integrated cohabitation of multiple miniature...

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INTEGRATED COHABITATION OF

MULTIPLE MINIATURE ANTENNAS

Presented by:

Raheel M. Hashmi PhD Student, 42664675

Supervised by:

Prof. Karu P. Esselle

Department of Engineering

Macquarie University, Sydney

13th June 2012

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• Introduction: SKA & Phased Array Feeds (PAFs)

• PAFs: What? Why? Limitations?

• EBG Structures: A Possible Remedy

• Research Objectives & Outcomes

• Project Plan & Progress

• Conclusions

Outline

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Square Kilometer Array • To be the largest Radio Telescope in history

o Location: Australia, New Zealand & South Africa

o Reflector dishes & aperture arrays over 3000 KMs

o Revolutionary discoveries in astronomical science

• Unparalleled Scalability

o Scaling current technology: Not Feasible!!

o High design complexity & cost barriers

• Main Objectives:

• Large Collecting Area

• Greater Field-of-View

ASKAP Antennas at Murchinson Radio Observatory (Courtesy: ATNF, CSIRO)

Australia’s Telescope Compact Array (Courtesy: ATNF, CSIRO)

Smart Feeds: Multi-Beam

Phased Array Feeds (PAF)

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Artist’s Impression of SKA dishes spread over the Radio-Quiet zone in Western Australia (Courtesy: Swinburne Astronomy Productions/SKA)

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Phased Array Feeds Designs

BYU/NRAO Dipole Feed

• BYU/NRAO, USA

• Thickened Dipoles

• Linear Polarization

• Frequency Ratio 1.3:1

Checker-Board Connected Array

• CSIRO, Australia

• Planar Connected Arrays

• Dense Focal Plane Sampling

• Orthogonal Polarizations

• Frequency Ratio 2:1

• Simple & Low-cost Structure

Phased Array Feed Demonstrator

• DRAO, Canada

• ASTRON, the Netherlands

• Vivaldi Elements

• Dense Focal Plane Sampling

• Orthogonal Polarization

• Frequency Ratio 3:1

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• Conclusions

Outline

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• Wide-Angle High-Resolution Radio Camera

• A Phased Array Feed offers:

o Adaptive Multi-beam Receiver (Multi-Pixel Feed)

o Complete coverage of available Field-of-View

o Sensitivity & Survey Speed (SVS) greater than Single-Pixel Feed

o Improved Radiation and Aperture Efficiencies

• Governing Factors (B. D. Jeffs et al., 2009):

SVS/unit Cost max.(SVS) & min.(Cost)

SVS Nb . b . B . (Aeff/ Tsys)2

Why PAFs?

Model of PAF illuminating a Reflector Dish (B. D. Jeffs et al., 2009)

(a) Primary pattern of reflector (b) Feed pattern by PAF (B. D. Jeffs et al., 2009)

No. of beams

Solid angle per beams

System Bandwidth

Effective Aperture / System Temperature

Sensitivity

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• Constraints

o No. of Beams (Nb) Signal Processing : tradeoff relationship

o System Bandwidth (B) Cost : strictly constrained variable

o Beam Solid Angle (b) Field of View : controllable but design-time variable

o Effective Aperture (Aeff) Reflectors & Effective Illumination : controllable variable

o System Temperature (Tsys) Design Complexity & Cost : controllable variable &

• Objective

“Maximize Sensitivity of Radio Telescope”

Design Constraints & Objectives

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Mutual Coupling & Tsys

System model of Phased Array Feed based receiver (K. F. Warnick et al., 2009: BYU/NRAO Arecibo Telescope Progress)

• LNA’s inherent noise: <50 Kelvin (strictly ) requirement for radio astronomy

• Inter-Channel mutual coupling • Independent LNA design: Insufficient!!! • Result: Decreased Sensitivity

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Scan Blindness & Surface Waves

• Physically: Common-Mode Currents (CMC)

o Differential Beam-Forming with Common-Mode loading

o Large input mismatch at certain scanning angle

• Scan Blindness: What and When?

o Floquet Mode = Propagation Const. of supported Mode

Common-mode currents on Connected Array at 1.7 GHz (above) and 0.9 GHz (below)

(S. G. Hay and O’Sullivan, 2008)

For a function ‘R’ periodic in ‘z’ with period ‘L’:

R(z) = e-jz U(z) R(z + L) = e-j(z+L) U(z + L)

by Fourier Series l.h.s. becomes

e-jz U(z) = An e-j(2πn/L)z . e-jz

R(z) = An e-jnz : n = + 2πn/L

n , L i.e. periodicity breaks

(B. Munk, 2009)

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• Conclusions

Outline

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• Engineered materials designed to have structural periodicity

