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MEASUREMENT AND SIMULATION OF PARALLEL PLATE
WAVEGUIDE STRUCTURES IN THE TERAHERTZ REGION
FOR SENSING AND MATERIAL CHARACTERIZATION
APPLICATIONS
Presented by J. Alex Higgins June 14, 2012
Thesis Committee:
Branimir Pejcinovic, Chair
Matrin Siderius, Ph. D.
Lisa Zurk, Ph. D.
NEAR-Lab
OVERVIEW
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 2 / 19
Introduction
Why Terahertz?
Terahertz Sensing and Material Characterization
How Does This Work Contribute?
Background and Theory
Parallel Plate Waveguide
Fourier Transform Mode Matching Technique
FDTD Simulation
TDS and CW-VNA Systems
Results and Discussion
PPW Multimode Radiation Patterns
PPW Resonant Structures (e.g. single notch and notched periodic)
Conclusion
Summary of Results
Summary of Contributions
Future Work
THE TERAHERTZ GAP
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 3 / 19
Communicationsand Radar
OpticalCommunications
MedicalImaging
Astro-physics
µ Wave
and RF
mm
Wave Terahertz Infrared Visible Ultraviolet X-ray
Electronics Photonics
1010 1011 1012 1013 1014 1015 1016 1017 1018
Frequency (Hz)
3× 10−2 3× 10−3 3× 10−4 3× 10−5 3× 10−6 3× 10−7 3× 10−8 3× 10−9 3× 10−10
Wavelength (m)
4.135× 10−5
4.135× 10−4
4.135× 10−3
4.135× 10−2
4.135× 10−1
4.135× 100
4.135× 101
4.135× 102
4.135× 103
Energy (eV)
FIGURE 1 – Electromagnetic spectrum indicating the “THz gap”.
TERAHERTZ SENSING AND MATERIAL CHARACTERIZATION
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 4 / 19
• Biomedicine and security industries
• Biomolecules and explosives have unique spectral signatures in
this region (e.g. DNA, MDMA, RDX, PETN)[1, 2].
• Paper products, plastics, and clothing fibers are virtually
transparent.
• Non-ionizing makes it well suited for health safety scanning of
foods and transportation security.
(A) Detection of illicit substances through paper envelope. (B) Specral fingerprint of explosives(urlhttp://www.pnl.gov).
TERAHERTZ SENSING AND MATERIAL CHARACTERIZATION
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 4 / 19
• Semiconductor industry
• Characterize current IC device fabrication materials (e.g.
packaging, substrates, isolating dielectric layers).
• Integrate with existing “cheap” CMOS technologies[3].
FIGURE 2 – CMOS mm-wave on-chip antennas and RFICs.[3]
HOW DOES THIS WORK CONTRIBUTE?
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 5 / 19
PARALLEL PLATE WAVEGUIDE (PPW) TO THE RESCUE!
• Sensing
• False readings are diminished by designing PPW filters that
detect only one material.
• Material Parameter Extraction
• By placing samples laterally inside the PPW the material-EM
field interactions occur over longer distances than in free
space.
y
x
z
PEC
PEC
W
d
l
µ0, ǫ0
HOW DOES THIS WORK CONTRIBUTE?
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 5 / 19
• Engineering challenges involved with using PPW
1. Waveguide theory introduces multiple modes of operation
which lead to excess energy loss in dispersion and mode
conversion.
2. Resonance of the PPW structure is dependent on its
geometric parameters; plate separation, notch width, depth,
pitch, and center spacing.
HOW DOES THIS WORK CONTRIBUTE?
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 5 / 19
• Engineering challenges involved with using PPW
1. Waveguide theory introduces multiple modes of operation
which lead to excess energy loss in dispersion and mode
conversion.
2. Resonance of the PPW structure is dependent on its
geometric parameters; plate separation, notch width, depth,
pitch, and center spacing.
