Source Antenna Research Articles

Creating a planar array of transversely polarized optical needles using a uniform line source antenna array

A method for generating a planar array of transversely polarized optical needles with prescribed characteristics is proposed firstly in this paper. The created needles are pure transversely polarized and located in the x–y plane, and perpendicular to the optical axis. In order to form the desired optical needle array, a virtual uniform line source antenna array, placed at the foci-pane of two high numerical aperture objectives, is employed to obtain the required illumination in the pupil plane by using the time-reversal holographic technique. Simulation results demonstrate that the focal field array of the identical transversely polarized optical needles constructed by the proposed method is located in the x–y plane. Parameters of the generated array can be readily controlled and customized according to practical requirements by adjusting the azimuthal direction, number, length, and spacing of needle elements. This particular array formed by transversely polarized optical fields has great potential applications in the area of parallel or synchronous operations, such as 2D simultaneous particle acceleration and manipulations and 2D parallel fabrication.

Issues of technical implementation of ground-based microwave radiometric system calibration

The theoretical bases of a method of carrying out calibration of microwave radiometric system on a noise signal of the external noise generator are analysed, the parameters setting value of gain of antenna temperature at introduction in structure of system of such external source of a calibration signal are determined. The questions of technical realization of an external source of a calibration signal for microwave radiometric system are considered, the structural scheme is presented, the place of its arrangement in structure of the antenna is determined. The necessity of using a horn antenna to create directional radiation towards the mirror antenna emitter is shown. The data on the design of such a calibration signal source for the case of its use in a three-band microwave radiometric system with the reception of a noise signal at the common antenna aperture and a sequential separation of the input signals of the three bands in the feeder path of the common mirror irradiator are presented. The influence of the design and, accordingly, the directional properties of the horn antenna of a microwave radiometric system calibration signal source on the coefficient characterizing the radiation divergence created by the noise generator horn, as well as the frequency properties of this coefficient are analysed. The results of measurements of radio-thermal radiation by a three-band microwave radiometric system when two calibration periods with reception of a radio-noise signal from an external calibration signal source located at the base of the antenna mirror are presented.

Imaging of Subwavelength Microstructures by Time Reversal and Neural Networks, From Synthetic to Laboratory-Controlled Data

Imaging of a subwavelength microstructure made of a periodic grid-like finite set of circular rods is carried out from transient scattered field data in different configurations of sources and receivers. The goal is to identify the position of possibly missing rods. Time reversal is confirmed as a cheap yet efficient first-order diagnostic method even in the demanding context of a subwavelength microstructure. Tools of deep learning, expected to be valid in general circumstances if data acquired in sufficient numbers, are in parallel developed to image the microstructure. To that effect, recurrent neural networks (RNN) and convolutional neural networks (CNN) are both used. Pros and cons of all approaches are illustrated by comprehensive simulations from synthetic data computed via a finite difference time domain method (FD-TD) software carefully tailored to the microstructure model and used also to make the networks learn the microstructures. The analysis is completed from examples of laboratory-controlled data acquired on a microstructure prototype set within a microwave anechoic chamber. These examples confirm the good promises of neural networks even with rather scarce data as exemplified in a forward scattering case—fixed source and receiver antennas face each other and the microstructure is rotated between them.

Wideband end‐fire circularly polarised complementary source antenna for millimetre‐wave applications

A millimetre-wave end-fire circularly polarised (CP) complementary source antenna is proposed. Circular polarisation is obtained by combining a quarter-wave shorted patch and a planar electric dipole. A direct-feeding method based on the use of substrate integrated coaxial line (SICL) is developed for wideband excitation of the antenna. The antenna element achieves a −10-dB impedance bandwidth of more than 32.4% and a 3-dB AR bandwidth of 30.1% with a stable gain around 5.5 dBic. To demonstrate higher antenna gain, a 1 × 4 CP antenna array fed by an SICL power divider is designed. Measurement of the fabricated prototype verifies that the CP antenna array achieves a gain up to 10.5 dBic. The competitive performances including wide bandwidth, stable gain, and simple planar configuration make the proposed CP antenna attractive for millimetre-wave applications such as the fifth-generation (5G) mobile communications and the next generation WiFi systems.

