A NOVEL 1.575-GHz DUAL-POLARIZATION TEXTILEANTENNA FOR GPS APPLICATION

Mohd I. Jais,1 M. F. Jamlos,1 Muzammil Jusoh,1

Thenna Sabapathy,1 and Muhammad R. Kamarudin2

1 Advanced Communication Engineering Centre (ACE), School ofComputer and Communication Engineering, Universiti Malaysia Perlis(UniMAP), Kampus Pauh Putra, Arau, Perlis 02600, Malaysia; Corre-sponding author: ilman_kun@yahoo.com2 Wireless Communication Centre (WCC), Faculty of Electrical Engi-neering, Universiti Teknologi Malaysia (UTM), Skudai, Johor 83100,Malaysia

Received 8 February 2013

ABSTRACT: This article presents a novel dual-polarization textile

antenna (DPTA) for Global Positioning System applications. In thisdesign, four sector radiating elements are centrally fed by a coaxial

probe. A novel antenna structure is successfully achieved by integratingelectronic components into a wearable textile antenna. Silver loadedepoxy adhesive is used in embedding four PIN diode switches on Shiel-

dIt super textile of the proposed antenna. The activation of certain PINdiode switches configuration determines the polarization of DPTA.Dimension-wise, this antenna is compact and small where it consists of

40-mm radius .The proposed DPTA design successfully generated dual-polarization omnidirectional radiation pattern with maximum gain 1.81

dB at angle of 0�/360�, 90�, 180�, and 270�. Its small size, flexible, andwearable features enables this DPTA to be easily integrated ontosafety jacket and rain coat for tracking, search, and rescue applications.VC 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2414–

2420, 2013; View this article online at wileyonlinelibrary.com. DOI

10.1002/mop.27822

Key words: dual-polarization textile antenna; PIN diode switches;global positioning systems

1. INTRODUCTION

Rapid growth in a wireless communication system has

demanded an antenna with a handy and highly mobility features

as well as good performances especially in tracking and rescue

applications. Therefore, the development of smart garment with

integrated wireless electronic into clothing is a potential solu-

tion. Future technology of wearable antenna is should be flexi-

ble to be integrated with Global Positioning System (GPS)

technologies as GPS has been increasingly used in various appli-

cations in transportation planning and operation [1].

Wearable textile antenna is a fundamental part of wireless

body area network [2]. The principal requirement for the weara-

ble antenna is the use of flexible materials so that it can be easily

integrated on the clothes [3,4]. These conductive textiles (or also

known as E-textiles) are typically made from conductive metals or

polymer threads with normal fabric threads or conductive threads

[5,6]. Such conductive textiles act like normal fabrics and can be

easily sewn into the garment. The proposed dual-polarization textile

antenna (DPTA) is designed on flexible material to fulfill the

requirement of wearable antenna prototype development.

In recent days, attention in research and development of the

reconfigurable antenna system has increased among researchers

in order to enhance efficiency as well as reduce the problems

associated with multipath propagation. Reconfigurable antenna

refers to an interpretation of similar conventional antenna with

the ability to reconfigure in term of operating frequency, radia-

tion patterns, polarizations, and directivity controlled by RF

switches. RF switches can be utilized by reconfigurable antennas

such as PIN diodes and micro electronic mechanical systems.

These devices can act as impedance matching devices, simply

by turning the switches “ON” state or “OFF” state [7–9]. In this

research, the utilization of silver loaded epoxy adhesive is effec-

tive in providing a solderless connection between the conductive

textiles and the implementation of the PIN diode switches.

