Uniform Amplitude Distribution Research Articles

Speckle reduction for single sideband-encoded computer-generated holograms by using an optimized carrier wave

Computer-generated hologram (CGH) is an evolving field that facilitates three-dimensional displays, with speckle noise reduction being a pivotal challenge. In hologram synthesis, complex data with random phase distributions are typically employed as carrier waves for wide viewing angles and a shallow depth of focus (DOF). However, these carrier waves are a source of speckle noise, which can significantly degrade image quality. In this paper, we propose a novel technique for speckle reduction for single sideband (SSB)-encoded holograms, applicable to any arbitrary 3D object. The proposed method focuses on optimizing the random carrier wave used in the hologram synthesis to achieve a uniform amplitude distribution at the object's location. This optimization results in a carrier wave that consistently exhibits uniform amplitude at specific depth planes, leading to a significant reduction of the speckle occurring from the carrier wave. The proposed method has been validated through simulations and optical experiments.

AN X/Ku DUAL-BAND SHARED APERTURE UNIFORM LINEAR ANTENNA ARRAY FOR AIRBORNE SYNTHETIC APERTURE RADAR APPLICATIONS

An amplitude distribution of shared aperture antenna array for airborne SAR applications using a dual-band (X/Ku-band) synthesis is presented in this research. It is utilizing a linear arrangement with 1 × 8 antenna elements and a series feeding mechanism to operate in the X/Ku bands. The proposed shared aperture antenna array has eight elements providing a uniform array in the X and Ku bands. To realize the proposed scanning array, the X/Ku-band antenna array takes an inter-element spacing of 0.7 λ, which provides a scanning angle of ± 25°. When the space between adjacent antenna arrays is effectively used to reduce the influence of mutual coupling, the synthesis array's X-band and Ku-band antenna arrays can perform well in isolation. The uniform linear array exhibits Side Lobe Level (SLL) of -23.9 dB in X-Band and -24.7 dB in Ku-Band, with maximum realized gains of 14.2 dBi in X-Band and 15.7 dBi in Ku-Band. The isolation between bands and ports exceeds 25 dB. The uniform amplitude distribution shared aperture antenna (UAD SAA) has accepted an SLL performance of -13.5 dB. Additionally, it displays a uniform (X/Ku-band 200/144 MHz) impendence bandwidth that is relatively wide.

Analysis of 5G Rotman beamforming lens antenna for higher beam angle and minimum phase error

Abstract Rotman lens beamforming networks are widely used for high gain, wide bandwidth applications in 5G communication. The uniform amplitude and phase distribution along with wide angle scanning at the array ports are mostly demanded for reducing the losses. Furthermore, minimum phase error is essential requirement for lens designs. Conventionally, for wide angle scanning, the lenses are designed by using most common expression between beam angle α and focal ratio (parameter ‘g’) i.e. g = 1 + 0.5α 2. The lenses obtained by such relation are inefficient for higher beam angle such as α = 45° due to the restricted shapes of beam and array contours. Hence suffer with large path length error limitation. In this paper, the mathematical relation between beam angle and focal ratio (parameter ‘g’) has been developed. The proposed relation offers phase error reduction more than 3× than the conventional expression based lens error. The simulation of the designed lens has performed using Software MATLAB which showed close agreement with the analytical values. Furthermore, three rectangular MPA arrays at center frequency 2.35 GHz have been proposed and simulated with lens design for 5G frequency range i.e. 2.3–2.4 GHz and offer high gain, directivity and wide coverage.

Strongly focused nonlinear surface acoustic wave beams in isotropic solids

A promising direction in the tailored control of quantum materials is the modification of their structure-function relationship via engineered laser-driven shock waves. In order to inform how the laser excitation should be tailored to optimize the effect of the shock waves, a model is desired for strongly focused nonlinear surface waves in crystals. A model was developed previously in the paraxial approximation for weakly diffracting nonlinear surface wave beams in isotropic solids [Shull et al., JASA 97, 2126 (1995)]. Harmonic generation and shock formation were investigated numerically in that work for sources with uniform amplitude distributions, with analytical solutions for the fundamental and second harmonic obtained for weakly focused Gaussian beams. Here, numerical results are reported for shock formation in focused nonlinear surface waves obtained using a model unrestricted by the paraxial approximation in order to accommodate strong focusing in isotropic solids. Removal of the restriction to isotropic solids is work in progress based on representation of the wave field in terms of its angular spectrum and a model for planar nonlinear surface waves in crystals [Hamilton et al., JASA 105, 639 (1999)]. [Work supported by the IR&D Program at Applied Research Laboratories.]

