Browsing by Author "Ullah, Naveed"

Now showing 1 - 4 of 4

Metadata only
16-elements helical antenna system integration with a solar cell powered IoT collector
(IEEE, 2019) Ullah, Naveed; Tekin, Ahmet; Electrical & Electronics Engineering; TEKİN, Ahmet; Ullah, Naveed
An 868MHz-915MHz 16-elements helical wire antenna array design with a solar-cell integration is presented. Each element is designed to be omni-directional with the corresponding tuning stubs and ground substrate. This is shared with distributed solar cell array, powering 16- Internet of Things (loT) transceivers operating at multiple Industrial Scientific and Medical (ISM) bands. 370mmx400mm design including the antennas, solar cells, and the tuning stubs can generate 8-watts solar power under direct sun, charging Lithium batteries. 1.6-mm thick planner design with horizontal radiation pattern resulted in average -15dB return loss at 868 MHz without using any external matching elements.
Metadata only
Comments on “A set square design metamaterial absorber for X band applications”
(Taylor & Francis, 2021-05-24) Ur Rahman, S.; Ullah, H.; Cao, Q.; Kabir Khan, M.; Ullah, Naveed; Ullah, Naveed
In a recently published paper, Chetan Barde et al. [Barde C, Choubey A, Sinha R. A set square design metamaterial absorber for X-band applications. J Electromagn Waves Appl. 2019:1–14.] have proposed a wideband metamaterial absorber and have attempted to elaborate reflection theory for the absorptivity. They have claimed a wideband absorption rate due to ignorance of cross-polarization component of the reflected wave. They have erroneously interpreted a linear reflective polarization converter as a wideband absorber.
Metadata only
High gain, low radar cross-section, and left hand circularly polarized antenna array based on metamaterial inspired elements
(Wiley, 2021-05) Rahman, S. U.; Cao, Q. S.; Khan, Z.; Deng, H.; Ullah, Naveed; Ullah, Naveed
In this research work, a wideband metamaterial-inspired circularly polarized antenna array is designed. The designed antenna array has a low radar cross-section (RCS) but high gain. The basic element of the planar array is analyzed as a dual-band electromagnetic absorber. Under normal incidence, the designed basic element has two absorbing peaks at 3.6 and 11.2 GHz. Further, four elements of the 4 x 4 elements array are connected to the feeding network through metallic vias. The feeding network is designed on the bottom layer. The circular polarization is archived by feeding the cross shape metallic resonator at two feed points, in a manner that there is a 90 degrees time phase difference between the fields of two. It is shown that a good axial ratio is obtained over a wideband. This design method simultaneously validates high gain antenna performance and also meets the conditions of low-RCS.
Open Access
Omni-directional wideband antenna array with solar cells
(SciELO - Scientific Electronic Library Online, 2021-03) Ullah, Naveed; Tekin, Ahmet; Electrical & Electronics Engineering; TEKİN, Ahmet; Ullah, Naveed
Distributed sensor networks are becoming more and more widespread due to their substantial benefits to our daily lives. These sensors, in most cases, are distributed in nature and even may require mobility. This, in turn, implies omnidirectional collector units to collect the data from various sensors at arbitrary directions. This work summarizes the performance outcomes of various integrated wide-band antenna structures and solar power generation topologies to achieve equal gain in all directions. Purpose of the array in this instance is contrary to enhance the received signal levels in all directions. Low-cost solutions ranging from the planar helical printed circuit board (PCB) designs to vertical wire helical antennas were investigated. An optimum design structure for multiple ISM bands (868 MHz to 915 MHz) was proposed and characterized considering the cost, size, directional coverage and most significantly RF sensitivity and range of the overall design. The final water-resistant solarpowered wideband transceiver front-end has provided range improvement and omnidirectional radiation pattern. The system consists of a 190mm x 190mm low-cost FR4 substrate and a Wilkinson network to combine the power of 8 helical wire antennas sprinkled along with the solar cells. The self-contained, Sun-powered unit resulted in 4.5-dB sensitivity improvement in measurements.