Lumped-Element Doherty Filter Combiner for Broadband Integration
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Doherty amplifiers require bulky transmission lines, which complicate integration and limit bandwidth, especially at lower frequencies.
Innovation Solution
A Doherty amplifier with a filter combiner using only lumped elements, such as π-type and T-type low-pass filters, to reduce the need for transmission lines and enhance bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If transmission lines are used in the combiner, then the reactive combination and phase correction are achieved, but the physical size becomes large and bulky especially at lower frequencies
Solution Approach 1:
The patent replaces the mechanical transmission line system with an electrical filter network system. The combiner uses cascaded low-pass filter sections with series inductors and shunt capacitors to achieve the same reactive combination and phase correction functions that were previously accomplished using physical transmission lines, thereby reducing the overall device volume and improving integrability.
Solution Approach 2:
The patent changes the operating parameters by using lumped element filters with specific L/C values designed to provide the required impedance transformations and phase shifts. The filter sections are configured with predetermined component values that achieve the combiner function at the target frequency, replacing the frequency-dependent transmission line parameters with fixed lumped element parameters.
2Adaptability or versatility
If transmission lines are used for combiner operation, then the reactive coupling is achieved, but the bandwidth is limited and the design is narrow banded
Solution Approach 1:
The patent divides the combiner into multiple cascaded filter sections, each contributing to the overall frequency response. By segmenting the combiner into several low-pass filter stages with progressively changing characteristic impedances, the design achieves broader bandwidth coverage while maintaining the required reactive coupling and phase correction functions.
Solution Approach 2:
The filter network serves multiple functions simultaneously: it provides reactive coupling between amplifier outputs, performs impedance transformation, achieves phase correction, and broadens the operational bandwidth. This multi-functionality is achieved through the cascaded filter structure that combines these functions in a single integrated network rather than requiring separate components.
3Ease of manufacture
If lumped elements are used instead of transmission lines, then the combiner becomes compact and easier to integrate, but the design complexity of the filter networks increases
Solution Approach 1:
The patent employs systematic parameter selection for the lumped elements, using standardized impedance values and structured L/C ratios that simplify the design process. The filter sections are designed with predetermined parameter relationships that reduce the number of independent variables, making the network easier to design and manufacture while maintaining compact dimensions and good integrability.
Data Source
Figure 1~3
Figure 4~7
AI summary
A Doherty amplifier (302) with a filter combiner (301) comprising a first port (303) with an impedance of Z0 connected to an output of a carrier amplifier (304); a second port (305) with an impedance of Z0·r/(1+r) connected to a load (306); a third port (307) with an impedance of Z0·r/(1+r) connected to a peak amplifier (308), wherein r is a power ratio for the carrier amplifier to the peaking amplifier; a fourth port (309) connected to an output port (310) of the Doherty amplifier (302); wherein the first port is connected to the second port via a first network (311), and connected to the third port via a second network (312); wherein the third port is connected to the fourth port via a third network (313); wherein the fourth port is connected to the second port via a fourth network (314).