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This research analyzes an approach to increase the radio link contact time of telemetry and telecommand data of low orbit satellites based on the data relay systems through Inmarsat-F4 GEO satellites constellation. For practical purposes, the orbital dynamics between a LEO and GEO satellites using TLE orbital parameters of the SAOCOM 1A satellite and Inmarsat-F4 constellation has been used. The results obtained allow us to determinate the radiation pattern characteristics that must be fulfilled by the proposed antenna. On the other hand, the link budget calculations shows that we could use an low gain antenna. In this way, an Conical Quadrifilar Helix Antenna with hemispherical radiation pattern in elevation angle, and omnidirectional in azimuth angle with Right Hand Circular Polarization (RHCP) has been designed. The main electrical parameters obtained are: HPBW: 198°, Axial Ratio (AR) lower 3dB with theta: −90° to 90°. |S 11 |: -40dB@1.61Ghz. Bandwidth: 239 MHz.

We present here the development of a rain sample model, based on real data of hydrometeors and simulate the response of this sample to a radar signal using the Method of Moments. The data used to create the model have details about the geometry and velocity of raindrops. After that, we compare the simulation results with reliable data in an attempt to validate this model for more accurate and elaborated studies of the polarization parameters and for search others and better ways to determine meteor characteristics.The response of the rain model to the electromagnetic wave is evaluated in terms of Reflectivity Factor and Differential Reflectivity, two of the most frequently used parameters in the meteorological radar area, to characterize the meteor subject of the measurement. The results are validated with data provided with the rain data source, obtained using 2D Video Disdrometers and real radar data obtained for place and time of the used sample of rain.

This work applies a new full-wave electromagnetic simulation code [1], to evaluate the performance of large-diameter lens antennas used in the microwave band. This code has great advantages over commercial software, which have great limitations when trying to simulate this type of lens antennas with a standard personal computer. Two types of lens antennas were analyzed, one with an hyperbolic profile and the other with an elliptical profile. The simulations results allowed to obtain the parameters that characterize the antennas, among them gain, beam width, etc. and compare the performance of both antennas.

In this work we study the radar cross section (RCS) of a raindrop using electromagnetic simulation sofware. Particularly we compare the response of two models of singular raindrops: the first one is a real raindrop shape model proposed by Pruppacher and Pitter and the other is a spherical model that contain the same water volume and is used to extract the meteorological parameters from the RCS, assuming that the RCS is the same of the real raindrop. We make this study for several raindrop sizes and for the most common frequency bands used for weather radars. We analyse here the difference of the RCS for both shapes and so on, the errors that could be occur by the assumption made.

The fractal antenna presents a multiband behavior in frequency, a property that can be used in the measurement of non-ionizing radiations, and thus knowing the level of signals present at certain frequency ranges of interest. This paper presents the design, simulation, construction and measurement of a printed fractal antenna with multiband characteristics using the Sierpinsky triangle according to the frequency requirements of the autonomous non-ionizing radiation meter [1].

This work describes a method of Terahertz (THz) imaging, which consists of irradiating different materials with THz radiation, emitted by a photoconductive antenna, excited by a femtosecond laser pulse. The detector used is a pyroelectric detector (thermal detector) operating at room temperature, calibrated for this frequency band. The method consists in recording the amplitude of the radiation transmitted by the materials, moving the sample both horizontally and vertically, between the antenna and the detector, generating a transmittance matrix for each sample. Results are obtained by determining the measurement range of the proposed system and the minimum sample size detected.

This work presents an analysis of optical vortices produced by homogeneous dielectric lens antenna with hyperbolic profiles in the millimeter waveband. The use of dielectric lenses can substantially improve the antenna parameters, especially the flatness of the radiated waves and the gain of the antenna. Simulations are performed using a recently published electromagnetic simulation code. The program yields field intensity and field phase graphics, allowing the analysis of the stationary field resulting from the feeder-lens array and its radiation pattern. In the phase graphics, diffraction effects are observed when the lens presents flat edges, evidencing the presence of optical vortices.

MANET is kind of mobile ad hoc network. MANETs are having self organizing and self configuring network and there is no centralized base station. In routing forwarding the data packets on one node to another node is core problem in the networks. Overcome to this problem to build up challenging task an efficient routing algorithm in MANET. Here we proposed method energy for routing in MANET and based on signal strength. Received Signal Strength (RSS) measured distance between two nodes. If value of RSS is greater than Th_RSS than intermediate node compare value of RSS and Th_RSS then accepted RREQ packet otherwise drop the packet and send to the next node it calculate node energy. If value of RSS is greater than Th_RSS than intermediate node will compare the value of residual energy RE with Energy_ threshold and value of queue length QLen with threshold of squeue length Th_QLen, then send RREQ packet next node otherwise drop the packet. This method is increases in network lifetime.

