Research On The Antennas Of Wireless Personal Area Network

Wireless Personal Area Network, WPAN in Abbreviations, is a short-range wireless communications technology which is developing rapidly in recent years. WPAN provide a wireless network for portable equipments in a small area and make it convenient to cooperative work between these equipments.With the development of the communication technology and electronic industry, WPAN is widely applied in many industries, and is leading the officing, home and building management, environment monitoring and industrial controlling come to a new epoch of intelligent and automation. The research of antenna is facing a great challenge.The antenna suiting for WPAN is studied in this thesis. The main points of the thesis are the characteristics of and the method to design an inverted-F antenna (IFA). The paper presents a design of printed inverted-F (PIFA) antenna.1. The design basis of antenna suiting for WPANThe most of equipments in WPAN are working in the indoor environment. The propagation of electromagnetic wave indoors has a complicated multi-path effect, that is, received signals by the receiver usually come from multiple signal paths which are consisting of direct signals, reflection signals, diffraction signals and scattering signals. Some of the signals have the same direction of electric field polarization with the original signals, but others have the changed direction. So antennas suiting for WPAN should be a cross-polarized, in order to receive the horizontally and vertically wave. In addition, equipments in rooms often are placed in mess, and sometimes communications are between upstairs and downstairs. So omnidirectional antennas are more suiting for WPAN applications. Because the most equipment is portable in WPAN, antenna should have compacted structures and easy to fixed or integrated on PCB.2. The characters of antennas suiting for WPANThe characters of several types of antennas suiting for WPAN are analyzed. Analysing with the cavity model theory, it is proved that the dimention ofIFA is smaller by 50% than microstrip antenna. Analysing with the transmission line model theory, the analytic formula of the input inmedance for the IFA is educed, and the radiation electric field is derived, which proves that the IFA has both omnidirectional and cross polarization characteristics.An IFA printed on PCB is called Printed IFA, which can be integrated on single chip PCB with feed and elements of the circuit. The new structure antenna is very flexible to design and is very cheap. Furthermore it just can be printed on the FR-4 board directly for its compact profile, which makes it very easy to feed through microstrip line.3. Research and design of Printed IFAThe impacts of all the dimension parameters on both input impedance and the resonant frequency of Printed IFA are simulated with Ansoft HFSS, and the impact regularity along with the antenna design method is given as well. A combined change of the three parameters is necessary in order to fing-tune the antenna. This gives freedom to the antenna designer to modify the dimensions of Printed IFA and impedance matching converter is needless.The thesis presents a Printed IFA design and the simulated results show that the antenna resonaces around 2.44 GHz, and the input impedance is 50?, the relative bandwidth is 10.7%, which is enough for the ISM 2.4~2.4835GHz band for WPAN application.The experimental results show that changing the shape of the short-point and adding a horizontal branch can widen the band and increase gain. The thesis also presents a improved Printed IFA design. The simulated results show that the antenna resonaces around 2.44 GHz and the input impedance is 50?, the relative bandwidth is 17.6%, and the gains in the three coordinate planes are 2.6dB, 2.4dB, 2.0dB. The antenna has better characters of omni-directional pattern and cross polarization character as expected.4. RF module based on CC2420The CC2420 is a true single-chip 2.4 GHz IEEE 802.15.4 compliant RF transceiver designed for low-power and low-voltage wireless applications. The module based on CC2420 need very few external components, and is low cost, high stability, with 250 kbps data rate and can realize multi-point to multi-point self-orgnizing network.As an application of Printed IFA, the thesis introduces a design of RF module based on CC2420. In order to test the module, a testing set is made consistent of STC89C58 microcontrollor, keys and LCD display module. Experiments are performed to test the transmition distance in spacious place and indoor environment. The results prove that the Printed Antenna has excellent characters of omnidirectional pattern and cross polarization character. Otherwise the thesis introduces the methods to matching the antenna and some regulation of PCB design and electromagnetic compatibility.