Switch-Free Carrier Aggregation LNA for Low-Noise RF Isolation
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Solution Overview
Problem
Current radio-frequency (RF) receiver configurations face challenges in maintaining low noise figure and high isolation between signal paths during carrier aggregation, especially when aggregating close frequency bands, often requiring multiple switches and separate LNAs, which increase complexity, size, and cost.
Innovation Solution
A carrier aggregation (CA) circuit design that eliminates switches along signal paths by using a low-noise amplifier (LNA) with a first and second signal path, each comprising amplification stages without switches, and a shared or separate cascode bias voltage, allowing operation in multiple frequency bands with reduced noise figure and increased scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If switches are used to route RF signals between different filters and amplification stages, then signal path isolation between frequency bands is improved, but noise figure increases and device complexity increases
Solution Approach 1:
The patent removes switches from the signal path between filters and amplification stages, extracting the problematic switching elements that caused noise figure degradation and complexity increases while maintaining signal path isolation through direct connected architectures
Solution Approach 2:
The patent designs a universal amplification stage that can handle multiple frequency bands without requiring separate switched paths, allowing a single amplification stage to serve multiple bands simultaneously through broadband design techniques
2Object-generated harmful factors
If multiple separate LNAs are used for different frequency bands, then noise figure performance is improved for each band, but device size and cost increase
Solution Approach 1:
The patent merges multiple band-specific LNA designs into a single shared amplification stage that can simultaneously or sequentially amplify signals from different frequency bands, reducing the total number of LNA components from multiple separate units to one unified structure
Solution Approach 2:
The patent employs dynamic biasing and tuning mechanisms that allow the single amplification stage to adapt its characteristics to optimize noise figure performance for different frequency bands being aggregated, enabling one LNA to perform the work of multiple fixed LNAs
3Adaptability or versatility
If switches are used in the signal path, then band selection capability is improved, but noise figure increases due to switch losses
Solution Approach 1:
The patent extracts switches from the RF signal path entirely, eliminating the source of switch-related noise figure degradation while maintaining band selection capability through alternative means such as filter-based frequency division and shared amplification resources
Solution Approach 2:
The patent introduces filter banks as intermediary elements that perform frequency-based signal routing without requiring switches in the amplification path, allowing band selection to occur at the filtering stage while the shared amplification stage processes all bands through a switch-free architecture
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 solution enables efficient carrier aggregation with low noise figure, reduced size and cost, and improved isolation between signal paths, allowing for scalable operation in multiple frequency bands without the need for multiple switches or separate LNAs.
Implementation Method 1
The first stage can include a first bipolar junction transistor (BJT) configured to receive the respective RF signal through its base and yield an output through its collector
Implementation Method 2
The shared second BJT can be configured to receive a cascode bias voltage Vcas through its base
Data Source
AI summary
A carrier aggregation method can include amplifying a first signal with a first current converter to generate a current representative of the amplified first signal, and amplifying a second signal with a second current converter to generate a current representative of the amplified second signal. The method can further include processing the amplified first signal and the amplified second signal with an adder circuit, with the first current converter and the adder circuit forming a first cascode amplifier, and the second current converter and the adder circuit forming a second cascode amplifier. The method can further include providing an output signal at a common output node that is coupled to an output of each of the first and second cascode amplifiers.