• The work for this thesis addresses these issues by
characterizing the behavior of PPW operating in a multimode
configuration and investigating the sensitivity of the geometric
parameters of PPW resonant structures.
HATS OFF TO THE MAXWELLIANS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 6 / 19
FIGURE 3 – James Clerk Maxwell
MAXWELL’S EQUATIONS
∇× E = −jωµH
∇× H = jωǫE + J
∇ · ǫE = ρ
∇ · µH = 0
(A) George Fran-cis Fitzgerald
(B) Sir OliverJoseph Lodge
(C) Oliver Heavi-side
FIGURE 4 – The Maxwellians[4]
PARALLEL PLATE WAVEGUIDE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 7 / 19
y
x
z
PEC
PEC
W
d
l
µ0, ǫ0
FIGURE 5 – Diagram of the geometry for a PPW.
β =√
k2 − k2c =
√
k2 −(mπ
d
)2
αc,TE =Pl
2P0=
2k2cωµβd
Rs
αc,TM = 2ωǫ
βdRs|Am|2
TRANSVERSE ELECTRIC (TE) MODE
Hz = Bm cos(mπ
dy)
e−jβz
Ex = jωµ
k2cBm sin
(mπ
dy)
e−jβz
Hy = jβ
k2cBm sin
(mπ
dy)
e−jβz
Ey = Hx = 0, m ∈ N
TRANSVERSE MAGNETIC (TM) MODE
Ez = Am sin(mπ
dy)
e−jβz
Ey = −jβ
k2cAm cos
(mπ
dy)
e−jβz
Hx = jωǫ
kcAm cos
(mπ
dy)
e−jβz
Hy = Ex = 0, m ∈ N0
PARALLEL PLATE WAVEGUIDE CONT.
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 8 / 19
z (mm)
y (m
m)
TE−modeEx−field [Mode = 1]
0 5 10 15 200
0.5
1
1.5
2
−30
−20
−10
0
z (mm)
y (m
m)
TM−modeHx−field [Mode = 1]
0 5 10 15 200
0.5
1
1.5
2
−30
−20
−10
0
z (mm)
y (m
m)
Ex−field [Mode = 2]
0 5 10 15 200
0.5
1
1.5
2
−30
−20
−10
0
z (mm)
y (m
m)
Hx−field [Mode = 2]
0 5 10 15 200
0.5
1
1.5
2
−30
−20
−10
0
z (mm)
y (m
m)
Ex−field [Mode = 3]
0 5 10 15 200
0.5
1
1.5
2
−30
−20
−10
0
z (mm)
y (m
m)
Hx−field [Mode = 3]
0 5 10 15 200
0.5
1
1.5
2
−30
−20
−10
0
FIGURE 6 – Comparison of PPW TE and TM mode field strength distributions.
PARALLEL PLATE WAVEGUIDE CONT.
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 8 / 19
0 0.2 0.4 0.6 0.8 1 1.2 1.4
0
y (mm)
Ex (
dB)
0 0.5 1 1.50
50
100
φ (°
)
(A) TE1
0 0.2 0.4 0.6 0.8 1 1.2 1.4
0
y (mm)
Ex (
dB)
0 0.5 1 1.5−100
−50
0
50
100
φ (°
)
(B) TE2
FIGURE 6 – First two TE field distributions between the plates of the PPW.
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
• The Fourier transform technique is especially well suited for EM
problems since it provides a convenient mathematic
representation of wave scattering, diffraction, and propagation.
• e.g. antenna radiation, diffraction, and interference.
• Fourier transform, mode-matching, and residue calculus offer a
robust set of techniques.
• When applied to solving EM scattering and boundary problems
they obtain simple, analytic, and rapidly converging series
solutions.
