Omnidirectional Circularly Polarized Antenna with High Gain in Wide Bandwidth

A novel omnidirectional circularly polarized (CP) slot array antenna with high gain is proposed, which is based on the coaxial cylinder structure, and the orthogonal slots radiated the circular polarization wave around the cylinder. Further, the improved dual circularly polarized (CP) omnidirectional antenna based on slot array in coaxial cylinder structure is presented too, and two ports are assigned in its two side as left hand circularly polarized (LHCP) port and right hand circularly polarized (RHCP) port, respectively. The simulation and experiment results show their novelty and good performance of omnidirectional circular polarization with about 5 dBi gain in 5.2–5.9 GHz

Dual CP Polarization Diversity and Space Diversity Antennas Enabled by a Compact T-Shaped Feed Structure

A compact T-shaped feed structure (IFS) is reported that enables the realization of two types of diversity antennas: a polarization diversity antenna (PDA) and a spatial diversity antenna (SDA). Both systems have a high potential for mobile wireless communication applications. The IFS includes four ports and two independent coaxial channels with effective isolation between them all. The PDA is a dual CP omnidirectional antenna. Its optimized prototype achieves measured impedance bandwidths of 16.4% and 15.28% in its LHCP and RHCP states, respectively, and realized gains in both between 4.8 and 6.46 dBic. The inner thin coaxial cable (ITCC) of the TFS directly drives its LHCP subsystem, facilitating its improved omnidirectional performance. This ITCC is also used to directly feed the SDA's low-profile directional planar equiangular spiral antenna and its side port drives its omnidirectional RHCP antenna. Good hemispherical coverage is realized with a measured common impedance bandwidth larger than 14.35% with more than 40-dB isolation between its two ports. The corresponding measured realized gain of the SDA is between 4 and 7.8 dBic. The measured results for both optimized prototypes confirm their simulated performance characteristics.National Natural Science Foundation [61571289, 61571298, 61701303]; Natural Science Foundation of Shanghai [17ZR1414300]; Shanghai Pujiang Program [17PJ1404100]Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Uniconazole and Adaptability of Transplantations by Enhancing the Competition Tolerance in a High Sowing Density of Rapeseed Blanket Seedlings

Having nursery rapeseed (Brassica napus L.) seedlings at a high density in a tray is an indispensable step to realizing mechanized transplanting for rapeseed. The reduction in seedling quality caused by high sowing density is one of the key factors affecting transplanting quality and yield. Uniconazole has been considered as a potential plant growth regulator to improve plant growth under diverse unfavorable circumstances. In two sowing densities (400 and 800 seeds per tray), an experiment was carried out between 2021 and 2022 to investigate the effects of uniconazole seed-coating treatments on pre-transplant and post-transplant seedling characteristics. The results demonstrate that uniconazole treatment can effectively reduce the high-density-induced reduction in seedling dry matter and leaf area, stem thinness, and stem and petiole overgrowth. Further evidence that uniconazole can improve seedling quality, enhance yield, and lessen yield loss due to high-density sowing was provided by yield at maturity. However, because of the uncontrolled growth during the late stage in the tray, the relative growth rate of seedlings after transplant in the transplant shock stage revealed that lower doses of uniconazole treatment have a negative effect on the seedling recovery. The results of principal coordinate analysis and partial correlation analysis proved that the yield and net assimilation rate were related to the improvement of seedling high-density tolerance by uniconazole treatment. Consequently, 500–750 mg L−1 uniconazole coating per 100 g of seeds in 5 mL is recommended by this study, considering the potential risk of seedling emergence and growth caused by an overdose of uniconazole treatment

A T-shaped feed structure to enhance the performance of a polarization diversity antenna

© 2017 IEEE. In this paper, a T-shaped feed structure is presented that enhances the performance of a polarization diversity antenna. It is a four-port network that consists of two input ports and two output ports. The -10 dB relative impedance bandwidth is 6.64 GHz from 2.31GHz to 8.95 GHz, i.e., 117.9%; and the isolation is at least 29.7 dB within the same band. Furthermore, the insertion loss is less than 0.5 dB in that band between 2.33GHz to 8.93 GHz

Truncated Circular Cone Slot Antenna Array That Radiates a Circularly Polarized Conical Beam

© 2017 IEEE. A truncated circular cone slot array antenna that radiates a circularly polarized (CP) conical beam is presented. The direction into which the conical beam radiates depends mainly on the tilt angle of the outer conductor as well as the proper arrangement of the positions of its two slot arrays. The CP property is realized by introducing quasi-perpendicular slots that are cut into the outer conductor of a truncated circular cone. To illustrate the performance characteristics of this CP conical beam antenna, the tilt angle is set to 45° and the beam angle is pointed at 45° from boresight within the operating band. A prototype was fabricated and tested. The measured results demonstrate that its-10 dB impedance bandwidth ($\vert S-{{11}}{\rm{\vert \,< \,-10}}$ dB) is 720 MHz, from 5.05 to 5.77 GHz; and its 3 dB axial-ratio (AR) bandwidth is 500 MHz, from 5.5 to 6.0 GHz. Its realized gain over this AR bandwidth ranges from 4.84 to 5.8 dB. The designed beam direction can be easily changed to meet specific application requirements. Moreover, it can be readily reconfigured to be a conformal antenna mounted on the top of a high-speed mobile platform