Investigations On Wideband Millimeter Wave Planar Antennas And Terahertz Antennas

Ultra-high-speed communication is the development trend of modern wireless communication technology,and the broadband millimeter wave and terahertz wireless communication technology are effective ways to achieve ultra-high-speed communication.As one of the key components of the communication system,the antenna has also evolved toward ease of integration,low profile,wideband,high gain,low sidelobe and low cross polarization.Therefore,the investigations on broadband high-performance millimeter-wave?MMW?and terahertz antennas have important significance.The dissertation focuses on the research and development of wideband millimeter-wave planar antennas and terahertz antennas.It is organized as follows:Chapter one mainly focuses on the wideband and low cross-polarization MMW planar dipole antennas.Firstly,a dual-mode dipole antenna can be created by etching a pair of gaps at the appropriate positions of the long arms.Therefore,the operating bandwidth of the dipole can be improved when it works in both half-wavelength mode and high-order mode.Then,a folded planar dipole antenna is proposed,and the cross-polarization of the folded dipole antenna can be improved by making the two parts of the vertical polarization electric fields inversely cancel.The measured results indicate that the proposed antenna achieves a wide-10 dB impedance bandwidth of 58.5%from 30.5 to 53.5 GHz,the measured gain is between 5.1 and 6.4 dBi,and the measured cross-polarization is lower than-15 dB over the operating band.Chapter two mainly focuses on the wideband MMW horizontally polarized omnidirectional antenna.The advantages of horizontally polarized omnidirectional antennas over vertically-polarized omnidirectional antennas in the indoor wireless communication systems and their design difficulties are first introduced in this chapter.To overcome this issues,a compact dual-mode SIW radial waveguide power divider is proposed as the feeding network.A wideband horizontally polarized omnidirectional antenna is proposed by combining the dual-mode SIW radial waveguide power divider with the rotational dipoles.In order to increase the gain while achieving conical beam in the vertical plane,a conical reflector is added in on one side of the omnidirectional antenna.The measured results indicate that the proposed antenna achieves a wide-10 dB impedance bandwidth of 22.9%from 39 to 49.3 GHz,the measured gain is between 4.1 and 5.2 dBi,and the gain ripples are lower than 3 dB over the operating band.The designs of this part have been published in IEEE Trans.Antennas Propag.Chapter three mainly focuses on the design of a low-profile wideband SIW cavity-backed E-shaped patch antenna.An SIW cavity-backed E-shaped patch antenna is proposed for the Q-LINKPAN applications in this chapter,the operating bandwidth of the antenna element can be improved by adopting the CPW probe-feeding structure.A 2×2 antenna array is designed by using the proposed antenna element and a differential feeding network.The measured results indicate that the proposed 2×2 antenna array has a wide impedance bandwidth of 34.4%and has different pattern characteristics in different frequency bands,which make our proposed antenna array particularly suitable for the Q-LINKPAN wireless communication system supporting both short-distance and long-distance high-speed communications.The designs of this part have been published in IEEE Trans.Antennas Propag.Chapter four mainly focuses on an E-band wideband and high-gain planar antenna array.Firstly,an E-band antenna element is designed by using an SIW cavity-backed patch and a stepped rectangular waveguide.The SIW cavity-backed patch is used to increase the operating bandwidth,and the stepped rectangular waveguide is employed to improve the gain.Therefore,the proposed antenna element has a wide impedance bandwidth of 21.8%from 69 to 86 GHz and a high gain between 7.9 and 10.3 dBi.Then,a 2×2 antenna array is designed based on the proposed antenna element.Meanwhile,a rectangular groove with a depth of?₀/4??₀ is the operating wavelength of the center frequency?is etched between the antenna elements.The rectangular groove can not only reduce the mutual coupling between the antenna elements but also can improve the gain and the sidelobe of the antenna array by constructing a secondary radiating source.The simulated results show that the proposed 2×2 antenna array has a-10 dB impedance bandwidth of 21.8%from 70 to 87 GHz,the simulated gains vary from 14.6 to 17dBi.Finally,using the 2×2 sub-array described above,a 16×16 high-gain antenna array has been designed.A prototype is fabricated and measured,the measured results show that the operating bandwidth of the antenna array covers the band of 71 to 86 GHz,the measured gains vary from 28.8 to 30.9 dBi.The proposed wideband and high-gain planar antenna array can be used in E-band MMW backhaul systems.The designs of this part have been submitted to IEEE Trans.Antennas Propag.Chapter five mainly focuses on a Q-band wideband and high-gain planar antenna array.Based on research in Chapter 4,two antenna elements with inverting characteristics are proposed to design the antenna array in this chapter,which makes the proposed antenna array in this chapter have more compact feeding network.A 16×16 high-gain antenna array has been designed based on the two antenna elements with inverting characteristics,and a prototype is fabricated and measured.The measured results indicate that the operating bandwidth of the antenna array has a-10 dB impedance bandwidth of 18.2%from 40 to 48 GHz,the measured gains vary from 28.3 to 31.4 dBi over the operating bandwidth.The wideband and high-gain planar antenna array proposed in this chapter can be used for Q-band point-to-point wireless communication systems.The designs of this part are intended to be submitted to IEEE Trans.Antennas Propag.Chapter six mainly focuses on the wideband and high-gain terahertz antenna.A broadband and high-gain terahertz quasi-planar dual-reflector antenna is designed and implemented based on high precision milling process.The cylindrical structure of the dual-reflector can reduce the difficulty of processing,and the choke slots can be used to improve the paraxial sidelobes.The measured results show that the operating bandwidth covers the band of 325 to 500 GHz,the measured gains vary from 26.5 to 32 dBi,the cross-polarization is lower than-30 dB over the operating bandwidth.The proposed quasi-reflector terahertz antenna has the advantages of wideband,high gain,low processing cost,and easy assembly.The designs of this part have been published in IEEE Trans.Antennas Propag.