In this paper, a modal analysis of a slot inserted in a finite ground plane is presented, giving physical understanding of its radiation behavior and the interaction effects between the slot and the plane. The Theory of Characteristic Modes (TCM) reveals that for the case of slotted planar antennas the modes of the slot do not appear as independent modes. This paper also shows that the slot resonance fixes the upper frequency of the excited modes in the combined structure formed by the slot and the finite plate. Moreover, the modal analysis demonstrates that the radiation pattern stability and the radiation bandwidth of the slot antenna are directly related with the size of the finite ground plane. The conclusions reached with the application of TCM can be employed to optimize the geometry and the size of the finite plate in order to prevent the excitation of non-desired modes.

The crossed dipole is a common type of antenna that is used to generate circularly polarized radiation in a wide frequency range. This antenna was originally developed in the 1930s and today is used in many wireless communication systems, including broadcast services, satellite communications, mobile communications, global navigation systems satellite system (GNSS), radio frequency identification (RFID), wireless local area networks (WLANs) and global interoperability for microwave access (WiMAX). This paper shows that it is possible to obtain circular polarization with two cross dipoles with different lengths and connected in parallel by applying the Theory of Characteristic Modes. The results obtained using this new approach is consistent with those obtained using the normal method of analysis of input admittances.

This paper describes the design and construction of a crossed slot antenna array to be applied to an Incoherent Scatter Radar for measuring parameters of the Ionosphere. The slot antenna was designed and optimized with electromagnetic simulation software. An analysis of the characteristic modes of the elementary antenna of the array is performed, in order to obtain a physical understanding of the radiating behavior. A prototype of a linear crossed-slot antenna array has been constructed and measured, as an intermediate step for the development of a two-dimensional array.

We propose the development of a printed logoperiodic antenna, by combining the operating principles of the conventional logoperiodic with the construction technique of printed microstrip. Hence we obtain a compact design and small size antenna whose frequency response is within the expected bandwidth. This antenna will be used in conjunction with a detector device for true RMS values of RF signals [1], an autonomous electronic equipment able to measuring the level of electromagnetic fields in the most used bands of the radio-electrical spectrum. The information on the levels of non-ionizing radiation (NIR)-obtained with this method-in sensitive environments to humans such as hospitals, schools or recreation centers, represents a topic of special interest to study in various disciplines. There are numerous safety standards and recommendations [2], [3], [4] formulated with a precautionary principle to minimize the possible effects of human exposure to radiofrequency (RF). Self-monitoring of NIR level is encouraged as a way to collecting regular, systematic and reliable information [5] needed for future research. The development of printed logoperiodic antenna is part of the Technological and Social Development Project "Optimization and Control of Non-Ionizing Radiation" [6].

Underwater Archaeology is a relatively young science in Brazil, if compared to its status in other countries such as Canada, the US, France or Spain. Scientific researches date back to the beginning of the 1990's, with some isolated previous references in the 70's and the 80's. Because of that, some essential geophysical methods and techniques are overlooked at the time the research parameters are drawn. The aim of this presentation is to point out the crucial role of one type of acoustic survey — side scan sonar — to provide data for future Underwater Archaeological scientific research. This presentation focuses on some case studies in Brazilian Underwater Archaeology that have successfully used side scan sonar to locate objects and structures of archaeological interest. I will focus on my Master's dissertation, in which was used an analog side scan sonar (Klein Hydroscan 530 model, 100 KHz), to find an 18th century British cast iron cannon in Cananeia bar, in the southern coast of the state of Sao Paulo. Some additional points will be made, by means of the analysis of side scan records of a 19th century Brazilian steamboat sunk at Cananeia's downtown ferry terminal in 1858 which has also been surveyed with the same analog sonar. In addition, we wish to highlight some situations in which even more sophisticated side scan sonars (digital models, with low and high frequencies transducers) were relatively useless to Archaeology. Because the goal of the surveys was the acquisition of geological data for engineering purposes, it was impossible for the archaeological team to determine whether some specific kinds of regular geometrical anomalies that were recorded were natural or human made. Only direct examinations — with scuba divers — revealed that those anomalies were related to lateritic rocks and rays. In those cases, although the side scan sonars were newer and more sophisticated than Klein 530, the survey's aims resulted in poor accuracy for archaeological purposes due to the fact that the operators of the sonar were not originally focused on the acquisition of archaeological data.