Dual-polarized antenna is a combination of a vertical polar-

ization (VP) and horizontal polarization (HP) [10–12]. With cer-

tain configuration of PIN diode switches, the proposed DPTA

achieved vertical/horizontal dual-polarization omnidirectional

antenna. The great advantages of proposed DPTA compared to

[13,14] is, its ability to perform as an on-textile dual-polariza-

tion for GPS applications. Dimension-wise, 40-mm radius of the

proposed DPTA can be considered small to be implemented

with smart garment [15–19]. The rest of this article is organized

as follows: In Section 2, the proposed DPTA design is explained

and the integration of the RF switches on the arm of radiating

element is investigated. Section 3 demonstrated the comparisons

of the measured and simulated result in term of return loss,

gain, and radiation pattern. Finally, a conclusion will be drawn

in Section 4.

Figure 1 Simulated structure of the proposed DPTA. (a) front view and (b) rear view. [Color figure can be viewed in the online issue, which is avail-

able at wileyonlinelibrary.com]

2414 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 10, October 2013 DOI 10.1002/mop

2. ANTENNA STRUCTURE AND CONFIGURATION

The structure of the proposed DPTA is depicted in Figure 1, has

the ability to exhibit dual-polarization omnidirectional radiation

pattern. It shows four sector radiating elements located at 0�/360�, 90�, 180�, and 270� and interconnected by PIN diode

switches with center. Substrate of this proposed DPTA is made

of Felt with permittivity and thickness of 1.22 and 2 mm,

respectively. This material has wearable and flexible ability.

Conductive textile (E-textile) is used as ground plane and radiat-

ing element to produce DPTA. ShieldIt super with conductivity

of 5.57 3 105 S/m is chosen as conductive textile in this work.

ShieldIt super is made of polyester substrate conductive nickel

with copper plated on top of it; then layered with nonconductive

adhesive on the other side. It has the advantages of excellent

shielding and low corrosion, it is also easy to be cut and addi-

tionally, its adhesiveness is activated at 130�C. It can be ironed

on to Felt or another substrate-type fabric. The polyester sub-

strate instead of nylon (as in another E-textile) makes it better

for moisture management as it is more hydrophobic. In other

words, it is difficult to become wet, thus allows for better con-

serve its electromagnetic properties [13]. For these attractive

reasons, ShieldIt super is adopted in this research.

PIN diode switches of (i), (ii), (iii), and (iv) which integrated

at the ideal location of the arm between four sector radiating

elements and center (Figs. 2 and 3). The PIN diode switches

configuration of “ON” state will allow RF current flow to the

radiating element and vice versa. This concept can be proven in

simulation by representing RF switches with a ShieldIt super

strip line. The presence of the ShieldIt super strip shows RF

switches in “ON” and vice versa.

Gain is the parameter describing the antenna performance.

The gain can be measured by two methods: absolute gain and

gain transfer (or gain comparison) measurement [15]. This

research used an absolute gain denoted as two antenna measure-

ment based on Eq. (1) and using an anechoic chamber as well

[1]. Absolute gain measurement required a point-to-point com-

mercialized horn as a transmitter and proposed DPTA as a

receiver in a free space environment.

PR5PT1GT1GR2 32:44120log10 Dð Þ120log10 fð Þ½ � (1)

where;

PR 5 received power (W)

PT 5 transmitted power (W)

GT 5 gain of the transmitting antenna (dBm)

GR 5 gain of the receiving antenna (dBm)

D 5 antenna separation (Km)

f 5 operating frequency (MHz)

Based on (1), the GT of horn antenna can be easily obtained

from the data sheet. During the measurement process at 1.575-

GHz frequency, the height of the horn and proposed antenna

must be the same to keep the good line of sight (LOS).

Figure 2 Schematic diagram of RF switches [9,14–17]. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

Figure 3 Pictures of the fabricated DPTA (a) front view and (b) rear view. [Color figure can be viewed in the online issue, which is available at

wileyonlinelibrary.com]

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 10, October 2013 2415

Therefore, the proposed antenna need to be aligned properly by

ensuring the point-to-point communication link is established.

The separation distance between both antennas is set to 1 m as

highlighted by the white arrow shown in Figure 4. The power

received that measured using by U2002A Agilent power sensor

and Power Analysis software is depicted in Figure 5. Equation

(1) is successfully resolved through all parameters collected.

