Tao Qi

Bio: Tao Qi is an academic researcher from Anhui Normal University. The author has contributed to research in topics: Polarization (waves) & Polarization rotator. The author has an hindex of 1, co-authored 5 publications receiving 2 citations.

A Broadband Ultra-Thin Polarization Rotator Using Periodically Loaded Parallel Strip-Lines

Abstract: A polarization rotator based on loaded parallel strip-lines is theoretically and experimentally investigated. The unit cells are short-stub loaded parallel strip-lines. The arrays on the front and back layers are rotated by 90° to each other. By loading the stubs, good coupling between the two layers is obtained. Such a structural rotation along with the loading stubs allow the $y$ -polarized wave to be converted to $x$ -polarized wave through field coupling. A broad transmission bandwidth of 30% (86-116 GHz) by using the proposed structure has been reached. In addition, the PTFE substrate is only 0.25 mm thick, which is less than $0.1\lambda $ at 86 GHz. Such a thickness allows the polarization rotator to be easily mounted on antenna radomes. The fabricated prototype demonstrates good agreement between simulation and measurement results.

Broadband Reflective Polarization Rotator Built on Single Substrate

Abstract: A broadband polarization rotator built on single substrate is presented in this work. The device is designed for operation in the K and Ka bands. A slant array is used to achieve polarization rotation by 90° in a reflective manner. Broadband has been obtained, with the operation frequency range covering 15–45 GHz for 3 dB criteria, which is almost 100% fractional bandwidth. In addition, the insertion loss is less than 0.3 dB over a moderate broad incident angle from 0°–20°. Furthermore, the polarization conversion ratio can be as high as 0.95. By using a bi-static method, the fabricated prototype is measured, and the measured results demonstrate satisfactory agreement with the simulation ones. In comparison with other reflective designs in the literature, this design provides good bandwidth as well as polarization conversion ratio. Miniaturization can be investigated to increase the angular stability.

Single-Substrate Double-Side High Selectivity Frequency Selective Surface

Abstract: Frequency selective surface is a key component in applications such as communication antenna and remote sensing radiometer. One of the core parameters is selectivity, which is usually realized using a multi-layer structure or through a complicated 3D structure. These methods, however, would impose much challenge on alignment or fabrication. This paper proposes a single-substrate and combined-united array to realize a high selectivity frequency selective surface. The unit cell is a combined pattern of cross dipole and square loop to generate double transmission zeroes out of the passband. Both sides of the substrate are printed with the same pattern to enhance the selectivity. Such a structure enables easy fabrication and assembly by avoiding using multi-substrates. A prototype in the Ku-band demonstrates that both sides of the passband show high selectivity.

Reflection type dual-band dual-rotation-direction microwave band linear-circular polarization converter

Abstract: The invention discloses a reflection type dual-band dual-rotation-direction microwave band linear-circular polarization converter. The polarization converter is formed by periodically arranging unit structures. Each unit structure is of a three-layer structure, the lower layer is a whole metal layer, the middle layer is a dielectric layer, and the upper layer is a metal pattern layer composed of asquare metal layer and a chamfered square ring. The reflection type linear-circular polarization converter efficiently converts x (y) polarized waves into right (left) circular polarized waves in a frequency band of 10.6 GHz to 14.0 GHz in two frequency bands, and converts the x (y) polarized waves into left (right) circular polarized waves in a frequency band of 17.8 GHz to 21.1 GHz. The converter is simple in structure and convenient to machine. The reflection type dual-band and dual-rotation linear-circular polarization converter can be applied to the fields of satellite communication, electronic investigation, radio and television and the like.