ANALYSIS OF DIFFERENT TAPERING TECHNIQUES TO REDUCE SIDE LOBE LEVEL OF A LINEAR ANTENNA ARRAY FOR X BAND SAR APPLICATIONS

Through amplitude and phase control, antenna arrays provide a wide range of options for varying their directivity patterns. Using amplitude control or weighting throughout the array aperture, peak side lobe levels (SLL) can be decreased. Several authors have contributed significantly to the development of procedures for synthesizing these aperture amplitude distributions for SLL control. A compact series-fed center-fed open-stub (SFCFOS) 10-element linear antenna array is presented in this work for X-band applications. A symmetrical Chebyshev amplitude distribution (CAD) is used to obtain a low side lobe level by comparing with uniform amplitude distribution (UAD). By adjusting the micro-strip patch element width, the amplitude is controlled, and an open stub is positioned close to the final antenna element to make better use of the radiating signal's energy. This study illustrates the utilization of two amplitude tapering strategies at the same time to produce the required SLL. The linear antenna array is designed with the center frequency of X-band is 9.65 GHz. The proposed tapering techniques applied to the antenna structure are very effective in reducing SLL. The design shows an SLL -28.6 dB for UAD and -34.7 dB for CAD. The simulation was performed in CST Microwave Studio.

Application of additional high-frequency modulation to reduce influence of residual amplitude modulation LiNbO3 phase modulator on fiber optical gyroscope signal

Residual amplitude modulation in LiNbO3 phase modulator is one of the key factors that limit the accuracy of high-sensitive fiber-optical sensors. A fiber-optical gyroscope is an angular velocity sensor whose sensitivity is better than 0.001 °/h. Optical light intensity changes after phase modulator is a reason for wrong phase difference that introduces an error in the angular velocity signal. Most existing residual amplitude modulation suppression methods are based on reduction of back reflections between an optical fiber and integrated optical waveguide, absorbing groove to suppress or reduce reflection on the bottom face, and algorithmic compensation. In this paper, new approach to reduce residual amplitude modulation in LiNbO3 for fiber optical gyroscope application is presented. Method feature is an application of additional differential signal modulation with uniform amplitude distribution in the input signal voltage range of the phase modulator. The proposed method allows to suppress residual amplitude modulation of the multifunctional integrated optical circuit phase modulator more than 3 times using additional triangle signal modulation with the frequency f = 200.09 MHz and power P = 36 dBm. This method is suitable for improving fiber optical gyroscope accuracy. Moreover, it could be applied for any fiber-optic sensors based on LiNbO3 phase modulator. The paper will be of interest to specialists in the field of highly sensitive fiber optical sensors, fiber, and integrated optics.

Generating high-energy densities by sidelobe suppression in the far-field of phase-locked lasers

Laser beams with high-energy densities are desired for both fundamental research and applied applications. We present a numerical study on the generation of high-energy densities by sidelobe suppression in the far-field intensity distribution of phase-locked lasers. The method relies on modifying the combined field distribution of phase-locked lasers to obtain uniform amplitude and phase distributions in a near-field plane, which enables the formation of a high-energy density main central lobe (zeroth order) in the far field. The method is applied to various one-dimensional (1D) and two-dimensional (2D) array geometries, such as square, triangular, Kagome, random, and 1D ring. The results show that for in-phase-locked lasers in 2D array geometries, the diffraction efficiency of the high-energy density region (zeroth-order lobe) can be increased in the range of 90%–95%. For in-phase-locked lasers in a 1D ring array, the maximum diffraction is found to be ∼ 75 % . Further, the effects of the range of phase locking, system size, as well as topological defects are examined on diffraction efficiency. The method is also applied to an out-of-phase-locked laser in the square array, and a high-energy density output beam is obtained.

