Research On Miniaturization And Low-scattering Technologies Of Ultra-wideband Dual-polarized Vivaldi Antennas

With the development of wireless communication systems,amounts of wireless applications contribute to the development of high-performance antennas,and meanwhile,the accompanying measurement technology should also be ensured for precisely evaluating the performance.In the near-field measurements,the probe antennas play vital roles and have been one of the research hotspots in the antenna field.Vivaldi antennas have garnered a great amount of attention due to its characteristics such as wide bandwidth,symmetrical radiation pattern,and low cross-polarization level.In this paper,the Vivaldi antenna is considered as the probe antenna.Their associated miniaturization and low-scattering technologies are analyzed,designed,and experimental verified according to its radiation and scattering characteristics.The work of this paper includes the following three parts:(1)A traditional Vivaldi antenna is designed as the reference antenna by analyzing and optimizing the exponentially tapered slot and microstrip feed structure of the Vivaldi antenna,.The operating band of this antenna covers from 1.7 GHz to 7 GHz,with a gain varying from 6 dBi to 11.1dBi,and a cross polarization level less than-25 dB.The size of the antenna is 0.838₀×0.736₀(₀is the free-space wavelength at the lowest operating frequency).(2)Two miniaturized dual-polarized Vivaldi antennas and arrays are proposed and verified.First of all,based on the analysis and improvement of the feed structure,the low-frequency characteristics of the antenna can be effectively improved without changing the size of the antenna by using the multi-level feed matching lines,and finally the miniaturization of the antenna can be achieved.A miniaturized Vivaldi antenna based on the improved feed structure is designed,and the dual-polarized radiation performance can be further realized by integrating two single-polarized elements orthogonal to each other.The electrical size of this antenna is 0.602₀×0.532₀(₀ is the lowest frequency corresponding to the wavelength),and this antenna achieves a-10dB impedance matched band covering from 1.9 GHz to 6.2 GHz,with a gain varying from 4.1 dBi to 10.2 dBi.On this basis,using slotting technology,periodic rectangular slots were loaded on the two sides of the metallic radiating surface to further increase the current path.Consequently,the low-frequency operating frequency band of the antenna can be reduced without changing the size of the antenna.The electrical size of the designed miniaturized dual-polarized Vivaldi antenna with rectangular slot loadings is 0.538₀×0.476₀(₀ is the wavelength corresponding to the lowest frequency),and this antenna achieves a bandwidth from 1.7 GHz to 6.3 GHz,with a gain varying from 4.1 dBi to 10.5dBi.Furthermore,for the near-field parallel sampling measurements,a 4-elements dual-polarized ultra-wideband probe array is designed using a miniaturized dual-polarized antenna with rectangular slots as an element.The isolation between each antenna element is higher than 22 dB,and the impedance and radiation characteristics of each antenna element are maintained well.The above antenna elements and arrays have been fabricated and measured,and the measured results corresponds with the simulated.(3)The low-scattering single-polarized and dual-polarized Vivaldi antennas are proposed and verified.The single-polarized Vivaldi antenna achieves broadband scattering suppression by cutting a pair of symmetrical but irregularly shaped angular slots near the bottom feedline of the antenna and introducing a pair of inclined rectangular slots near the tapered radiating aperture of the antenna.This antenna exhibits a-10 dB impedance matching bandwidth from 1.5 GHz to 7 GHz,with a gain ranging from 3 dBi to 11.5 dBi.The RCS of the single-polarized low-scattering Vivaldi antenna has a great drop in the 1.5 GHz-2.8 GHz and 3.7 GHz-6.5 GHz bands,the achieved averaged RCS reduction over the entire band is 6.1dB,and the maximum reduction is 20 dB is at 2.3 GHz.Furthermore,a dual-polarized Vivaldi antenna was designed by integrating two single-polarized elements orthogonal to each other based on the low-scattering single-polarized Vivaldi antenna and loading the complementary split resonant ring(CSRR).When the incident wave is x-polarized,RCS reduction is achieved in the 1.8 GHz-2.9 GHz and 3.8 GHz-6 GHz frequency bands.The achieved averaged RCS reduction over the entire band is 5.4 dB with a maximum reduction of 17 dB occurring at 4.5 GHz.When the incident wave is y-polarized,the RCS reduction is achieved in the 1.8 GHz-3.3 GHz and 3.7 GHz-6 GHz frequency bands.The achieved averaged RCS reduction over the entire band is 6.5 dB with a maximum reduction of 15dB happening at 4.9 GHz.