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An approach for improving the gain of the leaky-wave antenna (LWA) is presented in this paper. Embedding cavities in the structure leads to gain improvement. To validate the proposed method, it was implemented on a half-mode substrate integrated waveguide (HMSIW) LWA. The proposed HMSIW LWA was realized on a low temperature co-fired ceramic (LTCC) structure to achieve a compact structure. The key novelty of the proposed antenna is the gain improvement by using embedded cavities without increasing the antenna size. Applying the novel design method results in a measured peak realized gain of 7.6 dBi. Tapering the aperture leads to about 6 dB reduction of sidelobe level (SLL) in the upper hemisphere as well. The impedance matching frequency bandwidth of the antenna ranges from 28.3 to 29 GHz that falls within the 5G mm-wave frequency bands. The length, width, and thickness of the antenna are 40 mm, 16 mm, and 1 mm, respectively. The compactness, medium gain, and low loss of the proposed antenna make it a suitable candidate for 5G wireless devices. A good agreement between the measured and simulated results is observed.

We investigate the effect of passivation contouring, surface roughness, and sidewall etch tapering on the FEM modelling accuracy of mm-wave couplers in CMOS BEOL. It is found that accurate passivation contouring leads to a marginal improvement of 0.15 dB in peak coupling prediction accuracy, but introducing a sidewall taper of 104ᵒ can improve the prediction of peak coupling by up to 0.37 dB. Including surface roughness of 5 % and 10 % of metal thickness did not have a notable improvement on prediction of peak coupling.

We demonstrate a low-loss in-fiber bandpass filter based on a tapered antiresonant hollow-core fiber. The insertion loss measured in its passband at 1060 nm is 1.06 dB.

Optical interconnections are a promising step for-ward to overcome the intrinsic limitations of electrical inter-connections in integrated circuits. In this work, we present a finite element method (FEM) simulation study of a dielectric waveguide etched through the full thickness of a silicon substrate. In particular, it is investigated the effect of the bridge-to-core size ratio on the first two supported modes. Then, the influence of the waveguide sidewalls tapering angle on the three-dimensional beam propagation is studied. Such optical through-silicon waveguide (OTSW), if nonadiabatically tapered can provide effective mode size conversion and favour the coupling of external light sources to photonic integrated circuits.

Next generation accelerators demand sophisticated beam sources to reach ultra-low emittances at large accelerating gradients. Capillary discharge plasmas can address these challenges by improving the energy and quality of laser-plasma accelerated electrons 1 . Significant improvements to the guiding properties of these structures can be achieved through the spatiotemporal manipulation of plasma channel density via laser heating 2 , fill density modulation, and radial tapering. We present 2D simulations of capillary discharge plasmas using FLASH, a publicly-available multi-physics code with specialized support for critical transport processes and magnetohydrodynamic evolution 3 . We demonstrate the application of laser energy deposition to model channel formation for guiding intense laser pulses. We consider parametric variations in heater laser intensity and timing to optimize the matched spot size. Lastly, we examine the control and tapering of density profiles through the tailoring of capillary geometry and gas flow.

Plasmonic crystals exhibit excellent waveguiding and extreme light localizing properties. However, if additionally perforated, their structure assumes vastly enhanced functionality and becomes the basis for e.g. double negative refractive index metamaterials and superabsorbers. In this work we consider 1D plasmonic crystal consisting of alternating metallic and dielectric layers perforated by an array of conical holes tapering off as they penetrate the multilayer. We utilized the finite element method (Comsol multiphysics®) to calculate the response of our proposed structures - electromagnetic field intensity and frequency dispersion of scattering parameters. Utilizing at the same time a multilayer and perforations with a varying cross section simultaneously broadens the useful spectrum and allows for additional plasmonic modes. In addition to an enhanced absorption associated with the plasmonic modes, the functionality of the structure is further increased by allowing spectral selection of dielectric layers with strong light localization. The proposed structure can be used for a multitude of practical applications. They include (but are not limited to) an alternative approach to superabsorber design, the enhancement of the performance of multianalyte biochemical sensors, photo detectors, solar cells and photocatalysts, as well as optical switching.

A study on the dispersion in the values of amplification within a linear phased arrays is presented. In a phase-only array in which the phase distribution is optimized the amplitudes of each radiating element should be the same. Indeed real world amplifiers have a dispersion in their parameters leading to variable amplification factors. In this paper a Monte Carlo statistic analysis on how this variability reflects in the radiation pattern is be analyzed.

