Commercial-Printed-Circuitry-Compatible Self-Superhydrophobic Antennas Based on Laser Direct Writing
Antennas are essential devices to build everything connected in the era of information. However, the quality of communications would be degraded with the presence of raindrops on the antenna surface. Additional antiwater radomes may generate radiation loss and dispersive impedance mismatch over a broad frequency range, which is not acceptable for next-generation communication systems integrating multiple bands. Here, we report the first experimental demonstration of self-hydrophobic antennas that cover the bands of 1.7 GHz, 3.5 GHz, and 8.5 GHz through a laser-direct-writing treatment. Experimental results show that the return loss, radiation pattern, and efficiency of self-superhydrophobic antennas can be maintained in the mimicked rainy weather. Furthermore, writing hydrophobic nanostructures on both dielectrics and metals is compatible with commercial printed circuitry techniques widely used in industries. Our technique will augment the laser fabrication technology for specialized electromagnetic devices and serve as a powerful and generalized solution for all-weather wireless communication systems.
Performance Investigation of Flexible UWB Antenna Near Human Body for Wearable Appliances
A very economical and compact size wearable antenna operating over Ultra-Wide Band (UWB) spectrum is investigated in the proposed work. The antenna is modelled on a thin FR-4 (0.2 mm) material that makes it flexible and well-suited for wearable appliances. The radiating patch structure is the combination of one square and two elliptical patches rotated at 45˚ and fed with a Coplanar Waveguide (CPW) to achieve a wide impedance bandwidth. The complete radiating structure looks like a flower shape, and it has a partial ground to support the radiation from the antenna over the complete UWB. The flexibility of the proposed structure is investigated by bending it along xz and yz planes using cylindrical shape foam. The peak Specific Absorption Rate (SAR) is demonstrated for 1 g and 10 g of tissues at different chosen frequencies like 3.7, 8.4, and 11.2 GHz using a three-layer phantom model. The presented antenna performance analysis and compact size confirm that it is a good candidate for wearable applications.
4-Port MIMO Antenna for Sub-1 GHz
, and Sub-6 GHz
5G New Radio Applications
A 4-port planar multiple-input multiple-output (MIMO) antenna system design is proposed. The antenna elements are modified meandered wideband antennas which cover frequencies from 674 MHz to 1 GHz, 1.9 GHz to 2.1 GHz, 3.175 GHz to 3.476 GHz, 4.529 GHz to 4.761 GHz and 5.254 to 5.513 GHz for long term evolution (LTE), Internet of Things (IoT), and sub-6 GHz applications and thus can be used for robotic navigation, logistics, healthcare, tracking, transportation etc. Due to very small envelope correlation coefficient (ECC) between the ports (< 0.5), the MIMO configuration can be efficiently implemented which helps in increasing the data rates. It is very compact in size and thus can be used for portable handheld devices. Since there is the problem of current localization due to common ground, the future work aims at minimizing coupling and improving the impedance matching using novel decoupling networks. These MIMO antennas are connected to a common slotted ground plane. Antenna simulation has been done using Computer Simulation Technology (CST) Microwave Studio Suite simulator. A low cost FR-4 substrate with dimensions 65 mm × 90 mm × 1.6 mm has been used for antenna fabrication, and experimental results are obtained using an anechoic chamber and a vector network analyser. ECC and realized gain of the antenna are also obtained experimentally and are almost similar to the simulated results.
Investigation on Vibration of Amorphous Alloy Transformer Core
Amorphous alloy transformers (AMDT) have become the mainstream of energy-saving and environmentally friendly distribution transformers, but the problem of environmental pollution caused by their noise has become more prominent. The high magnetostriction of amorphous alloy strip and its sensitivity to stress are the main reasons for the vibration of AMDT core. Accurate calculation of the overall core vibration of transformers is the key issues in transformer noise research. This paper studies the vibration of amorphous alloy transformers under operating conditions, and establishes a three-dimensional magnetic-mechanical coupling model considering the magnetostrictive effect of the power transformer core, and the magnetic field distribution and core vibration displacement of the dry-type transformer under no-load conditions are calculated by finite element method. Combined with experiments, the mechanism of vibration generation of amorphous alloy transformer core is studied, and an iron core vibration prediction calculation based on electromagnetic field coupling analysis is proposed. The research results not only have important academic value for exploring the vibration mechanism and noise suppression mechanism of amorphous alloy transformers, but also have important significance for ensuring their efficient operation.
Design of Three-Mode Filtering Power Divider for Ship Anti-Signal Interference
This paper presents a novel microstrip three-mode filtering power divider (FPD) with high frequency selectivity and high isolation, which integrates only a single resonator and a resistor to realize the dual functions of the power division and filtering. In order to further improve its frequency selectivity and obtain wide upper stop band, three open stubs are loaded into the input and output ports of the filter power divider. The measured and simulated results show that the range of S11 < -10 dB is 1.86~2.1 GHz; the relative bandwidth of 3 dB is 17.9%; the in-band isolation is higher than 26 dB; and it has a relatively simple topology.