Post on 07-Aug-2015
Daniel Rogers Duotech Services, Inc.
Leaky Waveguide Antenna Design Methodology
Computational Electromagnetics, Testing, Construction, and Lessons Learned
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.
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