Study On Triple-Mode Resonant Wideband Sectorial Dipole Antennas

With the deployment of 5G mobile communications,high performance base station antennas are becoming more and more desirable.Modern base station requires its internal antenna to achieve miniaturization,wide bandwidth and high isolation.In the past few decades,various wideband antenna design approaches have been extensively developed.However,these approaches may add certain complexities to the design and fabrication of wideband antennas while achieving the performance.Therefore,the antenna element with simple configurations will be the key component of the base station antenna system in the future.Recently,the multi-mode resonance concept has been widely used in wideband antenna design by simultaneously exciting multiple resonant modes to broaden the available radiation bandwidth,relatively simple configuration can be yielded.In this thesis,based on the theory of multi-mode resonance,a series of sectorial dipole antennas with simple structure,low cost and good performance are proposed,and they are applied to the design of dual-polarization antennas.They are expected to be used for the design of base station antenna.The main contributions of this thesis are as follows:1.The multi-mode resonance theory of 2-D sectorial dipole antenna is extended to the design of triple-mode resonant sectorial dipole antenna.The mode synthesis design method of the triple-resonant sectorial dipole antenna is proposed.Then,the closed-form expression of key parameters of multi-resonant antenna is derived.At the same time,the related technical background of wideband antenna using multi-mode resonance theory is also introduced.2.In this thesis,some 2-D sectorial dipole antenna samples are designed at the center frequency of 2.4 GHz.A full-wavelength sectorial dipole antenna with a flared angle of 240°is initially fabricated,which simultaneously excites TE_3/4,1,TE_9/4,1and TE_15/4,1 mode.In order to further broaden the bandwidth,a 1.5-wavelength sectorial dipole antenna with a flared angle of 300°is fabricated,which simultaneously excites TE_3/5,1,TE_9/5,1 and TE_3,1 mode.Both of them employ stub-and slit-loaded techniques and generate a wideband,octave radiation characteristic.In order to verify the correctness of the design approach,the fabricated triple-resonant sectorial dipole antennas are measured and compared with the simulation results.3.Distinct loading methods of the sectorial dipole antenna for achieving triple-mode resonance are studied.Another 1.5-wavelength sectorial dipole antenna with a flared angle of 300°is fabricated by employing multiple tuning stubs on the periphery of a sectorial dipole.The experimental verification shows that sectorial dipole antenna loaded with double stubs also exhibit a stable,triple-resonant wideband radiation characteristic as expected.Meanwhile,the performance is not significantly different from stub-and slit-loaded samples,which proves that the stub-and slit-loaded techniques perturb high-order mode is useful for the sectorial dipole antenna.4.Finally,a dual-polarized cross-dipole antenna is fabricated by placing two 300°sectorial dipoles orthogonally and mounting above a circular metallic planar reflector.As verified,the designed antenna sample has excellent performance.It validates the potential of the wideband antenna for base station applications.