Creating a spatial optical tube of prescribed characteristics

Based on the radiation pattern of a spatial uniform magnetic current line source (UMLS) antenna, we propose a method for creating a spatial optical tube with a variable length and arbitrary orientation for a 4π focusing system. A virtual spatial UMLS antenna situated at the foci of two high numerical aperture objectives is used to obtain the required illumination at the entrance pupil plane. Numerical results demonstrate that the length of the created optical tube is approximately equal to that of the UMLS antenna. Its orientation is consistent with that of the line source. Its polarization is pure azimuthal, and the transverse size of the optical tube shell and the dark tunnel is uniform over the entire depth of focus. This optical tube can be customized according to application requirements. The generated optical tube can be used for such applications as arbitrary orientation particle trapping and guiding, micromanipulation, and optical microscopy.

Generating an optical needle with prescribed length and polarization direction through reversing the radiation pattern from a spatial ULS antenna

Unlike the conventional optical needle directed along the optical axis, we propose an approach to generate an optical needle with prescribed polarization direction and length by inversely focusing the radiation pattern from a spatial uniform line source (ULS) antenna in a 4Pi focusing system. The spatial ULS antenna situated at the foci of the 4Pi configuration is employed to obtain the required illumination at the pupil plane for creating the above optical needle through the use of a time-reversal holographic methodology. Numerical results show that the spatial polarization direction of the created optical needle is consistent with that of the spatial ULS antenna, that its length is approximately equal to the length of the ULS antenna, and that the transverse size of the optical needle is over its extent. The proposed method is more flexible than traditional methods for customizing the optical needle with prescribed characteristics.

Beam‐steering transmitarray with active frequency selective surface for wireless power transmission

This letter presents a beam-steering antenna with an active frequency selective surface (AFSS). The proposed AFSS-based antenna consists of a source antenna and an active frequency selective surface as a superstrate. The AFSS unit consists of three layers, where the upper and lower layers are identical and the middle layer has a slight variation. This structure makes it possible to obtain 360° phase variation, which can be achieved by changing the bias voltage at both ends of the varactor diodes in the case of three layers. Its passband is about 40 MHz (from 5.14 to 5.18 GHz). Finally, the proposed unit cell was stacked into a 5 × 5 array; both simulated and measured results demonstrated that the transmitarray has the scan ability of ± 25° at 5.16 GHz. The proposed transmitarray is suitable for dynamic wireless power transmission.

Field scattering localization based on compressed sensing

In the present study, a regional localization system is proposed based on the variation of the scattering field in ultrawide band (UWB) frequencies. The system uses the UWB antennas to transmit and receive the sweep sparse signal in the measured area. Subsequently, the compressed sensing (CS) algorithm is employed for localization. To increase the positioning accuracy, the randomness of signal distribution should be improved. Different from the previous designs, the scattering obstacles are introduced between the target and the antennas. Through simulation and experiment, a localization system composed of two transmitters and one receiver working at 10–20 GHz is proposed, leveraging the UWB source antennas and grid metal barriers. By complying with the sparse reconstruction algorithm of the CS method, the positioning accuracy of 1.4 mm is obtained in the area of 40 × 40 mm2 at 40 mm distance. The system is capable of locating in small areas effectively based on simple setup, and potentially applied to human-computer interaction of wearable devices and other local positioning applications.

Some Advances in Shooting-Bouncing-Rays Asymptotic Propagation Methodologies

We present an overview of some recent advances including work in progress in different shooting-bouncing-rays asymptotic techniques for electromagnetic modeling of reflection, transmission, and diffraction propagation phenomena. These propagation phenomena computations, coupled with antenna or plane wave source modeling, can cover a wide spectrum of electromagnetic field solutions that offer a versatile approach to modeling of electromagnetic structures and systems at high frequencies.

