High Frequency Switch LNA Reflection Reduction
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Solution Overview
Problem
Conventional high-frequency switches used as automatic gain control (AGC) circuits cause total reflection at the LNA terminal, leading to degradation of reception characteristics and unstable operation.
Innovation Solution
A high-frequency switch design incorporating transistors and a resistor configuration, along with a control unit, that switches between states to allow or block signal passage, reducing reflection by attenuating signals during reception and ensuring proper termination during transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional high-frequency switch is used as an AGC circuit, then the LNA can be protected from excessive power input, but total reflection occurs at the LNA terminal causing degradation of reception characteristics and unstable operation
Solution Approach 1:
The patent segments the high-frequency switch into multiple transistors (first transistor, second transistor, third transistor) with distinct functions. The first transistor handles signal routing, the second transistor provides attenuation for AGC, and the third transistor manages termination. This segmentation allows each transistor to be optimized for its specific function, reducing total reflection while maintaining LNA protection.
Solution Approach 2:
The patent applies local quality by giving different transistors different on-resistance characteristics suited to their specific positions and functions in the circuit. The second transistor is specifically designed with appropriate on-resistance to provide attenuation without causing total reflection, while the first and third transistors have characteristics optimized for their routing and termination functions respectively.
2Ease of operation
If all transistors are in on-state during transmission to allow signal passage, then the switch functions as intended, but total reflection from the LNA terminal degrades receiving characteristics
Solution Approach 1:
The patent employs dynamic control where transistors switch between on-state and off-state based on operational mode (transmission vs. reception). During transmission, the first transistor is on to allow signal passage, while during reception, it switches off to prevent total reflection. The control unit dynamically adjusts transistor states to optimize performance for the current operational mode.
Solution Approach 2:
The high-frequency switch operates in periodic alternation between transmission mode and reception mode. During transmission, specific transistors are activated to allow signal passage; during reception, different transistor configurations are used to minimize reflection. This periodic switching of transistor states enables the system to maintain both signal passage capability and receiving characteristics.
Data Source
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AI summary
A high-frequency switch (100) includes: a first transistor (7) connected to an input terminal (1) and a first output terminal (3); a second transistor (9) connected to the first output terminal; a third transistor (10) connected to the second transistor and grounded; a resistor (11) connected to a connection between the second and third transistors and grounded; a switching circuit switchable between a state in which the switching circuit allows passage of a transmitted/received signal between the input terminal and a second output terminal (2) and a state in which the switching circuit cuts off the transmitted/received signal; and a control unit (101) to control the first, second, and third transistors and the switching circuit. At the time of reception, the control unit brings the switching circuit into the state in which the switching circuit cuts off the transmitted/received signal, places the first and third transistors in an on-state, and places the second transistor in an off-state. At the time of transmission and reception with an automatic gain control operation, the control unit brings the switching circuit into the state in which the switching circuit allows the passage of the transmitted/received signal, brings the first and third transistors in an off-state, and brings the second transistor in an on-state.