Capacitive Inner-Tapped Passive Filter for High-Order Rejection
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Solution Overview
Problem
Higher order analog filters using passive components require multiple inductors and capacitors, consuming more circuit area and presenting a trade-off between filter order and area efficiency.
Innovation Solution
A high-order filter with a capacitive inner tapping technique that uses a center-tapped inductor and impedance matching capacitors to increase the effective order without increasing inductor area, implemented in both single-ended and differential filter configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple inductors and capacitors are used to achieve higher order filtering, then the rejection outside passband is improved, but the circuit area consumption increases
Solution Approach 1:
The patent combines multiple resonant circuits by sharing a common inductor L1 among the first and second resonant circuits. This merging approach allows the filter to achieve higher order filtering (fifth order) with fewer discrete inductor components, thereby reducing the overall circuit area while maintaining the required rejection characteristics outside the passband.
Solution Approach 2:
The inductor L1 serves multiple functions simultaneously by being shared across different resonant circuits. It participates in forming both the first resonant circuit (with capacitor C1) and the second resonant circuit (with capacitor C2), enabling a single component to contribute to multiple filtering functions and reducing the total component count.
2Measurement precision
If the filter order is increased to achieve higher rejection, then the filtering performance is improved, but the number of components increases
Solution Approach 1:
The patent merges resonant circuits by having the first resonant circuit (L1, C1) and second resonant circuit (L1, C2) share the common inductor L1. This consolidation achieves fifth-order filtering functionality with a reduced number of components compared to traditional designs where each resonant circuit would require separate inductors.
Solution Approach 2:
The filter is segmented into multiple resonant circuits (first resonant circuit with L1 and C1, second resonant circuit with L1 and C2, and third resonant circuit with L1 and C3) that work together to achieve high-order filtering. Each resonant circuit segment contributes specific poles to the transfer function, collectively providing the desired fifth-order rejection characteristics.
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
Achieves a sharp rejection out of band with significantly less area consumption than comparable filters, enabling higher order filtering with fewer components and improved area efficiency.
Implementation Method 1
a first resonant circuit including a first portion of the inductor and a first capacitor. The first resonant circuit is configured to attenuate first frequency components of an input signal above a cutoff frequency to generate a filtered signal
Data Source
AI summary
A high-order filter with a capacitive inner tapping technique is disclosed. The filter includes an inductor and a first resonant circuit including a first portion of the inductor and a first capacitor. The first resonant circuit is configured to attenuate first frequency components of an input signal above a cutoff frequency to generate a filtered signal. The filter further includes a second resonant circuit coupled in parallel with the first resonant circuit and including the first portion of the inductor and a second capacitor. The second resonant circuit is configured to attenuate the first frequency components of the input signal to generate the filtered signal. A third resonant circuit includes a second portion of the inductor and a third capacitor, wherein the third resonant circuit is configured to attenuate second frequency components of the filtered signal above the cutoff frequency to generate an output signal.