Transformer-Coupled Doherty PA for Wideband RF Efficiency
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Solution Overview
Problem
Conventional Doherty power amplifiers are unsuitable for wideband operation due to their quarter wave transmission lines being frequency-specific, leading to inefficiency and high current consumption, especially in wireless systems using higher frequency bands like 5 GHz and 6 GHz.
Innovation Solution
A Doherty power amplifier configuration with a transformer circuit that includes a matched transmission line and a 2:1 impedance transformation, coupled to a main and auxiliary power amplifier, allowing efficient operation over a wideband frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a quarter wave transmission line is used in a Doherty power amplifier, then the amplifier achieves efficient operation at a single frequency, but it becomes unsuitable for wideband operation
Solution Approach 1:
The patent transforms the static quarter wave transmission line into a dynamic structure by introducing a transformer circuit that can adapt its electrical length and impedance characteristics. The transformer with adjustable turns ratio allows the transmission line to present different electrical lengths at different frequencies, enabling the Doherty amplifier to maintain efficiency across a wide frequency bandwidth rather than being fixed at a single frequency.
Solution Approach 2:
The patent changes the electrical parameters of the transmission line by introducing a transformer circuit with variable turns ratio. This allows the characteristic impedance and electrical length of the transmission line to be dynamically adjusted, enabling the system to maintain optimal performance across multiple frequency bands. The transformer modifies the impedance transformation ratio and electrical length parameters to compensate for frequency variations.
2Reliability
If conventional linear power amplifiers are backed off from peak power to accommodate signal excursions, then linearity is maintained, but efficiency deteriorates and current consumption increases
Solution Approach 1:
The patent divides the power amplification function into two separate amplifiers: a carrier amplifier that handles the main signal and a peak amplifier that handles the peak excursions. This segmentation allows each amplifier to operate in its optimal efficiency region while collectively maintaining signal linearity. The carrier amplifier operates at higher efficiency with reduced backoff, while the peak amplifier supplements during high-power conditions, eliminating the need for excessive backoff in conventional single-stage amplifiers.
Solution Approach 2:
The patent employs partial action by having the peak amplifier activate only during peak signal excursions rather than continuously. The carrier amplifier operates continuously at a moderate backoff level, and the peak amplifier provides supplemental gain only when needed, allowing the system to achieve high efficiency during most operating conditions while maintaining linearity during peak conditions.
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 enables high efficiency and reduced power consumption across a wideband frequency range, including 5G and 6G applications, by minimizing frequency sensitivity and impedance losses.
Implementation Method 1
a first secondary winding inductively coupled to the first primary winding to provide the first amplified RF signal to the load circuit; and a second primary winding coupled to the output of the second PA and a second secondary winding inductively coupled to the second primary winding
Data Source
AI summary
In on example, an apparatus includes: a first power amplifier (PA) to receive a first input radio frequency (RF) signal and output a first amplified RF signal; a second PA to receive a second input RF signal and output a second amplified RF signal; and a transformer circuit coupled to an output of the first PA and an output of the second PA. The transformer circuit is to provide, to a load circuit, an RF output signal comprising the first amplified RF signal and the second amplified RF signal.