RF Filter Circuit Using Negative Mutual Inductance for Wideband Attenuation
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Solution Overview
Problem
Existing radio-frequency filters experience attenuation decreases in higher frequency bands due to parasitic inductance, making it difficult to achieve wide frequency band attenuation, particularly in applications like 5G and UWB.
Innovation Solution
The implementation of a radio-frequency circuit with series-connected first and second inductors coupled via a magnetic field and a capacitor between the inductors and a ground terminal, utilizing negative mutual inductance to reduce combined inductance components and shift resonant frequencies to higher ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional low pass filter structure with series inductors and shunt capacitor is used, then basic filtering function is achieved, but parasitic inductance causes attenuation decrease in higher frequency bands
Solution Approach 1:
The patent introduces a parasitic inductance compensation circuit that generates a negative inductance signal to counteract the harmful parasitic inductance. By converting the harmful parasitic inductance into a compensatable parameter, the system maintains attenuation characteristics in higher frequency bands where traditional filters fail.
Solution Approach 2:
The patent uses an intermediary compensation circuit between the signal path and ground that generates an opposing inductance effect. This intermediary element (the compensation circuit) mediates between the harmful parasitic inductance and the desired filtering performance, canceling out the unwanted inductance effects.
2Adaptability or versatility
If filter is designed for wide frequency band attenuation including 5G and UWB bands, then broader coverage is achieved, but parasitic inductance effects become more significant and harder to control
Solution Approach 1:
The patent dynamically adjusts circuit parameters through the parasitic inductance compensation circuit, which modifies the effective inductance values in the signal path. By changing the compensation parameter (inductance cancellation), the filter maintains reliable attenuation performance across the extended frequency range including 5G and UWB bands.
3Reliability
If ground terminal connection is made to reference potential electrode through circuit board, then proper grounding is achieved, but additional parasitic inductance is introduced between ground terminal and reference potential electrode
Solution Approach 1:
The parasitic inductance compensation circuit acts as an intermediary that compensates for the ground path parasitic inductance. By introducing a compensating inductance element in the compensation circuit, the system counteracts the harmful inductance in the ground connection path, maintaining grounding effectiveness without suffering from the parasitic effects.
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
This configuration enhances attenuation characteristics over a wide frequency band, including higher frequency sides, by minimizing parasitic inductance effects and broadening the attenuation range.
Implementation Method 1
a first inductor L1 and a second inductor L2 that are connected in series between a first terminal T1 and a second terminal T2 and are coupled to each other via a magnetic field
Implementation Method 2
utilizing negative mutual inductance to reduce combined inductance components
Data Source
AI summary
A radio-frequency circuit includes a circuit board on or in which a ground electrode is provided, a first inductor and a second inductor provided on the circuit board, and a capacitor provided on the circuit board. The first and second inductors are cumulatively connected to each other. Relationships of Lp+Lg−M≥0 and Lp−M<0 are satisfied, where Lp denotes an inductance of a path between a connection portion between the first and second inductors and a ground terminal, Lg denotes an inductance of a path between the ground terminal and the ground electrode, and M denotes a mutual inductance between the first and second inductors.