Multi-Band Doherty Amplifier With Filter-Based Main-Aux Switching
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Solution Overview
Problem
Existing Doherty amplifiers require complex control mechanisms to manage amplifying elements for different operating frequencies, which complicates their operation in multiple frequency bands.
Innovation Solution
The implementation of a Doherty amplifier with filter circuits that attenuate input signals differently for each frequency band, allowing the same amplifiers to operate as both main and auxiliary amplifiers without needing to adjust their gate bias voltage, and an output combination circuit that modulates load impedance to achieve high efficiency across multiple frequency bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control mechanisms are used to manage amplifying elements for different operating frequencies, then the Doherty amplifier can operate in multiple frequency bands, but the device complexity increases
Solution Approach 1:
Filter circuits are introduced as intermediary components between the signal source and the amplifying elements. These filter circuits selectively attenuate signals for different frequency bands, allowing the amplifying elements to automatically operate in appropriate modes without requiring complex control mechanisms. The filter circuits mediate the frequency selection, replacing the need for complex control logic.
Solution Approach 2:
The amplifying elements are designed to automatically switch between main and auxiliary amplifier modes based on the frequency characteristics of the input signal. By fixing the gate bias voltage and using frequency-selective filter circuits, the system enables the amplifying elements to self-regulate their operation mode without external control signals, thereby simplifying the overall control mechanism.
2Adaptability or versatility
If gate bias voltage is adjusted to switch between main and auxiliary amplifier modes, then the amplifier can adapt to different frequency bands, but the ease of operation decreases
Solution Approach 1:
The gate bias voltage is fixed at a specific value that enables the amplifying element to automatically transition between main and auxiliary amplifier modes based on the input signal frequency. The system eliminates the need for manual or automated bias voltage adjustment, allowing the amplifier to adapt to different frequency bands through the inherent frequency-selective characteristics of the filter circuits while maintaining operational simplicity.
3Loss of energy
If filter circuits with different attenuation characteristics are used for different frequency bands, then the amplifier efficiency improves across multiple bands, but the device complexity increases
Solution Approach 1:
The signal path is divided into multiple segments, each containing filter circuits with specific attenuation characteristics for different frequency bands. By segmenting the frequency handling into distinct filter stages, the system achieves high amplifier efficiency across multiple bands while organizing the complexity into manageable, modular filter sections rather than a single complex control system.
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
Enables the Doherty amplifier to operate efficiently in multiple frequency bands without requiring control over the amplifying elements, achieving high efficiency and balanced performance across different frequency ranges.
Implementation Method 1
a first filter circuit to, when an input signal lying in a first frequency band is inputted, output a first input signal obtained by attenuating the input signal lying in the first frequency band by a first amount of attenuation, and to, when an input signal lying in a second frequency band different from the first frequency band is inputted output a second input signal obtained by allowing passage of the input signal lying in the second frequency band
Implementation Method 2
a second filter circuit to, when an input signal lying in the first frequency band is inputted, output a third input signal obtained by attenuating the input signal lying in the first frequency band by a second amount of attenuation smaller than the first amount of attenuation, and to, when an input signal lying in the second frequency band is inputted, output a fourth input signal obtained by attenuating the input signal lying in the second frequency band by a third amount of attenuation larger than or equal to the first amount of attenuation
Implementation Method 3
a first amplifier in which a gate bias voltage is fixed, to operate as an auxiliary amplifier when the first input signal from the first filter circuit is inputted, and to operate as a main amplifier when the second input signal from the first filter circuit is inputted
Data Source
AI summary
A Doherty amplifier includes: a first filter circuit to output a first input signal obtained by attenuating an input signal lying in a first frequency band, and to output a second input signal obtained by allowing passage of an input signal lying in a second frequency band; a second filter circuit to output a third input signal obtained by attenuating an input signal lying in the first frequency band, and to output a fourth input signal obtained by attenuating an input signal lying in the second frequency band; a first amplifier to operate as an auxiliary amplifier when receiving the first input signal, and to operate as a main amplifier when receiving the second input signal; and a second amplifier tip operate as the main amplifier when receiving the third input signal, and to operate as the auxiliary amplifier when receiving the fourth input signal.