Study Of High-efficiency And High-gain Planar Reflectarray And Transmitarray For Millimeter Wave And Terahertz Applications

High-gain antennas are indispensably significant components for modern wireless communication systems,which have been widely employed in radar detection,radio astronomy,high-resolution imaging and high-speed wireless communication systems.Due to the advantages of simple feeding structures,low profile and low cost,spatial-fed high-gain antennas have become an important research branch in the field of antenna since the end of last century.According to the beam direction,plannar spatial-fed high-gain antennas can be divided into reflectarray antennas and transmitarray antennas.However,there still exists some challenges to realize wideband plannar spatial-fed high-gain antennas at high frequency band,especially at terahertz region.Therefore,the research on plannar spatial-fed high-gain antennas at millimeter wave and terahertz frequency band has important theoretical and practical significance.This dissertation focuses on the topic of "Study of High-Efficiency and High-Gain Planar Reflectarray and Transmitarray Antennas for Millimeter Wave and Terahertz Applications" and the main research works are as follows:(1)A 140-GHz hign-gain LTCC-integrated transmitarray antenna is proposed.First,a compact transmitarray unit cell with wideband performance is proposed based on the reciving/transmitting principle,which is rectangular and composed of two reciving/transmitting antenna elements and a phase delay structure.In this design,a pair of magnetoelectric dipole antennas are employed as as the receive/transmit elements,and the aperture-coupled SIW transmission line between the receive/transmit elements are used for phase adjustment.The phase shift is realized by changing the length of the SIW transmission line,and a 360° phase coverage is obtained by the proposed phasing element.Second,a transmitarray antenna including 1280 unit cells is designed and fabricated based on the ray tracing method.The measured results show that the maximum gain of the antenna is 33.45 d Bi at 150 GHz with the aperture efficiency of 44.03%,and the measured 3 d B gain bandwidth is 124–158 GHz(24.29%).Finally,the gain difference between the simulation and measured results within frequency band of interest is also analyzed.The relevant work has been published in IEEE Transactions on Antennas and Propagation.(2)Two designs of Q-band wideband reflectarray antennas based on PCB technology are proposed.The first one is based on the reflective phase delay lines.The phase-shifting unit cell is made up of two parts.A SIW cavity-backed E-shaped patch antenna is employed as the radiation element,and the phase adjustment relys on the open SICL with variable length.Compared with SIW transmission lines,the SICL has the advantage of low dispersion and low loss.The slopes of phase delay are similar within a wide frequency band,which indicates the proposed unit cell is capable to support a wide operating frequency band.The measured peak gain is 32.83 d Bi at 43 GHz,and the 1 d B gain bandwidth is 12.94%(39.5–45GHz).In addition,a Q-band single-layered reflectarray antenna based on multi-resonant elements is also proposed in this chapter.The reflective unit cell is composed of a square ring and a Jerusalem cross structure,which can achieve a 360° phase coverage.The measured results show that the proposed reflectarray antenna has good good radiation performance with maximum gain of 28.2 d Bi.Relevant works have been published in IEEE Antennas and Wireless Propagation Letters and NCMMW 2017.(3)A reflectarray antenna and a folded reflectarray antenna working at THz region are proposed based on the lithography technology in this chapter.First,a THz-TDS system is used to extract the dielectric properties of quartz and Taconic TLY-5 substrates,including relative permittivity and loss tangent.A G-band multi-resonant reflective element is designed,and a prototype of the offset-fed reflectarray antenna with a 43.2-mm circular aperture is fabricated for verification.The measured peak gain at 178 GHz is 33.2 d Bi with aperture efficiency of 32.5%.To reduce the profile of the reflectarray antenna,a 400-GHz high-gain folded reflectarray antenna is proposed.A dual-polarized unit cell,made up of Jerusalem cross and an open square ring,is proposed to compensate the spatial phase difference and implement the polarization rotation.The folded reflectarray antenna is fabricated,assembled and tested.The measured gain at 400 GHz is 33.66 d Bi with the aperture efficiency of33.65%.Relevant works have been published in IEEE Antennas and Wireless Propagation Letters and IEEE Transactions on Terahertz Science and Technology.(4)Two Airy beam generators working at millimeter wave and terahertz frequency band are proposed.First,a single-layered unit cell is proposed to control the magnitude and phase of the cross-polarized wave at the same time.The 1-D Airy waves can be launched at millimeter wave band by fitting the amplitude and phase distribution of Airy function.However,this generation method based on single-layered transmission metasurface suffers from low efficiency.Second,a Fourier-transform-type 2-D Airy beam generator is proposed using a folded reflectarray structure,which can reduce the profile of the system and improve the generating efficiency.All the phase modulation can be implemented by a single-layered metasurface,and the lens phase distribution to implement the Fourier transform is loaded onto the proposed metasurface together with the cubic phase distribution.The measured results show that the proposed folded reflective structure can launch 2-D Airy beams,and both the unique transverse acceleration behavior and self-reconstruction property are verified through experiment at 400 GHz band.Relevant works have been published in IEEE Asia-Pacific Microwave Conference 2018 and IEEE Transactions on Antennas and Propagation.(5)A planar circularly polarized retrodirective reflector is proposed.First,based on the principle of polarization isolation,circularly polarized wave can reduce the reflection interference effectively.Second,a wideband circularly polarized antenna element is proposed.The antenna elements are connected using SICL structure with low dispersion and low loss.The phase response can be controlled by the length of the transmission line.Finally,a K-band passive 1-D retrodirective array,including 16?2 antenna elements,is designed and fabricated.The measured results show that the the circularly polarized retrodirective reflector covers a scan angle of ?30°.The measured bandwidth of the retrodirective property is 24.85-25.45 GHz.The relevant work has been published in IEEE Antennas and Wireless Propagation Letters.