RF Power Amplifier Envelope Tracking Using Transistor Rectification
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Solution Overview
Problem
Existing RF power amplifiers face challenges in achieving high linearity and efficiency due to the contradictory nature of these requirements, with conventional DC/DC converters being inefficient and parasitic elements reducing performance, especially in space applications where weight and cost are critical.
Innovation Solution
A RF power amplifier with envelope tracking using a fast DC/DC converter implemented with two RF power transistors as both the switching and rectifying elements, allowing high commutation speed and handling of high currents and powers, thereby avoiding the diode bottleneck and minimizing parasitic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional switching converters are used for envelope tracking, then efficiency is improved, but the switching frequency must be kept low (100 kHz) which limits the envelope bandwidth
Solution Approach 1:
The patent changes the operating parameters of the converter by using RF power transistors that can operate at much higher frequencies (several MHz to tens of MHz) compared to conventional switching converters (100 kHz). This parameter change in switching frequency enables the converter to track fast envelope variations while maintaining high efficiency through switching operation.
Solution Approach 2:
The patent employs RF power transistors that are designed for high-frequency operation and can handle the demanding conditions of envelope tracking. These transistors are optimized for short-duration high-power pulses and can operate at frequencies where conventional transistors would fail, effectively using components designed for the specific demanding application.
2Power
If commercially available power rectifiers are used in the DC/DC converter, then high currents and powers can be handled, but the switching frequency is limited to a few kHz or hundreds of kHz
Solution Approach 1:
The patent uses RF power transistors configured to operate as rectifiers, replacing conventional power rectifiers. These RF transistors are designed for high-frequency operation and can handle both high currents and high switching frequencies simultaneously, a capability that conventional rectifiers lack.
Solution Approach 2:
The patent changes the operating parameters by using transistors that can operate at RF frequencies (several MHz to tens of MHz) while handling high power levels. This is achieved by configuring the RF transistors in specific operating modes that enable both high-frequency switching and high current handling, unlike conventional rectifiers that are limited to low frequencies.
3Power
If discrete components are used in the DC/DC converter, then high power can be handled, but parasitic capacitances and inductances increase reducing performance
Solution Approach 1:
The patent integrates the DC/DC converter circuitry directly with the RF power amplifier on a single monolithic chip. This merging of functions eliminates the need for discrete external components and their associated parasitic elements, while maintaining the ability to handle high power through the integrated RF transistors designed for high-power operation.
Solution Approach 2:
The patent uses RF power transistors that serve multiple functions: they act as both the power amplifying devices and the switching elements in the DC/DC converter. This multi-functionality reduces the total number of components needed and minimizes parasitic elements by eliminating the interfaces between separate discrete components.
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
This solution enables high-efficiency envelope tracking with bandwidths of up to 36 MHz, eliminating the need for linear stages and reducing parasitic elements, thus improving power amplifier performance in both ground and space telecommunications.
Implementation Method 1
a rectifying transistor, whose gate is connected to a second terminal while the drain and source form a two-terminal device connected to a third terminal
Implementation Method 2
a switching transistor, whose gate is connected to a first terminal while the drain and source are connected together to a second terminal
Data Source
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AI summary
A radio-frequency power amplifier with envelope tracking, comprising: a power RF amplifying device for amplifying a RF signal; and a switching DC/DC converter, comprising a switching device and a rectifying device, for providing said power RF amplifying device with a DC power supply at a. voltage level proportional to an envelope of said RF signal; wherein said switching device is a RF power transistor; characterized in that said rectifying device, and preferably also said power RF amplifying device, is also a transistor of a same technology, connected as a two-terminal device. Preferably, said power RF amplifying device is also a transistor of said same technology. A low-pass filter can also be provided for reducing the bandwidth of the envelope signal on which the PWM signal driving the DC/DC converter depends.