Azimuth Radiation Pattern Research Articles

Modeling of a Compact, Implantable, Dual-Band Antenna for Biomedical Applications

Different implantable antenna designs exist to establish communication with implantable devices depending on the domain of use and the implantation space. Owing to their nature and purposes, these antennas have many imposed criteria on various characteristics, such as bandwidth, multiband behavior, radiation pattern, gain, and specific absorption rate (SAR). This presents a challenge when it comes to achieving satisfying results without a major compromise in any of these crucial parameters. Additionally, many of the existing designs do not follow a specific approach to obtain results. Measuring different parameters of such fabricated structures requires special conditions and special environments mimicking the tissues where they are supposed to be placed. For such issues, the use of biological or synthetic phantoms is widely employed to validate what is obtained in simulation, and a multitude of formulas exist for the creation of such phantoms, each with its advantages and drawbacks. In this paper, a miniature dual-band structure derived from the first iteration of the Koch fractal structure is designed to operate 2 mm below the skin in the arm of the human body, with the MICS (Medical Implant Communication System) and ISM (Industrial, Scientific, Medical) 2.4 GHz bands. The purposes of the design are to derive structures from commonly used shapes with certain behavior while maintaining miniaturization, and to easily design dual-band implantable antennas. More than one band is used to diversify uses, since bands such as the MICS band are mainly dedicated to telemetry. The structure is characterized not only by its low profile compared to various structures found in the literature with dimensions of 17.2 × 14.8 × 0.254 mm3, but also its ease of design, independent shifting of resonant frequencies, and the absence of the need for a matching circuit and a shorting pin (via) for miniaturization. It exhibits satisfying performance: bandwidths of 23 MHz in the MICS band and 190 and 70 MHz in the vicinity of the ISM 2.4 GHz band, and measured gain in the latter band of −18.66 and −17 dBi in the azimuth and elevation radiation patterns, respectively. To validate the antenna’s properties in a skin-mimicking environment, two simple phantom formulas found in the literature were explored and compared in order to identify the best option in terms of accuracy and ease of fabrication.

Hybrid lumped‐distributed loading design approach to wideband dual‐mode resonant monopole antennas

A dual-mode resonant monopole antenna using lumped and distributed loading is proposed. The third-order resonant mode within a monopole antenna is excited by a pair of stubs, so as wideband, dual-mode resonant characteristic can be attained. Two lumped inductors are loaded in a certain position of the paired stubs, so as the occupied space can be shrunk to yield compact antenna size. As is experimentally validated, the hybrid lumped-distributed loading scheme can effectively tune the third-order resonant mode downward, with the fundamental resonant mode rarely changed. Compared to the pure distributed, stub-loading scheme, the length of the perturbed stub can be reduced by 65%, while the impedance bandwidth is basically unchanged. The resultant dual-mode monopole antenna can operate in a wide frequency range from 3.66 to 5.80 GHz (i.e., fractional bandwidth of 45.2%) with an omnidirectional azimuth radiation pattern as evidently validated in experiment. The advanced design approach can maintain the intrinsic linear profile of resonant monopole antennas and exhibit low configuration complexity. It may be suitable for multi-mode resonant antennas development in space-limited portable terminals.

A New 3-D Imaging Technique Integrating Ultrafast Compounding, Hadamard Encoding, and Reconfigurable Fresnel Lensing

Crossed electrode arrays address some of the challenges associated with 3-D ultrasound imaging because of the significant reduction in the number of elements ( 2N versus N2 ). However, creating a two-way focused 3-D image in real time is difficult with these arrays because azimuth and elevation dimensions cannot be beamformed at the same time. This work describes a new 3-D imaging technique that uses the flexibility of bias-sensitive substrates to create a high-quality elevation focus on a crossed electrode array. The principle behind this technique is to perform conventional compound imaging with an azimuth set of electrodes while implementing a bias controllable elevation lens with an elevation set of electrodes. On transmit, the biases are chosen to mimic a Fresnel lens. Then, on receive, the Hadamard coding is implemented along the elevation dimension. After decoding, we gain the RF data for each element across the elevation aperture even though there is effectively only one channel in that dimension. A 30-MHz, 128-element crossed electrode relaxor array was fabricated on a 1-3 electrostrictive composite substrate and was used to demonstrate the performance of the imaging technique. The on-axis -6-dB beamwidths were simulated to be 175 and [Formula: see text] in the azimuth and elevation directions, respectively, and the focus remained isotropic in the furthest elevation slice. Images were generated of a wire phantom to confirm the performance of the azimuth and elevational radiation patterns with good agreement between simulation and experiment. High-resolution 3-D volumetric images were generated of an ex vivo rat brain. Images of the cerebellum showed that the white and gray matter tracts could clearly be visualized with isometric resolution in both the azimuth and elevation dimensions.

