Dual-Fed Doherty Antenna Combining Without Matching Networks
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Solution Overview
Problem
Existing active antenna transmitters face challenges with excessive power losses, high cost, and large size due to independent design of power amplifiers and antennas, leading to inefficient energy use and beam deformation in wireless communication systems.
Innovation Solution
A dual-fed antenna element is used, which acts as a Doherty combiner network, impedance matching network, and radiator, eliminating the need for intermediate matching networks and combining power at the circuit level to reduce size and power losses, while maintaining high efficiency and beam stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If intermediate matching networks and Doherty combiner networks are used between power amplifiers and antennas, then impedance matching and power combining are achieved, but power losses increase, size increases, and cost increases
Solution Approach 1:
The patent merges the antenna element with the Doherty combiner network by integrating the combiner's impedance transformation function directly into the antenna's feeding structure. The antenna element is designed with specific impedance characteristics that simultaneously serve as both the radiating element and the combiner network, eliminating the need for separate intermediate matching networks and reducing power losses.
Solution Approach 2:
The antenna element is designed to perform multiple functions: it acts as both the radiating antenna and the Doherty combiner network. By configuring the antenna with specific impedance characteristics, it simultaneously achieves power combining, impedance matching, and radiation functions, thereby reducing the overall system complexity and power losses.
2Ease of manufacture
If power amplifiers and antennas are designed independently with standard 50-ohm interface impedance, then design simplicity is maintained, but excessive power losses and large size result
Solution Approach 1:
The patent applies local quality by designing the antenna element with non-standard impedance characteristics specifically tailored for the Doherty combiner function. Instead of using uniform 50-ohm impedance throughout, the antenna is configured with localized impedance variations that optimize power combining efficiency and reduce losses at critical interfaces.
3Power
If spatially separated antenna elements are used for Doherty power combining, then power combining is achieved, but beam deformation and gain variation occur
Solution Approach 1:
The patent merges the power combining function with the antenna radiation function by integrating the Doherty combiner network directly into the antenna element structure. This ensures that the power combining process and the radiation process occur at the same location, preventing beam deformation and maintaining stable radiation patterns.
4Device complexity
If two spatially separated patch antennas are fused into one radiating element, then Doherty combiner function is achieved, but inter-element separation distance becomes too large for beam-steering arrays
Solution Approach 1:
The patent applies the nested doll principle by integrating the Doherty combiner network structure within the antenna element itself. The combiner's impedance transformation function is nested within the antenna's feeding structure, allowing both functions to coexist in a compact configuration that minimizes inter-element separation distance for array applications.
Data Source
AI summary
System including a dual-fed antenna element is designed to present 2×2 port impedances that guarantee high efficiency operation of the main- and auxiliary transistors at peak- and backed off power. The proposed solution eliminates the need for lossy power combining, such as PCB based circuit combining or impedance matching networks between the antenna element and the main- and auxiliary amplifiers. The power from the main- and auxiliary transistors are combined at the circuit level by the antenna element.