2.1. Practical Antenna MeasurementPower measurement applications were conducted to sense multi-

ple power points for a various distance, mechanically moving

the sensor further at every step. The U2002A Agilent power

sensor is deployed as a device to verify the power received to

analyze, compute, and display the data. Illustration of practical

measurement is clearly shown in Figure 5(a). The transmitter

(Tx) antenna is placed at a height of H1 is aligned exactly face

to the antenna under test (AUT), so H1 must be same with H2

to keep the good LOS. The practical prototype measurement is

performed in the outdoor environment of Universiti Malaysia

Perlis (UniMAP) as shown in Figure 5(d).

Signal (1.575-GHz) will transmit from Tx to the AUT

through commercialize horn antenna injected by signal genera-

tor. Power received sense through AUT connected with U2002A

Agilent power sensor at Rx and Agilent Power Analysis soft-

ware will be analyzed and the data will be displayed.

The difference in angles of AUT face to Tx contributes to

the different path losses and received power at the same mea-

surement points. Investigation on received power crucial for

identified proposed DPTA function at outdoor environment with

various angles face to Tx as depicted in Figure 5(b).

3. RESULT AND DISCUSSION

3.1. Simulated and Measured Radiation Pattern ResultAn antenna radiation pattern is determined in the far-field region

and it is represented as a function of the directional coordinates.

An omnidirectional antenna radiates and receives energy uni-

formly in all azimuthal directions in a particular plane. Proposed

DPTA resembles the monopole antenna behavior of omnidirec-

tional radiation pattern. Such a radiation pattern is similar to a

“doughnut” pattern as the nulls of the pattern resemble the holes

in a doughnut. Figure 6, shows the 3D-polar plot of proposed

DPTA. Figure 6(a) depicts the radiation pattern which measured

in the Antenna and Microwave lab (Amrellab) in UniMAP. Fig-

ure 6(b) demonstrates the simulated radiation pattern of the pro-

posed DPTA. Observation to both simulated and measured

radiation patterns of proposed DPTA shows that the patterns are

similar.

In Figure 7, the simulated x-y axis 3D radiation pattern at

operating frequency of 1.575 GHz is shown. The maximum gain

toward the 180� direction in Figure 7(a) as PIN diode switch (i)

was activated, with a gain of 1.81 dBi. Meanwhile, Figure 7(b)

shows the VP and maximum gain of 1.8 dBi toward the 270�

direction. When the next switch (iii) was turned on, a gain of

1.81 dBi with HP is obtained toward at the 0�/360� direction as

shown in Figure 7(c). The activation of switch (iv) the maxi-

mum gain of 1.8 dBi tilting toward the 90� direction with VP,

see Figure 7(d). The proposed DPTA has been successfully

demonstrated to tilt maximum gain toward four different direc-

tions in dual-polarization as summarized in Table 1.

It is worth mentioned, that the dual-polarization of switch-

able wearable antenna is efficiently accomplished through the

Figure 4 Panel of power analysis software. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

2416 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 10, October 2013 DOI 10.1002/mop

structure of four sectors which are combined to the center patch

by the activation of the PIN diode switch at one time. There-

fore, the ability of silver loaded epoxy to act as lead solder to

PIN diode switches has been yet to exploit on conductive tex-

tiles to attainable dual-polarization controlled by PIN diode

switch.

3.2. Measured Power Received ResultFigure 8 depicts the received power of proposed antenna DPTA

performed at the targeted operating frequency of 1.575 GHz

was tested at site with various distances of 0.5 and 2.5 m away

from the Tx. Theoretically, the received power is inversely pro-

portional to distance, so increasing the distances of AUT far

Figure 6 Measured and simulated radiation pattern of the DPTA. (a) simulation and (b) measured. [Color figure can be viewed in the online issue,

which is available at wileyonlinelibrary.com]

Figure 5 Practical measurement setup (a) illustration, (b) AUT face to Rx, and (c) practical measurement setup at outdoor. [Color figure can be

viewed in the online issue, which is available at wileyonlinelibrary.com]

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 10, October 2013 2417

away from Tx will decrease the value of received power. Con-

figuration of all PIN diode switches show almost similar plot.

