| Modern wireless communication is gradually moving towards a new journey from the Internet of Everything to the Intelligent Connection of Everything.Fresh applications and new tasks,for example,sensing and interconnection,emerge in an endless stream,which show unlimited growth in the requirements of communication capacity and com-munication rate.The millimeter-wave（mm Wave）and terahertz（THz）technologies con-form to the above trends and have become one of the indispensable roles in the future wireless system.The mm Wave and THz band have advantages of abundant spectrum re-sources and larger absolute bandwidth which can eliminate the spectrum congestion and the limit of both bandwidth and rate in the microwave band.On the other hand,because of high spatial resolution and low photon energy in the THz band,THz technologies are widely applied in medical imaging,radar detection,etc.As one of the key components in the wireless systems,the mm Wave and THz antennas have received tremendous attention.The mm Wave and THz bands have natural broadband merit,but the limited device size associated with the short wavelength characteristics leads to the severe challenges in both antenna design and manufacture.Because of the increasingly large atmospheric at-tenuation and path loss in this extremely high frequency（EHF）band,the related antennas are required to have high gain and high efficiency.The high-gain array antenna can en-hance the working range of the wireless system,but the narrower beamwidth limits the system coverage.Thus,the research of the mm Wave and THz array antenna still faces extensive needs and challenges.Considering the above perspectives,especially the mm Wave and THz antenna design,the advanced microelectromechanical system（MEMS）micromachining technology is employed in this dissertation,in particular to deep reactive ion etching（DRIE）process.This fabrication technology has unique advantages of single-layer high-precision etching and multilayer three-dimensional stacking.For the demand-ing application of the future wireless communication and detection imaging,this disser-tation focuses on the efficiency improvement,bandwidth improvement,wideband decou-pling and beam steering of the mm Wave and terahertz array antennas based on the MEMS-DRIE micromachining technology.The main works and achievements are sum-marized as follows:For the radiation efficiency decrease of the W-band thick slot caused by the MEMS-DRIE micromachining technology,the thick slot’s radiation characteristics are analyzed and an efficiency improvement method of loading the TEM stepped cavity is proposed.The effective radiation aperture of the antenna can be enlarged and the radiation gain and efficiency can be enhanced by 1.5 d B and 8%.Then,for the difficulty of the pattern shap-ing in the mm Wave array antennas,the array implementation method is proposed which combines the unequal corporate feeding network and the waveguide thick slot array an-tenna.Finally,the W-band micro-waveguide slot array antenna with two-dimensional low sidelobe and high efficiency is achieved.The impedance bandwidth is 91.85～96.42 GHz and both E-and H-plane sidelobe levels are below-19 d B.Besides,the high radiation efficiency of better than 80%is achieved within the frequency range of 92.30～96.30 GHz.For the contradictions among the series-fed topology,the radiation gain and the op-erating bandwidth in the large-scale array antenna,wideband array design method is pro-posed which is composed of broadband feeding network and broadband subarray antenna.Multistage impedance matching strategy with TM120-mode cavity is proposed in the broadband subarray design and the multiple resonance method loading the pins in the waveguide sidewall is employed to improve the bandwidth of the corporate feeding net-work.Finally,a D-band 16×16 wideband high-gain high-efficiency array antenna is pro-posed based on the MEMS-DRIE micromachining technology.Thanks to the fully en-closed air-filled structure,the radiation leakage and the dielectric loss is avoided and the radiation efficiency is improved.Both impedance bandwidth and 1-d B gain bandwidth of more than 20%are achieved in the proposed large-scale D-band array antenna.The meas-ured gain and the radiation efficiency are better than 31.17 d Bi and 62.10%,respectively.For the restricted antenna aperture antenna and wide bandwidth requirement of mm W short-range high-speed wireless communication system,the array layout is ana-lyzed and a W-band 8×8 wideband array antenna with unequal corporate feeding network is proposed.The two identical arrays are arranged along the array E-plane and integrated by the the MEMS-DRIE micromachining technology to construct the transmitting and receiving antenna subsystem.In this scenario,there exists strong TM-mode surface wave on the common ground plane which leads to the coupling between the transmitting-re-ceiving antennas.To solve this wideband decoupling problem,the transverse resonant condition,the excitation and suppression methods of the TM-mode surface wave are an-alyzed.The TEM-mode wave excitation method is proposed and the surface impedance analysis model is established.Then,a“quasi-two-dimensional”triangular-grid choke slot array embedded on the common ground plane is proposed and its wideband merits can be verified by the proposed analysis model.Despite the extremely edge distance of two closely spaced antennas,the transmitting-receiving coupling can be decreased by 2～20d B covering a range of 88～100 GHz and the isolation can be enhanced whith the whole operating bandwidth of the proposed wideband transmitting and receiving array antennas.For the contradiction between the antenna gain and the beam coverage in terahertz high-efficiency imaging system,325～400 GHz high-efficiency planar integrated fre-quency scanning array antennas are proposed.Firstly,the feasible THz beam-steering schemes are discussed and a MEMS-DRIE high-efficiency electronically-controlled fre-quency scanning solution is promoted.Secondly,the THz micro-waveguide is studied and two kinds of THz typical structures are demonstrated to examine the fabrication per-formance of the MEMS-DRIE micromachining technology and the THz measurement solution.Then,a one-dimensional frequency scanning scheme based on the parabolic cy-lindrical reflection lens and continuous transverse stub antenna is proposed.Finally,a two-dimensional frequency scanning scheme based on the scalable progressive delay line network and leaky-wave stepped thick slot antenna is proposed.The analytical model is established to denote the relationship between the beam direction and the progressive path difference of the adjacent delay line in the phase-shifting network,and the two-dimen-sional beam-steering performance of 22.7°×60°can be realized. |
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