Aerial Array Research Articles

Устранение неоднозначности измерений в фазовых пеленгаторах с двумя ортогональными линейными антенными решетками

The algorithm of estimating the bearing in phase direction finders with a flat aerial array is suggested according to a set of differences in signal phases measured between the elements of the aerial system. The aerial system presents two linear lattices located orthogonally. The law of distributing the error probabilities of the phase measurements does not influence the algorithm. The algorithm can be applied for the direction finders equipped with the orthogonal linear lattices having any number of phase-measuring bases.

Accumulated error elimination method of aerial array image stitching

Accumulated error elimination method of aerial array image stitching

Method of multichannel calibration for unmanned aerial vehicle surveillance radar

Amplitude and phase errors among the different channels including antenna and receiver of the unmanned aerial vehicle surveillance digital array radar will deteriorate the beam pattern and cause the invalid digital beam formation, and then severely affect the performance of radar. Based on in-the-field calibration method, this study presents a practical calibration method that combines the external and internal calibration together. Experiments are designed for an X-band linear antenna array with 16 unit cells, whose period is about half wavelength, and the measured results show that the proposed algorithm is an attractive way to calibrate the digital array radar efficiently.

Antenna systems for small spacecraft radio data communication channels

Antenna-feeder devices are used on spacecraft, which are part of various on-board systems and complexes. One such system is a radio communication channel for transmitting target information. A model of the aerial array of the radio data communication of target information from waveguide transmitters is developed and its characteristics are determined.

Development of communication models of wireless environment in emergency situations

Two-point communication model of the wireless environment with one-beam and multi-beam propagation of radio waves were developed. The specified models make it possible to create various particular two-point communication models of wireless environment, taking into account the assigned geometry of location of shadowing and scattering structures in the environment. The practical use of the proposed models is limited to arbitrary points of radiation and reception in the environment, taking into account location of directional aerials in them. To study known multipoint technologies under conditions of emergency situations, we developed the multipoint communication models with one-beam and multibeam propagation of radio waves from each radiation point to each reception point, predetermined by the presence of shadowing and scattering structures in the environment. The developed multipoint models make it possible to create specific models at the physical level for various multi-aerial technologies, taking into consideration the use of aerial arrays of arbitrary configuration at the transmitting and receiving sides. Verification of the developed communication models of the wireless environment was performed. It was found that the use of directional aerials at the transmitting and receiving sides of the wireless environment in the presence of considerable shadowing and scattering structures makes it possible to significantly improve noise immunity. It is noted that with the use of the developed communication models, it is possible to carry out in-depth examination of the physical level with a view to developing a reliable and stable architecture of communications under conditions of emergency situations.

An efficient traffic monitoring and control system using aerial platforms and vertical arrays

In this paper, a reliable traffic monitoring system is proposed based on aerial platform (AP) wireless sensor network with a new adaptive vertical linear array beamforming technique. This proposed beamforming technique improves the system performance compared with recent techniques using the same number of antenna elements which makes aerial platforms more feasible to establish wireless sensor network for traffic monitoring application. Four coverage scenarios of the proposed AP traffic monitoring system are examined at coverage diameters of 16 and 60 km and two bit rates of 38.4 and 250 kb/s. The simulation results depicts better performance of the proposed antenna technique in all the four examined coverage scenarios. At the worst case (60 km coverage diameter, 2400 MHz frequency and bit rate of 250 kb/s), the probability of bit-energy to noise-spectral-density (\(E_{b}/N_{o})\) to be less than 4 dB is zero for the proposed technique while it was 0.14 in the case of optimized concentric circular array technique and 0.76 for the conventional spot-beam antenna. Also, at the coverage diameter of 16 km and bit rate of 38.4 kb/s at 868 MHz, the results show that the probability of \(E_{b}/N_{o} < 34\) dB of the proposed technique is zero while it was 0.15 in the case of optimized concentric circular array and 0.72 for the conventional spot-beam antenna.