This result proves the functionality of the proposed DPTA

which is omnidirectional regardless of the antenna polarization.

Ideally, AUT placement in good LOS recorded better received

power from U2002A Agilent Power sensor compared with

others at NLOS angles.

3.3. Simulated and Measured Return Loss (S11) ResultThis research proposed a DPTA operating at 1.575 GHz under

tolerable return loss of 210 dB. The ultimate goal of this

research is to ensure at least 90% of power transmitted and 10%

of power reflected. Figure 9 clearly shows comparison of simu-

lated and measured return loss results at 1.575 GHz depicted S11

in Figures 9(a)–9(d), respectively. The acceptance measured

return loss has slightly lower compared to the simulated. Figure

9(a) shows optimum measured return loss (S11) value is 220

dB. This pattern also produced when an RF switch (ii) and (iii)

“ON” state as depicted in Figures 9(b) and 9(c). The peak meas-

ured return loss (S11) value is 217.2 and 217.4 dB, respec-

tively. PIN diode switch (iv) “ON” contributes maximum return

TABLE 1 RF Switches Configuration of Measured and Simu-lated of Radiation Pattern Proposed DPTA Result

Parameter

Activated PIN Diode Switch

i ii iii iv

Simulated gain (dBi) 1.81 1.8 1.81 1.8

Simulated degree of main lobe 180� 270� 0�/360� 90�

Measured gain from anechoic

chamber (dBi)

0.9 0.95 0.85 1

Measured degree of main lobe 180� 270� 0�/360� 90�

Simulated return loss (dB) 220.4 220.3 220.4 220.3

Measured return loss (dB) 220 217.2 217.4 18.3

Power received (dBm) at

1 m from Tx

231.2 231.5 231.1 231.4Figure 8 Receiving power of Proposed SBTA at various distances.

[Color figure can be viewed in the online issue, which is available at

wileyonlinelibrary.com]

Figure 7 3D simulation radiation pattern of the DPTA. (a) Switch (i) is ON (HP). (b) Switch (ii) is ON (VP). (c) Switch (iii) is ON (HP). (d) Switch

(iv) is ON (VP). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

2418 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 10, October 2013 DOI 10.1002/mop

loss of 218.3 dB. The output of the PIN diode switching

scheme is shown in Table 1.

4. CONCLUSION

A novel textile antenna design with dual-polarization capabilities is

proposed for GPS application. This research successfully found the

switchable wearable textile antenna using RF switch to achieve

dual-polarization ability for the proposed DPTA. The DPTA

designed by a coaxial probe technique to feed current flow to center

of DPTA and distribute the current to four sector radiating ele-

ments. The four PIN diode switches are integrated at an ideal loca-

tion of each arm without any external circuit. Assisted with certain

diode switch configuration, the SBTA collectively achieved dual-

polarization with maximum gain at angle of 0�/360�, 90�, 180�,and 270�. The proposed DPTA has a radius of 40 mm and it is con-

siderably small and compact and it has the capability to radiate in

dual-polarization which HP or VP with peak simulated and meas-

ured gain of 1.81 and 1 dBi, respectively. With all capabilities dem-

onstrated and discussed, the proposed antenna has big potentials to

be fixed on safety jacket and rain coat for application of tracking

and rescue in GPS communication systems.

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Figure 9 Measured and simulated return loss of the SBTA. (a) Switch (i) is ON. (b) Switch (ii) is ON. (c) Switch (iii) is ON. (d) Switch (iv) is ON.

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VC 2013 Wiley Periodicals, Inc.

