Antenna Orientation Research Articles

The Impact of Space-Based AIS Antenna Orientation on In-Orbit AIS Detection Performance

In this paper, a study on the impact of changing the space-based Automatic Identification System (AIS) monopole antenna orientation on its message reception performance in orbit has been conducted. The study has been carried out by maneuvering the attitude of LAPAN-A2, an equatorial orbiting microsatellite with AIS antenna fixedly mounted on the satellite’s body, into the desired orientation. Based on the analysis of the datasets collected during the maneuver, the orientation of AIS monopole antenna 45° toward its flight direction increases the overall detection performance of the AIS message, including class A ship to 208.80% and also class B ships to 175.93%. This orientation also increases the detection of AIS messages in ocean areas having low detection probability due to AIS signal collision. The result of this research could become a reference in order to specify AIS antenna position and orientation in a small satellite carrying a space-based AIS system for maritime surveillance & monitoring purposes.

Optimizing 802.15.4 Outdoor IoT Sensor Networks for Aerial Data Collection

Rural IoT sensor networks, prevalent in environmental monitoring and precision agriculture, commonly operate over some variant of the IEEE 802.15.4 standard. Data collection from these networks is often challenging, as they may be deployed in remote regions where existing backhaul infrastructure is expensive or absent. With the commercial and industrial success of Unmanned Aircraft Systems (UAS), there is understandable interest in using UASs for delay tolerant data collection from 802.15.4 IoT sensor networks. In this study, we investigate how to optimize 802.15.4 networks for aerial data collection, which, unlike other wireless standards, has not received rigorous evaluation for three-dimensional aerial communication. We analyze experimental measurements from an outdoor aerial testbed, examining how factors, such as antenna orientation, altitude, antenna placement, and obstruction, affect signal strength and packet reception rate. In our analysis, we model and predict the quality of service for aerial data collection, based on these network configuration variables, and contrast that with the Received Signal Strength Indication (RSSI)—a commonly used signal strength metric. We find that network configuration plays a significant role in network quality, which RSSI, a mediator variable, struggles to account for in the presence of high packet loss. We conclude with a discussion of strategies for optimizing sensor network configuration for aerial data collection, in light of our results.

A compact two element MIMO antenna with improved isolation for wireless applications

This paper presents a compact 55× 20 mm2 wideband multi-input-multi-output (MIMO) antenna. The proposed structure consists of two antenna elements excited using CPW feeding technique and is printed on a low cost and easily available FR4 substrate. In the proposed MIMO design, the first antenna at port 1 is fixed in its position and orientation while, the second antenna at port 2 is placed in six different orientations by keeping the overall dimension constant. The observation is made on the variation in the insertion loss as the orientation of the second antenna is altered. With this analysis, the orientation of second antenna element giving the least interference and insertion loss is proposed, and all the parameters are studied. The proposed design exhibits an average peak gain greater than 2.8 dBi, envelope correlation coefficient (ECC) less than 0.0001, insertion loss less than -38 dB and stable radiation patterns over the entire wide bandwidth. The antenna operation (i.e. |S11| and |S22|<-10 dB) ranges from 4.1 to 6.4 GHz at port 1 and 4.35 to 6.5 GHz at port 2, thereby making the antenna suitable for Wireless Local Area Network (WLAN) and Wireless Fidelity (Wi-Fi) applications.

Comparing Channel Emulation Algorithms by Using Plane Waves and Spherical Vector Waves in Multiprobe Anechoic Chamber Setups

This paper evaluates the performances of channel emulation algorithms in the multiprobe anechoic chamber (MPAC) by using plane wave (PW) and spherical vector wave (SVW) theories. Channel emulation in MPAC enables the over-the-air (OTA) testing of performances of wireless devices under realistic propagation scenarios, through setting excitation voltages of probes and utilizing the polarized radiation patterns, locations, and orientations of probe antennas to emulate desired fields in test zone. Accurate emulation of radio wave propagation in target scenario guarantees that the device under test (DUT) be assessed fairly in the laboratory. Dynamic multipath scenario and orthogonal polarization can be emulated by exciting the multiple probes in such a way that the total fields from probes resemble the target impinging field in the test zone. The excitation voltages can be either calculated by PW or SVW theories. Despite the fact that PW and SVW are mathematically equal in the far field, different treatments on rotation and translation of waves as well as different linear equations used in two methods result in different computed voltages, hence, different emulated fields. The emulation performances of the two methods with different MPAC setups (e.g., test zone size, probe number, probe sphere radius, and probe directivity) are investigated. Both scenarios of the 2-D field emulation with the 2-D probe configuration and the 3-D (or 2.5-D) field emulation with the 3-D probe configuration are discussed, and instructions on how to wisely use the emulation algorithm are provided.

