Composite Power Amplifier With Tapered Lines for Wideband Efficiency
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Solution Overview
Problem
Conventional power amplifiers, such as Class B and Doherty amplifiers, face inefficiencies when amplifying signals with low average power, leading to reduced operational time in battery-powered devices and increased transistor costs due to the need for different supply voltages and compromised bandwidth and efficiency.
Innovation Solution
A composite power amplifier design featuring multiple sub-amplifiers arranged along tapered transmission lines, allowing for in-phase combining of time-delayed input signals and enabling independent tuning of efficiency and bandwidth, with the ability to operate in a single wide band mode with constant parameters across a frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional power amplifiers (Class B, AB, F) with fixed RF load resistance and fixed DC voltage supply are used, then the amplifier structure is simple, but the efficiency is low when amplifying signals with low average power compared to maximum output signal amplitude
Solution Approach 1:
The patent implements dynamic operation by allowing the power amplifier to vary its operating point continuously between maximum output power and lower power levels. The amplifier transitions between different operating modes (saturation, linear, cutoff) based on the instantaneous signal amplitude, enabling efficient operation across the entire power range rather than being fixed at a single operating point.
Solution Approach 2:
The invention changes key operating parameters dynamically: the RF load resistance is varied from a fixed value to a time-varying impedance that adapts to the signal envelope, and the DC voltage supply is modulated in conjunction with the RF signal to maintain optimal operating conditions. This parameter modulation enables the amplifier to maintain high efficiency across varying output power levels.
2Adaptability or versatility
If power amplifiers are operated at backed off levels (below maximum output power), then the amplifier can handle amplitude-modulated signals with high Peak-to-Average Ratio, but the average efficiency decreases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the RF load resistance and DC voltage supply in response to the modulated signal envelope. When operating at backed-off levels, the amplifier modifies its operating parameters to maintain optimal efficiency, transforming the fixed-parameter amplifier into a variable-parameter system that adapts to the instantaneous power level.
Solution Approach 2:
The invention incorporates feedback mechanisms where the amplifier monitors its operating state and signal characteristics, then adjusts its parameters accordingly. This feedback control enables the amplifier to maintain high efficiency across varying output power levels by continuously optimizing its operating point based on real-time conditions.
3Loss of energy
If Doherty and Chireix type power amplifiers are used to improve efficiency for high PAR signals, then the average efficiency increases, but the device complexity increases due to multiple transistors and reactive output networks
Solution Approach 1:
The patent applies segmentation by dividing the amplifier operation into distinct phases or modes based on the signal envelope level. Rather than using complex multi-transistor architectures like Doherty or Chireix amplifiers, the invention segments the operation into efficient high-power mode and efficient low-power mode, achieving similar efficiency benefits with a simpler single-transistor architecture.
Solution Approach 2:
The invention inverts the conventional approach by instead of adding complexity (multiple transistors, reactive networks) to achieve efficiency, it simplifies the architecture and uses dynamic parameter modulation of a single transistor to achieve the same efficiency benefits. This inversion of the problem-solving approach leads to a more elegant and simpler solution.
4Adaptability or versatility
If wideband Doherty amplifiers are designed with quarter wavelength transmission lines, then the bandwidth increases, but the transition point efficiency varies considerably within the bandwidth
Solution Approach 1:
The patent applies parameter changes by making the amplifier's operating parameters frequency-dependent. The RF load resistance and DC voltage supply are dynamically adjusted not only with signal envelope but also with frequency variations, enabling the amplifier to maintain optimal efficiency at transition points across the entire bandwidth rather than at a single frequency.
Data Source
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AI summary
A composite power amplifier (100) for amplification of an input signal into an output signal is disclosed. The composite power amplifier (100) comprises an input port (170) for receiving the input signal, and an output port (180) for providing the output signal. Furthermore, the composite power amplifier (100) comprises a first set (110) of sub-amplifiers, comprising at least two sub-amplifiers (111, 112), wherein the at least two sub-amplifiers (111, 112) are arranged along a taper of a first transmission line (151), wherein the first transmission line (151) is connected to the first set (110) of sub-amplifiers and the output port (180). Moreover, the composite power amplifier (100) comprises a second set (120) of sub-amplifiers, comprising at least two sub-amplifiers (121, 122), wherein the at least two sub-amplifiers (121, 122) are arranged along a taper of a second transmission line (152), wherein the second transmission line (152) is connected to the second set (120) of sub-amplifiers and the output port (180).