Magnetically Coupled LNA Topology for Noise and Impedance Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing low noise amplifier (LNA) topologies struggle to achieve a low enough noise figure for integration with CMOS or CMOS SOI circuit blocks, leading to higher costs and larger system solutions when external LNAs are used, and face challenges in simultaneous impedance and noise matching.
Innovation Solution
A low noise amplifier topology with multiple magnetic coupled inductors and capacitors, including a cascode configuration and dual gate field effect transistors, to achieve improved impedance and noise matching, reduced inductor sizes, and enhanced stability, while incorporating electrostatic discharge protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LNA topologies are used, then the circuit can be implemented with standard components, but the noise figure is too high for integration with CMOS circuit blocks
Solution Approach 1:
The patent combines multiple inductors (L1, L2, L3) with magnetic coupling into a unified circuit structure that achieves superior noise figure performance. This merged topology enables integration with CMOS circuit blocks by achieving the required low noise figure that conventional separate components cannot provide.
Solution Approach 2:
The patent optimizes specific parameters including the magnetic coupling coefficient (k) between inductors, the quality factor (Q) of each inductor, and the transistor bias conditions. By carefully controlling these parameters, the noise figure is reduced to levels suitable for CMOS integration while maintaining manufacturability.
2Area of stationary object
If inductor sizes are reduced to decrease device area, then the area occupied by inductors is reduced, but the thermal noise contribution increases
Solution Approach 1:
The patent merges multiple inductors with magnetic coupling to create an equivalent inductance that achieves the required value with smaller individual inductors. The magnetic coupling between L1, L2, and L3 allows the circuit to function with reduced inductor areas while the coupled structure helps manage thermal noise through distributed resistance characteristics.
Solution Approach 2:
The patent applies different quality factor requirements to different inductors in the circuit. By optimizing each inductor's Q factor locally and using magnetic coupling, the overall circuit achieves low noise performance even with smaller inductor areas, as each inductor contributes differently to the total noise based on its position and coupling.
3Manufacturing precision
If impedance matching is optimized, then the input impedance matching is improved, but noise matching becomes difficult to achieve simultaneously
Solution Approach 1:
The patent combines impedance matching and noise matching functions into the same magnetic coupled inductor structure. The coupled inductors L1, L2, and L3 provide degrees of freedom that allow simultaneous optimization of both impedance matching (through input resistance control) and noise matching (through noise figure optimization) without compromising either parameter.
Solution Approach 2:
The patent uses the magnetic coupling coefficient as a dynamic parameter that can be adjusted to balance impedance matching and noise matching requirements. By varying the coupling strength between inductors, the circuit can simultaneously achieve both matching conditions that would be impossible with fixed, uncoupled inductors.
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
The proposed topology achieves lower noise figures, wider bandwidth, and better linearity, enabling integration with CMOS or CMOS SOI circuit blocks, reducing system size and cost, and improving signal-to-noise ratio for low-power input signals.
Implementation Method 1
The first, second, and third inductors may be magnetically and positively coupled with one another
Data Source
AI summary
A low noise amplifier topology can achieve very low noise figure by applying multiple magnetic coupling between gate matching inductors and source degeneration inductor of a field effect transistor. The resulting low noise amplifier has smaller inductors, which can have lower thermal noise contribution, and can maintain good gain and linearity performance. For example, a low noise amplifier includes a first inductor to receive an input; a second inductor coupled to the first inductor in series; a first field effect transistor device whose gate receives a signal from the second inductor; and a third inductor coupled to a source of the first field effect transistor device, where the third inductor is magnetically positively coupled to the first inductor and the second inductor.