A Source Stirred Reverberation Chamber Using a Robotic Arm

In a reverberation chamber, the stirring efficiency of the source stir technique is very high. However, to apply the source stir, the configuration (position, orientation, or polarization) of the transmitting (Tx) antenna has to be changed every time in the stirring process. To solve this problem, we use a three-dimensional printed robotic arm to control the position and orientation of the Tx antenna; thus, the source stirring process can be performed automatically. The measurement results are validated and compared with that from mechanical stirrers. Figures of merit such as autocorrelation, average K -factor, and total scattering cross-section are presented. The statistical distribution is also verified by using Kolmogorov–Smirnov test. Results show that the source stir technique outperforms the mechanical stirring technique significantly.

An Extremely Safe Low-SAR Antenna with Study of Its Electromagnetic Biological Effects on Human Head

In this paper, a new low-Specific Absorption Rate (SAR) antenna is proposed for the sake of safe communication in all situations. The proposed antenna involves a Microstrip patch antenna and a metallic casing loop which leads to SAR reduction. The structure operates at 0.9 GHz and 2.4 GHz which produces 0.52 W/kg and 0.25 W/kg SAR value on the human head, respectively. Then, in order to guarantee the antenna safety feature, the experiments are carried out when the human wear an earring. The impact of metallic earrings in different sizes on SAR distribution is investigated. Also, the antenna orientation and rotation effect is considered in detail. It is concluded that the change of Antenna position or use of metallic earrings makes an extremely significant impact on SAR value. But, the results of the presented antenna demonstrate that the produced SAR value in all positions, do not exceed the safe rate. It makes the antenna a suitable candidate for employing in most telecommunication applications.

A Crane-Based Portable Antenna Measurement System—System Description and Validation

A portable near-field (NF) antenna measurement system for frequencies up to Ka -band is presented and evaluated in detail. The system follows the idea to collect measurement samples on arbitrary scan surfaces in the NF, where strong irregularities of the sample distribution may be tolerated as long as appropriate sampling criteria are fulfilled. The radio frequency (RF) equipment is integrated in a gondola, which is positioned by a standard overhead crane. During an NF scan, the exact position and orientation of the probe antenna are measured by a 6-D laser tracking system with high accuracy. The RF measurement system works with a phase-coherent measurement loop, where the signal transmission from the ground station to the RF equipment within the portable gondola is performed by an optical fiber transmission system with three optical fibers, realizing magnitude as well as phase compensation. The NF measurement samples are merged with the position and orientation data and, finally, transformed into the far-field by a flexible and highly efficient equivalent source algorithm. The complete setup of this measurement system is presented and discussed in detail, focusing on both hardware and software aspects. A series of validation and practical antenna measurement results is presented to demonstrate the feasibility of this approach.

Experimental Analysis of Ultra-Wideband Body-to-Body Communication Channel Characterization in an Indoor Environment

This paper presents an experimental and analytical investigation of ultra-wideband (3-8 GHz) body-to-body (B-to-B) channel characterization. The channel parameters obtained are compared with off-body (off-B) and no-body (no-B) links. Measurements have been carried out considering different body positions and orientation of the Tx-Rx pair. The type of channel link and position of the wearable antenna lead to significant changes in the radio link channel. Path loss (PL) computed shows the increase in magnitude for non line of sight (NLOS) in comparison to line of sight (LOS), though the variation over a distance of 5 m is more significant for LOS (10 dB) than NLOS links (4-5 dB). For total NLOS links, B-to-B channels have slightly higher PL and delay spread parameters in comparison to off-B channel. The B-to-B LOS channels have least PL (44-56 dB), rms delay spread (0.5-4 ns), and multipath components (3-20) which can be attributed to the directional radiation pattern due to the presence of the human body for both Tx and Rx nodes. For back-to-back antenna orientation of the B-to-B channel, maximum signal strength degradation and multipath are observed. It can be concluded that for certain links, the B-to-B channel shows a significant change in channel behavior in comparison to off-B/no-B scenario.

