Modeling the Installed Performance of Antennas in a Ship ... · Modeling the Installed Performance...

Modeling the Installed

Performance of Antennas in a

Ship Topside Environment

CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com | Nov-10

Enow Tanjong

Electromagnetic SystemsComplete Technology in Action

Antenna

Filter Shielding

RCS

Installed Performance


Electron Tube

FSS

Array

Connectors PCB

Package

Cabling

System Level DesignAll-Encompassing EM-Simulation

EM Interaction

System analysisCoupling analysisRadiation analysis


Installed PerformanceEMC/ EMI/ E3

Challenges: Electromagnetic size, Complexity, Aspect ratio

Electrical Size

Frequency Application

1 MHz Lightning

10 MHz HF communications

100 MHz EMP

1 GHz L-Band

Communications

10 GHz Radar


El. Length

0.5λ

5λ

50λ

500λ

5000λ

FEM TD MLFMM AsymptoticMoM

Aspect Ratio

300 MHz

18 m

18 λ

1.575 GHz

160 m

840 λ


4 mm notches

0.9 mm radius feed pin3 mm wire radii

Approach 1: Brute force!


� Small detail � small time step

� longer simulation.

� HPC options: CPU, GPU, MPI.

� Mesh quality important

� Increased meshing in small

detail leads to high memory

requirement

� HPC options: CPU, MPI.

MLFMMTime Domain

Approach 2: Field Decomposition

FIT, TLM, FEM, MoM, MLFMM


Near-field source

Far-field source

FIT, TLM

MoM ,MLFMM, Asymptotic

Advantages of Field Sources

Near-field Source Far-field Source


� Small simulation volume � fine features can be simulated

accurately.

� Simulate source with appropriate mesh and solver.

� Can import external (measured) fields.

� No knowledge of antenna structure necessary (Intellectual Property).

Real World Navy FrigateComplete Technology in Action

1 GHz JTIDS antenna(FEM + MLFMM)


10 MHz HF whips (TD, MoM)

TD (FIT) Solution


FIT Solver

40 minutes, 1.3 GB RAM10 Million mesh cells

Far-Field Results at 10 MHz

Single antenna excited


Surface Current due to HF Antenna


MoM Solution

MoM Solver

60 minutes, 12 GB RAM


Low frequency stabilization available

Anisotropic mesh

refinement

JTIDS for L Band TDMA Network Radio

JTIDS antenna (1.0875 GHz)


Installed performance of antenna required

JTIDS Antenna Array Design


Rapid, automatic design of validated antenna elements

Convenient building block for larger, more complex designs

Synthesis, Optimization

Element Level Simulation


Snap nodes to boundaryReferences true geometry

Sensitivity Analysis


Sensitivity AnalysisParametric tolerance analysis with only a single simulation run

2nd Order 325000 Tetrahedrons

Mixed Order Elements


3rd Order Mixed 98000 Tetrahedrons

JTIDS Antenna Pattern in Isolation


Automatic phase center calculation

Arbitrary slant polarization

JTIDS Far Field Source on Ship

JTIDS antenna pattern imported and positioned on ship mast


Ship is 500 wavelengths long @ 1.0875 GHz

Characterization of Water Surface


At higher frequencies characterization of sea water as a

surface impedance material significantly reduces the amount of required computational resources

Surface Mesh at 1.0875 GHz

1,400,000 surfaces


1,400,000 surfaces

MLFMM Solver => 12 hours and ~84 GB RAM

JTIDS + Ship Results at 1.0875 GHz

Surface current

Far field pattern


Far field pattern

Complex Ship Model

USS Winston S. Churchill (DDG-81)

Provided by


Tactical Air Navigation (TACAN) Antenna


1.087 GHz TACAN antenna

Gain cut

3D Far-field

Antenna Gain not optimized

TACAN AntennaGain


TACAN Far Field Source on Ship

TACAN antenna pattern imported and positioned


TACAN Far Field + Ship meshed at 1.087 GHz

1,950,098 surfaces (including sea water) => Solvable with MLFMM but would require a large amount of RAM. MPI would be an option


Asymptotic SolutionShooting Bouncing Ray (SBR) method� Multiple bounces taken into account� Plane wave source for RCS analysis Incident Rays

Scattered Rays


Robust meshing enables discretization of complex models and Asymptotic solution requires far less computational resources making it ideal for this problem

TACAN + Ship Results at 1.087 GHz


Asymptotic solver => 3 hours, 600 MB RAM

Model size is approximately 783 wavelengths at 1.087 GHz

S-Band Radar Antenna


Radar Unit Element Patch Antenna


Right-hand Circular Polarized pin-fed Square Truncated Patch Antenna

designed for 3 GHz

Array Construction and Excitation

Array wizard constructs the array and applies

excitation

25 X 25 Array

Transient Solver


All 625 Ports created automatically by wizard

3 GHz S-Band Radar Array Results

Far-field

Surface Current


Simultaneous port excitation requiring 35 GB of RAM and 6 hours to run

S-band Radar Antenna Field source on Ship


Radar Antenna Array Pattern imported and Positioned

Single Radar + Ship Results at 3 GHz

Far-field


Model size is approximately 2160 wavelengths at 3 GHz

Multiple Far-Field Sources

Possible to import multiple FF sources and excite all at once


Antenna Analysis/Placement Features

• All standard antenna performance results (Gain, Surface Current, . . )

• Sensitivity analysis

• Up to 3rd order TET elements

• Frequency tabulated surface impedance

• Parameterization/ optimization


• Parameterization/ optimization

• Far-field and Near-field Source imports

• Array Wizard

• High Performance Computing Options

Summary

• CST MWS has the capability of solving electromagnetic problems both

at the component level and at the system level

• The complete technology available means the best tool can be used for

a particular analysis

• At the system level field decomposition techniques can be used for


• At the system level field decomposition techniques can be used for

more efficient analysis.

• The asymptotic method implemented in CST MWS can be used for very

complex electrically large simulations reduce the amount of resources

required

Modeling the Installed Performance of Antennas in a Ship ... · Modeling the Installed Performance...

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