Phased Array Design in CST STUDIO SUITE - CST - Computer

Phased Array Design in CST STUDIO SUITE Marc Rütschlin, Tilmann Wittig, Zeev Iluz CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com

Our Example: Airborne SATCOM

Required: beam steering and polarization tracking

Ku-band SATCOM:

 linear polarization  Uplink: 14.0 – 14.5 GHz  Downlink: 12.25 – 12.75 GHz "Earth gravity" by NASA/JPL/University of Texas Center for Space Research. http://www.jpl.nasa.gov/news/news.cfm?release=2007-147. Licensed under Public Domain via Commons https://commons.wikimedia.org/wiki/File:Earth_gravity.png#/media/File:Earth_gravity.png

CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com

Simulation Challenge: Antenna


Simulation Challenge: Array


Simulation Challenge: Integration


Simulation Challenge: Integration element: fine geometry

array(s): 100s of elements

via radius = 0.4 mm

aircraft: electrically large length = 42.6 m (2059 λ at 14.5 GHz )


Array Design Overview Element design

Of interest:  Active Element Impedance (AEI) and Active Element Pattern (AEP)  predict large array performance

Array design

Of interest:  real scanning behaviour  non-periodic structure effects


Place on platform

Of interest:  effect of platform on antenna  coupling from array to other antennas

Array Design Overview Element design

Array design

Place on platform

Different solvers required at each stage…

FEM

FIT


Field source coupling

MLFMM

SBR

SAM Workflow Design Element design

Array design

Place on platform

Element design Array design Place on platform


All stages of workflow in one environment

Antenna Element Design


Antenna Magus: Antenna Design Requirements: low profile, broadband, dual-polarised


Modification of Design Fully parameterized model from

“top substrate” air gap “bottom substrate”

2 x 0.787 mm


Modification of Design 1. Add a second port 2. Modify top substrate 3. Reduce to unit cell λ/2 at highest frequency

2 x 0.787 mm


Modification of Design 1. 2. 3. 4.

Add a second port Modify top substrate Reduce to unit cell Add via ring to suppress surface waves


Modification of Design 1. 2. 3. 4.

Add a second port Modify top substrate Reduce to unit cell Add via ring to suppress surface waves


Antenna – Unit Cell Simulation Full Floquet port unit cell boundary conditions Higher order curved tetrahedral mesh


Optimization for Array Operation We need to modify the patch geometry for operation in the array. aim: S < -10 dB in 14-14.5 GHz range 11

1 2 3


Antenna Element in an Array Properties of antenna element change with scanning direction! We need to optimise Active Element Impedance for all scan angles of interest broadside: θ = 0º, φ= 0º

scanning to θ = 50º, φ= 0º


scanning to θ = 50º, φ= 90º

Optimization for Array Operation Goal: Active Element Impedance (AEI) < -10 dB for all scan angles and frequencies of interest! outside loop

Modify key geometric parameters inside loop

feed position

patch radius

Sweep unit cell boundary phase to record AEI for multiple scan angles.


Active Element Impedance AEI at 14.0 GHz


AEI at 14.5 GHz

Port Isolation |S21| at 14.0 GHz


|S21| at 14.5 GHz

Active Element Pattern Active Element Pattern at 14.0 GHz


Active Element Pattern at 14.5 GHz

Active Element Pattern Active Element Pattern at 14.0 GHz

Active Element Pattern at 14.5 GHz

φ = 0º

Scanning from θ = 0º to 50º  predicted drop in gain of 1.8 dB CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com

φ = 0º

Scanning from θ = 0º to 50º  predicted drop in gain of 2.0 dB

Array Design


Full Array – Reference Solution Unit cell with array layout gives full array geometry

for 26 dB gain, -20 dB SLLs CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com

Simulation Setup

PBA conformal meshing

~300 million mesh cells


Parameters autodefined to allow easy switching of scan angles

Array Simulation - Reference Gain at 14.5 GHz, scanning at θ = 0º


Gain at 14.5 GHz, scanning at θ = 50º

Array Simulation - Reference Beam scanned to θ = 0º


Beam scanned to θ = 50º

Full Array with Radome Addition of full curved radome to array

quartz

honeycomb


Full Array with Radome With radome


Without radome

Full Array with Radome Beam scanned to θ = 0º


Beam scanned to θ = 50º

Installed Performance Analysis


Installed Performance Antenna array on aircraft  equivalent field source aircraft length: 42.6 m (= 2069 λ) wingspan: 34.9 m (≈ 1687 λ)

E-field at 14.5 GHz


Installed Performance Simulate with Asymptotic solver (SBR) Directivity vs θ


Installed Performance Simulate with Asymptotic solver (SBR) Directivity vs θ

Peak gain: θ = 50º Peak gain: θ = 49º


Array Design Summary All design stages with best solvers in one environment  Element design: optimisation for all scan angles simultaneously  Full array: full model with non-periodic effects  Installed performance: platform effect and coupling Element design

Array design


Installed performance

Phased Array Design in CST STUDIO SUITE Thank you for your attention! CST – COMPUTER SIMULATION TECHNOLOGY | www.cst.com

Phased Array Design in CST STUDIO SUITE - CST - Computer

Phased Array Design in CST STUDIO SUITE - CST - Computer

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Phased Array Design in CST STUDIO SUITE - CST - Computer