SWIPT Enabled Intelligent Transportation Systems With Advanced Sensing Fusion

Internet of Things (IoT) is the connections of embedded sensing technologies that can be integrated with intelligent transportation systems (ITS), which can take advantage of the advanced sensing fusion to implement the intelligent interaction. Moreover, the environmental wireless signals was harvested and utilized to power the charging sensors, which can be used to assist and enhance the ITS and have attracted extensive attentions in industries. The simultaneous wireless information and power transfer (SWIPT) enabled ITS was designed and proposed with the advanced sensing fusion, where the sensor nodes of the source and destination were all equipped with multiple antennas and the maximum ratio transmission (MRT) precoding and maximum ratio combination (MRC) were adopted respectively in the proposed system, where the sensing nodes can be embedded into the data addressing equipment to fusion the sensing information. For the established massive sensing node transmission system, the transmission power, the number of source antennas and destination antennas were considered to fuse and optimize to obtain the maximum energy efficiency (EE) of the ITS. Since the original fusion problem was non-convex and difficult to solve, which can be transformed to convex problem via the large SNR approximation method and thereby the optimal solution of the sensing fusion problem was derived through the Lagrange algorithm and the Lambert function W. The simulation results showed that the proposed fusion algorithm can achieve remarkable EE compared with other algorithms and be utilized to the massive sensors to improve the intelligent predication and transportation for vehicle network.

3D conformal bandpass millimeter-wave frequency selective surface with improved fields of view

Conventional planar frequency selective surfaces (FSSs) are characterized in the far-field region and they are sensitive to the incidence angle of impinging waves. In this paper, a spherical dome FSS is presented, aiming to provide improved angular stable bandpass filtering performance as compared to its planar counterpart when the FSS is placed in the near-field region of an antenna source. A comparison between the conformal FSS and a finite planar FSS is presented through simulations at the frequency range between 26 to 40 GHz in order to demonstrate the advantages of utilizing the conformal FSS in the near-field. The conformal FSS is 3D printed and copper electroplated, which leads to a low-cost and lightweight bandpass filter array. Placing it in the near-field region of a primary antenna can be used as radomes to realize compact high-performance mm-wave systems. The comparison between simulated and measured conformal FSS results is in good agreement. The challenges that arise when designing, manufacturing, and measuring this type of structure are reported and guidelines to overcome these are presented.

Physical layer security analysis of a dual-hop hybrid RF-VLC system

Abstract In this paper, we investigate the secrecy performance of a dual-hop hybrid radio frequency–visible light communication (RF–VLC) system in which we consider a single source antenna (S) transmitting data signals via RF channel through decode and forward (DF) relay (R) toward an authorized receiving antenna (D) at the destination via VLC channel. In this system, we assume that the eavesdropper (E) attempts to eavesdrop the RF channel (S,R) during transmission of the signal. The relay decodes the incoming RF signal into corresponding optical signal and retransmits toward destination via VLC channel (R,D). The RF and VLC channels of the hybrid system are modelled using generalized-K fading distribution and generalized Lambertian radiant intensity distribution respectively. Also the receiver is assumed to be mobile and its mobility is defined by random waypoint (RWP) model. The channels statistics are used to derive the exact analytical expressions for average secrecy capacity and intercept probability in terms of Meijer’s G-function. The derived closed form analytical expressions are the efficient tool to illustrate the impact of variation in different channel parameters on the secrecy performance, namely, shadowing parameters of RF channel, field of view (FOV), semiangle, and the order of Lambertian emission of the VLC channel. Further, numerical analysis is carried out to support the mathematical analysis of the RF–VLC hybrid system.

