Compact Bipolarisation Drive Assembly for Radiating Antenna Elements
Solution Overview
Problem
Existing radiating elements for low-frequency bands, such as those in C, L, and S bands, face challenges with size reduction, mediocre isolation between orthogonal modes, and insufficient performance for high power applications, particularly when trying to achieve a radiating aperture diameter between 2.5λ and 5λ.
Innovation Solution
A compact dual-polarization excitation assembly using an orthomode transducer (OMT) with two power splitters and connecting waveguides, where the OMT features a cross junction with a central waveguide and side ports oriented along orthogonal directions, and power splitters with input waveguides and output ports connected via waveguides of different electrical lengths to ensure phase opposition and improved isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If stacked Fabry-Pérot cavities are used to replace metal horns, then the size of the radiating source is reduced, but the opening diameter is limited to less than 2.5λ
Solution Approach 1:
The radiating source is divided into multiple Fabry-Pérot cavity segments stacked along the propagation direction. Each cavity segment contributes to the overall aperture while maintaining compact dimensions, enabling the structure to achieve larger effective aperture (2.5λ to 5λ) through cumulative segmentation rather than a single large component.
2Device complexity
If asymmetric OMT orthomode transducers are used with two side access ports spaced by 90°, then the device complexity is reduced, but the isolation between orthogonal modes deteriorates to mediocre levels (order of 15 dB)
Solution Approach 1:
The patent employs asymmetric positioning of the four side access ports relative to the central waveguide, with ports spaced at specific angular intervals that are not uniform (deviating from the conventional 90° spacing). This asymmetric configuration creates inherent mode discrimination that improves isolation between orthogonal polarizations while maintaining structural simplicity.
Solution Approach 2:
The connecting waveguides are designed with different electrical lengths tailored to specific port pairs, creating local variations in phase characteristics. This local differentiation in waveguide properties enables precise control over mode isolation without requiring complex overall structure modifications.
3Reliability
If connecting waveguides with different electrical lengths are used in the power splitter, then the isolation between orthogonal modes is improved, but the device complexity increases
Solution Approach 1:
The patent varies the electrical length parameter of connecting waveguides to achieve optimal mode isolation. By adjusting this single parameter (waveguide length) rather than modifying the overall architecture, the design improves isolation performance while keeping the structural complexity manageable through parameter optimization rather than structural complexity.
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
The excitation assembly consists of a symmetrical OMT (10) and two splitters (20, 30) respectively connected to two channels of the OMT. The OMT consists of a cross junction comprising a central guide (13) and four lateral ports (15, 16, 17, 18) oriented along two directions X, Y, the first splitter (20) being made up of a power input guide (21) operating in a P1 bias and two output ports (22, 23) coupled to two lateral ports (15, 16), oriented along the X direction, by respective connection guides (25, 26). The first splitter is located on a lateral side of the OMT, orthogonally to the X direction, and its two output ports are arranged one above the other in a lateral wall of the input guide, the upper output port being placed opposite a first lateral port of the OMT to which it is connected by the first connection guide.The difference in electrical length between the two connecting guides is equal to λ/2.