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Research On Filtering Characteristics Of Ultra-Wideband Antenna And Directional Characteristics Of Slot Antenna

Posted on:2020-05-31Degree:DoctorType:Dissertation
Country:ChinaCandidate:H L YangFull Text:PDF
GTID:1368330611953130Subject:Electromagnetic field and microwave technology
Abstract/Summary:PDF Full Text Request
Ultra-wideband(UWB)technology is widely used in radar,wireless communication and indoor location technique.Due to the wide operating band and low radiation power of the UWB system,UWB systems are vulnerable to interference from narrowband signals in the UWB band and other wireless communication systems out of band.Usually,we avoid the interference signals and improve the selectivity of the UWB system by designing a filter at the end of the antenna.However,this method increases the dimension and costs of RF front-end in the UWB system.Therefore,the research on UWB antenna with good filtering characteristics in-band and out-of-band is of great theoretical significance and application value for the development of UWB technology.In this paper,slot antenna and monopole antenna are taken as the research objects to study the band-edge selectivity characteristics and in-band filtering function of UWB antenna,and several different UWB filter antennas are proposed.At the same time,according to the characteristic of slot antenna showing directional characteristics at high frequency,we study the directional characteristics and MIMO antenna on the basis of filtering slot antenna.The main contents and achievements of this paper are described as follows:1.Two UWB slot antennas with good band-edge are proposed.By using a stepped impedance resonator with low-pass filtering function as a feeding line and adding a narrow slot the band-edge selectivity of the proposed antenna is improved.The proposed antenna has good radiation characteristics and shape factor K.The ratio of the-3dB bandwidth to the-10dB bandwidth is 1.04,which is very close to ideal shape factor.Furthermore,in order to solve the problem of unsatisfactory in-band impedance characteristics of step impedance feed antenna,a filter slot antenna with defective ground structure(DGS)is proposed.By introducing DGS to increase more resonance mode and generate more transmission zeros,the antenna can not only obtain better band-edge selectivity,but also greatly improve the impedance characteristics in the band.The shape factor K of the DGS filtering antenna is as low as 1.05,and the maximum reflection coefficient in the band is reduced to-14dB,and the radiation efficiency is increased to 90%.Compared with the stepped impedance fed filter slot antenna,the impedance and radiation efficiency of DGS filtering antenna is increased by 40%and 12.5%,respectively.2.A circular monopole filter antenna is proposed.Comprehensively evaluate the structure and characteristics of the antenna and filter.The radiation structure of the circular monopole antenna is used as the branch loading.A band-pass filter with circular loading multimode resonance is designed,and the filter is used to replace the 50? feeding line.The filter has the same resonance mode as the antenna,which avoids the problem of using impedance transformation to increase the antenna size.The measured results show that the shape factor K?1.15 and the bandwidth reaches 119%,covering the frequency from 2.8GHz to 11GHz.3.A multi-band notched UWB antenna with wide notched band and sharp selectivity.By introducing a variety of slot structures and parasitic structures,the quad and quintuple band-notched functions of monopole antenna are realized.Furthermore,based on the principle that a wide resonant frequency can be formed between multiple resonant structures,a band-notch antenna with controllable wide bandwidth and good selectivity is designed.4.Two different reconfigurable filtering antennas are proposed.One is a reconfigurable UWB filter antenna based on a circular monopole.The PIN diode is used to control the connection between the T-type microstrip lines in the antenna radiation,and three working modes can be reconstructed.The other is a reconfigurable slot antenna based on DGS filtering slot antenna.The antenna can realize both in-band and out-of-band filtering functions,and retain the out-of-band filtering characteristics of the defective slot antenna.Four working modes are realized by introducing two parallel microstrip lines and two diodes.The notch structure and antenna are independent of each other,there is no need to add a capacitance,the bias circuit is relatively simple,and has little effect on the radiation patch.5.Based on the relationship between the DGS filter slot antenna and the F/B of other slot antennas as a function of frequency,a DGS filter slot antenna with directional radiation characteristics is proposed.By using the closely-space loading principle,by introducing a passive terminal and a rectangular slot in the opening direction of the slot,the slot antenna exhibits a large F/B and directional characteristics in the entire operating frequency band.Angle diversity is achieved by using the directional characteristics of the antenna,so that different unit radiations in the MIMO antenna are not intersected,thereby achieving high isolation between MIMO antenna elements.The two-unit MIMO slot antenna has an isolation of more than 15 dB in the operating frequency band of 2.5-11.6 GHz and an isolation of more than 30 dB in the 6-11 GHz without adding any decoupling structure.
Keywords/Search Tags:Ultra-wideband antenna(UWB), slot antenna, band-edge selectivity, filtering antenna, directional antenna, MIMO antenna
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