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Design Applications ofDefected Ground Structures
Authored by:Jason YunPeter Shin
Ansoft Corporation
Ansoft 2003 / Global Seminars: Delivering Performance
Presentation #9
w Introductionw DGS Definition and Characteristicsw Design Challengew Ansoft Design Solution
w DGS Bandpass Filter Designw Design Procedurew Unit DGS Modeling and Analysisw DGS Bandpass Filter Design using Ansoft Designer and HFSSw DGS Bandpass Filter Design with an Additional DGS
w Design applications using DGSw Lowpass Filter Designw Branch Line Coupler Designw Unequal Wilkinson Power Divider Design
w Conclusionw References
Outline
w A Defected Ground Structure (DGS) is an etched lattice shape, which locates on the ground plane
w Evolution from Photonic Band Gap (PBG) Structurew Periodic or non-periodic w Easy to represent as an equivalent circuit (LC resonator)
w Applicationsw Planar resonators w High characteristic impedance transmission linew Filter, Coupler, divider/combiner, Oscillator, Antenna. Power Amp.
What is a DGS?
DGS Characteristics
gw
b
a
w Disturbs shielding fields on the ground planew Increases effective permittivityw Increases effective capacitance and inductance of transmission linew One-pole LPF characteristics (3dB cutoff and resonance Frequency)w Four design parameters (a, b, g, and w) under given substrate
S11
S21
DGS Design Challenges
w DGS has an arbitrary shape which locates on the backside metallic ground plane
w Accurate EM simulator is necessary
w Equivalent circuit modelingw Equivalent circuit modeling is important for rapid designw Co-simulation or dynamic link is needed between EM and
circuit simulators to extract an equivalent circuit
w Many design parametersw Automated parameter sweep w Powerful optimization
Ansoft DGS Design Solution
Design Spec.equivalent circuit, cutoff, and resonance freq.
System/CircuitMixed Circuit design (lumped,distributed)
Planar EM2.5D pattern analysis
HFSS v9.0Full 3D analysis
Physical dimension (3-dimensional configuration : lattice dimension, gap distance and transmission line width, layer stackup)
Ansoft provides the best solution for integration between physical design and circuit modeling.
Ansoft Designer v1.1 Ansoft Dynamic Link
- Full 3D FEM Solver- Built-in Parameterization
- Implicit to entire system - Complete Integration of Optimetrics™- Parameter sweeps and optimizations are an
integral part of the entire design environment - Easy-to-set-up sweeps, optimizations, sensitivities,
and statistical analyses- Wideband Fast Frequency Sweep
- fast frequency sweep technology- Adaptive Lanczos Pade Sweep
- Circuit Co-simulation with Ansoft Designer v 1.1- Powerful Field Post-Processor
measuremen
t
measuremen
t
Simulation
Simulation
Ansoft HFSS v9.0
- Include Circuit/System and Planar EM Solver
- Dynamic Link with HFSS v9.0- Full model parameterization- Automated parameter sweeps- Mixed-meshing capabilities- Automated transmission and reflection
calculation- Circuit and EM Integration- Dynamic postprocessor
Ansoft Designer v1.1
Ansoft Scalable 3D Dynamic Link
Design parameters werepassed from HFSS v9.0into Ansoft Designer v1.1
DGS Bandpass Filter Design
Design Procedure
Fabrication for Verification
Extracting Physical dimensions using HFSS
DGS Filter Design using Ansoft Designer
Propose Equivalent circuit of DGS
Propose DGS structure
Proposed Unit DGS
gw
b
a
cLCL XX
ωωω ===
1 '
(4)(1)
(2)
(3)
(5)
221
1
coo
c
gZC
ωωω
−⋅=
CfL
o ⋅=
2241
π
Equivalent Circuit for the DGS
10 )( −−=
o
oLC CX
ωω
ωω
ω
1' gZLX oL ⋅== ωω
Unit DGS Modeling with HFSS v9.0
w Define project variablesw Create 3D model
w Ground planesw Tracesw Dielectrics
w Draw unit DGS sectionw Slotsw Traces
w Define material propertiesw Define boundary conditionsw Define excitationsw Setup solution informationw Analysis
w Unit DGS library can be build using fully parameterized Ansoft Designer™ Planar EM and HFSS™
w Modeling parameterw Etched lattice dimension w Gap distancew Substrate thickness
w Design validation can be done by measurement at the end
The lattice, and gap distance can all be varied with a few central Project Variables to permit analysis of any similar DGS. Or, a parametric sweep can generate and maintain
results for many variations at once.
