Study Of Miniaturization Of Ultra-wideband Antennas

With the development of modern communication technology,the requirements of communication systems and equipment are constantly improving.The complexity of carrier environment also makes more restrictions on the performance of antennas equipped on it,and sometimes even requires extremely small antenna size.At the same time,multiple narrowband antennas can be replaced with one single ultra-wideband antenna for communication,which avoids the coupling effect between multiple antennas and improves the stability of the communication system.Therefore,in this paper,the miniaturized ultra-wideband antennas are studied as follows:(1)Two different types of planar dipole antennas fed directly by subminiature version A(SMA)connectors are designed to meet the demand on omnidirectional communication in ultra-high frequency(UHF)band.The structures of the antennas are modified to reduce the effect of unbalanced current and free from the space occupied by a balun.The shapes of the antennas are adjusted to achieve ultra-wideband characteristic.The antennas work from1.3GHz to 2.5GHz and from 1.3GHz to 3.5GHz,respectively,with the relative bandwidth of 63.2%and 91.7%.Both antennas occupy narrow space and achieve miniaturization.(2)An ultra-wideband Vivaldi antenna is designed to meet the demand on broadband communication on airborne platform.The antenna is based on a conventional Vivaldi antenna,and its lower operating frequency is further reduced by loading slots and resistors at specific positions.Final form of the proposed antenna works from 0.3GHz to 3GHz with a relative bandwidth of 163.6%and a size of 0.18λ_L×0.09λ_L×0.002λ_L(λ_L is the wavelength corresponding to the lowest operating frequency),which achieves miniaturization.(3)An ultra-wideband electric small slot antenna is designed to meet the demand on direction finding in extremely small size,which achieves ultra-wideband characteristic with loading resistors.The characteristic impedance of the antenna is large,which makes the voltage standing wave ratio relatively high when the antenna is fed by a SMA connector.Thus,an air layer structure is used to reduce the characteristic impedance,and an array is composed to further improve the performance.Final form of the proposed antenna works from 100MHz to 600MHz with a relative bandwidth of 142.8%and a size of0.033λ_L×0.030λ_L×0.018λ_L,which achieves electric small characteristic.