Theoretical Study of Millimeter Wave Attenuation in Particulate Environment

Abstract: Particulate environment is frequently encountered in the millimeter wave propagation path. The particles usually produce scattering and absorption to the millimeter wave. Unfortunately, these particles usually have different size, ingredients and even a mixture of many elements. This paper presents a preliminary study of the attenuation of particles on millimeter wave transmission. The dielectric property of water sand and ice were also discussed. The study was conducted at 110 GHz and 220 GHz. Calculation was based on the Mie theory. A full wave simulation was also conducted to better understand the attenuation effect.

Broadband Reflective Polarization Rotator Built on Single Substrate

Abstract: A broadband polarization rotator built on single substrate is presented in this work. The device is designed for operation in the K and Ka bands. A slant array is used to achieve polarization rotation by 90° in a reflective manner. Broadband has been obtained, with the operation frequency range covering 15–45 GHz for 3 dB criteria, which is almost 100% fractional bandwidth. In addition, the insertion loss is less than 0.3 dB over a moderate broad incident angle from 0°–20°. Furthermore, the polarization conversion ratio can be as high as 0.95. By using a bi-static method, the fabricated prototype is measured, and the measured results demonstrate satisfactory agreement with the simulation ones. In comparison with other reflective designs in the literature, this design provides good bandwidth as well as polarization conversion ratio. Miniaturization can be investigated to increase the angular stability.

Ultra-Broadband Angular-Stable Reflective Linear to Cross Polarization Converter

Abstract: An ultra-broadband angular-stable reflective linear to cross polarization converter based on metasurface is developed. The unit cell of the converter is formed by a slant end-loaded H-shaped resonator. The slant arrangement is to create polarization conversion. The end-loaded stubs are useful for miniaturization and the slots are responsible for enlarging bandwidth. The simulated results show that the polarization conversion ratio of the proposed design is better than 90% in the range of 9.83–29.37 GHz, corresponding to a relative bandwidth of 99.69%. It is also demonstrated that the mean polarization conversion ratio is larger than 80% even though the incident angle reaches 40° for both x-polarized and y-polarized incidences. To validate the design, a prototype of the proposed structure is fabricated and measured. Satisfactory agreement has been observed between measurement and simulation. Compared with the designs in the literature, the developed converter exhibits good performance of high efficiency, ultra-broadband and angular stability. Potential applications can be expected in polarization-controlled devices, stealth surfaces, antennas, etc.

Design and research of highly selective frequency selective surfaces

Abstract: A Frequency Selective Surface(FSS), constituted by a periodic array of either metal patch unit or periodically arranged aperture unit on a metal screen, can effectively control the transmission and reflection of the incident electromagnetic wave. Based on the design process of FSS, we replace the traditional multi-layer design with a parallel form by using two parallel structures having complementary selectivity behavior. The simulation was carried out at the frequency range of 12GHz∼18GHz.

Dual-band polarization conversions and optical diode based on bilayer T-shaped metamaterial

Abstract: • The work achieved x- to -y / y- to -x conversions at 106 / 163 THzfor +z propagation. • The incident waves are blocked for – z propagation. • The T xy and T yx are increased to 0.74 and 0.75 with the PCR s reach up to nearly 100%. In this work, we propose a dual-band optical diode based on a bilayer T -shaped metamaterial. This optical diode can conveniently convert the x -polarized wave to y -polarized one at about 106 THz and convert the y -polarized to x -polarized wave at around 163 THz when linearly polarized waves impinge on the sample under a forward normal incidence (+z direction). The dual-band polarization conversion ratios can reach up to 99.9 % and 99.6 % at 106 and 163 THz, respectively. In addition, the bi-layer metamaterial works as an optical diode located around the frequencies 106 and 163 THz, i.e. the x - and y -polarized plane waves can pass through the metamaterial in the forward direction, however, they are prevented from backward. The maximum asymmetric transmission parameters are 0.46 and 0.50. At last, both the ratios and bandwidth of dual-band cross-polarization conversion can be conveniently manipulated by the rotation angle θ . This proposed dual-band polarization conversions and optical diode may have promising applications in optical nano-devices, such as optical switches and polarization converters.