Omnidirectional Antenna Diversity System for High-Speed Onboard Communication

In this article, an omnidirectional dual-polarized antenna with synergetic electromagnetic and aerodynamic properties is propounded for high-speed diversity systems. The propounded antenna comprises a probe-fed cavity for horizontally polarized radiation and a microstrip-fed slot for vertical polarization. Double-layer metasurfaces are properly designed as artificial magnetic conductor boundaries with direct metal-mountable onboard installation and compact sizes. An attached wedge-shaped block is utilized for windage reduction in hydrodynamics. The propounded antenna is fabricated for design verification, and the experimental results agree well with the simulated ones. For vertical polarization, the operating bandwidth is in the range of 2.37–2.55 GHz, and the realized gain variation in the azimuthal radiation pattern is 3.67 decibels (dB). While an impedance bandwidth in the range of 2.45–2.47 GHz and a gain variation of 3.71 dB are also achieved for horizontal polarization. A port isolation more than 33 dB is obtained in a compact volume of 0.247 λ 0 × 0.345 λ 0 × 0.074 λ 0 , where λ 0 represents the wavelength in vacuum at the center frequency, wherein the wedge-shaped block is included. The propounded diversity antenna has electromagnetic and aerodynamic merits, and exhibits an excellent potential for high-speed onboard communication.

Experimentally Analyzing Diverse Antenna Placements and Orientations for UAV Communications

A vast array of potential applications is emerging for drones and other devices to collaborate from disaster relief and search and rescue missions to smart agriculture and IoT systems. As drones move across multiple altitudes, they must have the ability to communicate across any direction in a three-dimensional (3D) space. However, due to the heterogeneous nature of the drone body and its interaction with the mounted antennas, different antenna positions on the drone can result in variations in the radiation pattern. While there have been a fair number of airborne communication works, few consider the role that antenna positioning has on the resulting transmission along the azimuth and elevation planes. In this work, we study the effects of the drone body and various antenna placements on the radiation pattern and fading of drone-based channels. Through systematic anechoic chamber and in-field measurements, we show that the drone body alters the radiation pattern of the mounted antennas, rendering the common assumption of a constant azimuth radiation pattern invalid. In addition, the body increases polarization mixing of drone-based channels, resulting in significant degradation of the cross-polarization discrimination (XPD). Hence, we propose using effective radiation pattern and XPD values instead of relying on measurements and/or assumptions that disregard drone-antenna interaction. We then analyze the shadowing and losses associated with the drone body for many antenna setups at various elevation angles and show that when mounted on the opposite side from the ground transmitter, shadowing increases with relatively-higher drone elevations. To account for these body-induced effects, we introduce rotational loss that results in better prediction results of the large-scale fading behavior compared to conventional models that neglect these body effects. Then, we analyze the small-scale fading for various antenna setups and show that the Rician K-factor is strongly dependent on elevation for polarization-matched vertical links, while it is approximately flat for cross-polarized links. To do so, we conduct a set of drone-to-drone (DtD) experiments at high altitudes with no surrounding reflectors and compare results to those obtained by our ground-to-drone (GtD) measurements. We find that, while at low elevations the ground can reduce the K-factor by 10 dB, at higher elevations, small-scale fading is dominated by the antennas, not the ground.