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
• The analysis method for scattering and boundary condition
problems has the following steps[5]:
1. Divide the scattering domain into closed and open regions.
2. Represent the scattered fields in their respective regions in terms of theFourier series and transform.
3. Enforce boundary conditions on the field continuities between regions.
4. Apply the mode-matching technique to obtain the simultaneousequations for the Fourier series modal coefficients.
5. Utilize the residue calculus method to represent the scattered field in afast convergent series.
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
x
z
r
θs
y
-a a
Eiy
Ery
Ety
Region II
Region I
k
k0
PECPEC
FIGURE 7 – Cross section diagram of a radiationpattern geometry for a flanged PPW.
Ety =
1
2π
∫
∞
−∞
Ety(ζ)e
−j(ζx−κ0z) dζ
Ety(ζ) =
∫
∞
−∞
Ety(x, 0)e
jζx dx
Ety(ζ) =
1
2π
∞∑
m
(cm + δmn) ama2Fm(ζa)
Fm(u) =eju(−1)m − e−ju
u2−
(
mπ2
)2
Hty(ζ) = ζp sin ap(x+ a)
−
∞∑
m
cmζm sin am(x+ a)
1
2π
(
Ipn +∞∑
m
cm
)
= a (ξpδnp − ξncn)
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
x
z
r
θs
y
-a a
Eiy
Ery
Ety
Region II
Region I
k
k0
PECPEC
FIGURE 7 – Cross section diagram of a radiationpattern geometry for a flanged PPW.
Imn =∫
∞
−∞a2κ0Fm(ζa)Fn(−ζa) dζ
Ety =
1
2π
∫
∞
−∞
Ety(ζ)e
−j(ζx−κ0z) dζ
Ety(ζ) =
∫
∞
−∞
Ety(x, 0)e
jζx dx
Ety(ζ) =
1
2π
∞∑
m
(cm + δmn) ama2Fm(ζa)
Fm(u) =eju(−1)m − e−ju
u2−
(
mπ2
)2
Hty(ζ) = ζp sin ap(x+ a)
−
∞∑
m
cmζm sin am(x+ a)
1
2π
(
Ipn +∞∑
m
cmImn
)
= a (ξpδnp − ξncn)
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
Re(ζ)
Im(ζ
)
R
−am
Γ1
am
Γ6
Γ5
Γ4
BranchCut
Γ2
Γ3
k0
Γ4
Γ7
FIGURE 7 – Contour path in the ζ-plane.
Imn =
∫
∞
−∞
2κ0
[
1− (−1)n ej2ζa
(ζ2 − a2m) (ζ2 − a2n)
]
dζ
∮
f(ζ) dζ =
∮
Γf(ζ) dζ = 0
.
.
.
Imn =2π
a
√
k20 − a2m
amδmn + (I2mn − I1mn)
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
Re(ζ)
Im(ζ
)
R
−am
Γ1
am
Γ6
Γ5
Γ4
BranchCut
Γ2
Γ3
k0
Γ4
Γ7
FIGURE 7 – Contour path in the ζ-plane.
Imn =
∫
∞
−∞
2κ0
[
1− (−1)n ej2ζa
(ζ2 − a2m) (ζ2 − a2n)
]
dζ
∮
f(ζ) dζ =
∮
Γf(ζ) dζ = 0
.
.
.
Imn =2π
a
√
k20 − a2m
amδmn + (I2mn − I1mn)
cm =
(
δmn −[
(I1mn+I2mn)
2πa(
ξn+√
k2
0−a2
m
)
]T)
−1
(I1pn+I2pn)
2πa(
ξn+√
k2
0−a2
n
)
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
x
z
r
θs
y
-a a
Eiy
Ery
Ety
Region II
Region I
k
k0
PECPEC
FIGURE 7 – Cross section diagram of a radiation pattern geometry for a flanged PPW.
Ety(r, θ) = ej(kr−
π
4 )√
k2πr cos θ
∑
∞
m (cm + δmn) ama2Fm (−ka sin θ) (9)
FOURIER TRANSFORM MODE MATCHING TECHNIQUE
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 9 / 19
0dB
−20
−40
−60
0
30
60
90
270
300
330
TE1
TE3
TE5
(A) First three even symmetric modes
0dB
−20
−40
−60
0
30
60
90
270
300
330
TE2
TE4
TE6
(B) First three odd symmetric modes
FIGURE 7 – Examples of PPW TE radiation patterns using (9) with a = 0.25 mm and ν = 2 THz.