The lattice, and gap distance can all be varied with a few central Project Variables to permit analysis of any similar DGS. Or, a parametric sweep can generate and maintain
results for many variations at once.
Parameterized Unit DGS
Parameter Sweeps
Effect of Lattice Dimension, a
gw
b
a
7mm
6mm5mm
4mm3mm
2mm
Freqa
dB(S11)
gw
b
a
Effect of Gap Dimension, g
300um 700um400um
500um600um
Electric Field on the DGS
Magnetic Field on the DGS
DGS Filter Design Using Ansoft Designer
Schematic of the coupled-line bandpass filter with two DGS sections.Substrate : ROGERS RT/Duroid 6010, Er=10.2, h=50mil, Center Frequency : 3 GHz, Bandwidth : 10%
Schematic of the coupled-line bandpass filter with two DGS sections.Substrate : ROGERS RT/Duroid 6010, Er=10.2, h=50mil, Center Frequency : 3 GHz, Bandwidth : 10%
Physical Dimension of DGS
Simulated and Measured Results for the unit DGSSimulated and Measured Results for the unit DGS
Planar EM Simulation
Circuit Simulation
Measuredgw
b
a
L = 2.573nHC = 0.64pF
fc = 2.871 GHzf0 = 3.92 GHz
L = 2.573nHC = 0.64pF
fc = 2.871 GHzf0 = 3.92 GHz
L
C
Final DGS dimension :
a=4.15mm, b=6.2mm,
g=0.5mm, W=1.2mm (50Ω)ROGERS RT/Duroid 6010, Er=10.2, h=50mil
Final DGS dimension :
a=4.15mm, b=6.2mm,
g=0.5mm, W=1.2mm (50Ω)ROGERS RT/Duroid 6010, Er=10.2, h=50mil
EM Simulation of DGS filter
Ansoft Desigenr™ Planar EM
Ansoft Designer™ Circuit
Results comparison between Circuit and EM SimulationResults comparison between Circuit and EM Simulation
(a) Top view
(b) Bottom view
Fabrication for Verification
Photograph of the fabricated coupled-line
bandpass filter with DGS.
Photograph of the fabricated coupled-line
bandpass filter with DGS.
Results comparison between EM simulation and measurement on the fabricated DGS coupled-line BPF
Results comparison between EM simulation and measurement on the fabricated DGS coupled-line BPF
Ansoft Designer PlanarEM
Measured
DGS Bandpass Filter with An Additional DGS
Schematic of the DGS coupled-line filter with an additional DGS section in coupled-resonator.
Schematic of the DGS coupled-line filter with an additional DGS section in coupled-resonator.
Physical Dimension Extractionof Additional DGS
Simulated Result for the additional unit DGSSimulated Result for the additional unit DGS
gw
ba
L = 1.11nHC = 0.66pF
fc = 4.8 GHzf0 = 5.9 GHz
L = 1.11nHC = 0.66pF
fc = 4.8 GHzf0 = 5.9 GHz
L
C
DGS Dimension : a=1.55mm, b=6mm, g=0.2mm
Conductor Line : w=1.2mm (50Ω)
Substrate : ROGERS RT/Duroid 6010, Er=10.2, h=50mil
DGS Dimension : a=1.55mm, b=6mm, g=0.2mm
Conductor Line : w=1.2mm (50Ω)
Substrate : ROGERS RT/Duroid 6010, Er=10.2, h=50mil
Planar EM Simulation
Circuit Simulation
EM Simulation Using HFSS
Circuit and EM simulated results comparisonCircuit and EM simulated results comparison
Ansoft HFSS™
Ansoft Designer™
(a) Top view
(b) Bottom view
Fabrication for Verification
Photograph of the fabricated DGS coupled-line bandpass filter with
an additional DGS.