In this paper we report the design, fabrication and measurement of a novel 8-core FiFo device using fused tapering method and trench-assisted bridge fiber. The device is constitutive of 8-core fiber, tapered bridge fiber bundle and single-mode fibers. The minimum and maximum insertion loss of the Fi/Fo device are 0.25 dB and 0.98 dB, respectively.

Taylor taper is most commonly used for linear arrays as it was modeled originally for linear arrays. However, it has been used for circular as well as rectangular arrays. In this paper, we show its use for an irregularly shaped array. The array is neither linear nor rectangular and has limited number of elements. Furthermore, a special approach towards the feed network design has been attempted which reduces the power division ratio in the feed network to a significant amount. The simulation results show good side lobe level with good directivity and gain.

To counter sidelobe nonstationary interference, the mismatch between training snapshots and applied data must be solved. Limited by the computational costs, it is impossible to update the weights frequently. To solve this problem, null widening methods based on covariance matrix tapering has attracted many attentions. However, existing methods do not fit the rea12-D plain array. In this paper, a null widening method for plain array based on spatial virtual interference cluster are derived. Besides, the degrees of freedom consumed by the null widening in plain array is preliminarily analyzed, and the upper bound of the degrees of freedom is obtained. The simulation results verify that the proposed method can effectively widen the adaptive null, and the derived degrees of freedom can be viewed as a guidance for the partial adaption system, which will promote its application in engineering.

In this paper, a wide-band distributed model that can approximate the behaviour of square and octagonal inductors, both with and without tapering, is presented. This paper also presents a novel way of accurately modelling the lateral coupling in the substrate. The presented model can be applied to any foundry process, and its validity has been demonstrated using a novel technology, the D01GH GaN process developed by OMMIC, which has a high resistivity substrate. To do so, seventeen inductors have been designed and manufactured. The proposed model has been verified against EM simulations and measurements of the designed inductors. Comparisons show that the model can correctly estimate the behaviour of the inductor, improving the results of the EM simulations for most cases. The root mean square (RMS) error calculated across the samples when estimating the inductance is 0.0565. The RMS error for the quality factor results (2.2727) is also adequate, although there is more deviation when comparing the results with the measurements.

On the basis of intensity modulation, a vibration sensor using a tapered photonic crystal fiber (PCF) is demonstrated. The fiber is a solid-core PCF with a central air hole embedded in the core region. The addition of the air-hole initiates the core/cladding intermodal coupling, and consequently, modulates the output light intensity when the fiber is under external disturbance. The sensing unit is configured by firstly tapering the PCF down to a waist of 72.6 μm, and then splicing its two ends to a single-mode fiber (SMF) and a multi-mode fiber (MMF), respectively. The sensor is then used for measuring a variety of vibrational signals, such as single frequency (in the range of 30~10000 Hz), dual-frequency vibrations, and vibration accelerations (with linear responses from 0.5 to 10 m/s2). In addition, the sensitivity, influenced by varying the length of the sensor head, is also investigated.

Amphibious robots can play important roles in tasks like field exploration and disaster rescue, where robots may need to cope with complex environments including both lands and water. However, the development of the propelling mechanism for amphibious robots can be challenging due to the distinct working conditions, respectively. In this paper, we report an amphibious quadruped that possesses four newly designed passively deformable flipper legs made of spring steel. These strip legs can act as paddles to propel the robot in water and be bent to c shape under the robot's weight on land to thrust the robot forward upon release. Specifically, we focused on the effect of stiffness distribution of these legs on the performance of the amphibious robot. Inspired by pectoral fins of mudskippers, we carefully designed five different tapering profiles for these legs such that they can have variable stiffness along the length direction. Experiments were then conducted under three different environments, grass, sand and water, to find the optimal stiffness distribution of the leg. Based on the evaluation of average forward velocity and Cost of Transport (COT) of the robot, we find that the flipper leg with decreasing stiffness from proximal to distal end yielded faster and more efficient performance, both on land and in water. This points out future direction for further development of the platform.

Antiresonant hollow-core fibers (ARHCFs) have attracted substantial research in the last decade because of their simple cladding structure as compared to conventional photonic crystal fibers, and applications ranging from high-power laser beam delivery, gas photonics to ultra-low loss transmission in mid IR region [1] . We report here CO 2 laser-assisted fusion splicing technique between a slightly tapered single-ring ARHCF (fabricated in house) and a large mode area solid core fiber (SCF-Nufern LMA-GDF-25/250-M) that selectively launches power into the fundamental mode of ARHCF with 90.8% coupling efficiency. The tapering and splicing recipe is optimised to prevent collapsing of capillaries and maintain the delicate microstructure in the ARHCF. Fig. 1 shows the cross-section of the pristine and tapered ARHCF before and after splicing.

