A rectangular metallic leaky waveguide loaded with liquid crystals (LC) and operating in its fundamental TE mode at 1 THz is proposed to mitigate the well-known trade-off between directivity and ...tunable angular range of dynamic beamscanning antennas. The radiating aperture consists of a partially reflecting surface (PRS) realized through a one-dimensional array of longitudinal slots etched on one of the metallic walls of the waveguide to efficiently couple with the propagating TE leaky mode. The antenna performance is evaluated by defining suitable figures of merit that take into account the beamscanning feature and the gain peak. These figures of merit are evaluated for different combinations of the antenna design parameters. After optimization, a tunable angular range of about 28° is reached, while maintaining a gain of around 7 dBi. A leaky-wave analysis of a simplified model of the structure allows to design the antenna without resorting to computationally expensive optimization processes. More rigorous models are then considered to accurately analyze the LC dynamics and the radiating properties of PRS. The three-dimensional structure is finally validated through full-wave simulations, showing a remarkable agreement with the theoretical predictions obtained with the simplified model.
An original liquid crystal (LC)-based substrate integrated waveguide (SIW) leaky-wave antenna is proposed. Inside the SIW, there is an embedded stripline sandwiched between an LC pool and another ...dielectric slab. The antenna couples the guided quasi-TEM mode into free space through a periodic set of complementary electric inductive-capacitive (cELC) resonators. Simulation results show that the antenna performs fixed-frequency continuous beam steering of 52° from backward −28° to forward 24° at 25.85 GHz. This relatively wide beam scan angle is achieved by tuning the LC permittivity through an applied quasi-DC bias voltage to the stripline. Simulation results show that the antenna has high realized gain through the entire scanning range (less than 1 dB degradation), relatively wide bandwidth, and good tolerance to frequency drift and fabrication errors.
An original liquid crystal (LC)-based substrate integrated waveguide (SIW) leaky-wave antenna (LWA) is proposed. Inside the SIW, there is an embedded strip line sandwiched between an LC pool and ...another dielectric slab. The antenna couples the guided quasi-TEM mode into free space through a periodic set of complementary electric inductive-capacitive (cELC) resonators. Simulation results show that the antenna performs fixed-frequency continuous beam steering of 52◦ from backward -28◦ to forward 24◦ at 25.85 GHz. This relatively wide beam scan angle is achieved by tuning the LC permittivity through an applied quasi-DC bias voltage to the strip line. Simulation results show that the antenna has high realized gain through the entire scanning range (less than 1 dB degradation), relatively wide bandwidth, and good tolerance to frequency drift and fabrication errors.We also present a reconfigurable one dimensional LWA in the terahertz region. The proposed LWA can steer its beam at a fixed operational frequency using LC. It consists of a rectangular waveguide filled with three layers of dielectric: an LC layer sandwiched between two spacers. The dominant TE10 mode leaks into the free space through a partially reflecting surface (PRS). Using numerical analysis, we optimized the PRS reactance and the LC ratio for maximum gain and beam steering angle and confirmed the results by full-wave simulation.
We review machine learning and its applications in a wide range of electromagnetic problems, including radar, communication, imaging and sensing. We extensively discuss some recent progress in ...development and use of intelligent algorithms for antenna design, synthesis, and characterization. We also provide some perspectives for future research directions in this emerging field of study.
A liquid crystal (LC)-based leaky wave antenna (LWA) capable of wide beam steering is proposed and numerically studied. The wide-angle beam-scanning (56°) is obtained at 13.6 GHz by biasing the LC ...with a simple uniform bias mechanism. The unique advantages of this LWA are high realized gain, low side lobes, simple mechanism for beam steering, frequency-fixed reconfiguration, non-complex design with much reduced bias lines and control circuits, low cost, low profile, compactness, and mature of LC technology.
A wide beam steering leaky-wave antenna (LWA) based on a liquid crystal (LC) phasing structure and metamaterial apertures is presented and simulated. The antenna continuously steers its beam from ...−48° to +44° at the fixed frequency of 13.6 GHz (Ku band) by biasing the embedded LC. As a result, the beam steering angle is 64% wider than the state-of-the-art LC-based LWAs in the Ku band to the best of our knowledge. This improvement is obtained by the design of a meander-line phasing structure as revealed from an analysis based on the array factor. The antenna design also offers compactness, lightweight, low-cost, simple beam steering mechanism, and design with much-reduced bias lines and control circuits, low bias power consumption, good power handling, good realized gain, and low sidelobes.
We present a reconfigurable one dimensional leaky wave antenna (LWA) in the terahertz region. The proposed LWA can steer its beam at a fixed operational frequency using liquid crystals (LC). It ...consists of a rectangular waveguide filled with three layers of dielectric: an LC layer sandwiched between two spacers. The dominant TE 10 mode leaks into the free space through a partially reflecting surface (PRS). Using numerical analysis, we optimized the PRS reactance for maximum gain and beam steering angle and confirmed the results by full-wave simulation.
A leaky wave antenna (LWA) based on a substrate integrated embedded metasurface (SIMS) is proposed and simulated. The SIMS is obtained by blind vias in the middle of a substrate integrated waveguide ...(SIW) and filling the gap beneath the blind vias with liquid crystals (LC). Different capacitive impedances are obtained by biasing the LC, which impacts the propagation characteristics of the LWA and thus changes its beam angle. A 30° beam steering at 52.5 GHz is achieved according to simulations of the proposed SIMS-LWA. The unique advantages of this LWA include high realized gain, simple mechanism for beam steering, frequency-fixed reconfiguration, non-complex design with much reduced bias lines and control circuits, low cost, low profile, compactness, and mature of LC technology, to name a few.
The buckling behavior of perfect and defective double-walled carbon nanotubes (DWCNTs) under axial compressive, torsional and bending loadings is investigated using a structural mechanics model. The ...effects of van der Waals (vdW) forces are further modeled using a nonlinear spring element.
Critical buckling loads, critical buckling moments and the effects of vacancy defects were studied for armchair nanotubes with various aspect ratios. The results show that vacancy defects greatly reduce the critical buckling load of DWCNTs. The density of defects plays an important role in buckling of DWCNTs. The results of this numerical model are in good agreement with their comparable existing works.