FINITE DIFFERENCE TIME DOMAIN SIMULATION
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 10 / 19
MIT ELECTROMAGNETIC EQUATIONPROPAGATION (MEEP)
• An open-source implementation of theFDTD method for numerically solvingelectromagnetic problems.
• Available for download at(http://ab-initio.mit.edu/meep).
• A port for the Apple Macintosh was writtenusing the Macports interface(http://www.macports.org).
• Also accessible as a resource tool at theNanoHUB website(http://nanohub.org/resources/Meep).
Some of its key capabilities of are:
• Simulations in 1D, 2D, 3D, and cylindricalcoordinates.
• Distributed memory parallelism on anysystem supporting the MPI standard.
• PML absorbing boundaries.
• Exploitation of simulation symmetries,which reduces computation size.
• Scriptable front-end or callable from a C++library or Python interface.
• Output results in the HDF5 standardscientific data format.
• Arbitrary material and source distributions.
• Field analyses including flux spectra,energy and power integrals.
FINITE DIFFERENCE TIME DOMAIN SIMULATION
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 10 / 19
MIT ELECTROMAGNETIC EQUATIONPROPAGATION (MEEP)
• An open-source implementation of theFDTD method for numerically solvingelectromagnetic problems.
• Available for download at(http://ab-initio.mit.edu/meep).
• A port for the Apple Macintosh was writtenusing the Macports interface(http://www.macports.org).
• Also accessible as a resource tool at theNanoHUB website(http://nanohub.org/resources/Meep).
MEEP!
Some of its key capabilities of are:
• Simulations in 1D, 2D, 3D, and cylindricalcoordinates.
• Distributed memory parallelism on anysystem supporting the MPI standard.
• PML absorbing boundaries.
• Exploitation of simulation symmetries,which reduces computation size.
• Scriptable front-end or callable from a C++library or Python interface.
• Output results in the HDF5 standardscientific data format.
• Arbitrary material and source distributions.
• Field analyses including flux spectra,energy and power integrals.
FINITE DIFFERENCE TIME DOMAIN SIMULATION
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 10 / 19
• MEEP has two built-in sourcefunctions, continuous-wave andgaussian-pulse.
• The Gaussian is a useful
representation of optical pulsesbecause of its straightforwardmathematical description andbroadband spectral content.
• The derivative of the Gaussian isused to model the distinct positiveand negative swing (pulse) of theTDS system.
Gaussian Function
f(t) = exp
(
−jωt−[
(t− t0)√2 δt
]2)
Gaussian-pulse Function
∂
∂tf(t) =
j
ωexp
(
−jωt−[
(t− t0)√2 δt
]2)
FINITE DIFFERENCE TIME DOMAIN SIMULATION
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 10 / 19
86 87 88 89 90 91 92 93 94
−1
−0.5
0
0.5
1
Time (ps)
Fie
ld S
tren
gth
(V
)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2−100
−80
−60
−40
−20
0
Frequency (THz)
Po
wer
Sp
ectr
um
(d
B)
Picometrix
Gaussian Model
FDTD
Gaussian
δ/δt Gaussian
Picometrix
∫ δt Picometrix
FDTD
FIGURE 8 – Gaussian-pulse model compared to TDS system waveform and FDTD source function.
MEASUREMENT SYSTEMS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 11 / 19
TIME DOMAIN
SPECTROSCOPY (TDS)
Picometrix T-RayTM 4000
Bandwidth 0.2 - 2 THz
Signal-to-Noise Ratio > 70 dB
Rapid Scan Range 320 ps
Rapid Scan Rate 100 Hz
TABLE 1 – Picometrix T-RayTM 4000 system specifications.