In this paper, a dual tapering Vivaldi antenna with impedance bandwidth in the frequency range of 2–15 GHz for UWB requests is introduced. The antenna structure includes an elliptical outer taper and a circular inner taper bounded by a rectangle. The proposed antenna has an average maximum gain of 7.3dBi and group delay changes of less than 0.3ns. Finally, the designed dual tapering antenna has a smooth transfer function.

A sidelobe suppressed, high aperture efficiency X-band Huygens dipole array is reported. The Huygens array consists of four magnetic and four electric dipole radiators. A collinear set of magnetic dipoles (MDs) is formed from a TE 0.5,0 mode open waveguide integrated with phase inverters. The electric dipoles (EDs) are produced by connecting two metallic plates to the aperture of the waveguide, one on each side of it and orthogonal to that vertical wall of the waveguide. The consequent pairs of MDs and EDs are orthogonally oriented and their phase difference is a natural 90°. These dipoles are excited by an electric pin probe inserted into the waveguide at its center through one vertical wall. The overlapped –10-dB impedance and 3-dB realized gain bandwidth is 800 MHz, covering 9.45 to 10.25 GHz. The sidelobe levels of the 1×4 array are significantly reduced to –23.3 dB thanks to the natural tapering of the amplitude distributions of the MDs and EDs from the center of the array to both of its ends. The peak realized gain value is 12 dBi. The aperture efficiency is 74%.

Fractal antenna array generation is depending on never ending pattern design methodologies. Concentric elliptical ring sub-array (CERSA) generator is one of the deterministic geometric design methodologies for the generation of polygon and narrow beam fractal array antennas. This paper presents modified CERSA design methodology for the improved array factor characteristics than the original or unmodified version. This modified version mainly includes insertion of the central antenna element on each sub-array of the considered fractal array and amplitude tapering. Rhombic fractal array antenna generated by CERSA have considered in this work, to demonstrate the proposed modifications. All corresponding results presented in this paper, simulated by the Scilab open and free source programming.

Wind power generation is proportional to the third power of wind speed. The speeds at the blades are further increased by using Wind Lenses. A wind lens turbine can generate 2–5 times, the power of an existing wind turbine for a given rotor diameter and the incoming wind speed. This paper has two parts the first part focusing on a review of wind lens and the second part is focusing on optimizing the wind lens parameters, including length and the tapering angle of the wind lens to get the maximum efficiency for a given wind turbine. A wind lens was simulated inside a controlled volume by using an open source numerical Computer fluid dynamics (CFD) software to get velocities at different parameters and an empirical model was developed using linear factor analysis by using the wind lens simulated inside a controlled volume.

A Distributed Power Amplifier (DPA) with a tapered drain line is presented in this paper. The drain line impedance tapering technique allows to obtain a higher output power and efficiency compared to the conventional approach, whereas a constant drain line impedance avoids impedance changes in the power supply drive signal. The design was implemented using the D01GH/Si technology provided by the foundry OMMIC. The DPA achieves a P sat of 32 dBm and a flat gain over 14 dB in a frequency range that ranges from 1 to 8 GHz. Moreover, this circuit achieves a Power Added Efficiency (PAE) of 50%. Finally, the occupied area of the DPA is 2.2x1.2mm2 excluding pads.

A W-band hybrid-fed mictrostrip patch array for advanced real-time imaging applications has been proposed in the article. It is fed by a novel hybrid feeding network with lower loss compared with the parallel-fed network. The proposed array is composed of 16 series-fed taper microstrip patch subarrays with Chebyshev amplitude tapering. The series-fed subarray is fed symmetrically in the midpoint to achieve non-dispersive patterns at different frequencies. In order to decrease the transmission loss, a hybrid feeding network is de-signed to replace the multi-level parallel one between series-fed subarrays. The tapering distribution is determined by the width of the quarter wave impedance transformer in the hybrid feeding network. Simulation results show that the antenna array achieves an impedance bandwidth of greater than 6 GHz and a gain of greater than 26.8 dBi. The side-lobe level of the pattern at the center frequency is -22.5 dB and -22.4 dB in E-and H- planes, respectively.

