RF Front-End Duplexer Tuning for Lower Transmit Leakage
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Solution Overview
Problem
Conventional front-end radio frequency architectures fail to optimize transmit leakage by inadequately considering factors such as RX end resonator, T/R separation, LNA matching, and LNA impedance, leading to insufficient performance due to high transconductance generated during transmission.
Innovation Solution
Incorporating a series resonator directly connected to the RX signal path of the duplexer to increase impedance, using a matching inductor on the LNA to lower its gain at the transmit band, and configuring the duplexer to have a coefficient Γ greater than 0.9, thereby reducing transconductance mismatch and improving TX leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional front-end architecture is used without considering RX end resonator and LNA impedance, then device complexity is reduced, but transmit leakage performance deteriorates due to high transconductance mismatch
Solution Approach 1:
The patent changes the impedance parameter of the duplexer at the RX end by introducing a series resonator. This modifies the electrical characteristics of the receive path to create intentional impedance mismatch that reduces transconductance during transmission, thereby improving transmit leakage performance without requiring complete architectural redesign
Solution Approach 2:
A series resonator is introduced as an intermediary component in the receive signal path of the duplexer. This resonator acts as a mediator that transforms the impedance characteristics of the RX end, creating the necessary transconductance mismatch to reduce transmit leakage while maintaining overall system functionality
2Reliability
If LNA gain is maintained at high levels across all bands, then receive signal amplification is improved, but transmit band interference increases due to insufficient LNA matching
Solution Approach 1:
The patent applies local quality by making the LNA's gain characteristic frequency-dependent. The LNA is designed to provide high gain in the receive band while having reduced gain in the transmit band, achieved through the interaction with the series resonator's impedance profile. This localized optimization allows simultaneous achievement of good receive sensitivity and reduced transmit leakage
Solution Approach 2:
The LNA's operating parameters are changed to be frequency-selective. By adjusting the LNA's matching network and operating point in conjunction with the series resonator, the LNA exhibits different gain levels at different frequencies - high gain for receive signals and low gain for transmit frequencies, thereby reducing transmit band interference
3Power
If duplexer impedance is optimized for transmit band only, then transmit power efficiency is improved, but receive band isolation deteriorates due to insufficient RX end resonator consideration
Solution Approach 1:
The series resonator in the duplexer's receive path serves multiple functions simultaneously: it provides impedance transformation for transmit band efficiency while also establishing transconductance mismatch for receive band isolation. This multi-functionality allows the single component to address both transmit and receive performance requirements without requiring separate optimization circuits
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 effectively reduces TX leakage by accounting for multiple factors, enhancing the performance of wireless devices by minimizing transconductance mismatch and improving signal isolation.
Implementation Method 1
the at least one duplexer including a series resonator directly connected to the second node along the receive signal path such as to increase an impedance of the at least one duplexer along the receive signal path when transmitting the transmit signal
Data Source
AI summary
A radio frequency module includes a transmit amplifier configured to amplify a transmit signal a receive amplifier configured to amplify a receive signal. The radio frequency module further includes at least one duplexer configured for operation in a frequency division duplex band having a transmit band and a receive band and further configured to filter the transmit signal to pass the transmit band and to filter the receive signal to pass the receive band. The at least one duplexer is coupled to the transmit amplifier via a first node and to the receive amplifier via a second node. A series acoustic resonator directly can be connected to the second node to increase a receive impedance of the at least one duplexer across the transmit band of the at least one duplexer.