Design Of Circularly Polarized And Dual Polarized Antenna Arrays

Antenna arrays are composed of multiple single antennas according to certain feeding requriments and spatial arrangements.Not only can antenna arrays enhance and improve directivity of their radiation patterns,but also they can increase gains.In comparision to linearly polarized arrays,circularly polarized and dual polarized arrays take their advantages of better adaptability for transmitting and receiving radiated singals,especially in the complex environment of the signal transmission.Circularly polarized arrays are widely applied in satellite communications,and dual polarized arrays are suitable for mobile communications.Based on the practical application importance of circularly polarized and dual polarized arrays,this thesis has investigated relevant design techniques in detail.The main work can be summarized as follows in two parts:1.The wideband circularly polarized antenna array is presented.Taking the advantage of the wideband feeding probe,more than 20 % impedance and axial ratio(AR)bandwidths are obtained for 2×2 and 4×4 arrays.The experiment and simulation confirmed that the 3D M-Probes are feasible to feed the patch antenna array with high gain and wideband characteristics.These arrays are designed and fabricated using multi-layer printed circuit board(PCB)technology,revealing a concise and reliable method for array design for mass production.The series of proposed antennas can be directly mounted on or integrated with circuit board of communication systems.This practical design has potential applications for satellite communications such as satellite TV in Ku-band and On-The-Move(OTM)Antenna System.2.Dual-band dual-polarized filtering antenna array is proposed.It consists of two 4×4 sub-arrays operating at 3G(1710-2170 MHz)and LTE(2490-2690 MHz)bands.For size miniaturization,the elements of the two 4×4 sub-arrays are interleaved with each other.The mutual coupling between the elements operating at different bands is suppressed by using filtering antennas with out-of-band radiation suppression.And the spacing between them can be decreased,resulting in array miniaturization.To obtain stable two-beam radiation patterns within the two operating bands,the beam forming networks with little magnitude and phase imbalances are specially designed for each band.For demonstration,the proposed 4×8 array is implemented.In the measurement,the array exhibits stable 10 dB beamwidth around 120° in the azimuth plane within the two entire bands.As a result,the two-beam radiation patterns satisfy the coverage requirement of 120° in the azimuth plane for base-station applications.Additionally,16.4 d Bi/15.5 dBi peak gains and around-10 dB cross levels at the junction of two beams are achieved within the two operating bands.Compared with typical industrial products,the proposed array features both compact size and stable radiation patterns.Moreover,the proposed method can be easily extended to multi-beam base-station array designs.