RF Front-End Power Amplifier Detuning for Lower Receiver Noise
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Solution Overview
Problem
In integrated radio-frequency front-end circuitry, the presence of a transmitter power amplifier, even when not in use, degrades the output of both the receiver and other transmitters due to shared connections to an external load like an antenna, leading to signal degradation and increased noise figure.
Innovation Solution
The implementation involves controllably detuning the transmitter power amplifier by switching an impedance element between the power amplifier and ground during receive mode to change its resonant frequency, thereby reducing its impact on the receiver, and switching it out or tuning it during transmit mode to ensure proper operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the transmitter power amplifier is integrated and shared with the receiver, then device integration and space efficiency are improved, but the receiver output quality deteriorates due to signal degradation and noise figure increase
Solution Approach 1:
The patent segments the shared radio-frequency front end into distinct transmit and receive signal paths by introducing a transmit switch that separates the power amplifier output from the receiver input during receive mode, while maintaining integration benefits through shared components like the balun and antenna connection
Solution Approach 2:
The patent introduces an intermediary transmit switch and impedance elements between the power amplifier and receiver that actively manage signal flow, preventing direct interaction between transmit and receive paths while allowing both to share the same physical infrastructure
2Device complexity
If the power amplifier remains connected to the shared output terminal, then circuit simplicity is maintained, but harmful interference and noise to the receiver increase
Solution Approach 1:
The patent extracts the power amplifier from the receive signal path by opening the transmit switch during receive mode, effectively removing the potential source of interference while keeping the amplifier physically connected to the shared terminal for quick reactivation during transmit mode
Solution Approach 2:
The patent converts the potentially harmful presence of the power amplifier into a beneficial filtering element by tuning its resonant frequency to match the transmit frequency, causing it to present high impedance at that frequency and naturally filter out transmit signals from reaching the receiver
3Measurement precision
If impedance elements are added to detune the power amplifier, then receiver noise figure is improved, but device complexity and component count increase
Solution Approach 1:
The patent makes the existing balun serve multiple functions by tuning its resonant frequency to match the power amplifier's output frequency, allowing it to act as both an impedance transformation device and a noise filtering element, thereby reducing the need for additional dedicated filtering components
Solution Approach 2:
The patent changes the resonant frequency parameter of existing components (balun and power amplifier) to match the transmit frequency, transforming them into active filtering elements that dynamically reduce noise figure without requiring additional fixed filtering 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 approach reduces signal degradation and noise figure by minimizing the loading on the receiver and optimizing the power amplifier's impedance, improving the signal-to-noise ratio and reducing insertion loss across different transmit modes.
Implementation Method 1
the switching into the radio-frequency front-end circuitry the at least one impedance element between ground and the one of the at least one transmit amplifier changes the resonant frequency of the one of the at least one transmit amplifier to reduce noise at the receive amplifier
Implementation Method 2
output of the one of the at least one transmit amplifier is controllably inductively coupled to the output terminal through a balun
Data Source
AI summary
Radio-frequency front-end circuitry includes an output terminal, a receive amplifier controllably coupled to the output terminal, at least one transmit amplifier controllably inductively coupled to the output terminal, and at least one impedance element controllably coupled between ground and one of the at least one transmit amplifier to reduce degradation of output of the radio-frequency front-end circuitry when the at least one transmit amplifier is not in use. In differential signaling, there is an impedance element between ground and each pole of the differential signal. A second transmit amplifier may generate second transmit signals and harmonics of the second transmit signals, and the second transmit amplifier may be switchably connected to the output of a first transmit amplifier so that output of the second transmit amplifier is filtered by the one of the first transmit amplifier. The transmit amplifiers may include a WiFi power amplifier and a BLUETOOTH® power amplifier.