Developing of new technologies
The development of new technologies and the improvement of existing ones is part of a constant improvement process. Specializing in technological evolution and material development, FDS Italy technicians focus on industrialization and technological development to ensure constantly monitored and reliable processes.
Characterization of materials
The characterisation of both commercial materials and those developed or modified by FDS Italy is part of a “zero-surprise” logic.
The complexity of composite materials and their relations with electromagnetic waves require analyses such as chemical-physical characterisation of composite materials and accelerated ageing tests to assess resistance to environmental conditions, as well as the search for high performance through in-depth study of flaws, anomalies and failures of parts during production and/or use.
Characterisation is finalized by tests performed in an anechoic chamber to verify and guarantee expected electromagnetic performances.
Electromagnetic Design
Electromagnetic performance of radomes depends on the type of antennas to be protected, i.e. operative frequencies, dimensions, illumination, etc. Different antenna applications lead to different critical RF parameters to be taken into account. Sidelobe levels are critical for 3D military antennas, whereas in other applications the sidelobes level is not the key factor in electromagnetic design of the radome. In this framework, FDS Italy engineers are used to analyse critical factors driving the design of specific radomes in order to meet every customer’s requirements.
Diameter and truncation of radomes have to be properly chosen in order to locate the centre of antennas as close as possible to radome centres in order to minimize induced BSE. Large radomes, being panelised, have junctions among panels scattering EM energy. In order to spread out the scattering energy on a wide angle, radomes must be designed based on “quasi-random geometry”. Exceptions may be specific antenna applications, special customer needs (for example oblate radomes) or extremely small radomes, all cases where an “orange-peel” geometry can be adopted.
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The main factors to be taken into account for correct design of large radomes are the following:
- Designing a wall tuned to applicable frequencies.
- Adopting quasi-random geometry.
- Designing a joint capable to limit scattering effects.
Insertion loss of the radome wall is minimized while structural stability of radomes is ensured by proper multi-layer design. Scattering effects are reduced by the right choice of panel geometries (“quasi-random”) and by adopting a joint configuration as the best compromise between electromagnetic and mechanical needs. The IFR (Induced Filed Ratio) of a joint is a key parameter for computation of the scattering energy level of radomes. In order to reduce the scattering level of a joint, special solutions can be provided as an option, mainly by means of the introduction in the joint layer stack of proper metal components allowing for reduction of the IFR. The joint is compensated, i.e. a sort of phase tuned is performed.
Electromagnetic Analysis at FDS Italy is carried out by means of internally-developed software, capable to compute the insertion loss of a stack of dielectric layers and to simulate the antenna pattern modification due to the presence of panelised radomes including the effects of the scattering of the joints.
Both the insertion loss of a panel and the IFR are measured in FDS Italy anechoic chamber on specific radome samples.
Several collaborations with Universities are constantly in progress for the development of new solutions to improve radome performance.
Laboratory analysis
FDS Italy has significantly invested in its Research & Development and Testing laboratory. Innovative instruments and constant staff training enable us to carry out much more accurate analyses.
At FDS Italy we have introduced instruments used in other high-tech sectors, by adapting them to our high standards. We have successfully introduced Thermal Analysis & Differential Scanning Calorimetry for chemical and process analysis, High Performance Narrow Band Digital Ultrasonic Flaw Detectors for product and process control.
Other instruments, such as A video-based goniometer to provide dynamic and static contact angle measurements, surface tension and surface energy and Pull-off Adhesion Testers Measures adhesion have been used for Product Application Process Development to obtain superhydrophobic surfaces that resist in time and have a contact angle > 140°. This has enhanced FDS Italy, which has contributed to taking radomes to new frontiers through R&D.
Engineering (Design)
FDS Italy designs and produces large panelised dielectric radomes with pseudo-random geometry and overlapping joints. Structures are self-supporting, requiring no over-pressure, the only metallic parts being bolts required for panels connections and radome fixation to the customer base interface. Typical wall configuration is an A-sandwich design with an additional external layer for environmental protection, but multi-layer walls have been developed for application at very high frequencies (up to 27 GHz), leading to a new class of large ground base radomes called ML radomes (multilayer radomes).
Standards require mechanical resistance to wind gust of 240 Kph, but special designs for higher values have been made on customers’ request.
Electromagnetic performance under rain is crucial for many types of radomes (for example in the event of radome covering weather antennas). Standard finishing has good features, but super-hydrophobic finishing can be requested for better electromagnetic performance under rain.
The expected life of a radome structure is 20 years or more. FDS Italy recommends minimum maintenance activities to be performed during radome life and can offer proper service activities to its customers. FDS Italy can install radomes or offer supervisors. Assembly and disassembly of FDS Italy radomes can be accomplished by using simple means. It is possible to remove and insert any single panel on radomes safely and easily from the inside of radomes.
FDS Italy has designed and produced truncated spherical radomes with diameters starting from 2.4 meters up to 20.7 meters. Special designs have included small spherical-conical radomes and oblate geometry for LVA antennas. Applications include radomes for ATC systems, weather antennas, surface movement (terrestrial and costal) radar and satcom antennas.
Structural Design
Design of radomes is a multi-disciplinary activity; radome development and engineering is a fine synthesis of structural, electromagnetic, environmental requirements and material mechanical and electromagnetic testing. Radome engineers have to comply with constraints due to the nature of radomes that must be RF transparent. Only thanks to its long experience in radome design, FDS Italy can offer adequate solutions to customers’ needs.
FDS Italy performs all engineering activities needed to develop radomes. In particular, radome structural design is performed at FDS Italy by means of FEA (Finite Elements Analysis), including static, buckling, modal and dynamic analysis (in particular Response Spectrum Analysis for earthquake verification). Proper partial safety factors are included in radome design. 3D modelling of radomes is performed by state-of-the-art commercial CAD software. 2D drawings are obtained directly from 3D models. Composite layer stack and accessories of radomes are included to provide a complete set of Manufacturing Drawings and Installation Drawings.
Wind loads are the most critical factors for radomes due to severe customers’ requirements on gust wind. Correct structural analysis is only possible if proper distribution of pressure is applied to radome models. CFD (Computational Fluid Dynamic) analysis has been carried out, which allows our structural engineers to analyse radomes based on a proper mathematical model of the effects of the wind.
Radomes are subject to severe environmental conditions along their operative life. Choice of materials is therefore strategic in radome design. All raw materials used in manufacturing of FDS radomes have been tested in accordance with several MIL, ASTM and ISO standards.