Compact Doherty Amplifier Using Vertical PCB Resonators
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Solution Overview
Problem
Conventional wideband Doherty amplifiers have a large physical size and high mechanical design costs due to their size, especially when designed for high-frequency and high-power applications, which results in the need for extensive transmission lines.
Innovation Solution
The Doherty amplifier configuration includes tightly electrically coupled phase shifters and baluns to reduce harmonic components, implemented as strip lines on a printed circuit board, achieving a compact footprint by mirroring phase shifters and transmission lines on opposing PCB surfaces, thereby enhancing linearity and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional wideband Doherty amplifier configurations are used with traditional transmission lines, then the amplifier can achieve high-frequency and high-power performance, but the physical size becomes large and mechanical design costs increase
Solution Approach 1:
The patent transitions from planar transmission lines to three-dimensional vertically coupled resonators, utilizing the vertical dimension of the PCB to achieve compact filtering functionality. The resonators are coupled between opposite sides of the PCB, creating a vertical electromagnetic coupling that replaces traditional horizontal transmission line structures.
Solution Approach 2:
The patent changes the operating parameters of the filtering structure by using vertically coupled resonators with specific coupling coefficients and resonant frequencies. The third and fourth resonators are designed with parameters that create transmission zeros at harmonic frequencies, achieving harmonic rejection without requiring large physical dimensions.
2Speed
If traditional phase shifters and transmission lines are used in Doherty amplifiers, then the amplifier can operate at high frequencies, but the footprint and manufacturing complexity increase
Solution Approach 1:
The patent combines the functions of phase shifters, transmission lines, and harmonic filtering into a single integrated structure using vertically coupled resonators. The resonators simultaneously provide signal transmission, phase control, and harmonic rejection, eliminating the need for separate components.
Solution Approach 2:
The vertically coupled resonator structure serves multiple functions: it acts as a transmission line for high-frequency signals, provides phase shifting capability, and simultaneously functions as a harmonic filter. This multi-functional design reduces the overall footprint and component count.
3Reliability
If conventional amplifier designs are used without harmonic cancellation, then the design is simpler, but linearity and bandwidth performance deteriorate
Solution Approach 1:
The patent converts the harmful effect of harmonic generation by amplifiers into a beneficial filtering mechanism. The vertically coupled resonators are specifically designed to create transmission zeros at harmonic frequencies, turning the presence of harmonics into an opportunity for selective rejection rather than requiring complex active cancellation circuits.
Data Source
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AI summary
A Doherty amplifier is disclosed, being adapted to receive an RF input signal and to output an RF output signal and comprising a main amplifier and a peak amplifier, each comprising: a first amplifier (T1, T1') and a second amplifier (T2, T2'), each amplifier having a respective input terminal and a respective output terminal, the first amplifier and the second amplifier being adapted to amplify a respective input signal derived from the RF input signal and received at the respective input terminal and to deliver a first output signal and a second output signal, respectively; a first phase shifter (14, 14') and a second phase shifter (15, 15') coupled to the output terminal of the first amplifier and to the output terminal of the second amplifier, respectively; a third phase shifter (16, 16'); and a fourth phase shifter (17, 17').