192 PIERS Proceedings, Hangzhou, China, March 24-28, 2008

The Planar V-dipole Antenna Fed by Marchand Balun

Cheng-Hung Lin1, Guan-Yu Chen2, Jwo-Shiun Sun2, Kwong-Kau Tiong1, and Y. D. Chen3

1Department of Electrical Engineering, National Taiwan Ocean University, Taiwan2Department of Electronic Engineering, National Taipei University of Technology, Taiwan

3Antenna and EMC Laboratory, High Tech Computer Corp. (HTC), Taiwan

Abstract— The Marchand balun for microwave band as a feeding network structure that ef-fectively excited tapered V-dipole antenna geometry is proposed. The microstrip line to coplanarstrip line transition then to fed tapered V-dipole antenna. The designed quasi-tapered TEM horn(V-dipole) antenna has the merits such as wideband, simple feeding network, low profile compactsize with fairly good antenna performances such as return loss, peak gain and radiation patterns.

1. INTRODUCTION

The radiation mechanism of a TEM horn antenna is based on traveling wave propagation alongthe tapered aperture slot, which results in an end-fire antenna. TEM horn or tapered slot antenna(TSA) exhibits some advantages such as wideband, wide scanning, high gain, low cross polarizationand symmetrical E and H plane radiation patterns [1] for an array or embedded circuits as antennaradiating elements. Some articles for analyses of tapered slot antenna were studied such as momentmethod [2], finite difference time domain method [3]. And the applications of TSA were proposedin dual polarized antenna array [4], spatial power combining [5] and waveguide transition [6]. Thegeneral feeding structures in a TSA were mentioned with a coaxial cable, a microstrip line or acoplanar waveguide (CPW) [7–9]. A novel design method [10] for a TEM horn antenna is proposedon the basis of parallel plate waveguide theory. An exponentially tapered wideband TEM hornantenna [11] having a balun is designed. The balun is used to improve the impedance characteristicof the TEM horn antenna. The designed antenna can be used not only for EMC measurements,but also for broadband communication systems. A novel stable beamwidth, ultrawide-bandwidthlow-scattering antenna [12] is presented. This antenna is a modified version of the conducting slot-line bowtie hybrid antenna with resistive sheets introduced into the guiding structure design. Theanalytical and design formula [13], based on conformal mapping, for the characteristic impedanceof the transverse electromagnetic horn antenna. In this paper, the Marchand balun with a balancedto unbalanced transition is shown good impedance matching and easy to integration and fabrica-tion and the frame of the planar structure on tapered TEM horn (V-dipole) was experimentallyinvestigated. Measured results indicate that effects have significant impacts on the return loss,input impedance, radiation patterns and antenna gain of the TEM horn (V-dipole) antenna.

Figure 1: V-dipole antenna fed by Marchand balun. Figure 2: V-dipole antenna structure and size.

Progress In Electromagnetics Research Symposium, Hangzhou, China, March 24-28, 2008 193

2. QUASI-TEM HORN (V-DIPOLE) ANTENNA

The coplanar stripline to feed planar tapered V-shape as quasi-TEM antenna radiator. The V-dipole antenna is a kind of traveling wave antenna that wave propagating along the tapered slotfor heading radiation. The basic geometry of the designed TEM horn antenna is like a double ridgeas shown in Figure 1. The transition provides wider balanced equal outputs, as well as a matchingsection for the traveling tapered slot of TEM horn antenna. The FEM software based on full wavefrequency domain method [14] was adopted to perform the simulation of the designed low profileand planar TEM horn antenna. The planar quasi-TEM horn was fabricated on the FR4 substrate(dielectric constant = 4.4 and dielectric loss = 0.02) and detail size is shown in Figure 2. Thesimple quasi-TEM horn antenna structures exhibits broadband and low profile compact structurefor UWB and impulse radio applications.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Frequency (GHz)

VSWR

1

2

3

4

5

V-Dipole

Figure 3: Measured data of VSWR.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Frequency (GHz)

Input Impedance (Zin)

-150

-125

-100

-75

-50

-25

0

25

50

75

100

125

150

Re(ZIN[1])

Im(ZIN[1])

Figure 4: Measured data of input impedance.

3. RESULTS

Figure 2 shows the layout of the quasi-TEM horn (V-dipole) antenna size and structure. The mea-sured VSWR and input impedance of V-dipole antenna (Zin = Rin+ jXin) shows good impedancematching based on the transition as shown in Figure 3 and Figure 4. The radiation characteris-tics of the TEM horn antenna based on the spherical coordinate and 3D chamber system [15] aremeasured. The measured data of H-plane and E-plane are shown in Figure 5.

Figure 5: Measured 3 GHz antenna gain pattern of E and H plane.

4. CONCLUSIONS

The designed V-dipole antenna fed by coplanar stripline and the transition is presented. It exhibitsthe merits of geometric simplicity, wide bandwidth, lightweight, low cross polarization, and highpeak gain. This V-dipole antenna is suitable for UWB impulse radio operation and application.

ACKNOWLEDGMENT

The authors acknowledge the Antenna and Wireless System Integration Department of High TechComputer, Corp (HTC), Taiwan for sport the wireless technique and measurement environment.

194 PIERS Proceedings, Hangzhou, China, March 24-28, 2008

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