Constraining the Dip of Shallow, Shallowly Dipping Thrust Events Using Long‐Period Love Wave Radiation Patterns: Applications to the 25 October 2010 Mentawai, Indonesia, and 4 May 2018 Hawaii Island Earthquakes

AbstractConstraining precise faulting geometry for shallow, shallowly dipping thrust earthquakes is a common challenge. Plate boundary megathrust faults near the trench and décollement faults beneath volcanic islands and nappes may dip only a few degrees. Long‐period point source moment tensor waveform inversions provide limited resolution of shallow fault dip angle. The possibility of splay faulting requires precise dip estimation. High sensitivity to dip is provided by long‐period Love wave amplitude azimuthal radiation patterns, which undergo rapid change from four lobed to two lobed as dip decreases from 10° to 0°. Modeling variability in Love wave nodal amplitudes allows the dip to be determined to within a few degrees. This is demonstrated for the 25 October 2010 Mentawai (MWW 7.8) tsunami earthquake, which ruptured the 2.0–5.0° dipping megathrust beneath the shallow sedimentary wedge offshore of Indonesia, and the 4 May 2018 Hawaii Island (MWW 6.9) thrust earthquake, which ruptured the 2.5–7.5° dipping décollement under the island flank.

Wideband Frequency-Domain and Space-Domain Pattern Reconfigurable Circular Antenna Array

This paper presents a wideband circular antenna array with a frequency-domain and space-domain reconfigurable radiation pattern. A wideband circular array antenna is designed with omnidirectional radiation pattern, in azimuth direction, throughout the whole frequency band. The antenna array consists of eight TEM horn antennas. The antenna array exhibits an omnidirectional azimuthal radiation pattern when all eight ports are excited with signals of the same magnitude and phase. The antenna array is fed through eight reconfigurable bandstop filters and a power splitter. This enables it to provide an omnidirectional azimuthal pattern along with a single directional pattern null in a given spatial direction and at a certain frequency. Both the spatial direction and the frequency can be altered. The antenna works from 0.8 to 3 GHz. The antenna array will be useful in combating interference in wideband communication systems. It will also be of value in surveillance military applications.

Compliance to Broadcast Standards of Patented Broadcast Antennas: the Circularly Polarized Antenna

Basic antennas in used today in FM broadcast antenna systems were developed at times where powerful computers are not yet available to do numerical computations on antenna performance. This paper aims to determine the compliance of a popular FM broadcast antenna to broadcast standards. Specifically, the paper presents the compliance of a broadcast antenna registered in the US patent office in 1970 on the requirements on bandwidth, polarization components and the circularity of the azimuth radiation pattern. The discussion on the compliance of the antenna under consideration to these standards is based on the results of the numerical analyses and computations using a reliable simulation antenna software. Based on the results, the antenna under consideration does not meet all of the standards. There is still a need for some adjustments in the structure of the antenna under consideration for it to satisfy the requirements stated above and at the same time optimize its performance.

Verification of Arbitrary Radiation Pattern Control Using a Cylindrical Impedance Metasurface

A cylindrical impedance metasurface can be used to arbitrarily reshape the radiation pattern of a vertically polarized enclosed two-dimensional source. We verify this theory, developed in a previous work, by reporting waveguide transmission measurements of a cylindrical metasurface fabricated using printed circuit board techniques. The transmission measurement results are in good agreement with the desired azimuthal image pattern, verifying the use of a cylindrical impedance metasurface to produce a desired azimuthal radiation pattern.

A Low-Profile Wide-Beamwidth Circularly-Polarized Antenna via Two Pairs of Parallel Dipoles in a Square Contour

A circularly polarized antenna with wide axial-ratio beamwidth is presented by placing two pairs of parallel dipoles in a square contour. Firstly, our study demonstrates that circular polarization can be achieved at the broadside by setting a 90° phase difference between the vertical and horizontal paired-dipoles. Secondly, the principle of wide-beamwidth circularly-polarized radiation is described under the similarity in polar and azimuthal radiation pattern for a pair of parallel dipoles. After the spacing between two parallel dipoles is studied, the similar radiation patterns in these two orthogonal planes are derived. As such, a wide-beamwidth circular polarization can be achieved by placing the two pairs of parallel dipoles vertically and horizontally while setting a 90° phase difference between them. In final, a circularly-polarized printed antenna is designed and fabricated on a single dielectric substrate. The two arms of its four dipoles are formed on the lower and upper interfaces of the substrate, and they are excited by a 1-to-4 probe-to-microstrip feeding network. Experimental results show good agreement with simulated ones in terms of radiation pattern/gain, axial ratio and returned loss. In particular, the 3-dB axial ratio beamwidth at the central frequency of 1.6 GHz has extended to 126 ° in an angular range from -63° to +63°. The fabricated antenna exhibits a low-profile property with the height of 0.0043 free-space wavelength.

