Research On Key Technology Of Antenna In Multi-antenna Communication System

Recently,with the rapid development of science and technology,the higher-speed,higher-reliability,and lower-delayed wireless communications have become increasing requirements in many new scenarios.The performance of wireless communication system greatly depends on the performance of the components,such as the antenna,signal processer,and receiver sensitivity.Among them,the antenna has an important influence on the entire wireless communication system.At the same time,in order to meet people’s demand for higher-speed wireless communication,multi-antenna technology has been widely studied,including MIMO technology and cognitive radio technology.In MIMO technology,multiple antennas are installed at the receiving and transmitting terminals to utilize the multipath effect of the wireless channel.The cognitive radio technology can dynamically adjust the characteristics of the equipment according to channel status.The higher-speed data transmission can be achieved without adding extra spectrum and transmission power based on the multi-antennal system.1.A couple of microstrip MIMO antennas with extremely high isolation are proposed.The scattering parameters,far-field radiation,correlation,efficiency,and gain are studied in detail.The single-frequency microstrip MIMO antenna at 5 GHz can be applied in WLAN.The two-unit antennas share the square radiating patch,which reduces the geometry of antenna by 50%.Slot loading further reduces the antenna by 8.48 %,and finally the antenna plane size was reduced to a square with length of 1cm.polarization diversity,and asymmetric perturbation feeding technology improve the isolation,and within the band S12 / S21 <-27.9 dB.The dual-band microstrip MIMO antenna resonates 2.4 GHz and 5 GHz,respectively,and can cover both the high and low frequency of the WLAN.The measured results verify the feasibility and reliability of the two antennas.2.A single antenna and MIMO antenna based on discrete parasitic element structure are proposed.This series antenna structure is mainly divided into two parts: discrete parasitic radiation structure and excitation feeding structure.The unit antenna has four parasitic elements and is a high-gain wide-band linearly polarized dual-substrate microstrip antenna with an impedance bandwidth of 27.0 % and a gain of 6.52 dBi.Two-cell microstrip MIMO antennas share six parasitic elements.The impedance bandwidths of the two antennas are 32.1 % and 26.6 % respectively,and their gains are 6.52 dBi and 6.47 dBi,respectively.In the four-cell MIMO antenna structure,ten parasitic elements are applied.The antenna impedance bandwidth and radiation gain are 23.8 % and 5.40 dBi,respectively.Using polarization diversity technology,MIMO antenna port isolation is less than-15 dB.The measured results also verified the feasibility and reliability of the four antennas of the system.3.Cognitive radio is another technology that can effectively improve spectrum utilization.The system’s main front-end device is a reconfigurable antenna.This paper proposes two reconfigurable antennas with similar structure.One is the use of PIN switch diodes to reconfigure the antenna feed structure to achieve polarization reconfigurability,and the other is based on continuous and periodic rotation of the radiation patch.The first antenna can be reconstructed between two frequency points of 5.36 GHz and 5.64 GHz in the online polarization mode;at the same time,the polarization modes can be reconstructed at the frequency of 5.36 GHz.The second antenna can be reconstructed between the 4.77 GHz and 5.03 GHz frequency in the linear polarization mode: At the same time,the three polarization modes can be reconstructed at the 4.77 GHz frequency.Both antennas achieved better radiation efficiency and radiation gain than single-layer microstrip antennas in each operating mode,reaching 93.2 %,5.57 dBi,and 80.6 %,2.73 dBi,respectively.4.A dual-band three-polarization mode reconfigurable CPW(Coplanar Waveguide)feed antenna is proposed.Two relative frequency bandwidth is 27.7 %(2.30 GHz ~ 3.04 GHz)and 7.32 %(4.34 GHz ~ 4.67 GHz),respectively.We have studied in detail the port and far-field radiation characteristics of this antenna.Because the antenna is a single-plane antenna and has radiation in both directions perpendicular to the plane of the antenna,the radiation efficiency of the antenna in dual bands are respectively up to 93 % and 92 %.The measured results verify the reliability of the antenna.