Receiver Chain Switching Circuit for Low-Noise Amplifier Protection
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Solution Overview
Problem
Existing low-noise amplifier devices in communications devices suffer from degraded noise figure due to parasitic resistances and stray capacitances, which also increase space requirements and electromagnetic coupling, making it challenging to find a balance between protection of amplification transistors and noise reduction.
Innovation Solution
Incorporating a controllable switching circuit within the amplifier device that selectively enables or disables the amplifier, reducing noise contributions from parasitic resistances and stray capacitances by isolating the amplification transistor from power supply terminals using controlled switching circuit modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If switching transistors are dimensioned with large dimensions to channel parasitic power under 10V, then the amplification transistor is protected from deterioration, but the noise figure of the low-noise amplifier device is degraded due to parasitic resistance
Solution Approach 1:
The switching circuit is divided into multiple independent switching transistors arranged in a matrix configuration. Each transistor handles a portion of the parasitic power, distributing the protective function across multiple smaller units rather than relying on a single large transistor, thereby reducing individual parasitic resistances while maintaining overall protection capability
Solution Approach 2:
The switching transistors are arranged in a nested matrix structure where multiple transistors are combined in series and parallel configurations. This nesting allows the circuit to provide sufficient protection through the collective effect of multiple transistors while minimizing the parasitic resistance impact on the noise figure
2Reliability
If more transistors are assembled in matrix form to protect the amplification transistor, then protection capability increases, but space requirements and electromagnetic coupling increase
Solution Approach 1:
The protection function is segmented into multiple small transistor units arranged in a compact matrix. This segmentation allows the circuit to achieve sufficient protection capability through the collective action of multiple small transistors rather than requiring a single large transistor, thereby reducing the overall space requirement while maintaining protection effectiveness
Solution Approach 2:
The matrix arrangement optimizes the local configuration of transistors to provide adequate protection in critical areas while minimizing the overall footprint. The local quality of each transistor position is optimized to contribute to the collective protection function without requiring excessive space
3Reliability
If more transistors are assembled in matrix form to protect the amplification transistor, then protection capability increases, but substrate and electromagnetic coupling phenomena increase which degrade noise figure
Solution Approach 1:
The switching circuit is segmented into multiple small transistor units distributed in a matrix pattern. This segmentation reduces the concentration of parasitic elements in any single location, thereby minimizing substrate coupling and electromagnetic interference effects while maintaining the collective protection capability of the switching network
Solution Approach 2:
The parasitic capacitances and substrate coupling effects are converted into beneficial shielding effects. The multiple switching transistors create a distributed capacitance network that actually helps filter high-frequency noise and protects the amplification transistor from deterioration, transforming the previously harmful parasitic effects into protective mechanisms
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 improves the noise figure of the amplifier device by eliminating noise contributions from parasitic elements and reduces space requirements while maintaining effective protection of the amplification transistor, resulting in enhanced performance and efficiency.
Implementation Method 1
The transistor T4 provides the grounding of the input of the amplifier device 4. The transistors T2 and T3 are open; they behave as stray capacitances Coff. The transistor T3 degrades the 'Noise Figure' of the amplifier 4.
Implementation Method 2
The transistors T2 and T3 are open; they behave as stray capacitances Coff. The stray capacitance of the transistor T3 allows a stray current to flow which supplies the amplifier device 4.
Implementation Method 3
The amplifier device conventionally comprises at least one amplification transistor T. The transistors T1, T2, T3 and T4 may be of the same type, for example MOSFET transistors with thick gate oxide
Data Source
AI summary
A communications device includes a transmission chain coupled to an antenna a receiver chain coupled to the antenna. The receiver chain includes an amplifier device having an input coupled to the antenna. A controlled switching circuit is included in the amplifier device and is operable to selectively disconnect conduction terminals of an amplifying transistor from power supply terminals when the transmission chain is operating to pass a transmit signal to the antenna.