| Antenna is a kind of converter which can convert the guided traveling wave of transmission line into space electromagnetic wave,so that the transmitted information can be transmitted through electromagnetic wave.It is an important device for energy conversion between wireless communication system and space.For an antenna,it is a converter that converts the guided wave of the transmission line into a spatial electromagnetic wave,thereby transmitting the information carried in the electromagnetic wave.Due to its reversible characteristics,the antenna can also convert electromagnetic waves in space into guided waves,which is an important device for energy conversion between wireless communication systems and space.Therefore,whether the communication quality is good or bad is determined by the radiation performance of the antenna used in the wireless communication system.Due to the rapid development and increasing demand of wireless communication systems,the development trend of military and civilian antenna systems is the miniaturization,anti-interference,high gain and large angle scanning of the equipment.Based on these situations,this dissertation systematically studies the design theory and implementation methods of high-performance multiple-input multiple-output antennas.Specifically,the miniaturization design of the antenna,the research on improving the anti-interference ability,the MIMO array decoupling research,improving the antenna directivity and realizing the large scan angle of the antenna are suitable for the requirements of the electronic communication system.In general,the research situation in this dissertation can be summarized as the following four aspects.1.According to the current demand for miniaturized antennas,theoretical research and implementation schemes for antenna miniaturization technology have been carried out.In recent years,the development of metamaterials has attracted great interest in the academic field.These unique electromagnetic properties of the metamaterials make it a huge application potential and development space for improving antenna performance.Artificial magnetic conductors can be applied to antennas to reduce the size of the antenna due to its zero reflection phase,sub-wavelength,and large parasitic capacitance and inductance.The micro-miniature design of the antenna is realized by the in-phase reflection characteristic of the artificial magnetic conductor.The in-phase reflection bandgap of the artificial magnetic conductor is analyzed.By combining the printed dipole antenna with the artificial magnetic conductor,a dual-polarized low-profile antenna with an operating frequency band of 2.4 GHz-3 GHz and a profile of less than 0.1?0 is designed.2.The deterioration of antenna performance is due to the fact that the out-of-band gain in the main direction of the antenna interferes with other signals.Therefore,under the premise of ensuring that the antenna works normally in the required frequency band and the radiation pattern is good,the out-band gain of the antenna is reduced.This dissertation proposes a dual-band adjustable notch antenna based on ultra-wideband communication system,which reduces the impact of WiMax and WLAN narrow-band communication systems on UWB and improves the performance of the antenna system.Moreover,three types of filtering antennas are designed.One is to introduce a stepped impedance resonator on the printed dipole antenna to achieve out-of-band rejection of 2.5 times frequency.The second one is to etch two pairs of stepped-impedance resonator and slit-ring resonators on the dipole antenna radiation sheet.The SIR and the SRR generate two resonant zeros on the left and right sides of the antenna operating band respectively,and a bandpass filtering dipole antenna is designed.The last one is to introduce a microstrip line connected to the ground through the metal via,a square open resonant ring and a stepped impedance resonator etched on the dipole into the dipole antenna,and finally realize the bandpass dipole filtering antenna with broadband rejection.In addition,a low-profile dual-polarization filtering antenna is designed based on the artificial magnetic conductor,which finally realizes miniaturization and anti-interference of the antenna.3.Based on the previously designed unit antenna,a variety of multiple-input multiple-output arrays are further formed,the operating characteristics of the array antenna are studied,and mutual coupling of the array antenna is reduced.This dissertation has designed a variety of decoupling structures to improve the isolation between the antennas.The first is to form a low-profile dual-polarized antenna unit into a 1×4 antenna array.By adding three decoupling branches between the antennas,a decoupling effect of 10 dB in the working bandwidth is achieved.At the same time,two rows metal vias are introduced on the artificial magnetic conductor reflector.The metal vias achieve 30dB port isolation for low profile dipole antennas.By introducing folded T-shaped branches and inverted H-shaped barriers on artificial magnetic conductor reflectors,the surface wave coupling and space wave coupling are reduced.Decoupling on the above achieves a coupling reduction of more than 20dB,effectively ensuring the independent performance of the MIMO antenna.4.Aiming at the requirements of high directionality and large scanning angle of the electronic system,this dissertation designs a dual-polarized substrate integrated waveguide antenna operating in the 5G millimeter wave band by using the low loss,miniaturization and easy integration of the SIW cavity.Then,according to the principle of Fabry-Perot resonator,a dielectric plane lens is loaded on the designed SIW antenna unit to achieve an improvement of the antenna gain of 7dB.The dielectric plane lens is applied to the array antenna,which leads to the gain effectively enhanced.Finally,a"well"shaped electromagnetic metamaterial lens is loaded onto the surface of the designed SIW antenna to broaden the beamwidth of the antenna.The maximum beam scanning angle of the designed 1×4,4×4 SIW antenna MIMO array is greatly improved than the previous antenna array scanning angle range.The proposed technical method of the dissertation provides a feasible technical guarantee for the 5G millimeter wave base station antenna. |
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