Split LNA Noise Shaping via Mutually Coupled Inductors
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Solution Overview
Problem
Achieving a simultaneous optimization of noise figure (NF) and output-to-output isolation in split LNA architectures is challenging, as improving one parameter often worsens the other, requiring careful design and optimization.
Innovation Solution
The use of mutually coupled inductors and adjustable inductance values allows for control of noise figure and output-to-output isolation, maintaining a set output matching condition by manipulating the mutual coupling coefficient and inductance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional split LNA architecture is used to achieve high output-to-output isolation, then isolation performance is improved, but noise figure deteriorates
Solution Approach 1:
The patent changes the electrical parameters of the inductive elements by introducing mutually coupled inductors with adjustable coupling coefficients. By varying the coupling coefficient k between 0 and 1, the design can continuously adjust the tradeoff between noise figure and output-to-output isolation, achieving both parameters within specification ranges simultaneously
Solution Approach 2:
The patent introduces mutually coupled inductors as intermediary elements between the two amplification paths. These inductors act as mediators that provide controlled magnetic coupling to achieve noise shaping, allowing the system to improve noise figure without sacrificing output-to-output isolation performance
2Reliability
If design optimization focuses on improving noise figure, then noise performance is improved, but output-to-output isolation worsens
Solution Approach 1:
The patent introduces dynamic adjustability through the coupling coefficient k of the mutually coupled inductors. This dynamic parameter allows the designer to optimize the balance between noise figure and isolation based on specific application requirements, rather than being fixed in a compromise design
3Reliability
If simultaneous optimization of noise figure and output-to-output isolation is attempted, then both parameters are improved, but device complexity increases
Solution Approach 1:
The patent merges the noise figure optimization and isolation optimization functions into a single inductive element structure with mutual coupling. Instead of requiring separate circuits for each function, the mutually coupled inductors achieve both objectives simultaneously through their coupled magnetic fields, reducing overall device complexity
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 provides a flexible design that can tailor noise performance and isolation to specific application requirements, achieving improved tradeoffs between NF and isolation.
Implementation Method 1
an inductive element comprising a pair of mutually coupled inductors... inductance values of each inductor of the pair of mutually coupled inductors and a degree of mutual coupling of the pair of mutually coupled inductors are selectable to control noise figure and output-to-output isolation values
Data Source
AI summary
Split low noise amplifier (LNA) architectures providing an improved tradeoff between the noise figure (NF) and the output-to-output isolation are disclosed. The described LNAs include cascode transistors in two amplification paths and an inductive element including a pair of inductors and a common inductor. The inductance values of the inductors and the common inductor can be selected to obtain an improved tradeoff between the NF and isolation while meeting the output matching conditions.