MICROWAVE TUNABLE NOTCH FILTERBASED ON LIQUID CRYSTAL USINGSPIRAL SPURLINE TECHNOLOGY

Javier Torrecilla,1 E. Avila-Navarro,2 Carlos Marcos,1

Virginia Urruchi,1 Jose M. Sanchez-Pena,1 Julia Arias,2 andMaria M. Sanchez-Lopez3

1 Departamento de Tecnologia Electronica, Universidad Carlos III deMadrid, Leganes, Madrid 28911, Spain; Corresponding author:jtorreci@ing.uc3m.es2 Departamento de Ciencia de Materiales, Optica y TecnologiaElectronica, Universidad Miguel Hernandez de Elche, Elche 03202,Spain3 Instituto de Bioingenieria, Universidad Miguel Hernandez de ElcheElche, 03202, Spain

Received 18 February 2013

ABSTRACT: In this article, the design, fabrication, and characteriza-tion of a tunable microwave notch filter based on liquid crystal (LC)using inverted-microstrip technology is presented. A spiral spurline

structure is used because of its good performance as a single-resonatornotch filter. Based on the LC dielectric anisotropy, a voltage-controlled

rejection frequency of the filter is achieved, ranging from 3.40 to 3.75GHz, which means that the tuning range relative to the central rejectionfrequency is about 10%. At the same time, this device exhibits negative

group delay around the rejection frequency and the measured valuesthroughout the tuning frequency range are presented. VC 2013 Wiley Peri-

odicals, Inc. Microwave Opt Technol Lett 55:2420–2423, 2013; View this

article online at wileyonlinelibrary.com. DOI 10.1002/mop.27812

Key words: LCs; notch filter; spiral spurline structure; tunable devices

1. INTRODUCTION

The increasing interest in the development of tunable microwave

devices has motivated the study of several approaches, such as

the use of ferrite films [1], microelectromechanical systems [2]

or varactor diodes [3].

Recently, the use of liquid crystals (LC) for the design of

microwave tunable devices has become an interesting alternative

due to benefits such as the possibility of small size, light weight,

low cost, low-power consumption, and continuous electrically

tuning. In particular, the dielectric permittivity value varies,

upon application of an external electric field, between two

extreme values, er? and er|, corresponding to two different orien-

tations of the LC molecules. This fact allows LC to be used to

design voltage-controlled tunable devices. Capacitors [4], phase

shifters [5], antennas [6], and filters [7] are reported examples

of LC tunable applications at microwave frequencies.

Conventional spurline structures are widely used as single-

resonator notch filters in microstrip technology due to their

good performance [8]. This kind of structure was used in a pre-

vious preliminary design of a LC-based tunable notch filter [9].

In this work, a variation of the conventional spurline structure,

namely the spiral spurline structure, is considered instead as the

spiral topology is expected to improve the filter selectivity and

to reduce the device size [10]. A LC-based tunable notch filter

of spiral spurline structure is therefore designed, fabricated, and

characterized. The rejection frequency tuning is measured, as

well as the negative group delay (NGD) variation, as a function

of the applied external voltage.

2. DESIGN OF THE TUNABLE NOTCH FILTER

Spurline structures are microstrip single-resonator notch filters

which offer a good band stop performance and easiness of man-

ufacture. These structures can be modeled by a parallel resistor-

inductor-capacitor (RLC) circuit, where the inductance (L) and

capacitance (C) values determine the filter rejection frequency

and the resistance (R) models the filter losses [11]. Several

kinds of spurline structures have been reported: conventional

[8], meander [12], and spiral [10].

Figure 1(a) shows a conventional spurline notch filter struc-

ture which consists of a microstrip line separated into two

coupled lines of a quarter wavelength at the central rejection

Figure 1 (a) Spurline structures considered. Conventional structure.

(b) Spurline structures considered. Spiral structure

2420 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 55, No. 10, October 2013 DOI 10.1002/mop