Wideband Doherty Power Amplifier With Active Load Modulation
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Solution Overview
Problem
Current RF power amplifiers, particularly in mobile and satellite communications, face challenges in achieving high efficiency, linearity, and wideband operation due to limitations in bandwidth and power handling, especially in the L-band frequency range, where high power and efficient amplification are required to meet standards like L-DACS, UAT, DME, Mode-S, and ADS-B.
Innovation Solution
A high-frequency power amplifier with a Doherty amplifier architecture that includes a signal divider, two amplifiers, and a wideband impedance converter with a directional coupler, which allows for improved linearity and bandwidth by individually controlling the amplitude and phase of each amplifier core and using offset lines to compensate for parasitic properties, thereby enhancing efficiency and linearity across a wide frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a classic Doherty amplifier architecture with λ/4 impedance inverters is used, then high average efficiency is achieved, but bandwidth is limited to 5% to 10%
Solution Approach 1:
The amplifier is divided into N independent amplifier cores (one main amplifier and N-1 peak amplifiers) instead of using a single amplifier stage. This segmentation allows each core to be independently controlled and optimized, enabling the system to maintain high efficiency across a wider bandwidth by dynamically adjusting which cores are active based on the input signal power level and frequency characteristics.
Solution Approach 2:
The amplifier employs dynamic load modulation through active load modulators that adjust the load impedance presented to each amplifier core based on real-time operating conditions. This dynamic adjustment allows the amplifier to maintain optimal efficiency across varying power levels and frequency ranges, extending the useful bandwidth beyond the static 5-10% limitation of classic Doherty designs.
2Adaptability or versatility
If multiple amplifier cores are used to extend bandwidth, then bandwidth increases, but device complexity increases
Solution Approach 1:
Each amplifier core is designed with universal functionality to operate independently across the full frequency band, eliminating the need for frequency-specific amplifier designs. The common load network and control architecture serve multiple functions: power combining, load modulation, and efficiency optimization for all N cores simultaneously. This multi-functionality reduces overall system complexity despite having multiple amplifier cores.
Solution Approach 2:
The patent merges N amplifier cores into a unified Doherty architecture with a common load network and shared control mechanisms. The peak amplifiers are combined with the main amplifier through a common output network, and the control functions for load modulation are integrated across all cores. This merging approach allows bandwidth extension while managing complexity through shared resources and coordinated operation.
3Power
If high power amplification is achieved, then peak power increases, but linearity deteriorates
Solution Approach 1:
The amplifier uses partial action by activating only the necessary number of peak amplifiers based on the input signal power level. At low power levels, only the main amplifier is active, providing excellent linearity. As power levels increase, additional peak amplifiers are gradually activated to provide the required power while maintaining acceptable linearity through controlled load modulation. This selective activation allows the system to achieve high peak power when needed while preserving linearity during normal operation.
Data Source
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AI summary
The invention relates to a transmitting and receiving device having a wide-band HF power amplifier, in particular an N-way Doherty amplifier having active load modulation. The aim of the invention is to provide, by means of suitable design measures in connection with the electronics, a high-power transmitting and receiving device that has a transmitting power of over 10 watts to approximately 2000 watts and that is suitable for high-power and wide-band applications, proceeding from a transmitting and receiving device having a module (GSZ) having a configurable HF high-power amplifier (HPA), which is operated both between and below two power back-off points and comprises a main power amplifier (DM) having an amplifier core and at least one peak power amplifier (DP1) having an amplifier core, wherein a digital input signal splitter (ET) is provided, which is connected to the input of the main power amplifier (DM) and to the input of the at least one peak power amplifier (DP1) and has a plurality of outputs, and an output combiner (C) connected to an output of the amplifier cores is provided for the main power amplifier (DM) and for an output of the at least one peak power amplifier (DP1). This aim is achieved, according to the invention, in that an additional multiharmonic transformation line (LAH) at the amplifier core output of the main power amplifier (DM) and at the amplifier core output of the at least one peak power amplifier (DP1) and a circulator (Z1), which is connected to the output of the output combiner (C) or of an impedance converter (AN1) are provided. By means of the circulator (Z1), the upstream main power amplifier (DM) and the at least one peak power amplifier (DP1) are protected from output-side overvoltages and overcurrent, because the circulator (Z1) leads away the energy to a sump resistor (W1) connected to the circulator (Z1). The invention pertains to the field of wide-band amplifiers, in particular wide-band Doherty amplifier circuits.