Branching Filter Capacitor Coupling for High-Band Attenuation

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Solution Overview

Problem

Conventional branching filters face a challenge in increasing pass attenuation in higher frequency bands without deteriorating the insertion loss of lower frequency filters, especially in compact mobile communication devices that require multisystem functionality.

Innovation Solution

Incorporating a capacitor that connects the first and second filters, forming an attenuation pole on the high-frequency side of the second passband, while maintaining the insertion loss of the first filter, thereby enhancing the pass attenuation of the second filter in higher frequency bands.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the pass attenuation of the second filter in the higher frequency band is increased, then the separation performance of the second signal is improved, but the insertion loss of the first filter deteriorates

Engineering Contradiction:

Improvepass attenuation of second filterVSAvoidinsertion loss of first filter

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

A capacitor is introduced as an intermediary component connecting the first filter and the second filter. This capacitor forms an attenuation pole on the high frequency side of the second passband, enabling the second filter to achieve higher pass attenuation without adversely affecting the insertion loss of the first filter. The capacitor acts as a mediator that selectively influences the high frequency characteristics while preserving the lower frequency performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the electrical parameters of the filter system by adding a capacitor with specific capacitance value. This parameter change creates an attenuation pole at a specific frequency point, which modifies the pass characteristic of the second filter to achieve higher attenuation in the higher frequency band while maintaining the insertion loss performance of the first filter through proper parameter selection.

Inventive Principle:

Principle #35Parameter changes

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 allows for increased pass attenuation in higher frequency bands while preventing a deterioration in the insertion loss of the first filter, effectively addressing the multisystem requirements of compact mobile communication devices.

Implementation Method 1

a capacitor, which has a first end and a second end, that connects the first filter and the second filter

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the capacitor may form an attenuation pole on a high frequency side of the second passband in a pass characteristic of the second filter

Methodology Applied

Scientific EffectAttenuation pole formation: Filter (electronic)

Data Source

PatentUS11705881B2Branching filter

Publication Date: 2023.07.18 TDK CORP

AI summary

A branching filter includes a common port, a first signal port, a second signal port, a first filter, which is provided between the common port and the first signal port, that selectively passes a signal of a frequency within a first passband, a second filter, which is provided between the common port and the second signal port, that selectively passes a signal of a frequency within a second passband different from the first passband, and a capacitor that has a first end and a second end and connects the first filter and the second filter.