Noise-Canceling LNA Circuit With Inverting Path Switch Noise Suppression
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Solution Overview
Problem
Existing low noise amplifiers (LNAs) in wireless transceivers face challenges in managing noise and space efficiency, particularly in mobile devices with multiple frequency bands, leading to large footprints due to multiple receive paths and individual impedance matching circuits.
Innovation Solution
A noise-canceling LNA circuit that splits the receive signal into a main path and an inverting path, using a multiplexer to generate switch noise, which is inverted and amplified in the inverting path, then destructively summed with the main path noise, reducing the need for duplicate impedance matching circuits and inductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple receive paths are used to support multiple frequency bands, then the adaptability of the receiver is improved, but the device footprint increases due to duplicate impedance matching circuits and inductors
Solution Approach 1:
The patent combines multiple receive paths into a shared infrastructure by using a single impedance matching circuit and inductor that serves both the main path and inverting path. This merging of shared components reduces the overall footprint while maintaining support for multiple frequency bands through the multiplexer-based path selection.
Solution Approach 2:
The impedance matching circuit and inductor are designed to be universal components that can handle signals from multiple frequency bands. By making these components multi-functional and shared across different receive paths, the circuit achieves frequency band adaptability without requiring separate dedicated components for each band, thus reducing the overall footprint.
2Device complexity
If a multiplexer is used to switch between frequency bands, then the device complexity is reduced, but switch noise is introduced into the signal path
Solution Approach 1:
The patent converts the harmful switch noise into a beneficial cancellation mechanism by deliberately generating an inverted copy of the noise through the inverting path. This inverted noise is then combined with the original noise at the summation node, causing destructive interference that cancels the harmful switch noise while preserving the desired signal.
Solution Approach 2:
The system performs preliminary anti-action by pre-generating the inverted noise signal through the inverting path before it combines with the main signal path. This anticipatory generation of the opposite-phase noise signal allows for proactive cancellation of the switch noise rather than attempting to filter it afterward, effectively neutralizing the harmful effect before it degrades the signal.
3Manufacturing precision
If individual impedance matching circuits are used for each receive path, then the manufacturing precision is improved, but the device footprint increases
Solution Approach 1:
The patent merges the impedance matching functionality into a single shared circuit that serves both receive paths. This consolidation maintains manufacturing precision by using a well-designed single matching circuit rather than multiple less-optimized circuits, while simultaneously reducing the footprint by eliminating redundant components.
Solution Approach 2:
The single impedance matching circuit is designed to be universal, handling impedance matching for signals from multiple frequency bands and both receive paths. This multi-functional design achieves the same or better manufacturing precision compared to individual circuits while occupying significantly less space due to the elimination of duplicate 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
This approach effectively cancels switch noise, reduces the size of the LNA circuit, and conserves space by sharing impedance matching circuits, maintaining a desirable noise factor while optimizing the LNA's footprint.
Implementation Method 1
The switch noise is inverted in the inverting path and also amplified. The inverted amplified switch noise and the amplified switch noise are then destructively summed to reduce or remove the switch noise at an output.
Implementation Method 2
The inverted amplified switch noise and the amplified switch noise are then destructively summed to reduce or remove the switch noise at an output.
Data Source
AI summary
A noise-canceling low noise amplifier (LNA) is disclosed. In one aspect, an LNA path may include a plurality of inputs that are split into a main path (having a main LNA) and an inverting path. A multiplexer (MUX) in the inverting path generates switch noise which passes into both the switch path and the main path. The switch noise is inverted in the inverting path and also amplified. The switch noise is also amplified in the main path by the LNA. The inverted amplified switch noise and the amplified switch noise are then destructively summed to reduce or remove the switch noise at an output. The inverting path uses an active element in the form of an amplifier, which allows for substantial consolidation of matching circuits, thereby reducing size of the LNA path.