Research On Electrically Beam Steering Antenna And Array

By introducing active components such as diodes,the electrically beam steering antenna and array provide the ability of flexibly controlling the energy distribution of electromagnetic wave in space.A high gain beam with wide beam coverage can be realized by beam steering antenna and array,which also have the advantages of low cost and ease of fabrication.The beam steering antenna and array are important for resolving the shortage of communication resource,improving the system capacity and communication quality,etc.,and have become a research hotspot in recent years.However,the reconfigurability of the existing beam steering antenna is relatively poor.Meanwhile,their performance in terms of size,complexity,and power consumption are relatively uncompetitive,and thus,the application of beam steering antenna in system and array design is limited.Besides,most of the researches mainly focus on the application of beam steering antenna in conventional half-wavelength phased array,where the advantages of beam steering antenna have not been fully considered and the researches of the applications of beam steering antennas in other kinds of arrays are needed.In this research,the electrically beam steering antenna and array are investigated.Design methods of beam and null scanning antenna,two-dimensional(2-D)beam steering antenna,and phasor beam steering antenna are presented.The proposed beam steering antennas are used for sparse phased array,conformal array,and 2-D direction finding array.An additional degree of freedom is introduced in array design.The research enriches the types of beam steering antenna and improves the performance of antenna and array,while the complexity and cost of system are reduced.The major innovations of this thesis are summarized as follows.1.The design method of beam and null steering patch antenna with shorting pins is proposed.By introducing four varactor loaded impedance reconfigurable circuits with edgeshorting pin at the center of the two parallel non-radiating edges of the patch,a continuously tunable phase difference between two equivalent radiating slots of the radiating edges can be provided and one-dimensional(1-D)beam and null scanning are thus achieved simultaneously.On this basis,the positions of the impedance reconfigurable circuits are further optimized.By loading four impedance reconfigurable circuits at the four edges of a square patch antenna,respectively,the beam and null scanning on two orthogonal planes are achieved without increasing the number of diodes and the input impedance is well matched.The proposed antennas can provide reconfigurabilities of beam and null scanning simultaneously with a compact size and only four diodes,and thus,is well suited for array design.2.The design method of 2-D and phasor beam steering patch antenna with stacked patches is proposed.By introducing four stacked patches integrated with PIN diodes along the diagonals of the proposed antenna as directors or reflectors,the phase gradients in different directions are generated,and 2-D beam steering on the E-,D-(diagonal),and H-planes can be delivered through nine modes.Furthermore,a phasor beam steering stacked patch antenna with amplitude and phase pattern reconfiguration is proposed.By introducing two stacked patches integrated with PIN diodes on the top of the proposed antenna,the amplitude and phase of the induced current on the surface of top patch are adjusted,and the phasor beam steering can be delivered.The proposed antennas can provide abilities of both amplitude and phase pattern reconfiguration with simple structure and fewer diodes,and thus,is well suited for array design.3.A grating lobe suppression method of sparse phased array by beam and null scanning antenna is proposed.By keeping the radiation pattern null pointing at the angle of the grating lobe of the array factor,the grating lobe of the proposed sparse phased array can be suppressed.Meanwhile,since the beam scanning of the proposed antenna element is also achieved with wide beam,the main lobe of array factor during beam scanning is located within the 3-d B beamwidth of the antenna element.Thus,the scan loss during scanning is improved as well.By introducing the proposed beam and null scanning antenna into a 2×4 sparse phased array,the measured sidelobe level(SLL)of the sparse phased array can be suppressed below-9.3 d B within the scan range from-76?to 75?.The maximum realized gain during beam scanning is17.0 d Bi,with an aperture efficiency of 69.86% and a gain fluctuation of 4.4 d B.Compared with half-wavelength phased array,a similar scanning performance can be provided by the proposed method while fewer antenna elements are needed.Thus,the complexity and cost of phased array can be reduced.4.The 2-D beam steering stacked patch antenna at Ka-band is used for improving the 2-D scanning ability of sparse phased array.The 2-D space is divided into nine subsets and covered by nine modes of the beam steering stacked patch antenna,respectively.A measured scanning range of ±60?on the E-and H-planes,and ±42?on the D-plane can be provided by the proposed2 × 2 sparse phased array,with a maximum gain fluctuation of 3.8 d B.The maximum realized gain during beam scanning is 14.6 d Bi with an aperture efficiency of 69.54%.5.The phasor beam steering stacked patch antenna is used for improving the aperture efficiency of conformal array.The phasor beam steering antenna is capable of amplitude and phase patterns reconfiguration.It can be used not only for phase compensation,but also for enhancing the contribution of antenna elements at the sides of conformal array to the array’s gain of axial beam.The measured realized gain of the proposed four-element arced conformal array with phasor beam steering antenna is 12.0 d Bi and the corresponding aperture efficiency is 51.48%.Compared with the results of conventional arced conformal array with phase compensation network,a better aperture efficiency is achieved by using phasor beam steering antenna.6.A 2-D direction finding method by two-element beam steering antenna array is proposed.By introducing the beam steering antenna,a new degree of freedom for 2-D direction finding can be provided and an equivalent multi-dimensional array is built by the two-element beam steering antenna array.With the introduction of same-direction and opposite-direction modes of beam steering antenna array,the elevation and azimuth angles can be estimated by the methods of time modulated array(TMA)and amplitude comparison,respectively.Meanwhile,a 2-D look-up table is built to correct the coning-error effect of the amplitude comparison.Compared with the conventional 2-D DF methods,the proposed method has the advantages of simple array structure,compact array size,and low cost,which is suitable for various applications.