Design of Wideband Dual-Circularly Polarized Endfire Antenna Array on Gap Waveguide

A wideband dual-circularly polarized (CP) linear antenna array is presented in this paper. Firstly, a dual-CP endfire antenna based on septum polarizer is designed as the element for the array. Secondly, the feeding network is realized by ridge gap waveguide. Then a 1 78 linear antenna array is built up by the elements. The proposed array antenna achieves wide impedance bandwidth of 44.6% with the reflection coefficient below -10 dB, the isolation between ports greater than 15 dB, and a wide 3-dB axial ratio (AR) bandwidth of 46.2%

A Compact Gap-Waveguide Dual-Polarized Ka-Band Feed for 50dBi Reflector Antennas With Tracking Function

A dual-polarized Ka-band feed based on gap waveguide (GW) technology for an ultra-high-gain reflector antenna is presented. The feed provides SUM-beams for data transfer and DIFF-beams for tracking. The whole reflector antenna is composed of the feed and a dual-reflector Cassegraine antenna. The feed has been prototyped, and the measured reflection coefficients for the horizontally and the vertically polarized SUM-beam ports are below -10 dB and -8 dB over 30.8-38 GHz, respectively. The measured feed radiation patterns agree well with the simulated ones. The dual-reflector Cassegraine antenna has been designed and simulated by using GRASP with the simulated far-field function of the proposed feed, showing that the reflector antenna achieves SUM-beam gains above 50 dBi and the null depth of the DIFF-beams are more than 30 dB below the maximum of SUM-beams

Optimal Designs of Wound Field Switched Flux Machines with Different DC Windings Configurations

Wound field switched flux (WFSF) machines exhibits characteristics of the simple robust rotor, flexible flux-adjustable capability, and no risk of demagnetization. However, they suffer from a poor torque density compared with permanent magnet machines due to the saturation. Therefore, in this paper, two WFSF machines with single- and double-layer DC windings, respectively, are optimized for the maximum torque. The end-winding (EW) lengths differ in these two machines, which can affect the optimal design. Design parameters including the DC to armature winding copper loss ratio, slot area ratio and split ratio are optimized when two machines have the same copper loss and overall sizes. In addition, the influence of the flux density ratio, total copper loss, air-gap length and aspect ratio on the optimal split ratio is investigated using the finite element method and results are explained through the analytical model accounting for the saturation. It is discovered that the EWs have no effect on the optimal copper loss ratio, which is unity. In terms of the slot area ratio, the machine with single-layer DC windings prefers smaller DC slot areas than armature slot areas. In the WFSF machine with longer EWs, the optimal split ratio becomes smaller. Moreover, compared with other parameters, the flux density ratio can significantly affect the optimal split ratio

An E-band Reconfigurable Phase Shifter Based on Gap Waveguide

A compact low-loss reconfigurable phase shifter based on gap waveguide (GW) is proposed. The phase shifter is realized by controlling the different lengths of the transmission line. A movable metal block is placed on the transmission line, and different phase shifts can be obtained through different moving distances to realize reconfiguration. The use of GW technology not only enables the design to achieve low-cost manufacturing and simple implementation, but also eliminates the resonance caused by the gap. The simulation S-parameters show that the impedance matching bandwidth with reflection coefficients below-15 dB is 19.1%, covering 71-86 GHz, and the maximum phase shift of 180\ub0 can be achieved

Hollow Fiber Membrane for Organic Solvent Nanofiltration: A Mini Review

Organic solvents take up 80% of the total chemicals used in pharmaceutical and related industries, while their reuse rate is less than 50%. Traditional solvent treatment methods such as distillation and evaporation have many disadvantages such as high cost, environmental unfriendliness, and difficulty in recovering heat-sensitive, high-value molecules. Organic solvent nanofiltration (OSN) has been a prevalent research topic for the separation and purification of organic solvent systems since the beginning of this century with the benefits of no-phase change, high operational flexibility, low cost, as well as environmental friendliness. Especially, hollow fiber (HF) OSN membranes have gained a lot of attention due to their high packing density and easy scale-up as compared with flat-sheet OSN membranes. This paper critically reviewed the recent research progress in the preparation of HF OSN membranes with high performance, including different materials, preparation methods, and modification treatments. This paper also predicts the future direction of HF OSN membrane development

