Balanced Acoustic Wave Duplexer Layout for Filter Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing acoustic wave duplexers for mobile communication systems suffer from insufficient isolation between transmission and reception filter chips, leading to deteriorated reception characteristics in the transmission frequency band due to induced currents caused by magnetic fields.
Innovation Solution
The acoustic wave duplexer incorporates at least one balanced filter chip with intersecting interconnections that are insulated from each other, improving the isolation characteristic between the reception and transmission filter chips, and potentially eliminating the need for a balun, thereby reducing device size and enhancing communication performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a transmission acoustic wave filter chip and a reception acoustic wave filter chip are surface mounted on a substrate to reduce the number of components, then the number of components is reduced, but the isolation between the transmission and reception filter chips deteriorates due to induced currents from magnetic fields
Solution Approach 1:
A ground electrode is introduced as an intermediary element between the transmission and reception filter chips. This ground electrode acts as a shield that intercepts and redirects magnetic field lines, preventing them from inducing currents in the reception filter chip during transmission operations, thereby maintaining isolation characteristics while keeping the component count low
Solution Approach 2:
The harmful magnetic field effect is extracted and redirected to the ground electrode. By providing a dedicated path for magnetic field lines through the ground electrode connected to ground potential, the harmful induced currents in the reception circuit are eliminated, separating the transmission and reception paths effectively
2Device complexity
If the reception acoustic wave filter chip has a balanced-to-unbalanced conversion function, then a balun can be omitted, but the isolation characteristic in the reception acoustic wave filter chip deteriorates in the transmission band-pass filter pass band due to induced currents
Solution Approach 1:
The ground electrode serves as a mediator that protects the balanced-to-unbalanced conversion structure from magnetic field interference. By positioning the ground electrode between the transmission and reception paths, it shields the IDTs and interconnections from induced currents, allowing the balun-less design to maintain both low complexity and high isolation
Solution Approach 2:
The magnetic field that would normally cause harmful induced currents is redirected through the ground electrode to ground potential. This converts the harmful effect into a beneficial shielding mechanism, where the ground electrode's proximity to the IDTs and interconnections provides automatic magnetic field cancellation without requiring additional balancing components
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 significantly enhances the isolation characteristic in the pass band of both transmission and reception filters, reducing the size of mobile communication devices and improving communication performance by minimizing the impact of magnetic fields on reception signals.
Implementation Method 1
each filter chip is an acoustic wave filter chip, such as a surface acoustic wave filter chip or a boundary acoustic wave filter chip
Implementation Method 2
each filter chip is an acoustic wave filter chip, such as a surface acoustic wave filter chip or a boundary acoustic wave filter chip
Implementation Method 3
a transmission current flows and a magnetic field occurs
Implementation Method 4
an induced current caused by the above-described magnetic field flows
Data Source
AI summary
An acoustic wave duplexer has a satisfactory isolation characteristic between a reception acoustic wave filter chip and a transmission acoustic wave filter chip, and includes a reception surface acoustic wave filter chip and a transmission surface acoustic wave filter chip mounted on a substrate. The substrate includes first and second balanced terminals and a common terminal. At least one of the transmission surface acoustic wave filter chip and the reception surface acoustic wave filter chip is a balanced filter unit that includes, as an input terminal or an output terminal, a first balanced signal terminal and a second balanced signal terminal. The acoustic wave duplexer further includes a first interconnection arranged to connect the balanced filter unit and the first balanced terminal and a second interconnection arranged to connect the balanced filter unit and the second balanced terminal. The first and second interconnections intersect with each other while being insulated from each other.