Acoustic Wave Duplexer Cancel Circuit for High Isolation
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Solution Overview
Problem
Existing duplexer designs face challenges in achieving improved isolation characteristics without increasing insertion loss, particularly in multi-band wireless communication devices, where the reduction of components like interstage filters necessitates enhanced performance from the duplexer itself.
Innovation Solution
Incorporating a cancel circuit with a longitudinal coupling type acoustic wave resonator connected in parallel with the duplexer's filters, which adjusts the amplitude and phase of signals to effectively cancel isolation signals, thereby improving isolation characteristics without significant increases in insertion loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase converter is connected in parallel with a resonator to convert phase by 180 degrees, then isolation characteristic is improved, but it is difficult to achieve low loss together with high attenuation and high isolation
Solution Approach 1:
The patent introduces a cancel circuit as an intermediary component that includes a resonator and a phase converter. This cancel circuit acts as a mediator to generate a cancellation signal that interferes with and reduces the isolation signal, thereby improving isolation characteristic without requiring the main filter to operate at compromised performance levels. The cancel circuit is connected in parallel to the filter, allowing it to independently handle isolation signal cancellation while the filter maintains its primary signal processing function with low insertion loss.
2Device complexity
If the number of components is reduced by removing interstage filters, then device complexity is reduced, but attenuation characteristic and isolation characteristic of the duplexer must be improved
Solution Approach 1:
The patent merges the functions of the filter and the cancel circuit into a single integrated duplexer system. The cancel circuit is connected in parallel to the filter, combining their functions to simultaneously achieve signal filtering and isolation signal cancellation. This merging allows the removal of separate interstage filters while maintaining or improving attenuation and isolation characteristics through the cooperative operation of the integrated filter and cancel circuit.
Solution Approach 2:
The cancel circuit operates by detecting the isolation signal that leaks through the filter and generating a cancellation signal with opposite phase. This feedback mechanism continuously monitors and compensates for isolation signal leakage, allowing the system to maintain high attenuation and isolation characteristics even with reduced component count. The feedback loop ensures that the duplexer adapts to maintain performance requirements.
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 solution enhances isolation characteristics by approximately 10 dB in both transmit and receive bands while maintaining low insertion loss, effectively addressing the need for reduced component count and improved performance in downsized wireless communication devices.
Implementation Method 1
a cancel circuit including a longitudinal coupling type acoustic wave resonator
Implementation Method 2
acoustic wave resonator
Implementation Method 3
adjusts the amplitude and phase of signals to effectively cancel isolation signals
Data Source
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AI summary
A duplexer includes: a transmit filter that is connected between an antenna terminal and a transmit terminal and has a plurality of acoustic wave resonators; a receive filter that is connected between the antenna terminal and a receive terminal and has a plurality of acoustic wave resonators; and a delay line or a longitudinal coupling type resonator that is connected in parallel with at least one of the plurality of acoustic wave resonators of the transmit filter and the plurality of acoustic wave resonators of the receive filter and has at least two IDTs (Interdigital Transducers).