Low-Cost Ball-Pen Gap Waveguide With Nearly Zero Friction for Sliding Movements

This letter presents a novel easy-to-manufacture ball-pen gap waveguide (GW) by utilizing commercial low-cost ball pens to have mechanical reconfigurability. The proposed ball-pen GW consists of a perforated bottom metal plate with ball pens\u27 tips inserted and a flat top plate. Compared with the other noncontact GWs with bed-of-pins structures obtained by milling, the realization of the new ball-pen GW requires only drilling holes on the bottom plate for inserting ball-pen tips to obtain the electromagnetic bandgap property, making it low cost. The more important advantage of the ball-pen GW is to make use of the balls of the ball-pen tips to realize smooth low-friction sliding movements for the mechanical reconfiguration. For the sake of verification, a double 90 degrees bend of the ball-pen GW has been designed, manufactured, and measured. Both simulated and measured results demonstrate its excellent transmission performance and the movable property

Pattern Distributed Pins in Half-mode Groove Gap Waveguide for Stable Performance and Low Cost

In this paper, a new concept of pattern distributed pin structure is proposed to improve the stability of the phase performance when there is a misalignment in a half-mode groove gap waveguide (HM-GGW) and therefore reduce the manufacture cost. To demonstrate the advantages of the pattern distributed pin structure, a non-collinear pin pattern and a rotated pin pattern are proposed and applied to a straight HM- GGW and a 90-deg bend HM-GGW. The dispersion diagram and simulation results show that the pattern distributed pin structure has a similar stop-band characteristics as the standard pin structure with much less sensitivity to misalignments between the upper pins and the lower wave-guiding structure. By applying a proper pattern distributed pin structure, a larger flexibility is obtained in design of GW devices and the manufacture cost can be reduced significantly

Design of a Low Sidelobe Monopulse Array Antenna with Hybrid Feeding Structure

A low sidelobe monopulse array antenna with hybrid feeding structure is proposed. The array consists of four subarrays which employ 6 7 8 microstrip patch elements on the top layer. The feed network, which is hybrid feeding structure, is composed of 1-to-48 microstrip power dividers on the top layer, microstrip to groove gap waveguide transitions and a gap waveguide-based monopulse comparator. The microstrip unequal power dividers are compact to achieve unequal amplitude distribution. And the monopulse comparator based on groove gap waveguide has low insertion loss. Hence, the array antenna achieves low sidelobe and high efficiency. The array antenna is designed with size of 400 7 320 mm2. The simulated VSWR is less than 1.5 from 10.52 - 10.68 GHz, the simulated gain is 28.7 dBi at 10.6 GHz and the sidelobe level is less than -19 dB. The null depth in the difference pattern is less than -35 dB

Displacement and Stress Characteristics of Tunnel Foundation in Collapsible Loess Ground Reinforced by Jet Grouting Columns

Collapsible loess tunnel foundation reinforcement is a new challenge in the construction process of tunnel engineering. According to the field displacement and stress monitoring of the Fujiayao loess tunnel, this paper investigates the reinforcing effect of a high-pressure jet grouting pile on a collapsible loess tunnel foundation in the deep large-span tunnel. The field monitoring method was employed to address the performance of tunnel foundation settlement, additional stress, earth pressure, rock pressure, etc. The results indicate that the stress on the pile tops and the earth pressure between piles increase gradually over time in two stages: stress increases rapidly in the first 45 days and, after this period, stress tends to gradually stabilize. Further, stress increases uniformly with the distance from the centerline of the tunnel, and the rock pressure of the tunnel sidewalls tends to be stable within two months of being constructed. Additional stress on the tunnel foundation increases linearly with time, and it is uniformly distributed in the vertical and horizontal directions of the tunnel section. Settlement of the tunnel foundation also gradually increases with time, and it tends to be stable at 50 days from the time of construction. Additionally, the settlements of different monitoring points are similar at the same depth. The research results will further improve the theoretical knowledge of tunnel bottom reinforcement in the loess tunnel, which not only can effectively guide the design and construction of the loess tunnel and reduce disease treatment cost but also can provide the necessary basic research data and scientific theoretical basis for revision of the corresponding specifications of highway tunnels and railway tunnels

Wideband High-Gain Circularly Polarized Antenna Array on Gap Waveguide for 5G applications

A wideband circularly polarized (CP) antenna array based on gap waveguide (GW) is presented in this paper. Firstly, a CP antenna based on septum polarizer is designed as the element for the array. Secondly, the feeding network is composed of T-junctions and realized by ridge gap waveguide (RGW). Then a 16 7 16 antenna array is built up by the elements. The novelty of this antenna is the combination of planar array and septum polarizer based on GW technology to achieve circularly polarization, high gain and high efficiency in wide bandwidth. The proposed array antenna achieves wide impedance bandwidth of 34.5% with the reflection coefficient below -10 dB, and a wide 3-dB axial ratio (AR) bandwidth of 26.5%. The simulated gain is higher than 32 dBic from 24.5 to 32.0 GHz, and the antenna efficiency is larger than 90%