Ear-to-Ear Propagation Model Based on Geometrical Theory of Diffraction

An ear-to-ear (E2E) propagation model based on geometrical theory of diffraction (GTD) is presented. The model uses the creeping wave loss along the geodesic paths that connect the ears. It is the first model to investigate which geodesic paths that link the ears. The model uses GTD expressions for a lossy dielectric material, which is a much better approximation of the human body than the perfect electric conductor approximation often used. The model is validated for the industrial, scientific, and medical band at 2.45 GHz. The model is valid at any frequency range as long as the propagation loss through the head is significantly higher than the propagation loss around the head. Similarly, the model could be used for other areas of the body. The comparison with simulations shows strong correlation. The antenna orientation and frequency sweeps were performed to further investigate the model. The sweeps change the radiation pattern of the antenna to utilize different paths around the head, but the model still correlates with the simulation. This validates the model's division of the E2E propagation into different geodesic paths around the head.

Wideband Monostatic Co-Polarized Co-Channel Simultaneous Transmit and Receive Broadside Circular Array Antenna

A novel wideband monostatic circularly co-polarized co-channel simultaneous transmit and receive (C-STAR) broadside circular array antenna with a partially shared beam-forming network (BFN) is proposed. The configuration consists of four sequentially rotated two-arm Archimedean spiral antennas, backed by a finite ground plane and driven by a BFN. Every two diagonal antenna pairs are fed with differential phases to obtain similar co-polarized broadside transmitting (TX) and receiving (RX) beams. Each individual element has single feeding port and operates simultaneously as TX and RX over the same frequency. The proposed C-STAR approach utilizes antenna orientation, geometric symmetry, and partially shared BFN to overcome self-interference. In the absence of asymmetry and BFN imbalances, complete wideband self-interference cancellation is achieved without relying on time-, frequency-, space-, pattern-, antenna/port-, or polarization-multiplexing. The fabricated prototype has measured TX/RX isolation >38 dB, axial ratio <;3.7 dB, and realized gain between 3 and 8.8 dBic over 1.25-2.5 GHz. The TX and RX radiation patterns are similar with envelope correlation coefficient >0.93.

Empirical analysis and modeling of Argos Doppler location errors in Romania.

BackgroundAdvances in wildlife tracking technology have allowed researchers to understand the spatial ecology of many terrestrial and aquatic animal species. Argos Doppler is a technology that is widely used for wildlife tracking owing to the small size and low weight of the Argos transmitters. This allows them to be fitted to small-bodied species. The longer lifespan of the Argos units in comparison to units outfitted with miniaturized global positioning system (GPS) technology has also recommended their use. In practice, large Argos location errors often occur due to communication conditions such as transmitter settings, local environment, and the behavior of the tracked individual.MethodsConsidering the geographic specificity of errors and the lack of benchmark studies in Eastern Europe, the research objectives were: (1) to evaluate the accuracy of Argos Doppler technology under various environmental conditions in Romania, (2) to investigate the effectiveness of straightforward destructive filters for improving Argos Doppler data quality, and (3) to provide guidelines for processing Argos Doppler wildlife monitoring data. The errors associated with Argos locations in four geographic locations in Romania were assessed during static, low-speed and high-speed tests. The effectiveness of the Douglas Argos distance angle filter algorithm was then evaluated to ascertain its effect on the minimization of localization errors.ResultsArgos locations received in the tests had larger associated horizontal errors than those indicated by the operator of the Argos system, including under ideal reception conditions. Positional errors were similar to those obtained in other studies outside of Europe. The errors were anisotropic, with larger longitudinal errors for the vast majority of the data. Errors were mostly related to speed of the Argos transmitter at the time of reception, but other factors such as topographical conditions and orientation of antenna at the time of the transmission also contributed to receiving low-quality data. The Douglas Argos filter successfully excluded the largest errors while retaining a large amount of data when the threshold was set to the local scale (two km).DiscussionFilter selection requires knowledge about the movement patterns and behavior of the species of interest, and the parametrization of the selected filter typically requires a trial and error approach. Selecting the proper filter reduces the errors while retaining a large amount of data. However, the post-processed data typically includes large positional errors; thus, we recommend incorporating Argos error metrics (e.g., error ellipse) or use complex modeling approaches when working with filtered data.