FIGURE 9 – Picture of a TDS input coupling experiment us-
ing quasi-optical Picometrix T-RayTM 4000 system.
CONTINUOUS WAVE VECTOR
NETWORK ANALYZER (CW-VNA)
VDI Extender Modules
Six Bands 75 - 750 GHz
Dynamic Range 80 - 120 dB
Compatible VNAsAglient, Anritsu,
Rhode & Schwartz
Output Power 5 - 7 dBm
TABLE 2 – Virginia Diodes Inc. (VDI) extender module spec-ifications.
FIGURE 10 – Picture of a CW-VNA radiation pattern exper-iment setup using VDI extender modules for the WR1.5 band.
RADIATION PATTERNS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 12 / 19
FIGURE 11 – Diagram indicating the PPW ge-ometry and setup for a radiation pattern experi-ment.
m TE (GHz) TM (GHz)
0 - 0
1 107.1 *
2 * 214.1
3 321.2 *
4 * 428.3
5 535.3 *
TABLE 3 – First five PPW cutoff frequencies cal-culated for TE and TM modes at a plate separa-tion of 1.4 mm.
• To maintain TM dominant mode operation d = 75 µm (TM2 = 4 THz)
• Reducing the dimensions of the PPW introduces propagation loss, group
velocity dispersion, and coupling issues[6].
RADIATION PATTERNS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 12 / 19
Angle (°)
Fre
quen
cy (
GH
z)
−50 0 50
200
400
600
800
1000
1200
1400
Pow
er S
pect
rum
(dB
)
−60
−50
−40
−30
−20
−10
0
FIGURE 11 – Measured TDS system radiationpattern of a PPW operating in TE mode.
Angle (°)
Fre
quen
cy (
GH
z)
−50 0 50
200
400
600
800
1000
1200
1400
Pow
er S
pect
rum
(dB
)
−60
−50
−40
−30
−20
−10
0
FIGURE 12 – FDTD simulated radiation patternof a PPW operating in TE mode.
• The Fourier transform mode-matching technique was implemented[7].
• A brute-force recursive minimal standard deviation algorithm wasimplemented to match results to their weighted analytic solution.
RADIATION PATTERNS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 12 / 19
0dB
−20
−40
−60
0
30
60
90
270
300
330
Analytic 100% TE1
Analytic Multimode
FDTD at 910 GHz
TE1: 51%
TE3: 25%
TE5: 17%
TE7: 7%
FIGURE 11 – PPW TE multimode radiation pat-tern of FDTD simulation compared to weightedanalytic mode contributions.
0dB
−15
−30
−45
−600
30
60
90
270
300
330
TDS at 385 GHz
Analytic Multimode
CW−VNA at 385 GHz
FDTD at 385 GHz
TE1: 85%
TE3: 15%
FIGURE 12 – PPW TE multimode radiationpatterns of TDS and CW-VNA system mea-surements, and FDTD simulation compared toweighted analytic mode contributions.
EXCESS LOSS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 13 / 19
0.1 0.3 0.5 0.7 0.9 1.1
0
0.1
0.2
0.3
0.4
0.5
Frequency (THz)
α c (dB
/cm
)
TDS TE
1
TE5
TE7
TE3
FIGURE 13 – TDS system measurements compared to theoretic of TE mode conductive attenuation.
EXCESS LOSS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 13 / 19
360 365 370 375 380 385 390 395 4000
0.05
0.1
0.15
0.2
0.25
0.3
Frequency (GHz)
Exc
ess
Loss
(dB
/cm
)
FIGURE 13 – Close-up of excess loss beyondthe lowest order TE1 mode.
• Black points indicate radiationpatterns with distinct side lobes.
• Red point indicates a radiation
pattern blurred out by diffraction.
0dB
−20
−40
−60
0
30
60
90
270
300
330
374.3 GHz
377.4 GHz
380.6 GHz
FIGURE 14 – TDS system radiation pattern blur-ring due to excess loss.
