RF Transformer TX/RX Switch for Low Loss Antenna Diversity
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Solution Overview
Problem
Current RF switches in wireless communication systems face challenges with transmit and receive low linearity, RF insertion loss, PA efficiency, power amplifier and LNA matching, ESD protection, and size limitations, particularly in meeting the requirements of modern wireless standards like 802.11, 3G, and 4G cellular systems.
Innovation Solution
An RF transformer-based transmit/receive (TX/RX) integrated RF switch that functions as a power amplifier output transformer during transmit mode and as series inductance in the LNA matching network during receive mode, eliminating the need for additional components like transistor switches or resonant circuits, and providing dual functionality to minimize RF losses and antenna diversity requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional transistor switches or resonant circuits are used in the transmit signal path, then switching functionality is achieved, but RF losses increase and linearity deteriorates
Solution Approach 1:
The patent merges the TX/RX switching function with the existing PA output transformer by utilizing its secondary winding as a switchable inductor. This integration eliminates the need for separate transistor switches or resonant circuits in the signal path, thereby reducing RF losses and component count while maintaining switching functionality between TX and RX modes.
Solution Approach 2:
The PA output transformer is designed to serve multiple functions: it acts as the power amplifier output transformer during transmit mode and as a series inductance in the LNA matching network during receive mode. This multi-functionality eliminates the need for additional dedicated components for each function, reducing overall device complexity and RF losses.
2Reliability
If separate TX and RX lines are used, then signal isolation is improved, but device size and manufacturing complexity increase
Solution Approach 1:
The patent combines the TX and RX signal paths into a single integrated path where the same antenna and matching networks are shared. The TX/RX switch and the dual-function transformer enable signal isolation between transmit and receive modes while using a unified hardware architecture, thereby reducing device size and manufacturing complexity compared to separate dedicated lines.
3Reliability
If additional components like transistor switches are added to the signal path, then switching control is achieved, but linearity and PA efficiency deteriorate
Solution Approach 1:
The patent merges the switching control function into the transformer's secondary winding, which is already present in the PA output stage. This eliminates the need for additional transistor switches in the signal path, thereby maintaining signal linearity and PA efficiency while achieving reliable TX/RX switching control through the transformer's inherent characteristics.
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 enhances RF switch performance by reducing RF losses, improving linearity and efficiency, and simplifying design complexities, while meeting the requirements of various wireless standards and reducing manufacturing costs and size, thus enabling high-power, high-efficiency, and high-bandwidth operations.
Implementation Method 1
The output power of a power amplifier is fed to the antenna load utilizing an output transformer
Implementation Method 2
the RF transformer plays a dual function or role. Such a TX/RX switch is suitable to be integrated into front end module (FEM) circuits, transceiver modules and other RF related modules
Data Source
AI summary
The present invention is a novel and useful RF transformer based transmit/receive (TX/RX) integrated RF switch. In one embodiment of the invention, the TX/RX RF switch circuit is based on the use of an RF transformer which functions as (1) the PA output transformer during TX mode and (2) as a series inductance in an LNA matching network during receive mode. Thus, the RF transformer plays a dual function or role. Antenna diversity is achieved by having multiple antennas each having an associated antenna switch connected to the output transformer. The TX/RX switch of the invention reduces the number of switches required for antenna diversity to a minimum and minimizes RF losses in the system. The TX/RX switch is suitable for use with modern wireless communication standards such as DECT, 802.11 WLAN, Bluetooth, ZigBee, etc. The configuration of the TX/RX circuit permits the use of common, relatively low cost semiconductor fabrication techniques such as standard CMOS processes.