Design and measuring performance of the ITER plasma position reflectometer in-port-plug antennas

Design parameters of the ITER Plasma Position Reflectometer (PPR) in-port-plug antennas are determined and their measurement performance is assessed using 2D full wave analysis. Two ITER scenarios were selected in order to determine the optimum antenna position and orientation, namely the ITER QDT = 10 baseline scenario (15 MA) and the low density one planned for the initial non-active phase at 7.5 MA. Using them to feed a 3D ray tracing code, the spatial position and optimum orientation angles of each set of emission and detection antennas were determined. Additionally, a far field analysis of the launching radiation patterns led to the definition of the antenna dimensions in terms of optimal power coupling. After this preliminary work, 2D full wave simulations using a finite difference time domain (FDTD) code were carried out to assess the measurement performance of the system. To this end, the detected wave amplitudes and phases were evaluated for each scenario and two models of the scrape-off layer (SOL) density profiles. By calculating the spectrogram of the complex amplitude of the detected wave, the reconstruction of the plasma density profile can be made and be directly compared with the input profiles. As a result from this synthetic diagnostic analysis, an estimation of the error in the determination of the last closed flux surface position was possible.

Implementación de un Sistema de Seguimiento Automático de Satélites Pequeños para la recepción e Interpretación de Señales Beacon desde la Estación Terrena del CTIC-UNI

In recent decades, universities and technology institutes have joined the construction of artificial satellites; they are developing small satellites for research in aerospace. These satellites require at least one ground station, which uses hardware and software to establish communication with the satellite. In addition, ground stations have computerized systems to manage data from the satellite. This document describes the procedures for automatic tracking of small satellites to receive Beacon signals, i.e. basic information that are sent by small satellites on a regular basis in the form of radio-frequency signals. The system uses a set of hardware devices such as radio, antenna, rotor, TNC, which will be responsible for receiving satellite data, the system also uses software for remote management of equipment and data received. Small satellites are usually low orbit, i.e., they are orbiting around the earth at an altitude of between 200Km and 800Km, moving at high speeds relative to ground station. Therefore, the position of the satellite transmitter and the frequency of the received signal changes continuously, then antenna orientation and radio frequency adjustment are required, these often are done manually. Automatic control of radio frequency and antenna orientation improves the reception of Beacon signals emitted by the satellite. The frequency shift and antenna angle values are obtained by orbit predictor software and equipment will be handled by open-source libraries; also, using the advantages of the internet, we can control the system from any PC with Internet access. The main objective is to improve the reception of satellite signals, reduce noise level, facilitate earth station monitoring and get automatic decoding with few errors. The information obtained through Beacon signal is coded using Morse code, which is why it is necessary to use a TNC to decode the information. The management software for small satellite data obtained is based on Mercury project, adapted to the hardware of CTIC-UNI ground station. We achieved on-line decoding of Beacon signals from several small satellites that are operational to date.

Computer simulated assessment of radio frequency electromagnetic waves for the detection of obstructive sleep apnea

