MIMO Low-Noise Amplifier Topology for Lower Switching Loss
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Solution Overview
Problem
Conventional low noise amplifier circuits face issues with noise figure deterioration due to switching loss and deteriorated isolation characteristics when supporting multiple-input multiple-output (MIMO) and carrier aggregation (CA) in high band frequency bands, requiring multiple LNAs and complex matching circuits.
Innovation Solution
A low noise amplifier circuit design featuring cascaded common gate and parallel common source structures with a DPDT output circuit and control circuit for selective amplification and switching control across multiple bands, reducing switching elements and improving isolation through optimized matching and impedance control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single pole multi throw (SPMT) switch is used in the input terminal to support multiple bands, then the number of LNA circuits is reduced, but switching loss increases and noise figure deteriorates
Solution Approach 1:
The patent extracts the switching function from the input terminal and relocates it to the output terminal using a DPDT switch. This removes the harmful switching loss from the signal path where it would directly affect noise figure, while still achieving the goal of supporting multiple bands with a reduced number of LNA circuits.
Solution Approach 2:
Instead of switching at the input terminal as in conventional designs, the patent inverts the approach by switching at the output terminal. This reversal allows the LNAs to operate continuously without switching, eliminating switching loss from the critical signal path while still enabling multi-band support through output switching.
2Adaptability or versatility
If the number of switch elements is increased to support more bands, then band coverage is improved, but switching loss increases
Solution Approach 1:
The patent extracts the switching operation from the input stage and places it at the output stage. This allows multiple bands to be supported by switching outputs rather than inputs, reducing the number of switch elements needed in the critical signal path while maintaining broad band coverage capability.
Solution Approach 2:
The DPDT switch at the output terminal serves multiple functions: it enables MIMO operation by routing signals to different outputs, supports carrier aggregation by selecting appropriate band combinations, and provides isolation between transmit and receive paths. This multi-functionality achieves broad adaptability without proportionally increasing switching loss.
3Adaptability or versatility
If separate input terminals are used for each band with shared output terminal, then MIMO structure is implemented, but isolation characteristics deteriorate
Solution Approach 1:
The patent introduces a DPDT switch as an intermediary component at the output terminal that actively manages signal routing and isolation. This intermediary provides controlled connections between LNAs and output terminals, ensuring proper isolation characteristics while maintaining MIMO capability through programmable switching patterns.
Solution Approach 2:
The patent implements dynamic switching control where the DPDT switch configuration changes based on operational mode (MIMO, carrier aggregation, or single-band operation). This dynamic reconfiguration optimizes isolation characteristics for each specific operating condition while maintaining the flexibility to support multiple functions.
4Manufacturing precision
If matching circuits are added to each input terminal for MIMO, then input matching is improved, but device complexity and component count increase
Solution Approach 1:
The patent merges the matching functionality into shared components that serve multiple LNAs simultaneously. Rather than providing dedicated matching circuits for each LNA input, the design uses common matching networks that can be effectively utilized across multiple input terminals, reducing the total component count while maintaining matching precision.
Solution Approach 2:
The patent implements universal matching circuits that can serve multiple functions and multiple LNAs. These matching networks are designed to provide effective impedance matching across different bands and operating modes without requiring separate dedicated components for each LNA, thereby reducing overall device complexity while maintaining manufacturing precision.
Data Source
AI summary
A low noise amplifier circuit includes a first low noise amplifier including a common gate structure cascoded with a parallel common source structure to selectively amplify a band signal among first and second band signals; a second low noise amplifier including a common gate structure cascoded with a parallel common source structure to selectively amplify a band signal among third and fourth band signals; an output DPDT circuit including a first input terminal connected to the first low noise amplifier, a second input terminal connected to the second low noise amplifier, and a first output terminal and a second output terminal for selectively outputting signals input through the first input terminal and the second input terminal; and a control circuit performing an amplification control and a switching control for the first and second low noise amplifiers and the output DPDT circuit in response to a predetermined communications scheme.