A Novel Metasurface Lens Design for Synthesizing Plane Waves in Millimeter-Wave Bands

With the development of communication technology has come several measurement applications requiring plane-wave conditions for wireless-device characterizations in anechoic chambers. In this paper, a metasurface lens with a 2 × 2 feeding-antenna array is proposed and characterized to synthesize a plane wave in a near field for a fifth-generation (5G) millimeter-wave radio-frequency (RF) devices test. The metasurface lens, based on Jerusalem-cross elements printed on a printed circuit board (PCB) substrate, is used for controlling the phase-shift distribution of incident spherical waves. The lens has a size of 0.4 × 0.4 m and is designed to operate at a range from 24.25 GHz to 27.5 GHz, and its feeding-antenna array is located at a focal plane of the lens, which is parallel to the metasurface lens. The lens is studied and verified through simulations and experiments, and a uniform amplitude and phase-field distribution at a reduced distance of 1.2 m generated by the metasurface lens throughout a QZ are achieved. The worst-case amplitude and phase variation of the designed metasurface lens are ±0.75 dB and ±7.5°, respectively. The results show a plane-wave condition can be achieved in 5G millimeter bands through the proposed compact and effective metasurface lens. Moreover, the proposed metasurface lens is shown to be capable of reducing the plane-wave synthesizing distance compared to the compact antenna test range (CATR) with a significantly reduced system cost, making it an attractive alternative to antenna testing in 5G millimeter-wave frequency bands.

Phase Optimization for Multipoint Haptic Feedback Based on Ultrasound Array.

Ultrasound-based haptic feedback is a potential technology for human–computer interaction (HCI) with the advantages of a low cost, low power consumption and a controlled force. In this paper, phase optimization for multipoint haptic feedback based on an ultrasound array was investigated, and the corresponding experimental verification is provided. A mathematical model of acoustic pressure was established for the ultrasound array, and then a phase-optimization model for an ultrasound transducer was constructed. We propose a pseudo-inverse (PINV) algorithm to accurately determine the phase contribution of each transducer in the ultrasound array. By controlling the phase difference of the ultrasound array, the multipoint focusing forces were formed, leading to various shapes such as geometries and letters, which can be visualized. Because the unconstrained PINV solution results in unequal amplitudes for each transducer, a weighted amplitude iterative optimization was deployed to further optimize the phase solution, by which the uniform amplitude distributions of each transducer were obtained. For the purpose of experimental verification, a platform of ultrasound haptic feedback consisting of a Field Programmable Gate Array (FPGA), an electrical circuit and an ultrasound transducer array was prototyped. The haptic performances of a single point, multiple points and dynamic trajectory were verified by controlling the ultrasound force exerted on the liquid surface. The experimental results demonstrate that the proposed phase-optimization model and theoretical results are effective and feasible, and the acoustic pressure distribution is consistent with the simulation results.

Sidelobe Suppression Beamforming Using Tapered Amplitude Distribution for a Microwave Power Transfer System with a Planar Array Antenna

This paper proposes a sidelobe suppression beamforming scheme using tapered amplitude distribution for microwave power transfer (MPT) with a two-dimensional planar array antenna (PAA). To overcome the undesirable effects of sidelobes, the magnitude of the sidelobes can be lowered by manipulating the amplitude distribution of the PAA. By analyzing the array factor of the PAA, we expressed the amplitude distribution as the product of two one-dimensional vectors. Moreover, we developed a method for obtaining these vectors from an expected sidelobe level (SLL). We used the Chebyshev taper, which has a higher directivity than other distributions given an expected SLL, for the amplitude distribution. To verify the proposed method, we designed and implemented a digital beamforming system with a 4 × 4 transmitter (Tx) array and a receiver (Rx) at 5.8 GHz. Compared with a uniform amplitude distribution, the proposed method reduced the SLL by 7.5 dB but the received RF power by only 0.6 dB. We compared the performance of the proposed MPT system with the results of previous studies.

Структура плоской эквидистантной антенной решетки с радиальной сеткой

The article proposes to consider the radial structure of the placement of radiating elements in the nodes of a flat equidistant antenna array. The known variants of rectangular and hexagonal structures of elements placement in flat antenna arrays are considered. The main calculated ratios of parameters for the radial structure of the pitch are given as well as the linear distances between the emitters in various orthogonal directions, along the radial and angular components. For the proposed structure, using a specific example of an antenna array consisting of nine circles, with a total number of 180 emitters and a uniform amplitude distribution, the radiation patterns in three-dimensional space are calculated, that are represented on the drawing plane by various sections along the angular coordinate φ with a step of 150. The proposed radial structure, unlike the known ones, ensures the identity of the DN with minimal discrepancies from each other in different planes φ at the level of -35 dB.

