Analysis of Antenna Positioning on Warship

Analysis of Antenna Positioning on Warship

Scope of Work:

Optimization of the locations of all the antennas (transmit as well as receive) based on a computer based electromagnetic simulation study of ship’s 3D CAD model including electromagnetic models of its antennas using contemporary software packages.

Report of the study includes coverage / blockage analysis and radiation patterns of antennas, coupling and predicted EMI between antennas & equipment connected to the antennas and prediction of RADHAZ (HERO, HERP, HERF, HERE, HERA) zones.

Technical Description:

Technical Description:

The overall study includes the following stages

• Standalone antenna modeling
• Platform modeling
• Installed antenna modeling
• EMI/EMC Analysis
• EMI/EMC Design & Optimization

Standalone antenna modeling includes CAD pre-processing, Meshing, Simulation, Post-processing, Reporting. This stage we shall CAD import & repair and work on Different mesh size for error control, simulation of antenna needs the Materials & Boundary conditions, Frequency range as an input, Results analysis and validation will be final output at this stage.

Platform Modeling includes CAD import & repair,Decomposition of model to allow reduced domain simulation depending on antenna position and frequency (domain of influence).Full platform simulation with generic antennas for different frequencies and positions, with different domains as preparation for installed antenna simulations

Installed antenna modeling – For this we need positioning & installation of antennas as input. Integration of standalone antenna CAD into relevant platform CAD, Surface meshing will be done as first stage of antenna integration and the Materials & Boundary conditions, Frequency range, Output specification will be given as input parameters for simulation.

EMI/ EMC Analysis gather information about standards and testing procedures. Specification of simulation setup for the installed antenna simulations according to measurement procedures frequency ranges, probe positions, type of output etc.

EMI/EMC Design & Optimization Based on EMI/EMC Analysis report, identiy issues and suggest alternative antenna locations or shielding measures and Simulation of alternative placements of antennas will be done.

Equipment	Frequency	Type	Solver antenna	Solver ant+platform
I-band radar	8-10 GHz	Patch array	MOM/MLFMM	SWE+MLFMM/HF
DGPS	285 – 315 kHz*	Choke ring	MOM	MOM
AIS	161.975 & 162.025 MHz	Wire	MOM	MOM/MLFMM
Magnetic compass	*
1 KW HF	3-30 MHz	Wire	MOM	MOM
V-UHF Tx Rx	156-162 MHz	Wire	MOM	MOM/MLFMM
Wave receiver	*		MOM
MSS Tx-Rx	1.5-2.5 GHz	Reflector	MOM	MLFMM/SWE+MLFMM
Ku band Satcom terminal	12-18 GHz	Reflector	MOM/MLFMM	SWE+MLFMM/HF
UHF SATCOM Terminal	225-400 MHz	Helical	MOM	MOM/MLFMM
INMARSAT Fleet Broadband	1.5-1.7 GHz	Reflector	MOM	MLFMM/SWE+MLFMM
GMDSS Equipment
a.       MF/HF Tx/Rx	1.65-25 MHz	Wire	MOM	MOM
b.       VHF MMB Tx/Rx with DSC	154-162 MHz	Wire	MOM	MOM/MLFMM
c.       INMARSAT ‘C’ terminal	1.5-1.7 GHz	Reflector	MOM	MLFMM/SWE+MLFMM
d.       NAVTEX Receiver	490KHz/4209Khz	Wire	MOM	MOM
Automatic weather observation system	*		MOM

CEM ONE A Complete Environment for Computational Electromagnetics (CEM)

PAM-CEM Simulation Suite operates mainly from medium to high frequency range. When targeting a wide frequency spectrum as usually managed with EMC/EMI issues, time-domain techniques are applied to investigate electromagnetic phenomena appearing along those complex cables networks connecting onboard electronics.

• Visual-CEM, a dedicated pre-processing module, proposing advanced features for the management of specialized Boundary Conditions, exciting waves or signals, 3D materials, including ideal or lossy grounds, and the specification of all targeted electromagnetic results. Also featuring wired antennas with the related loading and/or exciting conditions, in order to manage realistic emitting or receiving devices.
• Visual-Mesh allowing the management of most CAD formats, the generation of major 2D/3D meshed models and the specification of structured FD grids, with 3D refinement areas and/or staircase wired structures.
• Visual-Viewer, post-processing tool shared by all disciplines integrated in the VisualEnvironment and upgraded in order to deal with typical electromagnetic data such as polar plots and antenna radiation patterns

Features:

EMC/EMI with Cable networks

• 3D explicit Finite Difference Time Domain with PAM-CEM/FD
• MultiConductor Transmission Lines (MTL) with CRIPTE
• Dedicated 3D/MTL coupling procedures to handle realistic scenarios gathering both conducted & radiated EM phenomena

Antenna placement & Radar signature

• MoM/MLFMM solver technology in Frequency Domain
• MDMM decomposition techniques to solve larger problems faster
• Dedicated MoM/MLFMM-PO & FDTD-FEM hybrid techniques
• PAM-CEM/HF PO (Physical Optics) solver for high-frequency scattering
• FDTD-PO extension for radiated near fields

Solvers:

Modeling of horn antennas or patch antennas can be done using frequency domain MoM. Large reflector antennas can be modeling using frequency domain MLFMM or MLFMM-PO. Broadband antennas are well suited to time domain FDTD. The frequency domain solvers are based on the Integral Equation (IE) or Finite Element Method (FEM).

The IE technique, usually called MoM in electromagnetics, uses a surface integral formulation of the electric and magnetic field of an arbitrarily shaped object consisting of conductors, dielectrics and thin wires. In IE the analysis is accurately carried out by representing the conductors, dielectrics and thin wires using surface triangular elements and beam segments. Only the surfaces and wires are discretized in and the technique leads to a dense matrix system which is solved.

In addition to the IE technique also FEM is available which is based on tetrahedral elements. It leads to a sparse matrix system which is solved.

Different solver modes and IE formulations are available in the solvers to be able to cover a very wide range of applications including antenna design, antenna integration, waveguides and radar cross section analysis. While standard MoM is the preferable choice for electrically small antenna or waveguide design problems the Multilevel Fast Multipole Method (MLFMM) or the Physical Optics method (PO) is the preferable choice for applications involving electrically large structures. Examples of applications where MLFMM and PO is the preferred choice are radar cross section analysis or antenna installation analysis. In addition to these three basic solver modes the solvers also include hybrid MoM-PO and hybrid MLFMM-PO solver modes.

Spherical Wave Expansion (SWE):

Automatic determinations of coefficients for a spherical wave expansion from one of the following five cases are possible:

• Near field data from the simulation, using an automatic spherical probe.
  • Near field data from the simulation, using a user-defined probe. The name of the probe can be entered manually or chosen from a drop-down list.
  • Near field data from a file in the near file format, see General set of Cartesian coordinates and fields.
  • Far field data from the simulation.
  • Far field data from a file in the far file format, see Far field.

In the spherical wave expansion determination the following items need to be provided:

The Nmax entry specifies the highest n index of the expansion typically given by

N_{max} = k r + max(10,3.6 \sqrt[3] {kr})

where k being the wavenumber and r the radius of the minimum sphere enclosing the antenna.

The Radius entry specifies the radius of the smallest sphere that contain the geometry of the antenna. An approximate value will be entered already, estimated from the entire geometry. A radius must be specified if the mode Near field with automatic probe is used. Nmax may optionally be set to 0, in which case it will be estimated from the radius and the frequencies used. The Medium specifies the medium of the used probe surface.