Dual-Reflector Antenna Sub-Reflector Design
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Solution Overview
Problem
Dual-reflector antennas face challenges in meeting the ETSI class 4 standard due to high secondary lobes and spillover losses, particularly in dense urban areas where frequency saturation is an issue, and existing solutions are either difficult to implement or result in bulky, expensive antennas.
Innovation Solution
A dual-reflector antenna design featuring a sub-reflector with a dielectric body of varying diameters, where the small-diameter end is connected to a metal tube filled with dielectric material, creating a space that traps air between the sub-reflector and the feed source, enhancing electromagnetic coupling and reducing spillover losses without increasing bulkiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the sub-reflector is made small in diameter to reduce the masking effect, then the secondary lobes are reduced, but the spillover losses increase and return loss deteriorates
Solution Approach 1:
The sub-reflector is nested within the feed source housing, with the small-diameter end of the sub-reflector positioned inside the housing that contains the dielectric-filled metal tube. This nested arrangement allows the sub-reflector to be small enough to reduce masking effects while the feed source housing and dielectric material provide the necessary support and reduce spillover losses.
Solution Approach 2:
A dielectric material is introduced as an intermediary between the sub-reflector and the feed source housing walls. This dielectric material (with relative permittivity between 2 and 3.5) fills the space between the sub-reflector and housing, improving electromagnetic coupling and reducing spillover losses without requiring the sub-reflector to be large.
2Loss of energy
If an absorbing shroud is attached to the periphery of the main reflector to reduce spillover losses, then the front-to-back ratio improves, but the antenna becomes bulky and expensive
Solution Approach 1:
The function of reducing spillover losses is extracted from the traditional external absorbing shroud and relocated to the interior region between the sub-reflector and feed source housing. The dielectric material fills this internal space, providing spillover reduction without requiring external bulky structures.
Solution Approach 2:
Instead of adding an external shroud that increases the antenna's external dimensions, the solution moves to the internal dimensional space between the sub-reflector and housing. The dielectric material utilizes this internal volume to achieve spillover reduction while maintaining a compact external profile.
3Loss of energy
If the sub-reflector is positioned close to the feed source to reduce spillover losses, then the front-to-back ratio improves, but the return loss deteriorates
Solution Approach 1:
The dielectric material's relative permittivity is optimized within the range of 2 to 3.5 to achieve the best compromise between reducing spillover losses and maintaining good return loss. This parameter optimization allows the sub-reflector to be positioned close to the feed source while maintaining electromagnetic performance.
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 design achieves high radio performance, meeting ETSI class 4 standards with reduced secondary lobes and spillover losses, maintaining a high front-to-back ratio and radio frequency performance while avoiding the drawbacks of previous solutions.
Implementation Method 1
the small-diameter end of the sub-reflector comprises an internal portion having a substantially cylindrical shape, able to fit into the housing, having an outer length and outer diameter. The outer length and outer diameter of the small-diameter end of the sub-reflector are respectively less than the inner depth and inner diameter of the feed source, so as to form a space between the inner portion of the sub-reflector and the dielectric wall of the housing.
Implementation Method 2
creating a space that traps air between the sub-reflector and the feed source, enhancing electromagnetic coupling
Implementation Method 3
The dual reflector includes a concave main reflector, most commonly a parabola or portion of a parabola, and a convex sub-reflector, much smaller in diameter, placed in the vicinity of the focus of the parabola
Data Source
AI summary
A dual-reflector antenna comprises a main reflector traversed by a feed source and a sub-reflector. The sub-reflector comprises a dielectric body extending between a first end that is small in diameter and a second end that is greater in diameter, the small-diameter end being connected to the end of the feed source constituted by a metal tube filled with a dielectric material. The end of the feed source connected to the sub-reflector comprises a housing, having an inner depth and inner diameter, built into the dielectric material. The small-diameter end of the sub-reflector comprises an inner portion having a substantially cylindrical shape, able to fit into the housing, having an outer length and outer diameter. The outer length and outer diameter of the small-diameter end of the sub-reflector are respectively less than the inner depth and inner diameter of the feed source, so as to form a space between the inner portion of the sub-reflector and the dielectric wall of the housing.