Study On Planar Multi-band/Broadband Magneto-electric Dipole Composite Antenna

In the field of high-speed WLAN, indoor communications and home network, the development of wideband wireless communication technology is drawing more and more attentions. The design of wideband miniaturized antenna is critical to the performance of wideband wireless communication systems. Thus, it is essential to develop miniaturized wideband antennas with high performance. In this thesis, the magneto-electric composite antennas based on offset feeding technique are studied. The operating modes and principle of the antenna are analyzed at first. Then, according to the operating modes, the design approach of the multi-band and wideband antennas is proposed. Finally, two kinds of antennas are developed by using this method. The main content of this thesis is organized as follows:1. At first, the performance of the center-fed dipole antenna and the offset-fed dipole antenna is studied and compared. Then, the current distribution and radiation patterns of the coupled offset-fed dipole antenna are analyzed and the approximate design formulas at different resonant frequencies are deduced as well. By adding two straight and vertical arms to the coupled offset-fed dipole, the operating principle and design approach are shown step by step.2. Based on the design approach, two kinds of miniaturized planar dual-band/wideband magneto-electric composite antennas are proposed. Both of them use the offset feeding technique and their sizes are 23 mm×26 mm and 27 mm×30 mm, respectively. The parameters are analyzed and optimized by using IE3 D.3. The prototypes of one kind of the antenna are fabricated and measured by Agilent’s 8720 ET vector network analyzer, NSI’s NSI-800F-10 x far-field antenna measurement systems and Satimo Starlab near field antenna measurement systems. The simulated and measured results agree well with each other. The measured impedance bandwidth is 2.36-2.58 GHz and 4.1-15.72 GHz and the average gain is about4.5dBi. The antenna has omnidirectional pattern at the lower band and quasi-directional pattern at the higher band, which makes it suitable for dual-band communication systems.