Dual-Reflector Antenna Geometry for Wideband Conical Beam Coverage
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Solution Overview
Problem
Existing antennas for aircraft and satellites fail to provide a wide coverage conical beam over multiple frequency bands without using movable elements or electronic beam steering, particularly struggling to operate effectively across substantial frequency differences like 20 GHz and 45 GHz.
Innovation Solution
An antenna design utilizing a sub-reflector and a main reflector, where the sub-reflector is formed by a portion of an axially-displaced ellipse and the main reflector by a section of a parabola, with a signal transmission feed between them, enabling a wide coverage conical beam with selectable beam peaks up to 90 degrees and a bandwidth ratio of more than 2.25:1, and a dual-band feed assembly for efficient signal transmission and reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a short back-fire cup-dipole driven element with a balun is used, then the antenna can be manufactured at gigahertz frequencies, but the matching characteristics vary with temperature variations and the balun is complicated to manufacture
Solution Approach 1:
The invention removes the balun component entirely from the antenna system. By using a different feed structure (horn antenna or waveguide feed) directly coupled to the reflector system, the patent eliminates the need for a balun, thereby removing the source of temperature-dependent matching variations and manufacturing complexity associated with baluns at gigahertz frequencies.
2Adaptability or versatility
If a conical helix antenna is used, then the antenna structure is simplified, but the bandwidth coverage is limited and dual band operation is not capable
Solution Approach 1:
The invention divides the reflector system into two distinct reflectors: a primary reflector and a secondary reflector. This segmentation allows each reflector to be optimized for different frequency bands, enabling dual-band operation. The primary reflector handles one frequency band while the secondary reflector handles another, thereby achieving adaptability across multiple bands with sufficient bandwidth coverage in each band.
3Adaptability or versatility
If a single reflector antenna is used, then the structure is simple, but wide coverage conical beam with selectable beam peaks cannot be achieved
Solution Approach 1:
The invention uses a segmented reflector system with a primary reflector and a secondary reflector, where each reflector can be independently shaped and positioned. This segmentation enables the creation of complex beam patterns and selectable beam peaks that cannot be achieved with a single reflector, while maintaining a manageable structural complexity through modular design.
Solution Approach 2:
The invention introduces a second spatial dimension by adding a secondary reflector that works in conjunction with the primary reflector. This dimensional addition allows for the creation of conical beams with selectable peak directions, providing adaptability in beam steering without requiring mechanical movement of the entire antenna structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The antenna achieves wide area coverage surveillance with iso-flux beam density and operates effectively across multiple frequency bands, including 20 GHz and 45 GHz, providing hemispherical and super-hemispherical coverage, and supports dual-band communication systems with high efficiency.
Implementation Method 1
The sub-reflector reflects radio waves towards a main reflector
Implementation Method 2
the main reflector which in turn reflects the radio waves to form the beam pattern emitted by the antenna
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
An exemplary embodiment of an antenna in accordance with the present invention utilizes a sub-reflector and a main reflector with each of them having its own focal- ring type geometry. The antenna cooperates with a signal transmission feed disposed at the center of the antenna axis between the first and main reflectors to emit radio signals towards the sub-reflector. The sub-reflector reflects radio waves towards a main reflector which in turn reflects the radio waves to form the beam pattern emitted by the antenna. The reflecting surface of the sub-reflector is formed by a portion of an axially-displaced ellipse rotated about the antenna axis. The reflecting surface of the main reflector is defined by a section of a parabola rotated about the antenna axis to form a reflecting surface that concavely slopes away from the antenna axis. An embodiment of the antenna provides a wide coverage conical beam with selectable beam peaks that operate over a 2.25: 1 frequency band range and provides substantially iso-flux beam density.