RF Switch Level Shifters for High Linearity MIMO Front Ends
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Solution Overview
Problem
Current RF switch technologies face challenges in providing targeted linearity and reducing complexity and cost in MIMO systems, particularly due to the increased number of RF hardware components required, which can be mitigated by implementing high-linearity switches with voltage level shifters that provide high positive and negative voltages efficiently.
Innovation Solution
The implementation of a voltage level circuit with multiple transistor stacks and cross-coupled PMOS transistors, along with charge pumps, to generate and control high voltages for RF switches, reducing the stress on transistors and improving switch performance by providing increased voltage outputs while minimizing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple RF hardware components are used to achieve MIMO functionality, then data throughput is improved, but device complexity and cost increase
Solution Approach 1:
The patent implements a universal voltage level shifter circuit that can serve multiple RF switches simultaneously. The circuit generates multiple voltage levels (e.g., ±3.3V, ±5V) from a single input voltage, enabling one circuit to control multiple switches for MIMO antenna switching, carrier aggregation, and other RF functions, thereby reducing the number of separate voltage generation circuits needed
Solution Approach 2:
The patent combines multiple voltage generation functions into a single integrated circuit. Instead of using separate voltage generators for each RF switch, the invention merges these functions into one circuit that produces multiple voltage levels simultaneously, reducing component count and simplifying the overall RF front-end architecture
2Reliability
If high voltage outputs are provided for RF switches, then switch performance and linearity are improved, but transistor stress increases
Solution Approach 1:
The patent segments the voltage generation into multiple stages using series-connected transistors. Instead of using a single transistor to handle the full voltage swing, the circuit divides the voltage stress across multiple transistors connected in series, with each transistor handling only a portion of the total voltage, thereby reducing individual transistor stress while maintaining high output voltage capability
Solution Approach 2:
The patent applies different voltage levels to different parts of the RF switch circuitry based on specific performance requirements. High voltage levels (e.g., ±5V) are applied only where needed for optimal switch performance, while other portions operate at lower voltages, thereby achieving high linearity without unnecessarily stressing all transistors throughout the circuit
3Reliability
If voltage level shifters are implemented, then RF switch control is improved, but circuit complexity increases
Solution Approach 1:
The patent changes the voltage parameter dynamically based on the operating mode. The circuit switches between different voltage levels (e.g., ±3.3V for normal operation, ±5V for high-performance modes) depending on the specific RF switch control requirements, thereby improving switch control precision without permanently increasing circuit complexity across all operating conditions
Data Source
AI summary
Disclosed herein are silicon-on-insulator (SOI) switches and associated control circuits having level shifters configured to provide increased voltages (positive and/or negative) to the switches. The disclosed level shifters can be configured to provide increased voltages and can be used with high-linearity switches and/or can improve the linearity of switches. The improved switch performance can improve front end module performance for applications such as carrier aggregation (CA) and multiple input multiple output (MIMO) as well as with protocols such as Long-Term Evolution Advanced (or LTE-A).