A tapered-microfiber sensor near the dispersion turning point (DTP) is theoretically researched and experimentally fabricated by carefully tapering a standard single mode fiber (SMF). With respect to other tapered fiber sensors, the microfiber sensor near DTP has quite high sensitivity, which is verified by the theoretical analysis in this work. The influences of two critical structural parameters, the tapering length and the waist diameter, on the occurrence of DTP are also studied. Furthermore, the preparation technology of this sensor is experimentally explored. As last, the transmission spectrum of the fabricated microfiber DTP sensor is highly consistent with that in theoretical calculation. These results show its potential for humidity sensing and other environmental trace detection.

We report on an etching-based fabrication method for conical core-maintained fiber tapers with adiabatic tapering angles, and discuss its adiabatic mode evolution compared to the conventional pulled fibers over the O-/C-bands. The far-field pattern from the etched fiber shows that the fundamental mode is maintained throughout the tapers.

The performance of adiabatic couplers depends on the width and separation of the constituent waveguide pair. We investigate the influence of these parameters using linear, exponential, and quadratic tapering in the mode-evolution region. A quadratic separation and exponentially varying width provide superior performance for a constrained length.

Going from more conventional aircrafts to eVTOL (electric Vertical Take Off and Landing), the electrification trends are forcing aircraft manufacturers to work on compact and safe electrical machine solutions. This paper utilizes a 2D approach for an adjustable air gap permanent magnet electrical machine to choose the best motor attributes. Firstly, the 2D model is calibrated using existing experimental measures, then, it is employed to find multiple solutions that accomplish the mechanical flux-weakening. It is demonstrated that the choice of the best combination of the motor tapering and axial displacement can be influenced by the mechanical system configuration and control accuracy.

In this paper, the force ripple and cogging force minimisation of single-sided consequent-pole linear vernier hybrid machines is investigated through the use of the Taguchi method. The study focuses on obtaining robust designs that minimise the force ripple and cogging force through optimal tapering of the translator teeth, the soft ferromagnetic consequent poles and the permanent magnets. It is found that by minimising the force ripple a better overall design solution can be found, effectively minimising both the force ripple and cogging force, while limiting the reduction in average thrust force. The percentage contribution of each parameter is analysed, from which a trend is identified and broad criteria for the taper ratios are defined.

A W-band series-fed microstrip patch array based on an optimization of tapering profile is proposed in the article. The proposed array is composed of 16 series-fed radiating patches. Dimensions of these microstrip patches are optimized to generate an array pattern with low sidelobes. The optimization procedure about the patch width tapering is performed by using the differential evolution (DE) algorithm. The post-optimized model is investigated in a three-dimensional full-wave simulator. Simulation results show that the sidelobe level of the series-fed array is below -23.8 dB. In addition, the voltage standing wave ratio (VSWR) in the operation frequency range 92 ~ 98 GHz is below 1.65.

We are reporting the characteristics of an ammonia gas sensor that has been fabricated by tapering the mid-region of a piece of multimode-fiber (MMF) and then coating it with a silica-gel film as the sensing layer. The sensor response to the fluctuations of ammonia gas concentration in the environment is manifested by the wavelength shift observed in the fiber transmission spectrum. The experiments show that the device sensitivity increases as the diameter of the waist of the tapered region decrease down to a certain size. The highest achieved a sensitivity of 15 pm/ppm belongs to a fiber sensor in which the diameter of the tapered region waist before the silica-gel coating was $4\ \mu \mathrm{m}$ . The response and recovery times of this sensor are 32 s and 19.5 s.

In this paper, the reliability of irregular subarrayed phased array antenna is analyzed. In order to access the performance of this kind of array structure, the failure rate of subarray tiles is simulated. Moreover, the low sidelobe tapering beam pattern degradation case is also proposed. Numerical results are presented to validate the effectiveness.

A method for improving gain in spoof surface plasmon polaritons (SSPPs) antenna including guiding and radiating parts is proposed. This method is based on using a curvy tapering area instead of linear one to matched the antenna to the air. The obtained results show that realized gain can be improved approximately 3 dBi by this method. Furthermore, by using corrugated unit cells and stubs an undesired frequency band can be rejected. Since the antenna works at 27.2-28.2 GHz, it can be used for 5G applications.