Rancang Bangun Multi Frekuensi Rectenna Untuk Energy Harvesting Gelombang Elektromagnetik

The increasing need for electrical energy encourages the birth of methods to utilize various forms of energy available in nature called energy harvestin. One of them is from electromagnetic waves that are massif used daily by the community. In this study, a rectifier antenna (rectenna) was created using a 5-stage voltage doubler method with the aim of generating DC electrical energy from the input of electromagnetic waves that propagate freely in the air. Electromagnetic waves are captured using two types of antennas with the aim of capturing different frequencies, namely UHF TV antennas with a working frequency of 470-806 MHz and WiFi antennas with a working frequency of 2400 MHz commonly used by the public. Because testing is conducted in open spaces, where environmental change conditions greatly affect the captured electromagnetic geombang encroachment, DC electrical power tends to change during testing. The largest DC electricity generated by WiFi antenna input is 1,420V and the average voltage is 231.7mV/min with a distance of 90cm from the largest frequency source and UHF TV antenna is 648mV and the average voltage is 478.16mV/min with a distance of 0 cm from the largest frequency source

Low-profile high efficiency transmitarray antenna using optimized phase compensation surface (PCS) and PEC sidewalls

A low-profile high efficiency transmitarray antenna (TA) using an optimized phase compensation surface (PCS) and PEC sidewalls is proposed in this paper. Generally, TAs are composed of a source antenna and a planar PCS, and the PCS makes the phase of transmitted wave through the PCS be in-phase, resulting in a highly directive beam. The unit cells of a PCS cannot have a 100% transmittance at all transmission phases. Since there may be combinations of PCS that make various in-phases, the transmit efficiency of the TA can be improved. Also, the four PEC sidewalls are employed to maximize the amount of power reaching the PCS from the source antenna. As a result, the 100% spillover efficiency is achieved without diminishing taper efficiency. To verify its feasibility, the square TA was designed and measured at 5.8 GHz and a high aperture efficiency of 54% was obtained through the above design methodology.

Numerical Modeling of Nondestructive Testing of Various Conductive Objects inside Metal Enclosures Using ELF/VLF Magnetic Fields

Nondestructive evaluation of various conductive objects through metal enclosures is investigated by using ELF/VLF magnetic induction fields in detailed simulations. ELF/VLF magnetic fields (<30 kHz) have a unique ability to penetrate highly conductive or permeable shields. Using a magnetic dipole source antenna, objects hidden inside a metal enclosure are imaged via examining distortions to the field outside the enclosure. The field distortion is parametrically studied by varying the size, conductivity, and permeability of the hidden objects. Furthermore, the importance of the conductivity of the enclosure itself is investigated using both low (106 S/m) and high (108 S/m) conductivity metallic shields. It is shown that the responses are quite sensitive to the object and shield parameters; both qualitative and quantitative properties of the field distortions are described in detail. The simulation results suggest that properties of hidden conductive or permeable objects, over a relatively wide range of parameters (both geometry and material), can be inferred nondestructively using ELF/VLF magnetic induction fields.

An S-Band Fabry–Perot Cavity Antenna With Wide 1 dB Gain Bandwidth

A high-gain Fabry–Perot cavity antenna (FPCA) with wide 1 dB gain bandwidth in the S -band is proposed. A partially reflective surface with a positive phase gradient in a wideband is adopted to effectively improve the radiation characteristics of the designed broadband source antenna. The proposed FPCA has a measured –10 dB impedance bandwidth of 2.9–3.95 GHz (30.65%), and a 1 dB gain bandwidth is 2.9–3.6 GHz (21%). In such a wideband, the realized gain is enhanced by up to 6 dB, and the measured maximum aperture efficiency is 39.3%.

