal connections to improve symmetry, and a fifth resistor is added between certain series connection points to balance impedance, amplitude, and phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional asymmetric circuit configuration is used, then the circuit is simpler to design, but impedance variations, amplitude errors, and phase errors occur due to unbalanced voltages and currents
Solution Approach 1:
The patent applies asymmetry in reverse - it introduces symmetry into an inherently asymmetric problem. By configuring the circuit with symmetric element arrangements (first and second reactance elements, third and fourth reactance elements with corresponding resistors), the patent balances the voltages and currents at output terminals that would otherwise be unbalanced in a conventional asymmetric design, thereby suppressing impedance variations, amplitude errors, and phase errors
2Manufacturing precision
If resistors and capacitors are connected in a simple series ring configuration, then the device complexity is reduced, but amplitude error and phase error occur due to unbalanced output voltages and currents
Solution Approach 1:
The patent segments the circuit into distinct functional sections with specific connection patterns. By dividing the circuit into segments with alternating resistors and reactance elements, and strategically connecting output terminals to specific series connection points, the patent achieves balanced voltage and current distribution across all output terminals, thereby improving amplitude and phase accuracy without requiring a completely complex circuit structure
Solution Approach 2:
The patent introduces a fifth resistor as an intermediary element connected between specific series connection points in the ring configuration. This intermediary component acts as a balancing element that equalizes the impedance and distributes voltages and currents more evenly across the circuit, thereby reducing amplitude error and phase error while maintaining a relatively simple overall structure
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A first resistor (11) to a fourth resistor (14) and a first capacitor (21) to a fourth capacitor (24) are connected together in series in a ring shape. A first output terminal (41) to a fourth output terminal (44) are connected to series connection points between the first resistor (11) to the fourth resistor (14) and the first capacitor (21) to the fourth capacitor (24), a first input terminal (31) is connected to a series connection point between the fourth capacitor (24) and the first resistor (11), and a second input terminal (32) is connected to a series connection point between the second capacitor (22) and the third resistor (13). Furthermore, a fifth resistor (15) is connected between a series connection point between the first capacitor (21) and the second resistor (12) and a series connection point between the third capacitor (23) and the fourth resistor (14).