Miniaturized Half-Bowtie Printed Dipole Antenna with an Integrated Balun W. S. Yeoh, K. L. Wong and W. S. T. Rowe School of Electrical and Computer Engineering RMIT University, Melbourne, Australia Email:
[email protected] Introduction Printed antennas are commonly used in wireless communication due to the simplicity in design and fabrication. These types of antenna are also suitable to be integrated into wireless electronic devices. Hence, research towards the miniaturization of printed antennas becomes very important. A dipole antenna with an integrated balun is reported to have better bandwidth than the conventional balanced dipole [1]. The previously reported designs of similar printed dipole antennas can be found in [2 - 5]. All of these reference designs are designed to operate between 2 GHz and 3 GHz. A size and performance comparison of these antennas is given in Table 1. The configuration of these antennas is very similar, in which the balun is integrated into the printed dipole antenna. This balun consists of a microstrip feed line grounded to one arm of the dipole antenna located on the other side of the substrate, with via hole that shorts the line to the opposing arm. In this paper, a miniaturized half bowtie printed dipole antenna is presented. It is a two layered printed antenna with the feed line on the top surface of a dielectric substrate, while the radiating arms are on the bottom surface. Agilent Momentum is used to simulate the performance of this design. It is proven to have better performance than the previously reported miniaturized printed dipole [5] in terms of its size and percentage bandwidth. Half-Bowtie Printed Dipole Antenna The main objectives of the miniaturization of a printed antenna are shrinking and optimizing the overall dimensions of an antenna in order to achieve a smaller board size while preserving its performance. The design presented in this paper is different from an ordinary dipole in that the dipole arms are replaced by half-bowtie shapes. In principle, a bowtie antenna requires shorter arm length than a normal dipole antenna that operates at the same resonance frequency. This can be observed by comparing a bowtie antenna with a normal dipole antenna that operates at same frequency. The wider the flare angle of the bowtie, the shorter the length of the arms is required for the particular frequency of choice [6]. In this work, the half bowtie shape is shown to closely resemble the characteristics of a full bowtie antenna, in that it achieves a wide impedance bandwidth with a short dipole arm length. The half bowtie dipole design consists of merely two geometries, which are the balun feed line and radiating arms. No additional structure is required to achieve this performance such as external impedance matching elements, as were used in [5].
978-1-4244-2642-3/08/$25.00 ©2008 IEEE
Reference Designs [2] [3] [4] [5] Our Design
Central Frequency (GHz) 2.55 2.95 2.52 2.57 2.85
Substrate r 4.6 10.2 4.4 3.48 2.2
Antenna Size Length × Width mm2 41mm × 40mm 40mm × 18mm 44mm × 20mm 41mm × 19.6mm 37.5mm × 19mm
1640 720 880 803.6 712.5
Bandwidth (VSWR
