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.

专注于微波、射频、天线设计人才的培养 易迪拓培训 网址：http://www.edatop.com

射 频 和 天 线 设 计 培 训 课 程 推 荐

易迪拓培训(www.edatop.com)由数名来自于研发第一线的资深工程师发起成立，致力并专注于微

波、射频、天线设计研发人才的培养；我们于 2006 年整合合并微波 EDA 网(www.mweda.com)，现

已发展成为国内最大的微波射频和天线设计人才培养基地，成功推出多套微波射频以及天线设计经典

培训课程和 ADS、HFSS 等专业软件使用培训课程，广受客户好评；并先后与人民邮电出版社、电子

工业出版社合作出版了多本专业图书，帮助数万名工程师提升了专业技术能力。客户遍布中兴通讯、

研通高频、埃威航电、国人通信等多家国内知名公司，以及台湾工业技术研究院、永业科技、全一电

子等多家台湾地区企业。

易迪拓培训课程列表：http://www.edatop.com/peixun/rfe/129.html

射频工程师养成培训课程套装

该套装精选了射频专业基础培训课程、射频仿真设计培训课程和射频电

路测量培训课程三个类别共 30 门视频培训课程和 3 本图书教材；旨在

引领学员全面学习一个射频工程师需要熟悉、理解和掌握的专业知识和

研发设计能力。通过套装的学习，能够让学员完全达到和胜任一个合格

的射频工程师的要求…

课程网址：http://www.edatop.com/peixun/rfe/110.html

ADS 学习培训课程套装

该套装是迄今国内最全面、最权威的 ADS 培训教程，共包含 10 门 ADS

学习培训课程。课程是由具有多年 ADS 使用经验的微波射频与通信系

统设计领域资深专家讲解，并多结合设计实例，由浅入深、详细而又

全面地讲解了 ADS 在微波射频电路设计、通信系统设计和电磁仿真设

计方面的内容。能让您在最短的时间内学会使用 ADS，迅速提升个人技

术能力，把 ADS 真正应用到实际研发工作中去，成为 ADS 设计专家...

课程网址： http://www.edatop.com/peixun/ads/13.html

HFSS 学习培训课程套装

该套课程套装包含了本站全部 HFSS 培训课程，是迄今国内最全面、最

专业的HFSS培训教程套装，可以帮助您从零开始，全面深入学习HFSS

的各项功能和在多个方面的工程应用。购买套装，更可超值赠送 3 个月

免费学习答疑，随时解答您学习过程中遇到的棘手问题，让您的 HFSS

学习更加轻松顺畅…

课程网址：http://www.edatop.com/peixun/hfss/11.html

`

专注于微波、射频、天线设计人才的培养 易迪拓培训 网址：http://www.edatop.com

CST 学习培训课程套装

该培训套装由易迪拓培训联合微波 EDA 网共同推出，是最全面、系统、

专业的 CST 微波工作室培训课程套装，所有课程都由经验丰富的专家授

课，视频教学，可以帮助您从零开始，全面系统地学习 CST 微波工作的

各项功能及其在微波射频、天线设计等领域的设计应用。且购买该套装，

还可超值赠送 3 个月免费学习答疑…

课程网址：http://www.edatop.com/peixun/cst/24.html

HFSS 天线设计培训课程套装

套装包含 6 门视频课程和 1 本图书，课程从基础讲起，内容由浅入深，

理论介绍和实际操作讲解相结合，全面系统的讲解了 HFSS 天线设计的

全过程。是国内最全面、最专业的 HFSS 天线设计课程，可以帮助您快

速学习掌握如何使用 HFSS 设计天线，让天线设计不再难…

课程网址：http://www.edatop.com/peixun/hfss/122.html

13.56MHz NFC/RFID 线圈天线设计培训课程套装

套装包含 4 门视频培训课程，培训将 13.56MHz 线圈天线设计原理和仿

真设计实践相结合，全面系统地讲解了 13.56MHz线圈天线的工作原理、

设计方法、设计考量以及使用 HFSS 和 CST 仿真分析线圈天线的具体

操作，同时还介绍了 13.56MHz 线圈天线匹配电路的设计和调试。通过

该套课程的学习，可以帮助您快速学习掌握 13.56MHz 线圈天线及其匹

配电路的原理、设计和调试…

详情浏览：http://www.edatop.com/peixun/antenna/116.html

我们的课程优势：

※ 成立于 2004 年，10 多年丰富的行业经验，

※ 一直致力并专注于微波射频和天线设计工程师的培养，更了解该行业对人才的要求

※ 经验丰富的一线资深工程师讲授，结合实际工程案例，直观、实用、易学

联系我们：

※ 易迪拓培训官网：http://www.edatop.com

※ 微波 EDA 网：http://www.mweda.com

※ 官方淘宝店：http://shop36920890.taobao.com

专注于微波、射频、天线设计人才的培养

官方网址：http://www.edatop.com 易迪拓培训 淘宝网店：http://shop36920890.taobao.com