Study Of Compact Differential Microstrip Antenna Based On LHMs

The rapid development of wireless communications technology has led to the need for compact and fully integrated radio frequency (RF) front-end products, where differential signals are preferable. Different from the traditional antennas, the differential signal is fed directly into the two ports of differential antennas. Thus, the differential antennas provide a new way for the fully integrated RF front-end. Due to the characteristics of light weight, low profile, ease of integration and so on, microstrip antenna has been widely used in many fields. Differential microstrip antenna has been widely attended by scholars.The left-handed materials (LHMs) are artificial periodic structures that have the characteristic with negative permittivity and permeability, which does not exist in nature. Because of the negative refraction, abnormal doppler effect, and perfect lens, the left-handed materials have caused lots of attentions. The LHMs can be used to improve the performances of antenna. This paper mainly introduces differential single-band patch antenna based on LHMs and differential dual-band slot antenna based on LHMs. The paper mainly includes the following parts:In part one, the status of differential microstrip antenna and LHMs are presented.In part two, the basic concepts and theory of microstrip antenna are firstly introduced. Then, the theoretical basis of LHMs and the extraction method of equivalent medium electrical parameter are proposed.In part three, a differential single-band patch antenna for Worldwide Interoperability for Microwave Access (WiMAX) applications is proposed. The miniaturization is realized by etching U-shaped slots in the radiating patch. Compared with the conventional half-wave length antenna, the antenna has a compact size of 15 mm × 15 mm (0.38 Ag×0.38 λg, λg is the guided wavelength of the antenna). In order to improve the bandwidth of the antenna, a novel periodic structure of left-handed materials (LHMs) is designed to cover the antenna. The LHMs is composed of dumbbell split rings and a metal wire. The results show that the bandwidth and gain of differential antenna with LHMs are improved.In part four, a differential dual-frequency slot antenna for radio frequency identification (RFID) and wireless local area network (WLAN) applications is mentioned. The miniaturization and dual-band are realized by etching slots in the ground. Compared with the conventional half-wavelength antenna, the antenna has a compact size of 60 mm × 60 mm (0.36 λg×0.36 λg, λg is the guided wavelength of lower band). In order to improve the bandwidth of the lower band, a novel periodic structure of double frequency LHMs is designed to cover the antenna. The results show that the bandwidth, gain and radiation characteristic of differential antenna with LHMs are improved.