Parallel Acoustic Duplexer Layout for High-Power Isolation

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Solution Overview

Problem

Current duplexer designs, particularly for high-power applications in base stations, face challenges with size, weight, cost, and power handling capabilities, as well as passive intermodulation (PIM) and isolation issues, where ceramic duplexers are often used due to their limitations in acoustic type duplexer designs.

Innovation Solution

The development of a duplexer using multiple acoustic wave or low temperature co-fired ceramic (LTCC) band pass filters in an electrically parallel configuration, combined with 90° hybrid couplers and impedance matching circuits, to enhance power handling, reduce PIM, and improve isolation between transmit and receive ports.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ceramic filters are used to achieve high power handling and low PIM, then power handling capability and PIM performance are improved, but size, weight, and cost increase significantly

Engineering Contradiction:

Improvepower handling capabilityVSAvoidduplexer weight

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The duplexer is divided into multiple independent acoustic wave filters (at least three filters with different center frequencies), each handling specific frequency bands. This segmentation allows each filter to be optimized for acoustic wave technology with low weight, while collectively achieving the power handling and PIM performance previously requiring heavy ceramic filters

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention combines multiple acoustic wave filter technologies (SAW, BAW, FBAR) with hybrid coupler circuits to create a composite duplexer system. This composite approach leverages the advantages of acoustic wave filters (low weight, small size) while achieving the power handling and isolation performance traditionally associated with ceramic filters

Inventive Principle:

Principle #40Composite materials

2Volume of stationary object

If acoustic type duplexers are used to reduce size and weight, then compactness is improved, but power handling capability and isolation performance deteriorate for high-power applications

Engineering Contradiction:

Improveduplexer sizeVSAvoidisolation performance

Core Design Contradiction:

Volume of stationary objectVSReliability

Solution Approach 1:

The invention converts the potential harmful effect of transmit signal leakage into a beneficial isolation mechanism by using hybrid couplers to deliberately create reflective paths. The hybrid couplers are designed to reflect transmit signals away from the receive port through controlled impedance matching, turning what would be leakage into active isolation

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

Hybrid couplers are introduced as intermediary components between the acoustic wave filters and the antenna ports. These couplers mediate the signal paths, providing the necessary isolation and impedance transformation to enable acoustic wave filters to achieve high-power performance with maintained isolation

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If a single transmit BPF is used in traditional duplexer design, then device simplicity is maintained, but power handling capability is limited

Engineering Contradiction:

Improvefilter configurationVSAvoidpower handling capability

Core Design Contradiction:

Device complexityVSPower

Solution Approach 1:

The single transmit BPF is segmented into multiple parallel acoustic wave filters (at least three filters), each handling a portion of the total power and specific frequency bands. This segmentation distributes the power handling load across multiple components, enabling the system to handle higher total power while maintaining acoustic wave filter advantages

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple acoustic wave filters are merged in parallel configuration with their outputs combined through hybrid couplers to the antenna port. This merging approach consolidates the power handling capability of individual filters into a unified system that achieves high-power performance while maintaining the low-weight benefits of acoustic wave technology

Inventive Principle:

Principle #5Merging (Combining)

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 results in smaller, lighter, and more cost-effective duplexers with improved power handling capabilities and reduced PIM, achieving higher isolation and efficient signal transmission, addressing the limitations of existing duplexer designs.

Implementation Method 1

The band pass filters may be acoustic wave, low temperature co-fired ceramic (LTCC) or other small form factor filters

Methodology Applied

Scientific EffectAcoustic wave: Surface Acoustic Wave

Data Source

PatentUS10944378B2Duplexer

Publication Date: 2021.03.09 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Duplexers for high power applications are disclosed. In some embodiments, a duplexer includes 2N band pass filters, where N is an integer greater than 1. The 2N band pass filters each have an input and an output and are in an electrically parallel configuration. The duplexer includes a first adaptation circuit configured to couple a transmit signal received from a transmitter to each one of the 2N band pass filters. The duplexer includes a second adaptation circuit configured to couple outputs of the 2N band pass filters to an antenna, the second adaptation circuit providing an isolated path between the antenna and a receiver.