Abstract Obstructive sleep apnea/hypopnea syndrome (OSAHS) is the most common form of sleep-disorder breathing (SDB). Recurring restriction or occlusion of the upper airway throughout the night concurrent with continued respiratory efforts lasting more than 10 s characterizes the disorder. Prevalence of OSAHS is increasing globally, with a high association with obesity, hypertension, and heart failure. Nocturnal polysomnography (NPSG), which is the gold standard for OSAHS diagnosis, is scarce, expensive, and cumbersome. Methods for home screening and diagnosis of the disorder, directly and indirectly, are highly sought after to amend or replace NPSG. Well-established norms and procedures for electromagnetic (EM) antenna design, radiation pattern and characterization, and signal reception and measurements can be employed for the direct detection of upper airway occlusion. The utilization of radio-frequency (RF) EM antennas is desirable, as it is inexpensive, and simple to design and implement. In this paper, a computerized simulation of a new EM sensing system for direct detection of the occlusion in the upper airway is presented. Electromagnetic, anatomical, and RF safety constraints are taken into consideration. The theoretical basis of EM, antenna design, and physiological interactions with EM waves are presented. The proposed methodology for creating an anatomically-correct neck and airway simulated phantoms to test the hypothesis and the results of the tests are presented. Hypothesis Radio-frequency electromagnetic waves transmitted through an open airway will have different energy levels at the distal side of the neck compared to those associated with a fully occluded airway. Methodology A system is designed comprising a simulated phantom model of the upper airway and neck with the approximate anatomical dimensions and dielectric properties of homogenous neck tissue. Additionally, an RF patch antenna is designed and matched to the phantom neck. An iterative process is developed and implemented for the patch antenna design and coupling with a tissue. Simulation of the EM wave propagation and dissipation throughout the neck in the open and closed airway cases is provided and calculated based on the specific absorption ratios (SAR). The results of several permutations of antenna orientation with respect to the neck and several gaps between the antenna and the neck are provided. Results the Computer simulations for all antenna orientation and location have shown that the EM energy levels recorded from open airway phantom models are statistically different and lower than those recorded from the occluded airway phantom models. Conclusions The results of this study support the hypothesis that it is theoretically feasible to use electromagnetic energy to distinguish between open and occluded upper airway.

Antenna array-enhanced attenuated total reflection IR analysis in an aqueous solution.

Attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) is a powerful technique that provides structural and functional information during dynamic reactions in aqueous solutions. One existing limitation is the sensitivity to extract the signals of trace-level analytes from the background water in situ and in real time. Here, we proposed a novel ATR-SEIRAS platform that integrated a large-scale triangle gold antenna array onto a conventional ATR-IR platform to increase the sensitivity of this analytical technique. A square centimeter level well-ordered gold antenna array was fabricated onto an Si prism via nanosphere lithography. The size-dependent antenna array resonance had weak correlation with the incident polarization and antenna orientation, allowing antenna array-enhanced IR detection without the requirement of a microscope. In addition, the antenna resonance shift that occurred due to analyte adsorption-induced refractive index variation could be minimized benefiting from the high refractive index of Si (3.4). As a demonstration, we dynamically monitored the adsorption of the trace levels of proteins on top of the antenna array with a real signal enhancement factor larger than 300. Our platform opens an avenue to apply antenna array-enhanced IR spectroscopy in an aqueous environment measured via commercial IR instruments, which is extremely promising for the interfacial applications that require signal enhancement.

Conformal coverage of liver tumors by the thermal coagulation zone in 2450-MHz microwave ablation

Purpose: To optimize treatment schemes using 2450-MHz microwave ablation (MWA), a novel conformal coverage method based on bipolar-angle mapping is proposed that determines whether a liver tumor is completely encompassed by thermal coagulation zones.Materials and methods: Firstly, three-dimensional (3-D) triangular mesh data of liver tumors were reconstructed from clinical computed tomography (CT) slices using the Marching cubes (MC) algorithm. Secondly, characterization models of thermal coagulation zones were established based on finite element simulation results of 40, 45, 50, 55, and 60 W ablations. Finally, coagulation zone models and tumor surface data were mapped and fused on a two-dimensional (2-D) plane to achieve conformal coverage of liver tumors by comparing the corresponding polar radii.Results: Optimal parameters for ablation treatment of liver tumors were efficiently obtained with the proposed conformal coverage method. Fifteen liver tumors were obtained with maximal diameters of 12.329–78.612 mm (mean ± standard deviation, 39.094 ± 19.447 mm). The insertion positions and orientations of the MWA antenna were determined based on 3-D reconstruction results of these tumors. The ablation patterns and durations of tumors were planned according to the minimum mean standard deviations between the ablative margin and tumor surface.Conclusion: The proposed method can be applied to computer-assisted MWA treatment planning of liver tumors, and is expected to guide clinical procedures in future.