Uso de la cápsula endoscópica en niños con sangrado de tubo digestivo de origen desconcocido

Intrucccion. La cápsula endoscópica (CE) es un dispositivo que permite examinar el intestino delgado. La cápsula es impulsada por la peristalsis a lo largo del tubo gastrointestinal y proporciona imágenes de video que son transmitidas por telerradiometría y captadas por una red de antenas adheridas al cuerpo. La cápsula puede detectar lesiones intestinales en pacientes con enfermedad de Crohn, con enfermedad celíaca; tumores malignos, alteraciones por el uso de antiinflamatorios no esteroides y síndromes que cursan con pólipos, malformaciones vasculares y hemangiomas. Presentamos la experiencia en nuestro hospital. Material y método. En el Centro Médico Nacional 20 de Noviembre ISSSTE México de enero 2008 a marzo 2009 se realizó un estudio prospectivo no aleoatorizado, en pacientes con sangrado de tubo digestivo de origen desconocido cuyos estudios con panendoscopia y colonoscopia eran normales. Además de los parámetros habituales se registraron el diagnóstico inicial, el diagnóstico final, el tratamiento médico, el quirúrgico o ambos y la evolución. Resultados. Fueron ocho pacientes entre nueve y 15 años de edad (media de 12). Seis masculinos y dos femeninos. Dos pacientes tenían hiperplasia linfoidea; un paciente tenía un hemangioma a 25 cm del Treitz. Dos pacientes, enfermedad de Crohn; un paciente pólipos en la porción media del íleon; un caso normal. En todos los casos excepto en el que el estudio fue normal, se resecaron las lesiones y se tomó una biopsia. La evolución fue satisfactoria en todos. Discusión: La cápsula endoscópica es útil para detectar sangrado del intestino. Se usa cuando la colonoscopia y la panendoscopia son negativas y el paciente continúa sangrando; proporciona una imagen de certeza y permite evaluar la necesidad o no de un tratamiento quirúrgico.

Evanescent Fields inside a Cut-off Waveguide as Near Fields

Usually, electromagnetic evanescent waves are some kinds of near fields. However, it looks as if the evanescent waves inside a cut-off waveguide had nothing to do with any near field. In this paper, we will show that the evanescent waves inside a cut-off waveguide can also be regarded as the near fields of an aerial array.

Large-area, scalable fabrication of conical TiN/GST/TiN nanoarray for low-power phase change memory

We demonstrate the fabrication and phase change memory performance of a conical TiN/Ge2Sb2Te5 (GST)/TiN nanoarray prepared viablock copolymer lithography and straightforward two-step etching. The created 30 nm scale phase change memory cell (aerial array density: ∼207 Gbit inch−2) showed a threshold switching voltage of 1.1 V, a value compatible to conventional phase change memory cells. More significantly, the cell could be amorphized by a reset pulse of 1.8 V height and 100 ns width, where the reset current was 100 μA. Such a low reset current, presumably caused by nanoscale small cell dimension, is greatly beneficial for low power consumption device operation. Reversibly, the set operation was accomplished by crystallization with a set pulse of 1.2 V height, 100 ns width, and 100 ns trailing. This work provides a significant step for low power consumption and ultra-high density storage based on phase change materials.

AN ANALYSIS AND APPRAISAL OF TOPOGRAPHIC INFLUENCE ON AERIAL ARRAY CCD IMAGES

Topographic factors such as hypsography and earth curvature are greatly responsible for remote sensing image distortion.Nevertheless,the earth curvature is often neglected by traditional aerial photogrammetry in processing the films.With the Multi-mode Aerial Digital Camera system(MADC) developed and produced by IRSA as the object,this paper analyzed the topographic influences on aerial array CCD imaging.On the basis of the imaging model and geometric configuration of MADC,the distortion models of hypsography and earth curvature were derived respectively for estimating topographic influences by simulating data.It is concluded that the earth curvature distortion must be rectified in precise processing of aerial array CCD images.

Three‐field photometer observations of short‐period gravity wave intrinsic parameters in the 80 to 100 km height region

A three‐field photometer (3FP) for making observations of airglow in the Mesosphere Lower Thermosphere (MLT) region has been operated at the center of the large MF aerial array located near Adelaide (138°E, 35°S) since 1993. Observations of the 557.7 nm airglow intensity emitted by atomic oxygen (OI) at heights near 97 km and the 730.0 nm airglow intensity emitted by hydroxyl (OH) near 87 km have been made simultaneously with MF spaced antenna observations of wind velocities in the 80–100 km height region. The 3FP measures the intensity of the 557.7 nm airglow in three fields separated by about 13 km at heights near 97 km, and then the intensity of the 730 nm airglow in three fields separated by about 12 km at heights near 87 km, on a 60 s cycle. These data have been analyzed to yield gravity wave observed phase speeds and horizontal wavelengths. Simultaneous MF radar data have been analyzed to yield measurements of the neutral wind velocity in 2 km height steps in the 80–100 km height interval every 2 min, and these have been used together with the observed wave parameters to calculate intrinsic gravity wave parameters. This paper presents a very brief overview of the system, the motivation for the work, and preliminary analysis of the data from 1995 until 2000.