Optimization of Coupled Periodic Antenna Using Genetic Algorithm with Floquet Modal Analysis and MoM-GEC

In this paper Genetic Algorithm has been integrated with Fouquet modal analysis to optimize radiation pattern of coupled periodic antenna. Floquet analysis is used with MoM-GEC (Moment-Generalized Equivalent Circuit) method to study a finite periodic array with uniform amplitude and linear phase distribution. This method is very advantageous for studying large antenna array since it considerably reduces the computation time and the number of operations. In this way, Genetic algorithm is introduced and combined with Floquet analysis to optimize the radiation pattern distribution of this coupled periodic antenna. The goal of the optimization is to provide a better radiation characteristic for the coupled periodic antenna with maximum side lobe level reduction.

Enhancement of a spin-wave self-focusing by a pulsed flat-top excitation field in a multi-domain state

We investigate a spin-wave (SW) self-focusing in a ferromagnetic FePd thin film with a perpendicular magnetic anisotropy by using micro-magnetic simulation. In a one-dimensional structure, a point-excitation of forward volume magnetostatic waves leads the SW propagation in the form of a wave packet. When SWs are excited over a wide area with a uniform amplitude distribution, the SW propagation occurs by taking not only a diverging component but also a focusing-like component. Interestingly, we can increase the focusing effect by reflecting the diverging waves at the magnetic phase boundary, such as domain walls. This SW focusing appears also in a two-dimensional system, and, furthermore, magnetic droplets can be easily formed at the focal points when the focused SW intensity exceeds an appropriate threshold. Based on these results, we can propose the flat-top excitation of the magnetostatic waves as an efficient way to generate the SW self-focusing and also to create magnetic droplets in a multi-domain state of perpendicularly magnetized systems.

Longitudinal distribution of the field intensity of a circular focused aperture

Microwave and millimeter-wave antennas focused in their Fresnel zone, which are usually named as near-field focused (NFF) antennas, are becoming increasingly popular. Indeed, when compared to conventional far-field focused antennas, they can guarantee performance improvement at a relatively limited implementation cost, in short-range communication systems, wireless power transfer arrangements, remote nondestructive sensing setups, and radiofrequency identification apparatus, among many others. In this paper, analytical expressions are obtained for calculating the main parameters characterizing the longitudinal distribution of the circular focused aperture field intensity with a relatively large diameter (2R/λ≥10) : the displacement of the intensity maximum relative to the focal point, focusing gain and depth of focus. Cases of uniform and decreasing amplitude distributions of the excitation field are considered. The found approximate relations make it possible to determine the values of the above parameters for any values of the longitudinal coordinate of the focal point, lying both in the Fresnel zone and in the far zone. Comparison with numerical calculations showed that the error in the obtained parameter values does not exceed 5%. The results of this paper will be useful when calculating the field of antennas in the form of a circular focused aperture, as well as focused antenna arrays operating in the Fresnel zone.

A novel receiver-transmitter metasurface for a high-aperture-efficiency Fabry-Perot resonator antenna* *Project supported by the National Natural Science Foundation of China (Grant No. 61871394) and Natural Science Foundation of Shanxi Province, China (Grant No. 2020JQ-482).

This paper presents a novel coupled receiver–transmitter metasurface (MS) which is used to realize a high-aperture-efficiency Fabry–Perot resonator antenna. The unit cell of the MS adopts a slot-coupling procedure to realize energy transmission from the receiver patch to the radiator patch. This approach makes it easier to independently control the transmission magnitude and phase. Based on this characteristic, the transmission coefficients of different unit cells on the MS can be optimized by a genetic algorithm. Then, nearly uniform electric amplitude and phase distribution across the aperture field of the antenna are achieved. Therefore, the gain and aperture efficiency of the antenna are improved. A prototype of the optimized antenna is fabricated and measured to validate the design. The measured gain of the fabricated antenna reaches 17.3 dBi with an aperture efficiency of 94.5%. A higher aperture efficiency is obtained with the proposed antenna which has a low profile and simple structure.