– Originally a domain of Solid State Physics

– Composed of metal, dielectrics, or both

– Assist/ Impede flow of EM waves of certain wavelengths

– Periodicity on the order of half-wavelength or more

• Applications

– High Gain & Directive Antennas

– Frequency Selective Surfaces (FSS)

– Waveguides & Filters

– High-Impedance Loading

Electronic Band-Gap Structures

1D, 2D and 3D EBG Structures (Joannopolous et al., 2008)

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Applications

Partially Reflective Surfaces: Metallic Loading (A. P. Feresidis et al., 2005)

Frequency Selective Surface (B. Munk, 2000)

High Impedance Ground Plane (R. F. J. Broas et al., 2005)

Optimized PRS-EBG Resonator Antenna (Y. Ge et al., 2007)

High Gain 1-D EBG Resonator Antenna (A. R. Wiley et al., 2005)

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• Defect-Mode Transmission Model (Jecko B. et al., 2007)

• Fabry-Perot Cavity Model (Y. Ge et al., 2012)

• Gain & Directivity Enhancement

o Tangential dimensions of EBG Layer

o Cavity Height

o Magnitude & Phase of cavity reflection coefficient

o Capacitive/Inductive loading of EBG layers

o Current Issues:

o Narrow radiation bandwidth (~300 – 700 MHz)

o Limited Beam-Steering support (~20-30 degrees)

Band-Gap Theory

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• Conclusions

Outline

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• Enhance radiation bandwidth of EBG resonant structures

– Engineering reflection phase gradient of the Partially Reflecting Surface (PRS) by loading

– Multivariable Optimization for PRS loading patterns

• Eliminate Scan Blindness & Mutual Coupling

– Applying high-impedance loading for CMC suppression

– Evaluating EBG superstrate effects for distant placement of elements

• Conserve planar low-cost structural advantage

• Increase array gain & beam steering angle

• Extract empirical models to assist design processes

• Integrating the findings to develop EBG focal plane array prototype

Research Objectives

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• Wide Radiation Bandwidth of EBG-PRS Resonant Structures

• Improved Radiation Efficiency

• Higher Reflector Illumination Effeciency

• Suppression of Surface Currents Less Power Transfer Mismatch

• Reduction of Noise Increased Sensitivity

• Possibility to use Sparse Arrays for dense sampling

Expected Outcomes

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• Conclusions

Outline

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Project Milestones

Period

Milestones From To

Mar 2012 Aug 2012 Extensive Literature Review & Skill Enhancement

Sep 2012 Feb 2013 Achieving Wide Radiation Bandwidth for EBG Structures

Mar 2013 Aug 2013 Elimination of Scan Blindness & Mutual Coupling

Sep 2013 Nov 2013 Formulating Analytical Basis & Data Reorganization

Dec 2013 Mar 2014 Optimizing EBG structures for Gain Enhancement & Beam Steering

Apr 2014 Aug 2014 Fully integrated PAF design verification and prototype fabrication

Sep 2014 Feb 2015 Experimental measurements of prototype and Thesis development

Mar 2015 Thesis submission & Examination

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Delivery Schedule

Deadline Deliverable

Aug 2012 Detailed Research Proposal

Feb 2013 Prototype A: Wide Radiation Bandwidth EBG surfaces

Feb 2013 Reporting results in IEEE Conferences

Aug 2013 Prototype B: EBG Focal Plane Array free of Scan Blindness & Mutual Coupling

Dec 2013 Empirical Models for Trend Analysis

Jan 2013 Reporting results in IEEE Letters/Journals

Aug 2014 Prototype C: Fully Integrated and Optimized Focal Plane Array

Dec 2014 Reporting of results in IEEE Conferences/Journals

Mar 2015 Thesis Document

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High-Level Execution Plan Years 1 2 3 Months 1-3 4-6 7-9 10-12 13-15 16-18 19-21 22-24 25-27 28-30 31-33 34-36

Literature

Review

Software

Training

Simulation

Development

Investigative

Analysis

Physical

Measurements

EBG

Incorporation

Formalization

& Optimization

Gain

Enhancement

Prototyping &

Fabrication

Thesis

Development

Publication

Process

Project Kick-off: 1st March 2012 Project Completion: 30th March, 2015

We are here

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• Conclusions

Outline

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• Square Kilometer Array (SKA) & Phased Array Feeds (PAF)

o Adaptive Multi-beam Receiver & Benefits

o Limitations of PAFs & Current Research Focus

• Objective: Maximize Sensitivity

• Electronic Band Gap (EBG) Structures

o Analytical Models

o Planar EBG Structures in PAFs

• Overcoming limitations, improving performance, conserving cost & simplicity

• Contribution to Science:

“Better feeds for Astronomy to support precise discovery of evolution of Universe

& Life”

Conclusions

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Thank you! Pulsar orbiting a black hole Cosmic Magnetism by Faraday Rotation

SKA dishes night impression

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