Research On Design And Test Method Of Conformal Antenna

In many applications such as satellite communications,aircraft and military airborne surveillance radars,antennas are required to work on curved surfaces.Equipping common antennas on aircraft and missiles can effectively address the problem of protruding antennas on the surface of weapons,complete the integrated design of antennas and fighter carriers,and maintain the stealth and mobility characteristics of fighter carriers to the maximum.Considering that the microstrip antenna has the characteristics of a simple structure,low profile,easy to be common and integrated,etc.,it is widely used in carrier common type antennas.Therefore,this paper designs two carrier microstrip common type antenna arrays and studies their test methods.The research work mainly includes:1.To study the changes of reflection coefficient and radiation performance before and after conformal plastic surfaces,a central embedded rectangular microstrip patch antenna is intended,which achieves suitable impedance matching in the Ku-band.A cascaded one-minute four-T power divider forms a 2×2 small planar array.Then,conformal with single and hyperboloid carriers,the variation rules of central frequency,bandwidth and maximum gain of 2×2 array antennas with three different curvature of cylindrical radius 50 mm,60mm and 70 mm,and radius of convex paraboloid and concave paraboloid with 300 mm 400mm and 500 mm curvature are discussed.Furthermore,variation rules of reflection coefficient and two-dimensional far-field pattern before and after conformal plastic surfaces are summarized.2.Through further study of the above four-element microstrip array,an 8×8 array antenna is formed,coincident with the aircraft carrier’s surface and the aircraft head.At the same time,the bending T-shaped power division structure is adopted in order to realize 1-minute 64 feeding.The space required for array arrangement is reduced,and the coupling efficiency is effectively decreased.The experimental results show that when the center frequency is 15 GHz,the-10 d B bandwidth is 320 MHz,23% wider than that of the planar array.Compared with the planar array,the E plane and H plane’s main beam gain decreases by 1.3d Bi and 1.4d Bi respectively,and the direction is deflected by 4° and 2°,respectively.The first sidelobe level decreases,which maintains the performance of the planar array.3.To better realize the low-sidelobe and high-gain design of the Ku-band carrier co-type array antenna,the Chebyshev synthesis method is used to directly weight the sidelobe level of the array unit pattern to complete the 1×8 sub-array pattern.For the sidelobe suppression,the sidelobe level value is-22.1d B.A 1-minute 8-series parallel hybrid feed network with a minimal structure,and low radiation loss is then designed.The return loss is lower than-15 d B in the entire Ku-band,the insertion loss is better than-10 d B,and the isolation is better than-20 d B.Finally,the sub-array and the feed network are cascaded to form an 8×8 array antenna,and the carrier is compatible with the aircraft.The experimental results show that at the center frequency of 14.8GHz,the|S11| value is better than-20 d B,and the matching is good.When φ=0°,the half-wave power beamwidth is 6.9°,which is less than 10°,and the sidelobe level value is-19.3d B,lower than-18 d B;when φ=90°,the half-wave power beamwidth is 6.4°,the sidelobe level value is-21.1d B,which is lower than-20 d B.The maximum antenna gain has reached 24.2d Bi and meet the index requirements of low-sidelobe and high-gain.