Defected Ground

8/2/2019 Defected Ground

1/38

Design Applications of

Defected Ground Structures

Authored by:Jason YunPeter Shin

Ansoft Corporation

Ansoft 2003 / Global Seminars: Delivering Performance

Presentation #9


2/38

w Introductionw DGS Definition and Characteristics

w Design Challenge

w Ansoft Design Solution

w DGS Bandpass Filter Design

w Design Procedurew Unit DGS Modeling and Analysis

w DGS Bandpass Filter Design using Ansoft Designer and HFSS

w DGS Bandpass Filter Design with an Additional DGS

w Design applications using DGSw Lowpass Filter Design

w Branch Line Coupler Design

w Unequal Wilkinson Power Divider Design

w Conclusion

w References

Outline


3/38

w A Defected Ground Structure (DGS) is an etchedlattice shape, which locates on the ground planew Evolution from Photonic Band Gap (PBG) Structure

w Periodic or non-periodic

w Easy to represent as an equivalent circuit (LC resonator)

w Applicationsw Planar resonators

w High characteristic impedance transmission line

w Filter, Coupler, divider/combiner, Oscillator, Antenna. Power Amp.

What is a DGS?


4/38

DGS Characteristics

gw

b

a

w Disturbs shielding fields on the ground plane

w Increases effective permittivity

w Increases effective capacitance and inductance of transmission line

w One-pole LPF characteristics (3dB cutoff and resonance Frequency)

w

Four design parameters (a, b, g, and w) under given substrate

S11

S21


5/38

DGS Design Challenges

w DGS has an arbitrary shape which locates on thebackside metallic ground plane

w Accurate EM simulator is necessary

w Equivalent circuit modeling

w Equivalent circuit modeling is important for rapid design

w Co-simulation or dynamic link is needed between EM andcircuit simulators to extract an equivalent circuit

w Many design parameters

w Automated parameter sweep

w Powerful optimization


6/38

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 v1.1Ansoft Dynamic Link


7/38

- 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

measu

remen

t

measu

remen

t

Simul

ation

Simul

ation

Ansoft HFSS v9.0


8/38

- Include Circuit/System and Planar EMSolver

- 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


9/38

Ansoft Scalable 3D Dynamic Link

Design parameters were

passed from HFSS v9.0

into Ansoft Designer v1.1


10/38

DGS Bandpass Filter Design


11/38

Design Procedure

Fabrication for Verification

Extracting Physical dimensions using HFSS

DGS Filter Design using Ansoft Designer

Propose Equivalent circuit of DGS

Propose DGS structure


12/38

Proposed Unit DGS

gw

b

a


13/38

cLCL XX

===

1'

(4)(1)

(2)

(3)

(5)

22

1

1

coo

c

gZC

=

CfL

o =

224

1

Equivalent Circuit for the DGS

1

0 )(

=

o

oLC

CX

1

'gZLX oL ==


14/38

Unit DGS Modeling with HFSS v9.0

w Define project variables

w Create 3D model

w Ground planes

w Traces

w Dielectrics

w Draw unit DGS section

w Slots

w Traces

w Define material properties

w Define boundary conditions

w Define excitations

w Setup solution information

w Analysis


15/38

w Unit DGS library can be buildusing fully parameterizedAnsoft Designer Planar EMand HFSS

w Modeling parameterw Etched lattice dimension

w Gap distance

w Substrate thickness

w Design validation can be

done by measurement at theend

The lattice, and gap distance can all be varied with a fewcentral Project Variables to permit analysis of any similarDGS. Or, a parametric sweep can generate and maintain

results for manyvariations at once.

The lattice, and gap distance can all be varied with a fewcentral Project Variables to permit analysis of any similarDGS. Or, a parametric sweep can generate and maintain

results for manyvariations at once.

Parameterized Unit DGS


16/38

Parameter Sweeps


17/38

Effect of Lattice Dimension, a

gw

b

a

7mm

6mm

5mm4mm

3mm2mm

Freq

a

dB(S11)


18/38

gw

b

a

Effect of Gap Dimension, g

300um 700um400um

500um600um


19/38

Electric Field on the DGS


20/38

Magnetic Field on the DGS


21/38

DGS Filter DesignUsing Ansoft Designer

Schematic of the coupled-line bandpass filter with two DGSsections.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 DGSsections.Substrate : ROGERS RT/Duroid 6010, Er=10.2, h=50mil,Center Frequency : 3 GHz, Bandwidth : 10%


22/38

Physical Dimension of DGS

Simulated and Measured Results for the unit DGSSimulated and Measured Results for the unit DGS

Planar EMSimulation

CircuitSimulation

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 (50)ROGERS RT/Duroid 6010, Er=10.2, h=50mil

Final DGS dimension :

a= 4.15mm, b= 6.2mm,

g= 0.5mm, W= 1.2mm (50)ROGERS RT/Duroid 6010, Er=10.2, h=50mil


23/38

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


24/38

(a) Top view

(b) Bottom view


Photograph of thefabricated coupled-line

bandpass filter with DGS.

Photograph of thefabricated coupled-line

bandpass filter with DGS.

Results comparison between EM simulation and measurement onthe fabricated DGS coupled-line BPF

Results comparison between EM simulation and measurement onthe fabricated DGS coupled-line BPF

AnsoftDesignerPlanarEM

Measured


25/38

DGS Bandpass Filterwith An Additional DGS

Schematic of the DGS coupled-line filter with an additionalDGS section in coupled-resonator.