Sequential 90° Rotation of Dual-Polarized Antenna Elements in Linear Phased Arrays with Improved Cross-Polarization Level for Airborne Synthetic Aperture Radar Applications

In this work, a novel rotation approach for the antenna elements of a linear phased array is presented. The proposed method improves by up to 14 dB the cross-polarization level within the main beam by performing a sequential 90° rotation of the identical array elements, and achieving measured cross-polarization suppressions of 40 dB. This configuration is validated by means of simulation and measurements of a manufactured linear array of five dual-polarized cavity-box aperture coupled stacked patch antennas operating in L-Band, and considering both uniform amplitude and phase distribution and beamforming with amplitude tapering. The analysis is further extended by applying and comparing the proposed design with the 180° rotation and non-rotation topologies. This technique is expected to be used for the next generation L-Band Airborne Synthetic Aperture Radar Sensor of the German Aerospace Center (DLR).

Highly Directive Microstrip Array Antenna with FSS for Future Generation Cellular Communication at THz Band

To establish a successful future generation cellular communication system in the Terahertz (THz) regime, there is a need to design high-directivity antennas, which will allow the signal to propagate beyond 0.1 km. Simultaneously, design wide bandwidth (BW) antennas to facilitate transmitting the information at a data rate up to 0.1 Tb/s. Two sets of microstrip array antennas have been designed, optimized, and simulated with the CST MWS simulator, in a hybrid fed with uniform amplitude distribution technique, the $$1{\text{st}}$$ one without frequency selective surface (FSS) feature and $$2{\text{nd}}$$ one with the FSS feature for further enhancing the antenna gain. To verify the simulation results of the $$1{\text{st}} - 2{\text{nd }}$$ antennas design, which simulated with the CST MWS simulator, these designs have been validated with the ANSYS HFSS simulator, and the simulation results obtained out of both simulators were close to each other. These antennas can establish a successful short-range 6G cellular communication system at the THz band.

Obtaining a uniform amplitude distribution over the aperture of an active phased array antenna by way of controlling the output power of microwave channels

Obtaining a uniform amplitude distribution over the aperture of an active phased array antenna by way of controlling the output power of microwave channels

Analytical Technique for Synthesizing a Leaky-Wave Antenna with a Semitransparent Wall of Metal Cylinders

We have developed an analytical technique for synthesizing a leaky-wave antenna in the form of an irregular hollow rectangular metal waveguide with a narrow wall in the form of an array of circular metal cylinders using an approximate expression for the reflection coefficient of a plane wave from a fine-periodic lattice of circular metal cylinders and the dispersion equation for a waveguide with a partially transparent wall. As an example of the application of this technique, two leaky-wave antennas are synthesized: with a uniform and sinusoidal distribution of the field amplitude along the antenna. We have performed electrodynamic modeling of synthesized antennas using the finite element method. For a synthesized antenna with a uniform amplitude distribution, the results of a numerical experiment are compared with the results of measurements of an experimental sample in the centimeter wavelength range.

Mechanical characterization of FDM filaments with PVDF matrix reinforced with Graphene and Barium Titanate

In past one decade number of studies has been reported on optimization of process parameters of fused deposition modelling (FDM) for in-house developed thermoplastic composite based feed stock filaments. This paper investigates smart polymer-based composites prepared with hybrid feed stock filament (comprising of polyvinylidene fluoride (PVDF) reinforced with graphene (Gr) and barium titanate (BTO) powder). This work started with the Functional prototypes were 3D printed for tensile and flexural characterization using inhouse developed filament (PVDF (78%)+Gr (2%) with BTO (20%)) at optimized settings of FDM. The printed specimens were subjected to destructive testing for mechanical properties (to analyze the process capability indices, Cp and Cpk). For morphological properties, scanning electron microscopy (SEM) images and 3D rendered images of the fractured surfaces of tensile and flexural specimen were used. It has been revealed from the SEM and 3D rendered images that the optimized settings of 3D printing process parameters resulted into uniform morphological features (based upon surface roughness (Ra) and amplitude distribution function (ADF), peak count (PC) and bearing ratio (BR) curve).