Differentially-fed Dual-polarized Antennas Backed By SIW Cavity

Substrate Integrated Waveguide（SIW）cavities have been widely used to various antennas due to its advantages of low-loss,high Q,small size and easy integration with systems.A differentially-fed antenna is fed by two ports,and can be directly connected to differential circuit of RF front-ends,avoiding the use of converting devices,such as baluns,which can effectively reduce input loss,improve antenna efficiency and make RF systems more integrated.Dual-polarized antennas can effectively combat multipath fading and improve the capacity of communication systems.Using dual-polarized antenna in mobile communication network can reduce interference and improve quality of Service.Since multiband antennas can cover multiple bands,they are useful for reducing system size and meeting the demands of miniaturization of equipment.Differentially-fed broadband/multiband dual-polarized antennas backed by SIW cavity are investigated in this thesis.The main contributions of this work include three parts as follows:1.A broadband differentially-fed dual-polarized antenna backed by SIW cavity is proposed.The proposed antenna consists of a Petal-shaped slot embedded in a SIW cavity;the slots re differentially fed by two orthogonal microstrip feedlines with the identical size.perimental results show that the bandwidth for|S_dd11|or|S_dd22|<-10 dB is about 24% 13.2–16.8 GHz).The isolation between the two ports is higher than 40 dB over the band or|S_dd11|or|S_dd22|<-10 dB.The average gain for both horizontal polarization（HP）and ertical polarization（VP）is about 6 dBi with stable radiation patterns.2.A low-profile differentially-fed dual-band dual-polarized antenna backed by SIW cavity is developed.The slots structure consists of four identical slot elements,each of which ontains a pair of C-shaped slots and an elliptical arc slot.The antenna embedded in a SIW cavity,which is also differentially fed by two orthogonal microstrip feedlines.The dual- band antenna covers the frequency bands of 2.4-2.5GHz and 4.97-5.96GHz for differential reflection coefficient(|S_dd11|)（27）-10 dB with an isolation better than 40 dB.The average gains for the lower and upper bands are 4.7 dBi and 7.4 dBi,respectively.The antenna has a low profile of 0.038l_2.4GHz(wherel_2.4GHz is the free-space wavelength at 2.4 GHz),which may find applications in WiFi wireless communication systems.3.A differentially-fed tri-band dual-polarized antenna is designed for WiFi/5G Applications.The radiating element evolves from the slot structure of the dual-band antenna developed above.The difference is that four short branches to the radiating slot,four pairs of L-shaped slots at the four corners and eight short pins in the SIW cavity are introduced.The tri-band antenna covers the frequency bands of 2.4-2.51 GHz,3.29-3.6 GHz and 4.8-5.05 GHz for differential reflection coefficient（27）-10 dB with an isolation better than 30 dB.The average gains are 4.8 dBi,5.1 dBi and 6 dBi for low-band,mid-band and high-band,respectively.The height of the antenna is only 0.054l_2.4GHz.These broadband/multiband differentially-fed dual-polarized antennas backed by SIW cavity may find wide applications in WiFi and 5G mobile communications.