Research Of The Terminal And Base Station Antennas In Mobile Communication Systems

Antenna,which acts as the forefront of the wireless communication system,is a component to effectively radiate and receive radio waves.It plays a significant role in the whole wireless communication system,and its properties will directly affect the working performance of the whole system.Therefore,it is of great importance to make a research on the terminal and base station antennas.Around this topic,we have been studying multifrequency/miniaturized antenna based on the Composite Right/Left-Handed Transmission Line(CRLH TL),space diversity antenna,polarization diversity ultra-wideband(UWB)band notched antennas,dual-polarized omnidirectional and directional base station antenna by using simulation software.At the same time,these antennas mentioned above have been manufactured in order to verify the feasibility and accuracy of the antenna designs.The main aspects of this paper can be concluded as follow: 1.A triband monopole antenna loaded with Zero Order Resonator(ZOR)unit of Composite Right/Left-Handed Transmission Line(CRLH TL)and covering the Wireless Local Area Network(WLAN)and the Worldwide Interoperability for Microwave Access(WiMAX)is developed.First,the two resonant points around 4.1 GHz and 5.6 GHz is obtained by curving an L-shaped slot in the monopole.Then,rectangle patches I and II along with a thin shorted stub are added to the original antenna.Series capacitance between rectangle patches I and II,along with shunt inductance formed by the thin shorted stub constitute the metamaterial unit,thus generating a resonant point at 2.4 GHz.Meanwhile,the original resonant points at 4.1 GHz and 5.6 GHz are shifted down.As a result,the proposed antenna can fully cover 2.4/5.2/5.8 GHz WLAN and 3.5/5.5 GHz WiMAX band.Because of the proposed antenna having a single working mode(monopole mode),the ground plane is no longer serving as radiator and the effective radiating area is decreased substantially.With the proposed antenna being fabricated and tested,we can get a conclusion that the simulated and measured results are basically matched,and that the proposed antenna can meet the standard of future wireless communication system.2.A four antenna MIMO system working at the WLAN band is discussed.The antenna unit is a monopole with interdigital shorting stubs,and it can cover the WLAN band with a small factor.Then,a design solution to realize four units MIMO antenna is given.A discussion on how to isolate the units and how the isolating structure affect the antenna's S-parameter is also conducted.Finally,L-shaped stubs,spiral stubs and L-shaped slits are adopted to the decoupling scheme.After fabricating and testing the S-parameters,radiation pattern,gain,efficiency and envelope correlation coefficient of the antennas mentioned above,we can summarized that the testing results and simulation results are basically matched,and that the antenna can meet the requirements of the MIMO system.3.An in-depth study on the UWB polarization diversity antenna with band-notched characteristics is conducted.First,we give the designs of the UWB polarization diversity antenna with dual-and triple-notched bands,and make a comparison and an analysis on the simulation and measurement results in regard to S-parameters,radiation pattern,gain,efficiency and envelope correlation coefficient.Then,we explore the prospect of the differential feeding mechanism in the field of the UWB polarization diversity antenna,and give three different designs.It turns out that the differentially-fed polarization diversity antennas with high port isolation,low cross polarization,and band-notched features are realized.In these designs,two orthogonally placed differential pairs are used to realize polarization diversity,and the arc-shaped slots,C-shaped slots,CSRR slots or opened stubs are adopted to filter the required narrowband systems.After fabricating and testing the proposed antenna,we can summarized that the antenna can better meet the requirements of the UWB wireless system.The design method that the author gives has a certain universality,and the other researchers can design this type of antenna according to this principle.4.The design principle and scheme on dual-polarized omnidirectional antenna is discussed.First,two vertically polarized omnidirectional elements which can separately cover 0.8 GHz-2.7 GHz and 0.8 GHz-6 GHz is developed according to the basic theory of the monopole antenna.These two vertically polarized elements are the deformation form of the traditional discone antenna.Then,a dipole antenna array are employed to realize horizontally omnidirectional radiation.In order to broaden the bandwidth of the horizontally omnidirectional element,four pairs of parasitical branches are added to the top edge of the dipoles' arm,thus covering 1.7 GHz to 2.7 GHz.The proposed antennas can provide an omnidirectional radiation in both the vertical and horizontal planes,and they have advantages of wide bandwidth,high isolation level,low cross polarization and flat gain.So the proposed antennas can be widely used in indoor distributed system,portable access point or mobile base stations.5.The dual-polarized base station antennas which covers 1710 to 2690 MHz,the dualpolarized base station antenna with anti-interference capability,and the dual-broadband,dual-polarized antennas are proposed.In the meantime,analysis in regard to the influence of some important parameters on the performance of these antennas is made.It has an instructional meaning for practical design.For the purpose of verifying the reliability of the antennas,the processing and testing procedure are also carried on.According to the results,the proposed directional antennas have good electrical and radiation characteristics,which are suitable to be applied in base stations.