An efficient air gap based nano plasmonic coupler deploying GaAs has been proposed here which can be used in between dielectric and plasmonic waveguibde for efficient coupling of EM-wave. The coupling efficiency has been observed numerically in three dimensions. FIT (Finite Integration Technique) based numerical simulation has been used to analyze the performance of the coupler. Simulations have shown that our proposed coupler can provide at best 78% coupling efficiency at optical communication wavelength, 1550 nm. The proposed coupler has fabrication friendly structure due to the use of metal-dielectric-metal (MDM) configuration as the plasmonic waveguide and due to the couplers simple rectangular shape with no tapering or bending. Different dimensions were varied and corresponding performance parameters like transmittance, reflectance, and absorbance were observed to get the most optimized structure that gives the maximum efficiency as a coupler. A broad range in terms of frequency or wavelength can also be obtained around the optical communication wavelength with very good coupling efficiency by the proposed coupling structure.

This work investigates circularly distributed antenna arrays of even and odd characteristic modal superpositions as it applies to a Hardy space. Examples are provided using a family of even (Sinc) and odd (Cosinc) modal tapers of the $L^{2}$ norm. Furthermore, this space has unique properties as it causes the negative spatial Fourier coefficients to vanish. This paper concludes with simulated results of newly defined modes within a Hardy space utilizing Sinc and Cosinc modes with and without amplitude tapering.

The modified-T shaped antenna for satellite uplink communication has been presented in this paper. The implemented modified-T shaped antenna resonates at 28.85 GHz. The parametric variation has been carried out, and an effect on S 11 is plotted. The antenna provides a gain of 5.97 dB and 13.38% (27. 46 - 31.15) GHz wide impedance bandwidth. The antenna gives the null pattern in the phi = 0° plane with a sidelobe level of -11 dB. The proposed antenna provides good time-domain characteristics as well as sufficient radiation efficiency of more than 92% over the entire band. The front to back ratio (FBR) is more than 10 dB over the entire band. The wideband has been achieved without tapering of the ground plane. The proposed antenna provides good simulation results that satisfy the satellite up-link communication requirements.

International audience; We designed an integrated long period grating based on the horizontal periodic tapering of a silicon nitride channel waveguide. The structure is studied for gas sensing applications, using Styrene AcryloNitrile as sensitive layer. Simulation results from the proposed architecture show a high sensitivity beyond 1700 nm/RIU using a wavelength interrogation method centered at 1550 nm for a 20pm large and 300pm long structure.

Design constraints for a plane wave generating array antenna at mm-wave frequencies are investigated. Focus is on how to realize the power distribution network and the amplitude tapering of the array element excitation in a cost-effective manner. These are key decisions that need to be made for a plane wave generator. In this paper, we specifically look at a few design solutions which are constrained by practically realizable tapering distributions. It is shown that the best tapering distribution, taking into account the design aspects of a realistic distribution network, is different from the best solution for an ideal radiating aperture. We also briefly discuss the impact of the radiating antenna element and show that it has a minor impact on the end performance.

An advanced design, adding a significant first sidelobes level (FSLL) improvement to a previously introduced wide-angular-scanning, linear array prototype with demonstrated scan-loss compensation (SLC) and sidelobes suppression features is discussed. The linear array makes use of in-line subarrays for SLC and an additional amplitude taper in its central, uniform region for lowering the FSLL with as much as $4\mathrm{d}\mathrm{B}$ at $\pm 60^{\mathrm{o}}$ scanning ($13\mathrm{d}\mathrm{B}$ at $\pm 20^{\mathrm{o}}$ scanning). Several Taylor-type amplitudes tapers are compared, the best overall performance improvement being observed for a -18dB prototype taper. The advocated solution is highly suitable to high-sensitivity radars requiring a fast-scanning, fan-beam.

Beamforming using Discrete Fourier Transform (DFT) based codebook is widely studied for millimeter wave (mmWave) communication systems. This design requires only phase-control for each antenna element and is therefore motivated by the possibility of lower complexity hardware. While this DFT-based design works well for single-user transmission, significant inter-beam interference is generated in multi-user multiple-input multiple-output (MU-MIMO) transmission. Recently, beamforming based on amplitude tapering has been demonstrated even for mmWave systems. The non-uniform amplitude in this design allows the possibility of significantly reducing inter-beam interference at the cost of slightly reducing the main lobe gain. Since the amplitude tapering is fixed and designed offline, the additional implementation complexity is not very high. In this paper, we show that Dolph-Chebyshev and Taylor codebook designs can provide significant improvement in performance over DFT-based codebooks in full-dimension MU-MIMO settings. For the MU-MIMO, we also propose a per-user power allocation algorithm for maximizing the sum rate under total power and rate constraints. The results show that the proposed algorithm gives high sum rates compared to equal power allocation among users. The simulations are carried out under the 3GPP full-dimension MIMO channel model.