Inverted Doherty Amplifier Layout for Broadband Impedance Matching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional Doherty amplifiers face bandwidth limitations due to the long electrical path length added by impedance-matching components, which restrict their RF fractional bandwidth, making them unsuitable for future broadband RF communication systems.
Innovation Solution
The design of an inverted Doherty amplifier configuration with an impedance inverter located between the combining node and the peaking amplifier, along with optimized impedance-matching components and phase delays, allows for broader RF fractional bandwidth by equalizing impedance transformations and increasing the phase delay of the impedance inverter to odd multiples of 90 degrees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional Doherty amplifier configuration is used with impedance-matching components, then power amplification is achieved, but RF fractional bandwidth is limited due to long electrical path length
Solution Approach 1:
The patent inverts the conventional Doherty amplifier configuration by relocating the impedance inverter from the main amplifier branch to the peaking amplifier branch. This inversion changes the signal flow path and impedance transformation sequence, allowing the combining node to be positioned earlier in the signal path. The inverted configuration reduces the total electrical path length through impedance-matching components while maintaining power amplification functionality, thereby expanding RF fractional bandwidth.
2Reliability
If long electrical path length is used for impedance matching, then proper impedance transformation is achieved, but signal bandwidth is restricted
Solution Approach 1:
The patent repositions components in the signal path dimension, moving the impedance inverter to a different location (peaking amplifier branch) and placing the combining node earlier in the signal flow. This dimensional rearrangement of the circuit topology allows impedance transformation to occur over a shorter effective path length while maintaining the necessary impedance matching ratios, thus expanding signal bandwidth without sacrificing transformation reliability.
3Device complexity
If conventional amplifier topology is used, then circuit simplicity is maintained, but RF and instantaneous bandwidths are limited
Solution Approach 1:
By inverting the conventional Doherty topology—specifically moving the impedance inverter to the peaking amplifier branch and repositioning the combining node—the patent achieves broader bandwidth while maintaining relatively simple circuit implementation. The inverted configuration allows the same functional blocks to be arranged differently, reducing electrical path length and improving bandwidth characteristics without adding significant circuit complexity.
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Apparatus and methods for an inverted Doherty amplifier operating at gigahertz frequencies are described. RF fractional bandwidth and signal bandwidth may be increased over a conventional Doherty amplifier configuration when impedance-matching components and an impedance inverter in an output network of the inverted Doherty amplifier are designed based on characteristics of the main and peaking amplifier and asymmetry factor of the amplifier.