Research And Design Of Ultra-wide Band Differential And MIMO Antennas With Band-Notched Characteristics

With the continuous progress of society,people have put forward higher requirements on the communication rate and communication effect of future communication systems.Since the United States Federal Communications Commission(FCC)officially allowed the application of the 3.1-10.6GHz spectrum in the civilian and commercial fields in 2002,UWB communication technology has been widely research and application because of its advantages such as high speed,low power consumption,and high stability.However,narrowband communication systems such as WLAN(5.15-5.825GHz)and satellite communication X-band uplink and downlink frequency bands(7.25-8.4GHz)also exist in this wide frequency band,which may cause serious congestion of the wireless spectrum and make the transmitted electromagnetic signals are subject to interference and distortion.In addition,UWB communication systems also have problems such as cross polarization and multipath attenuation.Combining the design of UWB antennas with differential feeding and MIMO(Multiple-input multiple-output)technologies can solve the above problems.Therefore,research on ultra-wideband differential and MIMO antennas with band-notched characteristics has become a very hot topic in recent years.In this paper,two UWB antennas with band-notched characteristics are designed by studying the development of band-notched UWB antennas.The antennas are designed using differential feed technology and MIMO technology.Both antennas achieve good notch characteristics and stable performance.The specific work in this paper are as follows:1.A differentially fed UWB antenna with band-notched characteristics is designed.The antenna consists of two symmetrical hexagonal radiation patches and a ground plate etched with an octagonal groove.The overall size of the antenna is 30 × 35 × 0.8mm3.It uses a Rogers Ultralam 2000(tm)substrate with a dielectric constant of 2.5.The working bandwidth of the antenna is 3-11 GHz.The radiation pattern shows that the cross polarization of the antenna is lower than-40dB,better than single-fed antenna.By loading a half-wavelength stub on the ground plate,the odd mode reflection coefficient and voltage standing wave ratio in the X-band are significantly increased,and the band-notched characteristic of the antenna is achieved.2.A coplanar waveguide-fed UWB-MIMO antenna with dual band-notched characteristics is designed,and the reconfigurable characteristics of the antenna unit are designed.The antenna adopts a coplanar waveguide feeding method,which increases the radiation area and resonance point of the antenna,so that the antenna bandwidth reaches 3-16GHz and the relative bandwidth is 137%.The antenna unit consists of a hexagonal radiation patch and a ground plate etched with a circular groove.By loading cup-shaped branches above the ground plate,the ground plate is coupled with it,and the radiant energy is limited,thereby realizing the notch in the WLAN fre-quency band.By etching the SIR structure on the antenna feeder,the X-band notch is realized.On the basis of the dual band-notched ultra-wideband antenna,switches are loaded between the antenna unit and the band-notched structure.By controlling the switch,the antenna can achieve the pass band/single band-notched/dual band-notched function,which verifies the antenna's band-notched frequency re-configurable characteristics.In order to solve the problem of multipath fading of antennas,the antenna units are arranged as MIMO antennas,and a periodic fence structure is designed to improve the isolation of the antenna,so that the isolation between antenna units is greater than 25dB.The simulation data proves that the UWB-MIMO antenna can work normally in 3-16GHz,and the band-notched structure can operate normally.3.In this paper,the designed antennas are processed in kind,and the simulation results are compared with the measured data.The two agree within the tolerance range.