Compact Doherty Combiner Using Lumped Elements
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Solution Overview
Problem
Current Doherty amplifiers face challenges with bulky, space-consuming distributed components that hinder integration into small-sized and low-weight products, leading to size and cost issues, particularly at lower frequencies, and require techniques to reduce the size and cost of the Doherty combiner while maintaining performance.
Innovation Solution
A compact Doherty combiner design utilizing impedance inverter and transformer circuits with lumped elements such as capacitors and inductors, which replace bulky transmission lines, allowing for a smaller and more efficient integration of the Doherty amplifier, including phase offset transmission lines and optimized component selection for high-power handling and low loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If distributed components (micro-strip transmission lines or strip-line transmission lines) are used in the Doherty combiner, then the combiner can achieve the required impedance transformation and signal combining functions, but the combiner becomes bulky and space-consuming
Solution Approach 1:
The patent transforms the physical state of the transmission lines from distributed (continuous) to lumped (discrete) by changing the electrical parameters. Instead of using continuous transmission lines with specific characteristic impedances, the invention uses discrete capacitors and inductors with carefully selected values to achieve the same impedance transformation and signal combining functions, thereby dramatically reducing the physical footprint of the combiner
Solution Approach 2:
The patent extracts the essential functional characteristics of the distributed transmission lines (impedance transformation ratio and phase shift) and separates them from their physical implementation. By taking out only the necessary electrical parameters and realizing them through discrete lumped elements, the invention eliminates the bulky physical structure while preserving the required signal processing functions
2Area of stationary object
If the physical size of transmission lines is reduced to decrease combiner size, then the combiner becomes more compact, but the performance degrades due to the proportional relationship between transmission line size and wavelength
Solution Approach 1:
The patent changes the fundamental approach from scaling down transmission line dimensions (which degrades performance) to completely replacing transmission lines with lumped elements. By changing from a distributed parameter system to a lumped parameter system, the invention achieves size reduction without the performance degradation that would result from reducing transmission line dimensions below wavelength-proportional scales
3Reliability
If bulky transmission lines are used in the Doherty combiner, then the required impedance transformation and load modulation functions can be achieved, but the integration into small-sized and lower weight products is impeded
Solution Approach 1:
The patent changes the physical implementation parameters of the combiner from distributed transmission lines to lumped discrete elements. This parameter change enables the combiner to be integrated into compact printed circuit boards without requiring large aluminum plates or blocks, thereby significantly reducing the overall weight of the power amplifier system while maintaining all required functions
Solution Approach 2:
The patent merges the combiner circuit with the printed circuit board structure by using discrete lumped elements that can be directly mounted on the PCB. This integration eliminates the need for separate bulky transmission line structures and large mounting plates, allowing the combiner to become a lightweight, integrated part of the overall amplifier assembly
4Area of stationary object
If the size of the Doherty combiner is reduced, then the amplifier can be integrated into small-sized products, but the cost of the integrated circuit die and module increases proportionally with size reduction
Solution Approach 1:
The patent segments the combiner function into discrete, independent lumped elements (capacitors and inductors) rather than using a monolithic transmission line structure. This segmentation allows each element to be independently selected, optimized, and manufactured using standard surface-mount technology, thereby reducing overall cost despite the integrated nature of the compact design
Solution Approach 2:
The patent employs inexpensive, commercially available discrete capacitors and inductors that can be easily sourced and replaced. These simple lumped elements are much cheaper than custom-fabricated integrated transmission line structures, especially at lower frequencies where integration would require complex, expensive process modifications
Data Source
AI summary
A combiner coupled to output terminals of a Doherty amplifier, the combiner comprising an inverter circuit and a transformer circuit. The inverter circuit comprising at least a first network and a second network, wherein each of the first network and the second network includes lumped elements. The transformer circuit comprising at least a third network and a fourth network, wherein each of the first third and the fourth network includes the lumped elements, wherein the lumped elements are selected from the group of capacitors and inductors.