4467 Wireless endoscopy.

Background: Miniaturization of electronic components might allow the development of a new type of wireless endoscopy. Advances in complementary metal oxide silicon (CMOS) technology allow high quality video images to be transmitted with much lower power consumption than with charge coupled devices (CCDs). Small bowel endoscopy is currently limited by problems of discomfort and failure to advance far into the small-bowel. Aim: To develop and test wireless capsule endoscopy. Methods: Using a CMOS imaging chip, miniature processor, white light emitting diode (LED) light source, short focal length lens, miniature transmitter and antenna powered by silver oxide batteries, a wireless capsule endoscope (Given Imaging) was constructed measuring 11 x 33 mm. Results: The video images were transmitted using a radio-frequency signal (approx. 410 MHz) at a rate of two frames per second to an array of aerials attached to the body which allowed image capture and were also used to calculate the position of the capsule in the body. The images were stored on a portable recorder carried on a belt and subsequently downloaded for analysis. The system allowed more than 5 hours of recording of images from the gastrointestinal tract. Live transmission of good quality video images were obtained for 6 hour periods in dogs. With ethical committee approval the first human volunteer studies were performed. The capsule was easily swallowed and caused no discomfort whatsoever. The capsule, propelled by peristalsis, successfully transmitted video images from the whole of the small bowel and reached the cecum in under 2 hours. The image window remained clear through out the whole of the transmissions. Trigonometric analysis of signal strength allowed continuous monitoring of anatomic endoscope position. Clear video images of the human small bowel were recorded from the pylorus to cecum. Conclusion: This study reports the development of a new type of endoscopy which for the first time allows painless endoscopic imaging of the whole of the small bowel for prolonged periods. Its development, testing and first application in man is described. Background: Miniaturization of electronic components might allow the development of a new type of wireless endoscopy. Advances in complementary metal oxide silicon (CMOS) technology allow high quality video images to be transmitted with much lower power consumption than with charge coupled devices (CCDs). Small bowel endoscopy is currently limited by problems of discomfort and failure to advance far into the small-bowel. Aim: To develop and test wireless capsule endoscopy. Methods: Using a CMOS imaging chip, miniature processor, white light emitting diode (LED) light source, short focal length lens, miniature transmitter and antenna powered by silver oxide batteries, a wireless capsule endoscope (Given Imaging) was constructed measuring 11 x 33 mm. Results: The video images were transmitted using a radio-frequency signal (approx. 410 MHz) at a rate of two frames per second to an array of aerials attached to the body which allowed image capture and were also used to calculate the position of the capsule in the body. The images were stored on a portable recorder carried on a belt and subsequently downloaded for analysis. The system allowed more than 5 hours of recording of images from the gastrointestinal tract. Live transmission of good quality video images were obtained for 6 hour periods in dogs. With ethical committee approval the first human volunteer studies were performed. The capsule was easily swallowed and caused no discomfort whatsoever. The capsule, propelled by peristalsis, successfully transmitted video images from the whole of the small bowel and reached the cecum in under 2 hours. The image window remained clear through out the whole of the transmissions. Trigonometric analysis of signal strength allowed continuous monitoring of anatomic endoscope position. Clear video images of the human small bowel were recorded from the pylorus to cecum. Conclusion: This study reports the development of a new type of endoscopy which for the first time allows painless endoscopic imaging of the whole of the small bowel for prolonged periods. Its development, testing and first application in man is described.

The new Adelaide medium frequency Doppler radar

The Buckland Park Aerial Array (35°S, 138°E) is situated about 40 km north of Adelaide, Australia, on a flat coastal plain. It was designed by B. Briggs with assistance from G. Elford and constructed between 1965 and 1968. The first results were published in the late 1960s (Briggs and Elford, 1968; Briggs et al., 1969). Since then some 250 papers have been published using data from the array. Some aspects of the history of the array are described by Briggs (1993). A new medium frequency (MF) Doppler radar utilizing the array has been developed, and this paper describes some of the technical details of this new facility.