Schematic of the DGS coupled-line filter with an additionalDGS section in coupled-resonator.


26/38

Physical Dimension Extractionof Additional DGS

Simulated Result for the additional unit DGSSimulated Result for the additional unit DGS

gw

b

a

L = 1.11nHC = 0.66pFfc= 4.8 GHzf0= 5.9 GHz

L = 1.11nHC = 0.66pFfc= 4.8 GHzf0= 5.9 GHz

L

C

DGS Dimension : a=1.55mm, b=6mm,g=0.2mm

Conductor Line : w=1.2mm (50)

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 (50)

Substrate : ROGERS RT/Duroid 6010,Er=10.2, h=50mil

Planar EMSimulation

CircuitSimulation


27/38

EM Simulation Using HFSS

Circuit and EM simulated results comparisonCircuit and EM simulated results comparison

Ansoft HFSS

Ansoft Designer


28/38

(a) Top view

(b) Bottom view


Photograph of thefabricated DGS coupled-line bandpass filter with

an additional DGS.

Photograph of thefabricated DGS coupled-line bandpass filter with

an additional DGS. Comparison results between EM simulation and measurement onthe fabricated DGS coupled-line BPF

Comparison results between EM simulation and measurement onthe fabricated DGS coupled-line BPF

Measured

AnsoftHFSS


29/38

Lowpass Filter Application


30/38

Proposed DGS LPF

(a) (b)

Designed lowpass filters with the proposed DGS unit sections with (a) T-junction opened stub forparallel 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 forparallel 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.


31/38

(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 forthe fabricated DGS lowpass filters

with the T-junction, the cross-junction type open stub, and the

conventional lowpass filter.

Comparison of measured results forthe fabricated DGS lowpass filters

with the T-junction, the cross-junction type open stub, and the

conventional lowpass filter.


32/38

Branch Line Coupler Application


33/38

(a) Top view

(b) Bottom view


Photograph of (a) topand (b) bottom sides of

the fabricated 90branch-line coupler

with DGS cells.

Photograph of (a) topand (b) bottom sides of

the fabricated 90branch-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 withDGS section

Substrate : RT/Duroid 5880, Er=2.2,

thickness=31mils.The physical length and width of conductorcorresponding to quarter wave 150ohmsline with 1-D periodic DGS are 26mm and1mm at 1.84GHz, respectively. The quarterwave length and width of 150ohms line onconventional microstrip are 31mm and0.2mm. 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 conductorcorresponding to quarter wave 150ohmsline with 1-D periodic DGS are 26mm and1mm at 1.84GHz, respectively. The quarterwave length and width of 150ohms line onconventional microstrip are 31mm and0.2mm. In left Fig., the period S = 8mm, a= b = 6mm, c = 12mm, d = 1mm and g =1mm.

a

gw

b

s

d

c


34/38

4:1 Unequal Wilkinson PowerDivider 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 andresistor values of N:1 unequal Wilkinsonpower divider

Reference [4] : Due to the increased effective inductance of the DGS, the aspect ratio of the 158 W microstrip line hasbeen increased to 235% and the length of l/4 has been reduced to 83%. The fabricated conductor width of the 158 Wmicrostrip line were 0.4mm, while 0.17mm for the conventional one. The enlarged conductor width and reduced length hasa great advantage in design and realization such a high impedance line and smaller circuit. The fabricated 4:1 dividershowed excellent matching and isolation, and exact dividing ratios of -1dB and -7dB at port 2 and port 3 without additionallosses 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 hasbeen increased to 235% and the length of l/4 has been reduced to 83%. The fabricated conductor width of the 158 Wmicrostrip line were 0.4mm, while 0.17mm for the conventional one. The enlarged conductor width and reduced length hasa great advantage in design and realization such a high impedance line and smaller circuit. The fabricated 4:1 dividershowed excellent matching and isolation, and exact dividing ratios of -1dB and -7dB at port 2 and port 3 without additionallosses induced by the DGS over 1.2 ~ 1.8GHz.


35/38

Unequal Wilkinson power divider with DGSUnequal Wilkinson power divider with DGS

Port 1

Port 2

Port 3

h

L2

Grounded plane

Dielectric Substrate

w

a

b

c

Rs

/4

/4

Z3

Z2

ZL3

ZL2

3

w2

wL3

w

Transmission line

Etched Defect

in 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


36/38

The simulated and measured results of the Power Divider with DGS sectionThe simulated and measured results of the Power Divider with DGS section


HFSS Measurement

Photograph of (a) top and (b) bottom sides of thefabricated 90 branch-line coupler with DGS cells.Photograph of (a) top and (b) bottom sides of thefabricated 90 branch-line coupler with DGS cells.

(a) (b)


37/38

Conclusion

w

Technical Summaryw 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 Designerw Ansoft HFSS


38/38

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 MicrostripDefected Ground Structure," IEEE Transaction on Microwave Theory and Techniques, Vol.49 No.1, pp.86-93, Jan. 2001.

[3] , ,

[4] " ," I EEEMi c r o wa v e a n d Wi r e l e s s Co mp o n e n t s L e t t e r s

[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 asall 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, IEEEMicrowave 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 forPlanar circuits," IEEE Microwave and Guided Wave Lett., Vol.10, No.04, pp.131-133, April, 2000.

Documents

Defected Ground