Research On The Ultra-Wideband Frequency,Polarization And Pattern Reconfiguration Antennas

Based on specific projects,the design method of the ultra-wideband(UWB)frequency,polarization and pattern reconfiguration antenna arrays are mainly researched in this thesis.The main contribution of the thesis can be summarized as follows:Firstly,the background and significance of the UWB frequency,polarization and pattern reconfiguration antenna arrays are expounded.And the research status and problems at home and abroad are discussed.The related basic theories and methods used in the thesis are also discussed.Secondly,the research work is divided into two parts: The UWB frequency and pattern reconfigurable printed dipole antenna arrays are developed in the first part;the low-profile reconfigurable microstrip antenna and array are studied in the second part.The contexts in this dissertation are concluded as follows:1.Research on UWB frequency and pattern reconfigurable printed-Yagi antenna arrayThe first part of the dissertation is the development of UWB frequency and pattern reconfigurable printed dipole antenna arrays.The research works include the following four reconfigurable antenna arrays which are designed in specific environments.(1)Development of wideband frequency reconfigurable antenna arrayAccording to the function requirement of the broadband frequency reconfigurable antenna array,the printed-Yagi antenna is selected as the cascading unit,and the wide-frequency characteristic of the antenna array can be realized through the aperture reconfigurable cascade design method.A 4×4 array prototype is manufactured to verify the feasibility of the design.The test results show that the impedance bandwidths of two working modes of the reconfigurable antenna array are 66.6%(1.0~2.0 GHz)and 66.6%(2.0~4.0 GHz),respectively.It can cover the entire frequency range of 1.0~4.0 GHz.Furthermore,it has stable gain and pattern characteristics to meet the design indexes.(2)Study on 52-octave frequency reconfigurable antenna arrayAccording to the latest 52-octave frequency bandwidth requirement,a 5-level cascaded frequency and aperture reconfigurable antenna array is proposed.The frequency bandwidth of each cascade is as follows: 50~100MHz,100~225MHz,225~500MHz,500~1300MHz and 1300~2600MHz.The upper and lower side frequencies of each frequency band are connected end to end,so that the antenna array can cover 50~2600MHz in time division.That is,the frequency range of 52 octave is achieved.Besides,according to the requirements of cross-polarization and array size,a cross printed dipole antenna array with an array size of 3×3 is designed when the operating frequency is 50~100MHz.Due to the large size of the antenna array,only a 3-level cascaded linear array prototype is fabricated to verify the feasibility of this design.The test results show that the 3-level cascaded reconfigurable performance meets the design indexes.It can be inferred that the designed 5-level cascaded large-scale array can also meet the needs of practical applications.(3)Research on pattern reconfigurable dipole antenna array(1)Research on reconfigurable antenna array based on varactorThe varactor-based pattern reconfigurable antenna array consists of two printed dipole antenna elements.In the array design process,by controlling the capacitance values of the varactor on the two antenna elements,real-time changes of the phase of the two antenna elements in the far field are achieved,so that the pattern of the array can be reconstructed.The prototype test results show that the impedance bandwidth of the antenna array is 3.2~4.0 GHz(22.2%).Within the impedance bandwidth,an angular offset(±13° ~ ±18°)of the maximum radiation direction of the antenna array can be achieved in the XOZ plane.(2)Research on pattern reconfigurable antenna array based on PIN diode switchThis antenna is designed to achieve wideband pattern reconfigurability.The feed network of the antenna array has a simple structure,and can realize the reconfigurable performance of three maximum radiation directions of-10° to-16°,0° and 10° to 16° in the range of 2.7 to 6.0 GHz(75.9%).Due to the expandability of the feed structure,loading multiple sets of RF switches can further increase the deflection range of the maximum radiation directions of the antenna array.2.Research on low-profile Frequency,Polarization and Pattern reconfigurable microstrip antenna arrayThe second part of the dissertation is the study of low-profile reconfigurable microstrip antenna and array.The research works are as follows:(1).Research on frequency reconfigurable microstrip antenna array with ultra-wide frequency spanAccording to the function requirement of the low profile and wide frequency span frequency reconfigurable antenna array,a one-dimensional cascaded frequency reconfigurable microstrip antenna array is proposed.By switching the radiation structure between Whip-type and E-type structures,the working bandwidth range is adjustable from 3.7~4.0 GHz to 13.4~15.0 GHz,which is translated to a tuning ratio of 4:1.To verify the feasibility of the design,a 4×4 antenna array is fabricated and tested,and the test results are consistent with the design requirements.(2).Research on pattern and polarization reconfigurable antenna based on microstrip structureThe pattern and polarization reconfigurable microstrip antenna is controlled by two sets of RF switches to realize the switch function of two working modes.The first mode is microstrip directional radiation mode.By introducing perturbation of multiple shorting pins,a right-handed circularly polarized(RHCP)directional wave is formed.And the second mode is microstrip monopole radiation mode.By controlling the feed positions and the number of shorting pins,a vertical linearly polarized(LP)omnidirectional conical wave is realized.The prototype test results show that the gains of the two modes are 9.0 dBic and 5.0 dBi,respectively.All the electrical characteristics meet the design requirements.Finally,the further study on these issues is also discussed.