Cascode Power Amplifier Switching to Cut Transmit Path Loss
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Solution Overview
Problem
Traditional front-end modules in power amplifier systems suffer from efficiency loss due to the use of a series switch in the transmit path, which is often implemented with different technologies on separate integrated circuits, leading to unwanted insertion loss.
Innovation Solution
A power amplifier system with N transistors configured to operate as amplifiers in an ON-mode and switches in an OFF-mode, eliminating the need for a traditional series switch by using a controller to manage transistor states, allowing for efficient signal amplification and transmission without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional series switch is used in the transmit path to disconnect the power amplifier when not in transmit mode, then the power amplifier can be isolated from the antenna, but insertion loss increases and efficiency decreases
Solution Approach 1:
The patent merges the switch function into the power amplifier circuit by using the power amplifier's own transistors to perform both amplification and switching operations. The cascode configuration allows the lower transistor to function as the power amplifier while the upper transistor acts as the switch, eliminating the need for a separate series switch component and reducing insertion loss.
Solution Approach 2:
The power amplifier transistor is designed to serve multiple functions: it operates as an amplifying device during transmit mode and as a switch during non-transmit mode. This multi-functionality is achieved through the cascode configuration where the same transistor structure provides both signal amplification and circuit isolation capabilities without requiring separate dedicated components.
2Reliability
If a separate series switch component is used in the transmit path, then the power amplifier can be disconnected from the antenna, but device complexity increases due to multiple components on different integrated circuits
Solution Approach 1:
The patent combines the power amplifier and switch functions into a single integrated circuit structure using a cascode configuration. This merging eliminates the need for separate components on different integrated circuits (such as GaAs power amplifier and SOI-CMOS switch), thereby reducing device complexity while maintaining the isolation function.
Solution Approach 2:
The cascode transistor structure provides universal functionality by simultaneously serving as both the power amplifier and the switch. This multi-functionality reduces the total number of components required in the system, as the same transistor performs dual roles depending on its operating state, eliminating the need for separate dedicated switch and amplifier components.
Data Source
AI summary
A power amplifier system is disclosed having an N number of transistors coupled together drain-to-source between a supply node and a fixed voltage node, wherein a first one of the N number of transistors coupled nearest to the fixed voltage node is configured to operate as an amplifying device in an ON-mode, and remaining ones of the N number of transistors are configured to operate as cascode devices in the ON-mode and to operate as turned-off switches in an OFF-mode. A controller is configured to place the N number of transistors in the first mode when a radio frequency (RF) signal is to be amplified by the first one of the N number of transistors and to place the N number of transistors in the second mode when the RF signal is not to be amplified by the first one of the N number of transistors.