Daniel Rogers Duotech Services, Inc.

Leaky Waveguide Antenna Design Methodology

Computational Electromagnetics, Testing, Construction, and Lessons Learned

Overview

❖ Purpose

❖ Approach

❖ Prerequisite Information

❖ Methods

❖ Analysis

❖ Synthesis

Purpose

❖ Develop a highly directional antenna

❖ 35dBi gain

❖ Less than 2 degree 3dB beam width

❖ Analyze potential design

❖ Synthesize a manufacturable approach

❖ Analysis of actual design before and after production

The Alphabet Soup

❖ Electromagnetics / Electrodynamics

❖ Waveguides

❖ Skin Depth

❖ Near Field / Far Field

❖ Maxwell (awesome)

The Slotted Array❖ Simple to fabricate (relatively)

❖ Linear polarization

❖ ~5% bandwidth

❖ Slotted vs. Phased

❖ Slotted array utilizes coherent relative phases from adjacent elements

❖ Phased array antenna can control relative phases of elements

❖ Essentially, a waveguide with holes

Array Factor

❖ From a dipole or other single element directional radiator

❖ To a tightly controlled, sharp beam

Grating Lobes

❖ We desire a single, strong lobe

❖ Unfortunately, the the array will radiation in other directions.

❖ These undesired beams of radiation are known as grating lobes.

❖ They occur when the antenna element separation is too large.

Taper Advantage

10x10 Array without Taper 10x10 Array with 30dB Taylor Taper

Prerequisite: Waveguide Knowledge

❖ Structure to guide electromagnetic waves

❖ Control transmission mode

❖ Phase velocity, phase velocity, phase velocity!

❖ Return loss

❖ Power splitter

❖ Boundary conditions and energy transfer (can someone get me a free-space transformer?)

❖ Cutoff frequency

Prerequisite: Materials & Manufacturing Familiarity

❖ Conductivity

❖ Skin depth

❖ Dip Brazing

❖ Material bonding

❖ Well suited for brazing aluminum because air is excluded (aluminum likes clean)

❖ Donor material used to bond individual pieces

❖ Individual components fixtures together, and dipped into a molten salt bath for heat transfer medium and flux

Simulation

❖ Investigated Approaches

❖ Differential equation solvers: Finite-difference time-domain

❖ Integral equation solvers: Method of moments (MoM)

❖ Other: EigenMode Expansion (EME)

❖ MATLAB®

❖ Various toolboxes

❖ Approaches: MoM, FDTD

❖ MathCAD®

❖ General Calculations

❖ MoM

Testing

❖ Near field

❖ Concept

❖ Flaws

❖ Far field

❖ Requires a large space

❖ Far field begins at ~116’ for this antenna

❖ Tools

Investment❖ GR-510 Mill and Tooling

❖ CAM/CAM Software

❖ Solidworks

❖ SolidCAM

❖ Number Smashing Software

❖ MathCAD

❖ MATLAB

❖ Mathematica

❖ Materials

❖ Inspection Tools

❖ Electronic Test Equipment

Lessons Learned

❖ Loughborough Antennas & Propagation Conference very worth while

❖ Possible to design with strong Electromagnetics, O.D.E, and Linear Algebra skills

❖ Knowledge about this design on IEEE Explore does not exist within any one document

❖ An EM solver tool would have been worth while to use in retrospect (e.g. Feko®, CST®, Comsol®)

❖ White boards are better than Mathematica® for this application

All rights reserved Duotech Services, Inc. 2015

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