Photograph of the fabricated DGS coupled-line bandpass filter with
an additional DGS. Comparison results between EM simulation and measurement on the fabricated DGS coupled-line BPF
Comparison results between EM simulation and measurement on the fabricated DGS coupled-line BPF
Measured
Ansoft HFSS
Lowpass Filter Application
Proposed DGS LPF
(a) (b)
Designed lowpass filters with the proposed DGS unit sections with (a) T-junction opened stub for parallel capacitance where the stub width and length are 5mm and 10mm, respectively (b) cross-junction opened stub for parallel capacitance where the stub width and length are 5mm and 6mm,
respectively.
Designed lowpass filters with the proposed DGS unit sections with (a) T-junction opened stub for parallel capacitance where the stub width and length are 5mm and 10mm, respectively (b) cross-junction opened stub for parallel capacitance where the stub width and length are 5mm and 6mm,
respectively.
(a) Top view (b) Bottom view
Fabrication and Measurement
Photographs of the fabricated DGS Lowpass filter with T-junction type open stub (a) Top view and (b) bottom view.
(a) Top view (b) Bottom view
Photographs of the fabricated DGS lowpass filter with cross-junction type open stub (a) Top view and (b) bottom view.
Comparison of measured results for the fabricated DGS lowpass filters
with the T-junction, the cross-junction type open stub, and the
conventional lowpass filter.
Comparison of measured results for the fabricated DGS lowpass filters
with the T-junction, the cross-junction type open stub, and the
conventional lowpass filter.
Branch Line Coupler Application
(a) Top view
(b) Bottom view
Fabrication for Verification
Photograph of (a) top and (b) bottom sides of
the fabricated 90°branch-line coupler
with DGS cells.
Photograph of (a) top and (b) bottom sides of
the fabricated 90°branch-line coupler
with DGS cells. The simulation and measurement results of the branch line coupler with
DGS section
The simulation and measurement results of the branch line coupler with DGS section
Substrate : RT/Duroid 5880, Er=2.2, thickness=31mils. The physical length and width of conductor corresponding to quarter wave 150ohms line with 1-D periodic DGS are 26mm and 1mm at 1.84GHz, respectively. The quarter wave length and width of 150ohms line on conventional microstrip are 31mm and 0.2mm. In left Fig., the period S = 8mm, a = b = 6mm, c = 12mm, d = 1mm and g = 1mm.
Substrate : RT/Duroid 5880, Er=2.2, thickness=31mils. The physical length and width of conductor corresponding to quarter wave 150ohms line with 1-D periodic DGS are 26mm and 1mm at 1.84GHz, respectively. The quarter wave length and width of 150ohms line on conventional microstrip are 31mm and 0.2mm. In left Fig., the period S = 8mm, a = b = 6mm, c = 12mm, d = 1mm and g = 1mm.
a
g w
b
s
d
c
4:1 Unequal Wilkinson Power Divider Application
Conventional N:1 unequal Wilkinson power divider
P1
P 2
P 3
Rint
Z2
Z3
R2
R3
N
1
Zo
100.025.0125.0158.139.54
86.628.9115.5131.643.93
70.735.4106.1103.051.52
R3 [W]R2 [W]Rint[W]Z3 [W]Z2 [W]N
Table 1. Characteristic impedance and resistor values of N:1 unequal Wilkinson power divider
Reference [4] : Due to the increased effective inductance of the DGS, the aspect ratio of the 158 W microstrip line has been increased to 235% and the length of l/4 has been reduced to 83%. The fabricated conductor width of the 158 W microstrip line were 0.4mm, while 0.17mm for the conventional one. The enlarged conductor width and reduced length has a great advantage in design and realization such a high impedance line and smaller circuit. The fabricated 4:1 divider showed excellent matching and isolation, and exact dividing ratios of -1dB and -7dB at port 2 and port 3 without additional losses induced by the DGS over 1.2 ~ 1.8GHz.
