Compact Low-Noise Amplifier with Broadband Phase Noise Cancellation
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Solution Overview
Problem
Existing low-noise amplifiers (LNAs) face challenges in achieving compact form factors while maintaining desirable noise figures over both lower and higher gain ranges, and previous noise cancellation techniques result in severe limitations in broadband capabilities due to parasitic capacitance at the impedance amplifier output.
Innovation Solution
A dual-path LNA architecture with an impedance amplifier providing input impedance matching and noise cancellation by splitting noise generated by the impedance amplifier into out-of-phase paths, combined with a main amplifier to reduce noise, and a segmented main amplifier for adjustable gains, all integrated in a standard semiconductor process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If noise cancellation techniques are applied to eliminate the input match inductor, then compact form factor is achieved, but broadband capabilities are severely limited due to parasitic capacitance at the impedance amplifier output
Solution Approach 1:
The LNA is divided into two separate paths: a first noise path containing the impedance amplifier and a second noise path containing the main amplifier. This segmentation allows independent optimization of each path's function while maintaining overall system performance across broad bandwidth.
Solution Approach 2:
A summation node is introduced as an intermediary element that combines the outputs of the first and second noise paths. This mediator enables the cancellation of parasitic capacitance effects by summing the out-of-phase noise signals from both paths, thereby preserving broadband capabilities while achieving compact form factor.
2Reliability
If noise cancellation is applied to fixed-gain LNAs or maximum gain state, then noise figure is improved at maximum gain, but noise figure degrades at lower gains
Solution Approach 1:
The LNA employs variable gain control that dynamically adjusts the operation of the main amplifier across different gain states. The noise cancellation mechanism remains effective across the full gain range by adapting the impedance amplifier's operation, ensuring consistent noise figure performance whether at maximum gain or lower gain states.
Solution Approach 2:
The system changes operational parameters by adjusting the gain state of the main amplifier while maintaining the noise cancellation architecture. The impedance amplifier's output is continuously adjusted to maintain out-of-phase noise cancellation across varying gain conditions, preventing noise figure degradation at lower gains.
3Reliability
If dual-path architecture with impedance amplifier is used, then noise cancellation and compact size are achieved, but device complexity increases
Solution Approach 1:
The first noise path and second noise path are merged at the summation node, combining the impedance amplifier and main amplifier into a unified noise cancellation system. This merging allows the two separate amplifiers to work together synergistically, achieving noise reduction while managing complexity through integrated design.
Solution Approach 2:
The impedance amplifier serves multiple functions: it provides input impedance matching and generates the out-of-phase noise signal for cancellation. The main amplifier simultaneously provides signal amplification and contributes to the noise cancellation mechanism. This multi-functionality reduces overall system complexity by eliminating redundant components.
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 LNA system achieves compact size, wideband amplification, improved linearity, and low noise figure with adjustable gains, reducing parasitic capacitive loading and minimizing leakage current, while maintaining noise reduction across varying gain states.
Implementation Method 1
the impedance amplifier is configured to provide a first noise path that passes through the impedance amplifier such that the noise generated by the impedance amplifier is substantially out of phase with the noise that passes through a second noise path that passes through the main amplifier to substantially cancel noise
Data Source
AI summary
Disclosed is a low noise amplifier system. Included is a main amplifier having a main input coupled to a RF input and a main output connected to an RF output and an impedance amplifier having an impedance input coupled to the RF input and an impedance output coupled to the RF output, wherein the impedance amplifier is configured to provide input impedance matching to the main amplifier. The impedance amplifier also provides a first noise path that passes through the impedance amplifier such that the noise generated by the impedance amplifier is substantially out of phase with the noise that passes through a second noise path that passes through the main amplifier.