Study Of New Pifa Antenna Based On Ebg Structure

With the rapid development of mobile and personal wireless communication technologies, the new requirements for antennas used to communication terminals have been proposed:On one side the antennas are required to be miniaturized, broadband, and multiband; On the other side we should minimize the influence of antenna radiation on human body. Planar inverted-F antenna (PIFA) coming out during these years has been rapidly and widely adopted because it has the structural advantages of small size, light weight, low profile, internally equipped, easily fabricated and mounted on the carrier. A PIFA has the properties of broadband and mufti-band.The research and application of new electromagnetic material are more and more concerned. Microwave photonic crystals, also referred an electromagnetic bandgap (EBG) materials, are periodic structures characterized by the existence of frequency band gaps, which has a great of applications in the future because of its new properties. Based on the basic principles of the PIFA antenna and EBG structures, the miniaturization of EBG structure and the application of EBG structures to PIFA are studied by using electromagnetic simulations and experiments. Furthermore, a broadband PIFA antenna and a mufti-band PIFA antenna are designed.The main work and achievements of this thesis can be summarized as follows:1. The operating principle and frequency characteristics of the EBG structures are discussed. By means of interdigitating structure to increase the equivalent capacitance, a new kind of miniaturized EBG structure is designed. Utilizing direct transmission method, we get the surface wave bandgap of the interdigitating EBG structures is 2.2-2.8GHz. Compared to the conventional rectangular EBG structures, the proposed EBG structure reduces the length of half and the area of one quarter. The miniaturization factor is about 50%.2. A detailed description on the configurations of PIFA antennas and the principal characteristics and analysis methods are introduced. Meanwhile, the miniaturized, broadband and mufti-band technologies about the microstrip antenna are analyzed and summarized. Based on this, a new triple-band PIFA with dual-L-shaped slot-loaded is proposed and studied, which can operate at GSM (0.89～0.96 GHz),DCS (1.71～1.88 GHz) and ISM (2.4～2.484GHz). In addition, by means of cutting slots on the ground plane suitably, a new kind of broadband PIFA was designed. The antenna operated at frequency range from 2.3GHz to 6.3GHz (S11≤-lOdB), with relative bandwidth up to 93%. The relationship between antenna parameters and performance of antennas are analyzed and discussed. The two new PIFA antennas have been fabricated to conduct experiments. The measurement results are in good agreement with simulation results.3. The interdigitating EBG structure is applied to the PIFA in mobile handset. The performance and the specific absorption rate (SAR) of new PIFA with EBG structures were analyze and compared with a conventional PIFA in the same environment. The results show that the PIFA integrated with EBG structures can reduce the SAR and improve the antenna gain and efficiency. Finally, the new PIFA with EBG structures was fabricated and the SAR was measured by using DASY5 system. The measured results agree well with the simulated results.