An approach to achieve directional low‐profile antenna of quintuple stable pattern band by utilising dipole with compound concave corrugated reflector

An approach to achieve directional low-profile UWB antenna by omnidirectional source with a reflector, is proposed. The general theoretical model about the direction and the phase conditions between the upward and reflected field are developed. A bow-tie dipole source antenna is investigated first. To modify its radiation defect, proper phase equations between the original upward field and the reflected downward field are derived so that the aperture field becomes uniform enough to guarantee directional radiation. The concave-shaped reflector is primarily adopted to satisfy the phase conditions. Then the concave-shaped reflector is decorated with corrugated structure to realize good impedance matching within the wide band. Consequently, the split beams caused by multiple long linear currents with phase difference at high frequency is focussed while the directivity at low frequency is also improved. The prototype antenna was fabricated with a profile of 20.5 mm, about 0.156 λ max (maximum wavelength in the work band), and the measured impedance bandwidth of VSWR ≤ 2.2 is over 2.27–26 GHz. Both simulated and measured results demonstrate the stable directional patterns within the quintuple band (2–10.5 GHz). The realised gain is over 7 dBi within the band (2–10.5 GHz) and peak is over 12 dBi.

A Design of Broadband 3-D-Printed Circularly Polarized Spherical Luneburg Lens Antenna for X-Band

This letter presents a broadband 3-D-printed circularly polarized (CP) spherical Luneburg lens (LL) with the linearly polarized feed antenna for the X -band. In order to implement spatially continuous varying effective refractive index (RI), the proposed LL is divided to many unit cells and their effective RI is simulated and calculated by effective medium theory. Since the effective RI of unit cells is anisotropic for two orthogonal linearly polarized (LP) waves, the proposed LL is an LP to CP polarizer realized by properly selecting the radius of the LL. The whole structure is fabricated by low cost 3-D-printing (3DP) technic, which is fed by an LP antenna source rotated to a certain angle with respect to the LL around the normal. The measured results indicate that the voltage standing wave ratio (VSWR), axial ratio, and gain enhancement are lower than 2, less than 2.8 dB, and more than 10 dB at X -band, respectively. The results of measurement agree well with the simulation.

A Transparent Artificial Periodic Structure for Beam-Tilting Antenna

A transparent anisotropic artificial periodic structure (APS) based on indium tin oxide (ITO) and its application in a beam-tilting antenna are proposed in this letter. The proposed APS is composed of double split-ring structures printed on both sides of a glass substrate. By tuning the size of the double split-ring structure, a refractive index variation ranging from 1.8 to 3.3 can be obtained. In the meantime, high optical transparency is achieved using a transparent conductor, ITO, with moderate surface resistance. To validate the proposed design, a transparent medium composed of the proposed APS unit cell is constructed to realize beam tilting in an endfire antenna. Simulation and measurement results show that the main beam direction of the entire antenna in E-plane is tilted by 13° and 17° with respect to the original endfire direction at 8.5 and 9.5 GHz, respectively. Compared with the initial feeding source antenna, the proposed beam-tilting antenna shows a gain enhancement of 2.2 dB at 9.5 GHz. The results show that the performance of the periodic structure using the low-conductivity ITO as the conductive layer is comparable with that using high-conductivity metal. This proposed technology can find potential applications in the internet-of-things, vehicular communications, and navigation systems.

Online Generalized Eigenvectors Extraction Via a Fixed-Point Approach

Generalized principal component analysis (GPCA) has been an active area of research in statistical signal processing for decades. It is used, e.g., for denoising in subspace tracking as the noise of different nature is incorporated into the procedure of maximizing signal-to-noise ratio (SNR). This paper presents a fixed-point approach concerning the principal generalized eigenvector extraction. It is based on the basis iteration for maximizing the generalized Rayleigh quotient (GRQ) with a given matrix pencil. The proposed approach extracts multiple generalized eigenvectors of a matrix pencil by exploiting the orthogonal complement structure of its estimation. It has no requirement to choose the commonly used step size. This enhances its practical applicability, as selecting an appropriate step size is a bottleneck for most gradient flow based algorithms. Our approach is more suitable for online processing because of its easy implementation and low computational complexity. To show the efficacy, efficiency and practical applicability of the proposed algorithm, we conduct several experiments, two of which concern smart antenna and blind source separation applications. Our simulation results show that the proposed algorithm outperforms several existing algorithms in terms of convergence speed as well as computational time.