Doherty Amplifier Phase Slope Circuit for Full-Power Bandwidth
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Solution Overview
Problem
Conventional Doherty amplifiers face a trade-off between low power bandwidth and full power bandwidth due to phase misalignment between the carrier and peaking input paths, limiting their wideband RF performance.
Innovation Solution
Incorporating phase slope adjustment circuitry, specifically a constant-k bandpass filter with resonant LC cells, to align the phase of the carrier signal with the peaking signal at the output combining node, reducing frequency dispersion and improving full power bandwidth without affecting low power performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Doherty amplifier architecture is used without phase slope adjustment, then low power bandwidth is maintained, but full power bandwidth is limited due to phase misalignment between input paths
Solution Approach 1:
A phase slope adjustment circuit is introduced as an intermediary component in the carrier amplification path between the power divider and carrier amplifier. This circuit specifically targets and corrects the phase misalignment issue without requiring changes to the overall Doherty amplifier architecture, thereby improving full power bandwidth while maintaining structural simplicity and low power performance.
2Adaptability or versatility
If phase slope adjustment circuitry is added to align phases at full power, then full power bandwidth is improved, but device complexity increases
Solution Approach 1:
The phase slope adjustment circuit is strategically placed only in the carrier amplification path where phase misalignment occurs, rather than modifying both amplification paths symmetrically. This localized approach corrects the phase issue specifically where needed, improving wideband RF performance while minimizing the increase in overall device complexity.
3Adaptability or versatility
If frequency deviation between input paths is increased to expand bandwidth, then low power bandwidth is improved, but phase misalignment at full power worsens
Solution Approach 1:
The phase slope adjustment circuit functions as a feedback mechanism that compensates for phase misalignment caused by frequency deviation. By introducing this corrective element in the carrier path, the system can tolerate larger frequency deviations in both input paths without sacrificing phase alignment precision at the combining node, thereby enabling expanded bandwidth in both low and full power 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 phase slope adjustment circuitry enhances the full power bandwidth of Doherty amplifiers while maintaining low power performance, reducing output power ripple and improving wideband RF performance across a broader frequency range.
Implementation Method 1
phase slope adjustment circuitry, specifically a constant-k bandpass filter with resonant LC cells
Implementation Method 2
The phase slope adjustment circuitry may include an input node, a first capacitor, a first inductor, an intermediate node, a second capacitor, a second inductor, an output node, a third capacitor, and a third inductor
Data Source
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AI summary
An amplifier device (600) having multiple amplification paths, such as a Doherty amplifier device, may include phase slope adjustment circuitry (606) configured to adjust the frequency-dependent slope of the phase of an input carrier signal along a carrier path of the amplifier (600). By adjusting the phase slope of the input carrier signal in this way, the phase difference between carrier and peaking signals at an output combining node of the amplifier (600) may be reduced, thereby reducing output power ripple of the amplifier (600). The phase slope adjustment circuitry (606) may be a constant-k bandpass filter. The phase slope adjustment circuitry (606) may have a zero-degree insertion phase at the center frequency of the amplifier (600). The phase slope adjustment circuitry (606) may be implemented using surface mount inductors and capacitors.