Isolation enhancement in wideband dual‐polarised suspended plate antenna with modified T‐type probes

An isolation enhancement technique for a wideband (1.71–2.17 GHz) and ±45° linear dual-polarised suspended plate antenna is proposed. Isolation (S 12, S 21) between channels is improved by making extensions on suspended plates (SPs) 1–2 and inserting a vertical ungrounded vertical wall under SP-1. The modified T-type probes in this design provide better coupling and return losses (S 11, S 22) for wideband operation. Based on the numerical simulations and measurements, it is observed that 8.2 ± 0.5 dBi gain and 66° ± 6° symmetric azimuth and elevation radiation patterns are obtained. Return losses ≤ − 15 dB and isolation ≤ − 30 dB are achieved in the entire band. This antenna is suitable for base stations of mobile wireless communication systems (PCS, DCS and IMTS ).

Designing a Switchable Stacked Patch Antenna for GPS Application

GPS receivers are used for civilian and defence applications extensively. The signals received from GPS satellites are very weak and susceptible to interference. The principle objective of the proposed project work is mitigation of intentional and unintentional jamming signals in the L5 frequency band. By employing an antenna having two patch antenna elements with similar azimuth radiation patterns but distinct elevation radiation patterns. The two antenna elements may be operated independently of each other by selectively disabling one or the other of the two elements. Index terms: Stacked Microstrip Patch Antenna. I. INTRODUCTION Method for mitigation of intentional and unintentional jamming signals using a dual element patch antenna. The antenna possesses two antenna elements having distinct radiation patterns. Either element may be independently selected using DC bias voltage. Diodes connected to the elements serve to disable one element when the other is selected. This combination of features is packaged in a single antenna unit that can be a direct replacement for the existing antennas. The dual element antenna has a low vertical profile and is suitable for mounting on high speed vehicles.This paper concentrates only on the design of the antenna which is used for mitigation of jamming signals. In this my work is to design the stacked patch antenna. Here we have a stacked patch antenna showing two rectangular patches placed one above the other which in turn placed over a ground plane, with single feed.

Decade Bandwidth Circularly Polarized Antenna Array

A circularly polarized antenna array design comprising of a feed network that splits an input signal into four orthogonal (0°, 90°, 180°, and 270°) phased signals with equal magnitudes and connected to four anti-podal Vivaldi antennas sequentially rotated by 90° is presented. The proposed antenna array yields 10-dB return loss and 3-dB axial ratio bandwidths from 1-10 GHz. The symmetrical structure gives the antenna array almost identical azimuth and elevation radiation patterns. Pulse reception from various angles show equi-amplitude outputs and very little distortion. The proposed design is suited for high-resolution microwave imaging systems.

능동전파반사기를 이용한 위성 SAR 시스템 방사 패턴 분석

Measurement and analysis results of the extracted radiation-patterns from the field-experiments which were conducted to acquire the generic technology for calibration and validation of the satellite SAR system(Synthetic Aperture Radar) are presented in this study. Prototype of active transponder is adjustable within maximum 63.1 dBsm of RCS (Radar Cross Section) and includes the receiving-function with external receiver. To increase an accuracy of these field experiments, we repetitively measured satellite SAR systems of the same operating mode(i.e., COSMO-SkyMed No. 2 & 3, hh-pol., strip-map himage mode, 3 m resolution). Then, the reliability of experimental results was cross-checked through analysis of the RCS of active transponder on SAR image. The property of azimuth radiation patterns of satellite SAR system extracted from them has of HPBW(half-power beamwidth), of FNBW(first-null beamwidth), and 11.17 dB of PSLR(peak to side lobe ratio), respectively.

Indirect Coupling Method of Chip Impedance Matched Dipole Antenna for UHF RFID Tag

Radio Frequency Identification is the wireless technology that uses radio waves to automatically identify items within certain proximity. This process involves tagging items with a transmitter which will send bursts of information. Passive RFID tag consists of a microchip connected with an antenna. The passive tag uses the electromagnetic pulse from readers as a power source to transmit its identifier. So proper impedance matching between the antenna and the chip is very important in passive RFID tag design. The RFID system performance characteristics and the range of a tag depend on the impedance matching. A load impedance of RFID microchip is a nonlinear whose complex part varies with the frequency and the input power [2]. This paper presents simulated results of a UHF RFID dipole antenna and inductively coupled with a small rectangular loop. Such a design provides controlled values of inductive reactance that is required for obtaining good impedance match of the antenna to microchip. The proposed dipole antenna is simple and robust in design, which enables low-cost while realization. General Terms Return-loss, 3D Radiation Pattern, 2D Azimuth and Elevation Radiation Pattern, S-Parameters.