Reference [4]Reference [4] : Due to the increased effective inductance of the DGS, the aspect ratio of the 158 W microstrip line has been increased to 235% and the length of l/4 has been reduced to 83%. The fabricated conductor width of the 158 W microstrip line were 0.4mm, while 0.17mm for the conventional one. The enlarged conductor width and reduced length has a great advantage in design and realization such a high impedance line and smaller circuit. The fabricated 4:1 divider showed excellent matching and isolation, and exact dividing ratios of -1dB and -7dB at port 2 and port 3 without additional losses induced by the DGS over 1.2 ~ 1.8GHz.
Unequal Wilkinson power divider with DGS Unequal Wilkinson power divider with DGS
Port 1
Port 2
Port 3
h
L2
Grounded plane
Dielectric Substrate
w
a
b
c
Rs
λ/4
λ/4
Z3
Z2
ZL3
ZL2
3
w2
wL3
w
Transmission line
Etched Defectin Ground plane
cc
Simulated result of unit DGSDimension : a=6mm, b=6mm, c=0.4m, d=0.4mm
Transmission line imp.=158 Ohmsubstrate : RT/Duroid 5880, Er= 2.2 h=31 mils
Simulated result of unit DGSDimension : a=6mm, b=6mm, c=0.4m, d=0.4mm
Transmission line imp.=158 Ohmsubstrate : RT/Duroid 5880, Er= 2.2 h=31 mils
Proposed Divider structureProposed Divider structure
a
b
b
c
cc
c
The simulated and measured results of the Power Divider with DGS section The simulated and measured results of the Power Divider with DGS section
Fabrication for Verification
HFSS Measurement
Photograph of (a) top and (b) bottom sides of the fabricated 90° branch-line coupler with DGS cells.
Photograph of (a) top and (b) bottom sides of the fabricated 90° branch-line coupler with DGS cells.
(a) (b)
Conclusionw Technical Summary
w Unit DGS and its equivalent circuit were derived and explained
w Field effects of unit DGS were shown by HFSS
w A coupled line 3-pole bandpass filter with DGS was designed and measured
w Various design applications using DGS were shown
w Defected Ground Structure Design solution : Ansoft Designer and HFSSw Fully parameterizable geometries, materials, analysesw Automated analyses, sweeps, optimization, post-processingw Integrated design environment with EM, circuit and system analysesw Flexible geometry types/shapes configurationw Efficient design flow
w Ansoft Products applied in this presentationw Ansoft Designer™w Ansoft HFSS
References[1] J. S. Yun, J. S. Park, D. Ahn, “A design of the novel coupled-line bandpass filter using defected ground
structure with wide stopband performance,” IEEE Transaction on Microwave Theory and Techniques, Vol. 50, No.9, pp.2037~2043, Sept. 2002.
[2] D. Ahn, J. S. Park, C. S. Kim, Y. Qian, and T. Itoh "A Design of the Lowpass Filter Using the Novel Microstrip Defected Ground Structure," IEEE Transaction on Microwave Theory and Techniques, Vol.49 No.1, pp.86-93, Jan. 2001.
[3] , “ ,”
[4] " ," IEEE Microwave and Wireless Components Letters
[5] T. J. Ellis and G. M. Rebeiz, “ MM-wave tapered slot antennas on micromashined photonic bandgapdielectrics,” IEEE MTT-s Int. Microwave Symp. Dig., June 1996, pp.1157-1160.
[6] V. Radisic, Y. Qian, and T. Itoh, “Broadband power amplifier using dielectric photonic bandgap structure,”IEEE Microwave Guide Wave Lett. Vol.8, pp.13-14, Jan. 1998.
[7] M. P. Kesler, J. G. Maloney, and B. L. Shirley, “ Antenna design with the use of photonic bandgap material as all dielectric planar reflectors,” Microwave Opt. Tech. Lett, Vol.11, No.4, pp.169-174, Mar. 1996.
[8] V. Radisic, Y. Qian, R. Coccioli, and T. Itoh, “Novel 2-D photonic bandgap structure for microstrip lines,” IEEE Microwave Guide Wave Lett. Vol.8, No.2, pp.69-71, Feb. 1998.
[9] C. S. Kim, J. S. Park, D. Ahn, and J. B. Lim, "A Novel 1-Dimensional periodic Defected Ground Structrure for Planar circuits," IEEE Microwave and Guided Wave Lett., Vol.10, No.04, pp.131-133, April, 2000.
