Recent research results by using CST

microwave studio at Antenna Lab., POSTECH

•Electromagnetic Bandgap (EBG) and Frequency Selective
Surface (FSS) type superstrate for directivity enhancement
-12x3 EBG superstrate for dual band directivity enhancement
-Compact EBG superstrate for wideband directivity enhancement
-11x11 strip-mesh FSS superstrate for dual band dual polarization

• Crosstalk of UTP(Unshielded Twisted Pairs) line

• Compact and dual band antenna for mobile application
-Compact aperture coupled antenna by using shorting wall
-Printed Monopole Antenna for 2.4/5.2/5.8GHz WLAN Operation

- Double negative index material (Metamaterial)

1 CST MICROWAVE STUDIO® • www.cst.com • Mar-05
 Electromagnetic Bandgap (EBG) Superstrates for
Dual-band Directivity Enhancement

We can estimate the center frequency of the directivity enhancement from the
simulation results of the unit cell, without simulating the entire structure.

2 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 Electromagnetic Bandgap (EBG) Superstrates for
Dual-band Directivity Enhancement

Directivity results of the EBG composite

20dB directivity enhancement at the desired dual band can be achieved by using a
dielectric rod superstrate with two defects.
3 CST MICROWAVE STUDIO® • www.cst.com • Mar-05
 A compact EBG superstrate for wideband directivity

Directivity results of the EBG composite

Compact 6x3 cross rod EBG composite

Field distribution of EBG superstrate

depending on their size
4 CST MICROWAVE STUDIO® • www.cst.com • Mar-05
Dual band dual polarized 11x11 strip-mesh FSS composite
y
Dual-band dual-
6.2mm
polarization patch
antenna Unit cell of the FSS
Z
Y x PML

X 5.6mm

gap

Substrate of
Mirrored the patch
by image
theory

Periodic
Boundary
PBC Condition
(PBC)

Dual-band and dual-polarization Plane wave

11x11strip-mesh FSS composite incidence

5 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

Dual band dual polarized 11x11 strip-mesh FSS composite

S21 results of strip-mesh unit cell Directivity results of strip-mesh FSS

composite

• From the results of the unit cell, we can design the FSS composite
• Dual band dual polarized directivity enhancement can be obtained from
the strip mesh FSS composite

6 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

Dual band dual polarized 11x11 strip-mesh FSS composite

The radiation pattern of the FSS The radiation pattern of the FSS
composite at 11.9 GHz composite at 12.75 GHz

7 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 Crosstalk of UTP(unshielded Twisted Pairs) line

UTP line

A Unit cell of UTP

An unit of a pair of UTP line

8 CST MICROWAVE STUDIO® • www.cst.com • Mar-05
 Crosstalk of UTP(unshielded Twisted Pairs) line

Obtain [S] of
[T] of [T] of [S] of
unit length
unit length overall length overall length
Using MWS

Transforming Transforming
Cascading
[S] to [T] [T] to [S]

9 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 Compact aperture coupled antenna by using
shorting wall

10 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 Compact aperture coupled antenna by using
shorting wall

< E-field > < Surface current >

Typical patch antenna

< E-field > < Surface current > < Partial shorting wall >

Proposed compact antenna

11 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 Printed Monopole for 2.4/5.2/5.8GHz
WLAN operation

<Top view>

<Bottom view>

Geometry of printed monopole antenna

12 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 Printed Monopole for 2.4/5.2/5.8GHz
WLAN operation

< Surface current at 2.4GHz > < Surface current at 5.5 GHz >
0 0

-5 -5

-10 -10
Return Loss(dB)

Return Loss(dB)
-15 -15

-20 -20

-25 -25
WT3=12mm
WT3=13mm
-30 WT3=14mm -30 simulated
WT3=15mm measured
-35 WT3=16mm -35
-40
0 1 2 3 4 5 6 7 -40
0 1 2 3 4 5 6 7
Frequency(GHz)
Frequency(GHz)

13 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 • Double negative index material (Metamaterial)
- Property of double negative index material
RHM(Right Handed Material)
Positive Permeability
and Permittivity
Positive Refractive
Index(PRI)
LHM(Left Handed Material)
Negative Permeability
and Permittivity
Negative Refractive
Index(NRI)

- RHM : support propagating forward wave ⇒ positive refractive angle

- LHM : support propagating backward wave ⇒ negative refractive angle

14 CST MICROWAVE STUDIO® • www.cst.com • Mar-05

 • Backward-wave Antenna Based on NRI L-C Networks

Antenna Configuration Backward-wave Antenna

backward broadside Structure

source y
θ x

longitudinal forward
polarization
z

CRLH dispersion diagram

ω = − β c0 ω ω = + β c0

II
LH
III
RH
- Antenna operated in both LH and RH RAD. regions
RAD. RAD.
- Possible to scan beam for operating frequencies
I IV
LH RH
GUIDANCE GUIDANCE

ω0
15
β CST MICROWAVE STUDIO® • www.cst.com • Mar-05