NOVEL FRACTAL ANTENNA ARRAYS FOR SATELLITE NETWORKS: CIRCULAR RING SIERPINSKI CARPET ARRAYS OPTIMIZED BY GENETIC ALGORITHMS

A novel fractal antenna-array type is proposed. The design is based on the Sierpinski rectangular carpet concept. However, the generator is a circular ring area, fllled with radiating elements, so the higher stages of the fractal development produce large arrays of circular rings which, besides the high directivity, have the advantage of the almost uniform azimuthal radiation pattern, attribute that many applications require. The introduced arrays can operate as direct radiating multi-beam phased arrays and meet the requirements of satellite communications links: high End of Coverage (EOC) directivity, low Side Lobe Level (SLL) and high Career to Interference ratio (C=I). These operational indices were further optimized by a synthesized multi-objective and multi-dimensional Genetic Algorithm (GA) which, additionally, gave arrays no more than 120 elements.

Radiation Pattern Synthesis for Arrays of Conformal Antennas Mounted on an Irregular Curved Surface using Modified Genetic Algorithms

An E-shaped conformal microstrip antenna array mounted on an irregular curved surface which is similar to an aerocraft cavity in shape is developed in this paper. In view of the narrow bandwidth of the microstrip antenna, an E-shaped element is applied instead of the traditional rectangular element. Furthermore, an element structure of uneven thickness is adopted in order to take into account the effects of the carrier on the resonance frequency and bandwidth of the conformal array. Then, an 8-element conformal microstrip antenna array is designed and the radiation pattern is synthesized using the modified genetic algorithms (MGAs). Compared with the standard genetic algorithms (SGAs), MGAs has a much more fast convergence speed and need less computational time to reach the expected value. The result shows that the optimized azimuth radiation pattern is almost omnidirectional and the elevation radiation pattern is concentrated in the horizontal direction. It can be seen that the proposed method of MGAs is an effective means for designing the conformal antenna array on an irregular curved surface.

Reconfigurable Beamwidth Antenna Based on Active Partially Reflective Surfaces

This letter presents a new method to design a new reconfigurable antenna by using an active cylindrical electromagnetic band-gap (EBG) structure for wireless communication systems. The antenna provides a reconfigurable elevation beamwidth while the azimuth radiation pattern maintained omnidirectional. The EBG structure that is composed of periodic discontinuous metallic strips and PIN diodes behaves as an active partially reflecting surface (PRS). By changing the diode states, the reflection coefficient of the structure is controlled so that the radiation beamwidth and directivity of the antenna can be reconfigured. To validate the proposed concept, the final prototype is fabricated, and measurement results are also presented and discussed.

Wide band planar modified triangular monopole antennas

AbstractVarious new configurations of planar triangular monopole antennas have been investigated. Effect of flaring angle of planar triangular monopole antennas on the bandwidth has been studied. A compact configuration of vertex chopped equilateral triangular monopole antenna has been proposed for ultra wide bandwidth ratio of 9.2:1. Orthogonal vertex chopped equilateral triangular monopole antenna is proposed for obtaining the improved azimuthal omnidirectional radiation pattern. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 628–632, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22214

Omnidirectional circularly polarized slot antenna fed by a cylindrical waveguide in millimeter band

AbstractA circularly polarized slotted array antenna is presented. The array is fed by a circular waveguide propagating the TM01, to properly generate the required polarization. An omnidirectional azimuth radiation pattern is obtained, as well as a −10°/+30° elevation antenna coverage. Low losses are achieved because of the waveguide feed. The slot array is mechanized over the metallic wall of the circular waveguide. Furthermore, the antenna presents a solid and rigid mechanical structure, which guarantees an optimum and repetitive response in a manufacturing process. A prototype antenna has been designed and measured. Satisfactory results have been obtained. The slotted array takes part from a signal detection system centered in 36.85 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 638–642, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22207