Laboratory investigations of pulsed RF plasmas relevant to CW arc pluming at high-power aerials. Part 2: Relevance of scale-model studies based on pulsed RF techniques

The paper describes experiments which extend the observations of RF breakdown events in nonuniform fields reported in Part 1 of the paper. In particular, emphasis is given to examining the relevance of laboratory observations on pulsed RF discharges to the understanding of the ‘pluming’ phenomenon occurring under CW conditions at high-power aerial arrays. This is achieved by examining the effects of various scaling factors on the breakdown characteristics using both scaled sphere-to-plane and scaled toroid-to-plane geometries. It is shown how the intrusion of objects with needle-point geometries can lead to dramatic reductions in the critical electric fields needed to initiate the unwanted ‘pluming’ phenomeonon.

Adaptive arrays—a theoretical introduction

Adaptive antenna arrays are aerial arrays which are able to adjust themselves automatically and electronically to meet particular constraints. In this paper, arrays in which the reception of interfering signals is minimised are considered. The theory of a particular form of these arrays, the linear uniformly spaced array of identical elements, is introduced and some of the possible adaptation algorithms are considered.

Adaptive antennas for u.h.f. broadcast reception

Adaptive arrays are aerial arrays which are able to adjust themselves automatically and electronically to meet particular constraints. The IBA&apos;s steerable adaptive broadcast equipment (s.a.b.r.e.) is designed for the reception of u.h.f. television signals where the constraint is that of minimising the level of cochannel interference relative to the wanted signal. The paper describes the first practical implementation, which has been in operation in the Channel Islands since March 1977, and also considers the future applications of adaptive arrays.

Radio communications for travellers on the Arctic Ocean

The Arctic Ocean covers an area of roughly 10 million km2. The terrain, in reality an ocean of ice, varies in altitude from sea level to pressure ridges and floes up to 60 m high, in which extensive leads of open water may well be encountered. In the short summer period the temperature can rise significantly above freezing point but during winter the air temperature will drop to levels well below —48°C. During the winter, high winds will buffet radio antenna installations and ice storms render an aerial array virtually useless. In the Arctic basin, periods of mist and fog frequently occur, and during these it will be impossible to determine bearing or position by conventional navigation methods. During any extended journey beyond the land mass surrounding the Arctic Ocean it is important, therefore, to establish communication with base headquarters at an early stage and at regular intervals thereafter to ensure adequate re-supply, provide a homing aid for the re-supply aircraft and to call for assistance or instructions in the event of an emergency.

The calculation of radiation patterns for transmitting aerial arrays using dipole reflector panels and operating in the broadcast bands

Equations have been developed for calculating the horizontal and vertical radiation patterns for radially mounted dipole arrays. Techniques such as phasing, current shaping, and horizontally-offset v.s.w.r.- compensated arrays, have been provided for. The infinite reflector has been assumed throughout, but the finite reflector has also been considered, for simple pole-mounted arrays. The array gain is calculated directly from the dipole equations, taking some mutual resistance effects into consideration. Provision is made in the calculations for the application of phase progression, beam tilt and null filling.

X-band microwave integrated circuits using slotline and coplanar waveguide

Experimental results are given for propagation in a selection of slotline and coplanar geometries. Examples are given of X-band planar circuits incorporating semiconductors including balanced mixers, and p-i-n-diode switches and attenuators. Finally, an example of how slotline dipoles may be used to produce a simple aerial array is presented.

A Long-range Ocean Radar for Ocean Surface Studies using Backscatter Via the Ionosphere

An HF Doppler radar, designed for use at long range via an ionospheric propagation mode, has been developed primarily for the determination of wave states over large ocean areas. The operating frequency is 21 �840. MHz, and the array is physically rotatable through a full 3600 of azimuth, thus allowing for great flexibility in the choice of target area. The experimental technique utilizes a well-known resonance interaction mechanism for electromagnetic waves backscattered from a moving sea wave surface to derive sea state parameters in the scattering region for input to oceanographic and meteorological synoptic data networks. An ultimate angular resolution of less than 10 of azimuth, coupled with high operational flexibility, suggest possible utilization of the aerial array for tracking and interrogating free-floating ocean buoys, tracking radio noise associated with tropical cyclones and investigating aspects of ionospheric dynamics.