Research On The Millimeter-wave Wideband Planner Array Antennas

With the development of wireless communication,it becomes more and more congested at the lower frequency band of the microwave spectrum,and suffers from the mutual interferences.Thus,people turn their eyes to the higher frequency band of microwave,i.e.millimeter-wave(MMW)band,which has abundant spectrum resources.However,atmospheric attenuation is very high at MMW band,high-gain antennas are needed to make the system can work effectively within a required range.Using an array antenna is a direct and effective method to obtain high gain,but the feeding and layout are difficult for MMW antennas due to the very small sizes of components,which are related to their high operational frequencies,especially for the MMW planar array antennas with low profile.Polarization diversity is another method to improve the system capacity besides using wide bandwidth and high gains.However,it is difficult to realize MMW wideband planar array antennas with circular polarizations(CPs)or dual polarizations(DPs)due to the size limit.Deepgoing researches on two main problems of how to realize wideband and high gain,and how to achieve wideband and CP or/and DP for MMW planar array antennas,have been done in this dissertation,including the design methods and topologies suitable for wideband high-gain or wideband DP/CP MMW planar array antenns,and all the proposed models are validated by experiments.The main works of this dissertation are listed as below:1.To slove the problem of how to realize both wideband and high-gain characteristics for MMW planar array antennas,a planar array antenna consisting of microstip,SIW and waveguide,is proposed in this paper.Firstly,a microstrip subarray is combined with a substrate integrated waveguide(SIW)feed network.In this way,a compact array layout is realized.Then,a novel feeding topology for the microstrip subarray is proposed to widen the working bandwidth.It achieves a hybrid mode of microstrip patches and equivalent dipoles.Based on the wideband array antenna,the relationship between the array scale and the antenna efficiency is studied and a design rule of choosing transmission lines according to the array scale is proposed in this paper.The validated 64×64-element microstrip-SIW-waveguide array antenna achieves a bandwidth of 14.6% and has a maximum gain of 39.2dBi.Comparing with microstrip array antennas as well as SIW array antennas,the gain of the proposed antenna is improved significantly.Comparing with the traditional waveguide array antennas,the fabrication cost of the proposed antenna is reduced a lot.2.To slove the problems of feeding and layout for dual-polarized MMW wideband planar array antenna,a dual linearly-polarized(DLP)planar array antenna consisting of co-aperture radiating elements and separate layers of feeding networks for different polarizations,is proposed in this paper.The radiating element of the proposed antennas is a pair of stacked patches including a driven patch and a parasitic patch.Direct feeding and aperture-coupled feeding are used to extract two orthogonal polarizations,and then the topology of the feeding networks is optimized to increase the port-to-port isolation.The validated 8×8-element DLP array antenna provides an operational bandwidth of 21.4% and the port-to-port isolation is higher than 30 dB.Wide bandwidth and high isolation are achieved simultaneously.3.To slove the problem of how to realize both wideband and high-efficiency characteristics for circularly-polarized MMW planar array antennas,a single-fed unidirectional CP planar array antenna fed by a feeding network of striplines is proposed in this paper.Firstly,a wideband single-fed CP element is proposed.It is formed by segamented pateches which are fed by a multi-branch strip line through a crossed slot.The single-fed aperture-coupled topology not only simplifies the CP feeding network,but also obtains the multiple resonance which contributes to the wide bandwidth.Then,a stripline feeding network loaded with metalized vias to suppress the parallel plate mode is proposed to realize a wideband and high-efficiency design for array antennas.Measured results of the validated 4×4-element single-fed CP antenna with a unidirectional beam show an AR bandwidth of 14% and an efficiency more than 60%.Both of the bandwidth and efficiency are considered,comparing with the traditional single-fed unidirectional array antennas.4.Based on the respective researches of MMW array antennas with wideband and high-gain,wideband and DLP,wideband and CP characteristics,a MMW wideband planar array antenna with dual circularly-polarized(DCP)and high-gain characteristics will be proposed in this paper.To improve the efficiency of MMW DP array antennas,a planar DP array antenna with a full waveguide structure is designed.The radiating elment is a square waveguide aperture.A hybrid cavity is used to feed the basic 2×2 subarray.It provides a reasonable element spacing and a compact array layout with wideband characteristics.Based on the subarray,a septum polarizer is integrated to form a DCP antenna.A high-gain high-efficiency wideband DCP array antenna is obtained by expanding the array scale.Measurement results show that the proposed 16×16-element DCP array antenna has a bandwidth of 16%,a gain more than 31.4dBi,and an isolation higher than 13 d B between left-hand and right-hand circularly polarized ports(isolation higher than 20 dB within bandwidth of 11.8%).