RF Front-End Filter Layout for Lower Band-Edge Insertion Loss
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Solution Overview
Problem
Conventional filter devices experience increased passband insertion loss due to insufficient attenuation in the low and high band sides, as the amount of attenuation in one filter affects the other filter's passband, leading to inefficient signal transmission in radio receiver circuits.
Innovation Solution
A filter device with parallel-connected filters, where the first filter includes series arm resonators of different fractional bandwidths and the second filter includes parallel arm resonators of different fractional bandwidths, to enhance attenuation at the band edges, thereby reducing insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two bandpass filters of different passbands are arranged in parallel for a wider passband, then the passband coverage is improved, but the passband insertion loss increases due to insufficient attenuation at band edges
Solution Approach 1:
The patent applies local quality by configuring series arm resonators with different fractional bandwidths (first series arm resonator with first fractional bandwidth, second series arm resonator with second fractional bandwidth) to create different attenuation characteristics at different frequency regions. This allows the low band sided filter to provide strong attenuation specifically at the high band edge where needed, while maintaining good transmission in the low band passband region.
Solution Approach 2:
The patent changes the fractional bandwidth parameter of series arm resonators to optimize filter performance. By setting the first fractional bandwidth different from the second fractional bandwidth, the filter achieves enhanced attenuation at band edges while maintaining low insertion loss in the passband, directly addressing the technical contradiction between passband coverage and insertion loss.
2Loss of energy
If the amount of attenuation of the low band sided filter in the passband of the high band sided filter is increased, then the insertion loss at the high band edge is reduced, but the filter complexity increases
Solution Approach 1:
The patent achieves targeted attenuation enhancement at the high band edge by assigning different fractional bandwidths to specific series arm resonators. The first series arm resonator with first fractional bandwidth and the second series arm resonator with second fractional bandwidth create localized attenuation poles that precisely address the insertion loss issue at the high band edge without requiring additional filter stages or complex circuitry.
Solution Approach 2:
By adjusting the fractional bandwidth parameter of existing series arm resonators rather than adding more components, the patent achieves the desired attenuation enhancement at band edges. This parameter optimization approach reduces filter complexity compared to structural modifications while effectively lowering insertion loss at the high band edge.
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
The proposed configuration effectively reduces passband insertion loss by increasing attenuation at both the low and high band edges, improving signal transmission efficiency in the filter device.
Implementation Method 1
The plurality of series arm resonators include a first series arm resonator and a second series arm resonator, and under a condition that a value obtained by dividing a difference between an antiresonance frequency and a resonance frequency of each series arm resonator by the resonance frequency is defined as a fractional bandwidth
Implementation Method 2
a value obtained by dividing a difference between an antiresonance frequency and a resonance frequency of each series arm resonator by the resonance frequency is defined as a fractional bandwidth
Data Source
AI summary
A filter device according to an embodiment of the present disclosure includes a first filter and a second filter that are connected in parallel between a first terminal and a second terminal. The first filter includes multiple series arm resonators. The series arm resonators are disposed in series in a path from the first terminal via the first filter to the second terminal. The series arm resonators include a first series arm resonator and a second series arm resonator. Under a condition that a value obtained by dividing a difference between an antiresonance frequency and a resonance frequency of each series arm resonator by the resonance frequency is defined as a fractional bandwidth, a first fractional bandwidth of the first series arm resonator is different from a second fractional bandwidth of the second series arm resonator.