RESONANT STRUCTURES
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 14 / 19
SINGLE NOTCH PARALLEL
PLATE WAVEGUIDE (N-PPW)
d
w
t
z Al
Al
FIGURE 15 – Cross section diagram of the N-PPW resonant structure.
d = 1000 µm (plate separation)w = 412 µm (notch width)t {variable} (notch depth)
NOTCHED PERIODIC PARALLEL
PLATE WAVEGUIDE (NP-PPW)
d
wp
t
g
z Al
Al
FIGURE 16 – Cross section diagram of the NP-PPW resonant structure.
d {variable} (plate separation)w = 112 µm (notch width)t = 93 µm (notch depth)
p = 280 µm (notch pitch)g = 162 µm (center span)
RESONANT STRUCTURES
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 14 / 19
SINGLE NOTCH PARALLEL PLATE WAVEGUIDE (N-PPW)
250 260 270 280 290 300 310−50
−40
−30
−20
−10
0
10
Frequency (GHz)
Fie
ld S
tren
gth
(dB
)
t/w ≈ 4 t/w ≈ 2 t/w ≈ 1 t/w ≈ 0.5
FIGURE 15 – FDTD simulation results com-parison resonant peak shift for varying N-PPWdepth to width ratios.
t (µm) ν (GHz) t/w ∆ν (%)
206 283 0.5 1.07
412 280 1 0
824 278 2 0.71
2060 277 4 1.07
TABLE 3 – Resonant frequency values of simu-lated FDTD single notch depths.
• The resonant peak increases for smaller depths and decreases for larger.
• The resonant peak shows little dependence on notch depth when thedepth-to-width t/w ratio is greater than 2.
RESONANT STRUCTURES
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 14 / 19
NOTCHED PERIODIC PARALLEL PLATE WAVEGUIDE (NP-PPW)
470 480 490 500 510 520 530 540 550 560−60
−50
−40
−30
−20
−10
0
10
20
30
Frequency (GHz)
Fie
ld S
tren
gth
(dB
)
FDTD for d = 100 µmFDTD for d = 200 µmTDS for d = 200 µmCW−VNA for d = 200 µm
FIGURE 15 – Comparison of TDS and CW-VNAsystem results and FDTD simulated transmis-sion characteristics of the NP-PPW resonator.
ν (GHz) d (µm)
TDS 498 200
CW-VNA 500 200
FDTD 489 200
FDTD 493 100
TABLE 3 – Resonant peak values for varyingplate separation.
• The resonant peak increases for smaller plate separations.
• Results from the dimensional analysis of the NP-PPW indicate that channel
dimensions deviate from their expected value by σ ≤ 5.
SUMMARY OF RESULTS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 15 / 19
• Identifying and characterizing the behavior of PPW multimode
operation
• Multimode operation is identifiable using radiation patterns.
• Energy coupled in to individual modes can be estimated using
radiation patterns.
• Distinct side lobes in the radiation pattern are crucial to correctly
weighting mode estimates.
SUMMARY OF RESULTS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 15 / 19
• Investigating the sensitivity of the geometric parameters to PPW
resonant structures
• The N-PPW resonant peak increases for smaller depths and
decreases for larger.
• The N-PPW resonant peak shows little dependence on notch
depth when the depth-to-width t/w ratio is greater than 2.
• The NP-PPW resonant peak increases for smaller plate
separations.
• Results suggest that the NP-PPW plate separation is less critical a
design parameter for the resonant peak than the geometry and
placement of notches.
SUMMARY OF CONTRIBUTIONS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 16 / 19
• Measurements were performed and presented on both
broadband TDS and narrowband CW-VNA systems.
• Custom PPW and fixtures were designed and fabricated for
each experiment.
• A configurable MATLAB package was developed to process
experimental results.
• An analytic solution for the radiation pattern of a flanged
PPW[7, 8] was implemented in MATLAB.
