Research On Low Profile Multi-Frequency Base Station Antenna Based On Composite Structure

In the large environment where 4G/5G dual-standard communication systems coexist,the sharp increase in the number of new 5G base stations has caused a shortage of mobile communication base station sites.At the same time,the rapid development of new applications such as the internet of Vehicles and industrial automation has also determined that millimeter wave technology with low latency and high reliability must become the inevitable development trend of new 5G communication technologies.Therefore,it is urgent to design miniaturized multi-frequency base station antennas for future dual-standard communication systems.The design of this thesis starts from the realization of multi-frequency and low-profile antennas,and is dedicated to the research and design of low-profile multi-frequency base station antennas applied to Sub-6G and millimeter wave frequency bands.Its main work content includes:1.A parasitic multi-frequency base station antenna with a composite structure is proposed.The antenna unit includes an LTE broadband dual-polarized leaf dipole antenna and four 4×4 millimeter wave rectangular microstrip array antennas.In the dipole design,the radiating oscillators are placed in a±45~o cross to achieve dual polarization,and rounded corners are introduced to expand the impedance bandwidth to achieve broadband.The millimeter array antenna adopts the central coaxial feed form of equal power division and parallel connection.The parasitic multi-frequency base station antenna of the composite structure is designed by the compound parasitic design method so that the dipole antenna and the millimeter wave array share the dielectric substrate.The radiator of the dipole also serves as the floor of the array while radiating.The research results show that the antenna realizes a millimeter-wave array antenna and low-frequency array element composite design scheme under the premise of ensuring that the electrical performance meets the requirements of 4G/5G mobile communication standards,and completes the integrated design of a large frequency ratio antenna.2.In order to further reduce the profile height and achieve miniaturization while ensuring its good impedance matching characteristics,a composite structure parasitic antenna loaded with a dielectric resonant cavity and loaded with an artificial magnetic conductor(AMC)reflector plate has been studied and designed separately.The original 1/4wavelength profile height is reduced to 1/6 wavelength and 1/8 wavelength.The loaded dielectric resonator uses the principle that the wavelength of electromagnetic waves propagating in the high dielectric constant medium will be shortened.The simulation results show that the gain will be reduced due to the dielectric loss,and the other radiation characteristics remain basically unchanged.Moreover,the loading of the AMC reflector uses the in-phase reflection characteristics of the AMC structure to reduce the overall height of the antenna.The test results of the prototype of the base station antenna loaded with the AMC reflector show that the relative working bandwidth of the Sub-6G and millimeter wave frequency bands are 38.2%and 10.7%respectively,and the radiation pattern has good consistency.In summary,the low-profile multi-frequency composite structure base station antenna designed in this thesis has the characteristics of large frequency ratio and low-profile,which is in line with the future development trend of 4G/5G dual-standard base station antennas.It can meet the practical application requirements of working in the Sub-6G communication frequency band and the millimeter wave communication frequency band at the same time.