Dual-Polarization Radome with Embedded Metallic Layers
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Solution Overview
Problem
Designing high-speed airborne radomes that require transmission at incidence angles exceeding 70 degrees for both transverse electric (TE) and transverse magnetic (TM) polarized energy while maintaining multi-bandpass capability at non-harmonic frequencies is challenging, as conventional radomes face issues with grating lobes and thermal limitations.
Innovation Solution
A radome design incorporating a dielectric wall with embedded or disposed metallic layers, featuring an inductive metallic grid and a repeating lattice of metallic structures, which acts as a sub-resonant reactive impedance surface at lower frequencies and a frequency selective surface at higher frequencies, optimized to prevent grating lobes and ensure dual-polarization transmission across a wide band separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an inductive metal grid is embedded in a thin-wall radome to form a resonant passband at a lower frequency, then multi-bandpass capability is achieved, but large grid size/spacing is required which creates grating lobes at the upper frequency
Solution Approach 1:
The radome wall is segmented into multiple functional layers: a thin dielectric radome wall and an embedded inductive metal grid. This segmentation allows each layer to serve a specific frequency band function, with the grid providing inductance for lower frequency operation while the thin wall maintains upper frequency performance
Solution Approach 2:
The inductive metal grid is strategically embedded only in specific regions of the radome wall where it is needed to create the resonant passband at the lower frequency, rather than uniformly throughout the entire structure. This localized approach minimizes the grid's negative impact on upper frequency operation
2Reliability
If the radome wall is made physically one half-wavelength thick at an upper frequency to achieve passband transmission, then transmission at the upper frequency is improved, but the wall becomes too thin to provide sufficient inductance for resonant operation at a lower frequency with large band separation
Solution Approach 1:
The invention merges two previously separate solutions into a single integrated radome structure: the thin dielectric wall optimized for upper frequency half-wavelength resonance and the embedded inductive metal grid that provides the necessary inductance for lower frequency operation. This combination allows both frequency bands to operate effectively simultaneously
Solution Approach 2:
The inductive metal grid acts as an intermediary element that bridges the gap between the thin dielectric wall and the requirement for sufficient inductance at lower frequencies. The grid's inductance compensates for the electrical thinness of the wall at lower frequencies while remaining transparent at upper frequencies
3Object-generated harmful factors
If a grid of metal mesh-patches is inserted orthogonal to the inductive grid to compensate for grating lobes, then grating lobe suppression is achieved, but the device complexity increases
Solution Approach 1:
Instead of using a symmetric orthogonal grid of metal mesh-patches, the invention employs an asymmetric compressed grid configuration where the grid elements are non-uniformly spaced and oriented. This asymmetric arrangement provides grating lobe suppression while maintaining simpler manufacturing compared to orthogonal mesh structures
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 solution achieves better than -1 dB insertion loss for both TE and TM polarized energy at incidence angles up to 90 degrees, enabling multi-bandpass, dual-polarization transmission with large non-harmonic band separation without inducing grating lobes, and allows for the use of monolithic dielectric materials.
Implementation Method 1
Pierrot, in U.S. Pat. No. 3,864,690, takes advantage of this inductive tuning and presents a multi-bandpass radome concept. Pierrot describes a monolithic radome wall that is physically one half-wavelength thick at an upper frequency F1 and virtually a half-wavelength thick at a lower frequency F2 by embedding an inductive grid into the radome in order to form a resonate passband with the capacitance of the thin, dielectric radome at F2.
Implementation Method 2
Each of the metallic layers is configured to act as a sub-resonant reactive impedance surface to form a first passband at the first, lower frequency and as a frequency selective surface to form a second passband at the second, upper frequency.
Implementation Method 3
Pierrot recognized that such a large grid creates grating lobes at F1 due to the repeating lattice dimension of the grid being larger than a free-space wavelength at F1. The grid and the metallic structures are tuned simultaneously to permit bandpass transmission at least at upper and lower frequencies and to inhibit generation of grating lobes at least at the upper frequency for incidence angles in excess of 70 degrees.
Data Source
AI summary
A radome is provided and includes a dielectric wall and metallic layers embedded within and/or disposed on the monolithic wall. Each of the metallic layers is configured to act as a sub-resonant reactive impedance surface at a lower frequency and as a frequency selective surface at an upper frequency.