4G/5G Multiband MIMO Antennas For Metallic Frame Mobile Terminal Application

With the rapid development of the mobile communication technology,mobile terminals have gradually become the link between individuals and the internet,playing an increasingly important role in our daily life.In recent years,mobile terminals with metallic frame are favored by more and more users for the high mechanical stability and excellent sensory experience.However,integrating a metal frame around the device is bound to adversely affect traditional mobile terminal antennas.According to the development characteristics of mobile terminals such as metallized body and large screen proportion,how to design terminal antennas suitable for modern mobile devices has important practical application value.In addition,China took the lead in releasing the frequency usage plan for 5G systems in Sub-6 GHz in 2017,and clarifield the frequency band of 3300-3600 MHz and 4800-5000 MHz as the working frequency bands for 5G systems.This means that the metal frame mobile terminal devices that can support 5G communication band will become a good choice in the future 5G era.Hence,how to integrate the 5G MIMO antenna system into a mobile terminal device with a metal frame is also a subject of research value.This thesis makes an in-depth study of the 4G/5G multi-band terminal antenna with metal frame.The main contributions of this thesis are summarized as follows.1.A smartphone antenna with metal frame applied in LTE/WWAN band is presented.The antenna adopts open-slot structure to reduce the effect of metal frame on antenna performance.This antenna has a simple structure,the L-shaped open slot on the system ground is excited by a single feedline,and the lower frequency impedance bandwidth of the antenna is extended by loading an LC band-stop matching circuit at the feed port,achieving the coverage of the lower frequency bandwidth of 698-960 MHz.At the same time,two metal plates are loaded on the top metal frame for better impedance matching characteristic.Finally,it covers 698-960 MHz and 1710-2690 MHz under the condition of only using a slot and a feedline with an LC matching circuit.The antenna efficiencies,radiation patterns and other performance indices satisfy the standard of terminal antenna.2.A metal narrow-frame tablet antenna for the LTE/WWAN band is presented.The antenna integrates the antenna clearance area and the metal frame into a T-shaped slot by setting a gap on the metal frame and adding metallic ground patches,and the antenna radiating element excites the T-shaped slot to generate a slot resonance to radiate,thereby effectively widening the antenna bandwidth.The highlight of the antenna is that the width of the narrow side is only 5 mm,and the bottom of the narrow side is 7 mm away from the top metal frame,which basically meets the requirements of the current consumer for the large screen.In addition,the antenna has a planar structure,and no lumped elements are loaded,which avoids unnecessary energy loss caused by loading the lumped elements and errors caused by the lumped elements in mass production.In the end,LTE/WWAN octa-band bandwidth coverage and higher measured efficiencies are realized,which make it more advantageous in practical applications.3.An eight-port dual-band antenna array for 5G(Sub-6 GHz)MIMO applications in metallic frame smartphones is presented.The proposed MIMO antenna consists of eight identical dual-band antenna elements and printed on the four corners of the system board symmetrically,the two antenna elements at each corner are perpendicular to each other to enhance the isolation between the two antenna elements.The antenna element comprises a driven strip and a coupling ground strip.In addition,the antenna clearance area,the metal frame and the gap on the metal frame are integrated into an open slot.The drive strip excites the open slot to generate a slot resonance to participate in the radiation.Finally,with an only 2 mm ground clearance,the antenna array can cover 3400-3600 MHz and 4800-5000 MHz bands,and the antenna performance in the operating frequency band meets the MIMO system standard.