SUMMARY OF CONTRIBUTIONS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 16 / 19
• A brute-force recursive minimal standard deviation algorithm
was implemented in MATLAB to estimate the energy coupled
into each mode.
• FDTD simulations were developed and performed for PPW
radiation patterns and resonant structures.
• Macintosh ports were written for the freely available MEEP
package[9] for Electromagnetic (EM) simulation.
SUMMARY OF CONTRIBUTIONS
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 16 / 19
• Contributing published works include:
• 2011 SPIE Defense, Security, and Sensing conference[10]
• 76th ARFTG conference[11]
• 34th MIPRO conference[12]
• 11th IEEE-NANO conference[13]
• 35th IRMMW-THz conference[14]
FUTURE WORK
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 17 / 19
• PPW Multimode Radiation Patterns
• Refine radiation pattern analytic solution mode weighting algorithm.
• Investigate mechanism behind “blurring” of side lobes in radiant patterns.
• Automate radiation pattern measurements.
• Develop GUI application for radiation pattern matching.
• PPW Resonant Structures
• Investigate mechanism behind N-PPW diminishing returns wrt t/w.
• Run FDTD simulations using NP-PPW dimensional analysis values.
• Investigate effects of modifying NP-PPW center span dimensions.
• Implement NP-PPW analytic solution using Fourier transformmode-matching technique.
REFERENCES
J. Alex Higgins, higginja@ece.pdx.edu June 14, 2012 19 / 19
[1] M. Nagel, P. H. Bolivar, and H. Kurz, “Modular parallel-plate thz components for cost-efficient biosensing systems,” SemiconductorScience and Technology, vol. 20, no. 7, p. S281, 2005.
[2] R. Mendis, V. Astley, J. Liu, and D. M. Mittleman, “Terahertz micofluidic sensor based on a parallel-plate waveguide resonantcavity,” Applied Physics Letters, vol. 95, no. 171113, 2009.
[3] F. G. Jr., T. S. Rappaport, and J. Murdock, “Millimeter-wave cmos antennas and rfic parameter extraction for vehicularapplications.” in VTC Fall. IEEE, 2010, pp. 1–6. [Online]. Available:http://dblp.uni-trier.de/db/conf/vtc/vtc2010f.html#GutierrezRM10
[4] B. J. Hunt, The Maxwellians. Cornell University Press, 1991.
[5] H. J. Eom, Electromagnetic Wave Theory for Boundary-Value Problems. Springer, 2004.
[6] R. Mendis, “Thz waveguides: The evolution,” in Infrared Millimeter Waves and 14th International Conference on TeraherzElectronics, 2006. IRMMW-THz 2006. Joint 31st International Conference on, sept. 2006, p. 367.
[7] T. Park and H. Eom, “Analytic solution for TE-mode radiation from a flanged parallel-plate waveguide,” IEE Proceedings-H, vol.140, no. 5, pp. 387–389, Oct 1993.
[8] C. H. Kim, H. J. Eom, and T. J. Park, “A series for tm-mode radiation form a flanged parallel-plate waveguide,” IEEETRANSACTIONS ON ANTENNAS AND PROPAGATION AP, vol. 41, p. 1469, 1993.
[9] A. F. Oskooi, D. Roundy, M. Ibanescu, P. Bermel, J. D. Joannopoulos, and S. G. Johnson, “MEEP: A flexible free-software packagefor electromagnetic simulations by the FDTD method,” Computer Physics Communications, vol. 181, pp. 687–702, January 2010.
[10] A. Higgins, B. Pejcinovic, C. Cowen, and F. Kernan, “An investigation of parallel plate waveguide terahertz radiation inputcoupling,” SPIE Proceedings, vol. 8023, no. 1, pp. 802 310–802 310–13, 2011.
[11] A. Higgins, F. Kernan, and B. Pejcinovic, “Multimode characterization of parallel plate waveguide,” in Microwave MeasurementSymposium (ARFTG), 2010 76th ARFTG, 30 2010-dec. 3 2010, pp. 1 –5.
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