Hybrid Wideband RF Filter Structure for 5G Bandwidth Limits

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Solution Overview

Problem

Current RF filters for 5G systems face limitations in bandwidth and selectivity due to material properties of piezoelectric materials, leading to restricted fractional bandwidth and high insertion loss, which are inadequate for the broader RF bandwidths and high signal bandwidths required in future mobile communication systems.

Innovation Solution

A wideband filter structure combining an acoustic resonator with an analog resonator and an additional component, allowing for improved filter characteristics by integrating the wide bandwidth of LC resonators with the high selectivity of acoustic wave resonators, enabling low insertion loss and steep filter skirts while overcoming material bandwidth limitations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If piezoelectric acoustic resonators (SAW, BAW, FBAR) are used for filtering, then selectivity and insertion loss performance are improved, but fractional bandwidth is limited to 4%-16% due to material properties

Engineering Contradiction:

Improveselectivity and insertion lossVSAvoidfractional bandwidth

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent combines acoustic resonators with lumped element resonators (LC circuits) to create a hybrid filter structure. The acoustic resonators provide high selectivity and low insertion loss, while the lumped element resonators extend the bandwidth beyond material limitations. This merging allows the filter to achieve both superior signal quality and wide bandwidth coverage required for 5G applications.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The filter employs a composite structure integrating piezoelectric acoustic resonator elements with electromagnetic lumped element resonators. This composite approach combines the advantages of acoustic wave propagation (high Q-factor, sharp selectivity) with the flexibility of LC circuits (tunable bandwidth, wide frequency coverage), overcoming the inherent bandwidth constraints of pure piezoelectric materials.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If LC analog filters are used to achieve wide bandwidth, then fractional bandwidth is improved, but insertion loss increases significantly

Engineering Contradiction:

Improvefractional bandwidthVSAvoidinsertion loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The hybrid filter structure merges acoustic resonators (low insertion loss, high selectivity) with LC resonators (wide bandwidth capability). The acoustic resonators handle the frequency-selective function with minimal energy loss, while the LC resonators extend the operational bandwidth, achieving both wide bandwidth and low insertion loss simultaneously.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If higher filter orders are used to achieve steep filter skirts and high stopband suppression, then selectivity is improved, but device area and complexity increase

Engineering Contradiction:

Improvestopband suppression and filter skirt steepnessVSAvoidfilter order and area

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the need for high-order acoustic filters with a hybrid structure where lumped element resonators provide additional attenuation poles. This substitution allows achieving steep filter skirts and high stopband suppression with fewer acoustic resonator stages, reducing the overall filter order and device area while maintaining superior selectivity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 hybrid filter approach provides a wider bandwidth, higher stopband suppression, and reduced area requirements, allowing for lower filter orders and lower transmission losses compared to pure analog filters, while enabling integration capabilities beyond traditional material limitations.

Implementation Method 1

Surface Acoustic Wave (SAW), Bulk Acoustic Wave (BAW) and Film BAR (FBAR) acoustic resonators

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

LC filters (analog filters using Inductances (L) and Capacitors (C))

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11050411B2Wideband filter structure and apparatus, radio transceiver, mobile terminal, method for filtering a radio signal

Publication Date: 2021.06.29 INTEL CORP

AI summary

Examples provide a wideband filter structure and apparatus, a radio transceiver, a mobile terminal, and a method for filtering a radio signal. The wideband filter structure (10) for a radio signal comprises a combination of at least one acoustic resonator (12) and at least one analog resonator (14). The acoustic resonator (12) is coupled to the analog resonator (14). The wideband filter structure (10) comprises a further component (16), which is coupled to the combination of the acoustic resonator (12) and the analog resonator (14).