A development of an Crossed Slot Antenna with ground plane is presented. This one was designed for work like Array Antenna Elementary Unit in an Incoherent Scatter Radar and was designed for 432 MHz. Here are described the requirements, the design process and optimization with software tools. Also there are description of measurements of a prototype, between 410 and 450 MHz, giving a VSWR

In the last decade, as demand for high quality materials are increased, the development of lightweight aluminum (Al) also increased especially in aerospace and automotive industries. It has been well known that Al based metal matrix composites (MMCs) offers a very low thermal expansion coefficient, high specific strengths, wear and heat resistance as compared to conventional Al alloys. In order to combine all these properties, MMCs have become a very attractive method for various industrial applications. The interest in Carbon Nano Tube (CNT) as reinforcements for aluminum (Al) has been growing considerably. Efforts have been largely focused on investigating their contribution to the enhancement of the mechanical performance of the composites. The uniform dispersion of Carbon Nano Tube in the Al matrix has been identified as being critical to the pursuit of enhanced properties. In this present research paper emphasis, the effect of Carbon Nano Tube content on the Mechanical properties of the composites like Tensile strength, Percentage of Elongation was investigated. The improvement of mechanical properties for composites of Al/CNT has been compared with pure aluminum.

This paper describes the preliminary design and construction of a development model of antennas proposed to be installed on satellites as microwave radiometers (MWR, Microwave Water Radiometer), at K and Ka bands. These instruments will be dedicated to study the global water cycle while analyzing geophysical parameters. Several antennas have been studied between the 23.8 GHz and 36.5 GHz frequencies to obtain a design which fulfills the technical requirements. An optimal result was obtained with multiple beam torus reflector antennas with an asymmetric feed array. The measured results are shown.

A waterborne GPR survey consisting of 50 profiles with a total length of about 37 km has been executed on the morainic lake of Candia northerly Turin (Italy). The survey tested the capability of GPR in shallow low-conductive waters to estimate bathymetry, water volume, bottom sediment type, bedding and porosity. Spotty measurements of electrical conductivity and temperature allowed for a better processing of GPR raw data. The results seem to confirm the effectiveness of GPR to give useful information providing suitable geometrical (water depth) and physical (water conductivity) conditions.

The match of research activity and paediatric healthcare services offered by the IRCCS “Burlo Garofolo”, produces a complex situation especially regarding IT security. World-wide IT Security issues in the recent years have had an exponential development of problems to face. Meanwhile, risks and threats are therefore growing and so all the problems tied up to the vulnerabilities’ management generating risks for the hospital security. These remarks aren’t involving only the continuous fitting to the application of the current Italian Regulation, but the search of tools (technological and organizational) that may guarantee security in an effective way. This study shows how the Hospital IT Dept. is providing the adjustment of technologies and procedures to increase IT security needs and giving access to data, information and knowledge to authorized personnel. To face these challenges the Hospital IT Dept. proposed both internally developed open-source technical solutions and information security risk assessment methods.

An External-Cavity Laser Diode was frequency locked on molecular absorption line R(3) of hydrogen iodide at 1.541 μm using the wavelength modulation technique. This molecular reference is very important in many fields like HD-WDW telecommunication system and interferometry. Preliminary measurements of the closed-loop error signal provided a relative frequency stability of 9.5 times 10-10 in a 160 Hz acquisition bandwidth.

This paper describes the design and development of a C-band Solid State Power Amplifier (SSPA) to be used as TWTA replacement in down-link transmitters.

An Extended-Cavity Laser Diode was used to perform high resolution spectroscopy of molecular absorption lines of hydrogen iodide. For the first time, this laser source was frequency locked to an HI transition at 1.5 mu m using the wavelength modulation technique. Preliminary measurements of the closed-loop error signal provided a relative frequency stability of 2 x 10(-9) in a 10 Hz acquisition bandwidth.

Laser spectroscopy measurements of HI molecule at 1.54 mum wavelength were achieved by means of an external-cavity laser diode and by using both direct and FM measurements techniques. Line broadening was investigated for HI transitions at different gas pressures and the first measurements of the corresponding pressure broadening coefficients were performed. In particular, the Voigt absorption profiles for the R(3) transition at 1541.06 nm were finely retrieved by FM spectroscopy and numerical integration of the 1st derivative signals

In this paper we present the first laser-spectroscopy measurements on CH/sub 3/D molecules at 1.54 /spl mu/m wavelength. In particular, the Voigt absorption profiles for the R(6) transition at 1543.78 nm were measured by FM spectroscopy and numerical integration of the 1-st derivative signals. From measurements of the collisional broadening contribution at 3 different gas pressures, the collisional broadening coefficient for the 1.54 /spl mu/m transition was obtained.

The development and characterization of single-mode 2-/spl mu/m Tm-Ho:KYF/sub 4/ (KYF) laser is here presented. In particular, both frequency noise and relative intensity noise measurements of the single-frequency oscillator have been realized. From the power spectral density of the frequency noise an emission linewidth of /spl sim/100 kHz has been measured for the 2 /spl mu/m source, whereas the intensity noise spectrum is quantum-noise limited for Fourier frequencies higher than 1 MHz.

