LNA Protection Switching for Reflected RF Energy Isolation
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Solution Overview
Problem
Low noise amplifiers (LNAs) in transceivers, particularly in time division duplex (TDD) transceivers, are vulnerable to damage from high power input during transmission and reception modes due to improper control signals and low isolation between components, leading to potential burning or damage.
Innovation Solution
A protection apparatus is introduced that includes a switch and transistors to control the routing of RF signals, ensuring that reflected RF energy during transmission is directed to a load instead of the LNA, and received RF signals are properly routed to the LNA during reception, using switch control signals generated based on drive control signals to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transceiver operates in transmission mode with high power amplification, then the transmitted signal power is improved, but the LNA is exposed to high power input that can damage it
Solution Approach 1:
The patent divides the RF signal path into separate transmission and reception paths using a circulator and switch. The transmission path handles high power signals while the reception path protects the LNA through proper isolation and switching, preventing high power from reaching the LNA during transmission mode.
Solution Approach 2:
The circulator acts as an intermediary component that directs RF signals to appropriate ports based on operation mode. During transmission, it directs high power signals away from the LNA input, while during reception, it allows received signals to reach the LNA safely, thus mediating between the high power transmitter and the sensitive LNA.
2Device complexity
If the isolation between transmission and reception paths is reduced, then the device complexity is decreased, but the LNA becomes vulnerable to high power input and self-excitation
Solution Approach 1:
The circulator serves as a passive intermediary that provides inherent isolation between transmission and reception paths without requiring complex active control circuits. This maintains reliability by physically isolating the LNA from high power while keeping the overall device complexity manageable through the use of a standard circulator component.
Solution Approach 2:
The patent replaces complex mechanical or active switching isolation mechanisms with a passive circulator-based solution. The circulator's inherent directional signal flow properties provide the necessary isolation without requiring complex control systems, thereby maintaining reliability while managing complexity.
3Ease of operation
If the switch control signal routing is simplified, then the ease of operation is improved, but the LNA may receive reflected RF energy during transmission mode causing damage
Solution Approach 1:
The circulator acts as an intermediary that automatically directs reflected RF energy to the appropriate load or isolation port during transmission mode, preventing it from reaching the LNA. This maintains ease of operation by using the circulator's inherent signal routing properties rather than requiring complex additional control circuitry.
Data Source
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AI summary
Example implementations of the present disclosure relate to low noise amplifier protection. In some example implementations, an apparatus used with a transceiver is provided. The apparatus includes a first transistor having a gate/base terminal to receive a first drive control signal used for controlling a driver stage of the transceiver and a drain/collector terminal coupled to a control terminal of a switch of the transceiver. The first transistor is switched on when the first drive control signal is at a first level that enables the driver stage to amplify a first RF signal. When the first transistor is switched on, the drain/collector terminal of the first transistor outputs to a control terminal of the switch a switch control signal at a second level that enables the switch to provide a portion of the RF signal reflected by the antenna to the load.