Динамический выбор радиолиний для систем подвижной спутниковой связи

In this paper presents suggestions for the noise immunity improval of mobile satellite communications lines in difficult physical and geographical conditions through the use of automatic dynamic identification algorithms for the suitability of radio lines and the dynamic antenna orientation devices of mobile satellite communications systems. Based on the results obtained, recommendations for practical application are formulated.

Glacier bed surveying with helicopter-borne dual-polarization ground-penetrating radar

ABSTRACTTraditionally, helicopter-borne ground-penetrating radar (GPR) systems are operated with a single pair of bistatic dipole antennas to measure the thickness of glaciers. We demonstrate numerically that the directivity of the radiation pattern of single airborne dipoles do not correspond to an ideal full-space solution if the antennas are employed at typical flight heights. These directionality effects can degrade the quality of the subsurface images significantly, when the GPR antennas are orientated unfavorably. Since an adjustment of the antenna orientation is impractical during flight, we have developed a novel dual-polarization helicopter-borne GPR system consisting of two orthogonal pairs of commercial antennas in broadside configuration. To overcome the image quality deficits of the individual channels, we apply a pseudo-scalar approach in which we combine the data of both polarizations. Results of helicopter-borne GPR surveys on two alpine glaciers in Switzerland reveal more coherent bedrock reflections in the summed data compared with single dipole pair profiles. Generally, the dual-polarization setup is more suitable than a single antenna systems, because it is more versatile and less prone to directional effects caused by the placement of the dipole antennas in relation to undulating subsurface reflectors.

Assessing Ground Penetrating Radar's Ability to Image Subsurface Characteristics of Icy Debris Fans in Alaska and New Zealand

Icy debris fans have recently been described as fan shaped depositional landforms associated with (or formed during) deglaciation, however, the subsurface characteristics remain essentially undocumented. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans (IDFs) at McCarthy Glacier, Alaska, USA and at La Perouse Glacier, South Island of New Zealand. IDFs are largely unexplored paraglacial landforms in deglaciating alpine regions at the mouths of bedrock catchments between valley glaciers and icecaps. IDFs receive deposits of mainly ice and minor lithic material through different mass-flow processes, chiefly ice avalanche and to a lesser extent debris flow, slushflow, and rockfall. We report here on the GPR signal velocity observed from 15 different wide-angle reflection/refraction (WARR) soundings on the IDFs and on the McCarthy Glacier; the effect of GPR antenna orientation relative to subsurface reflections; the effect of spreading direction of the WARR soundings relative to topographic contour; observed differences between transverse electric (TE) and transverse magnetic (TM) antenna polarization; and a GPR profile extending from the McCarthy Glacier onto an IDF. Evaluation of the WARR soundings indicates that the IDF deposits have a GPR signal velocity that is similar to the underlying glacier, and that the antenna polarization and orientation did not prevent identification of GPR reflections. The GPR profile on the McCarthy Glacier indicates that the shallowest material is layered, decreases in thickness down fan, and has evidence of brittle failure planes (crevasses). The GPR profile and WARR soundings collected in 2013 indicate that the thickness of the McCarthy Glacier is 82 m in the approximate middle of the cirque and that the IDF deposits transition with depth into flowing glacial ice.

Broadband Printed Antenna with Modified Rectangular Patch and U-Slot in Ground Plane

A broadband patch antenna is presented with a modified rectangular patch containing three symmetrical slots and an asymmetrical slot. A U-slot is inserted into the ground plane, which enables a wide operational fractional bandwidth of 143% ranging 2.9–17.5 GHz. The modified rectangular patch offers acceptable omnidirectional radiation pattern at higher frequencies with radiation efficiency of 83 to 95%. The maximum achievable gain is 5.48 dBi across the entire bandwidth. The electromagnetic wave modeling is conducted using high frequency simulator structure (HFSS) and the circuit model is simulated with Advance Designing System (ADS) software. The housing effect is studied using vertical orientation of antenna to approximate its performance in the presence of conducting bodies. The proposed antenna architecture has small electrical dimension of 0.17×0.11λ. Simple configuration and wide bandwidth makes proposed patch antenna a suitable candidate for versatile communication applications.