Absolute frequency stabilization of 2.1 /spl mu/m diode-pumped Tm-Ho:YAG lasers at 2.1 /spl mu/m is reported. Different rotovibrational absorption lines of CO/sub 2/ were used as absolute frequency references. The frequency control of a custom made, single-frequency and tunable Tm-Ho:YAG lasers was achieved by means of two linear spectroscopy methods: the fringe-side locking method and the wavelength modulation technique. Comparison between the experimental results obtained using these two methods is also reported. With both locking methods a significant improvement of the laser frequency stability was obtained. In particular a minimum value of frequency stability of 20 kHz at 1 s integration time was achieved using the wavelength modulation method, whereas for the fringe-side technique a minimum stability of 100 kHz was obtained for an integration time of 10 ms. The achieved stability levels are more than one order of magnitude better than typical Doppler- Lidar system requirements.

A novel, compact, and reliable Er-Yb:glass laser operating at around 1.54 /spl mu/m wavelength was developed, with single-frequency and linearly-polarized output power in excess of 10 mW over a continuous tunability range of 17 nm. An external Fabry-Perot resonator containing a low-pressure acetylene cell was used to perform saturation spectroscopy of different absorptions in the (v/sub 1/+v/sub 3/) rotovibrational band. By using two nested control loops, the laser was frequency locked to the 1 MHz Doppler-free P(16) line of /sup 13/C/sub 2/H/sub 2/ at 1. 543 /spl mu/m wavelength. This particular transition of the acetylene molecule was very recently recommended by the CCL (Comite Consultatif de la Longueur) of the CIPM for the mise en pratique du metre. The frequency stability achieved, as evaluated from the loop error signal, way in the range of /spl plusmn/40 kHz peak-to-peak (/spl Delta/v/v/spl cong/2/spl times/10/sup -10/) and the correspondingly calculated Allan deviation is /spl sigma//sub y/(/spl tau/) 70 s. This is the first Italian optical frequency standard in the 1.5 /spl mu/m band, namely at a frequency of 194 369 569.4(5) MHz and it is now ready for international intercomparisons.

The system for four-terminal pair intercomparison of unlike impedances of IEN has now been provided with a new direct-digital synthesis generator, having multiple outputs, isolation among the channels, and high amplitude and frequency stability. Experimental results in the new and old configuration are shown and compared.

We developed a new compact and massive bulk Er-Yb laser and locked its emission wavelength to various lines of the /sup 13/C/sub 2/H/sub 2/ (/spl nu//sub 1/+/spl nu//sub 3/) rovibrational transition at around 1.54 /spl mu/m. Peak to peak frequency stability of the locked laser was /spl plusmn/40 kHz over an observation time of 500 s.

A high-stability and excellent spectral purity 72-GHz Gunn oscillator was realized to characterize ultra-wide-band Schottky diodes based on intrinsic InP InSb semiconductors. The developed microwave oscillator shows a relative frequency stability of 2x 10-9 for observation times of 1 s and a collapse frequency of 4THz. Preliminary frequency measurements of different emission lines of a far infrared laser demonstrate good detection efficiency with a typical bandwidth of a 1 THz for these novel optical receivers.

Deals with the experimental characterization of the frequency modulation spectroscopy method by means of a frequency-doubled Nd:YAG laser and saturated absorptions of /sup 127/I/sub 2/ at the wavelength of 532 nm. A power of 8.7 mW at 532 nm with a continuous frequency tuning range of 80 GHz has been obtained by doubling 80 mW of the infrared Nd:YAG radiation incident on a self made external cavity doubler. In order to obtain a high degree of stability and reproducibility of the 532 nm radiation locked to a saturated absorption of /sup 127/I/sub 2/, linewidth, sensitivity, and signal to noise ratio of the demodulated signals have been characterized for different phase modulation conditions, iodine vapor pressures and for different optical power levels.

Optical frequency discriminators based on Fabry-Perot cavities are analyzed with particular attention to their amplitude-noise response and to the sensitivity limits imposed by detection shot-noise level. Comparison between different schemes are carried out.

The work is aimed at the study and development of a high-accuracy frequency standard at 1.5 /spl mu/m, by combining the intrinsic frequency stability of a solid-state laser to the accuracy and reliability of Doppler-free molecular lines. A diode-pumped Er-Yb microlaser is frequency stabilized to the center of /sup 13/C/sub 2/H/sub 2/ saturated absorption lines by means of the frequency modulation technique. A resonant Fabry-Perot cavity containing acetylene at low pressure is used to enhance the field intensity in order to saturate the 1.5 /spl mu/m overtone transitions of the molecule. Two stabilization loops are used to lock the Fabry-Perot cavity to the laser frequency and this last to the peak of the saturation dip. Preliminary experimental results on the Er-Yb laser frequency noise are reported.