Zugl.: Chemnitz, Techn. Univ., Diss., 2008.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / A simplex or ‘passive’ continuous wave and monopulse seeker tracks specific attributes of a target’s radio frequency (RF) radar return in some coordinate frame. In particular, a return carries dynamic information in amplitude (ω) and frequency (ω) at some point in azimuth (r,θ) and elevation (r,θ) planes. A passive seeker requires an illuminator beam, I(ω,φ,θ), and may require a frequency modulation on the illuminator. To model a simplex target return, we have based the dynamics on a point source radar cross section (RCS) along a line of sight (LoS) radial. The Az and El angles are equivalent to antenna placement, the attenuation and frequency dynamics are modeled in commercial off-the-shelf (COTS) software.

The primary reason for the wireless technology evolution is towards building capacity and obtaining higher data rates. Enclosed locations, densely populated campus, indoor offices, and device-to-device communication will require radios that need to operate at data rates up to 10 Gbps. In the next few years, a new generation of communication systems would emerge to better handle the ever-increasing demand for much wider bandwidth requirements. Simultaneously, key factors such as size, cost, and energy consumption play a distinctive role towards shaping the success of future wireless technologies. In the perspective of 3GPP 5G next generation wireless communication systems, the X band was explicitly targeted with a vast range of applications in point to point radio, point to multi point radio, test equipment, sensors and future wireless communication. An X-band RF front-end circuit for next generation wireless network applications is presented in this work. It details the design of a low noise amplifier and a power amplifier for X band operation. The designed amplifiers were integrated with a wideband single-pole-double-throw switch to achieve an overall front-end structure for 10 GHz. The design was carried out and sent for fabrication using a GaN 0.15µm process provided by NRC, a novel design kit. Due to higher breakdown voltage, high power density, high efficiency, high linearity and better noise performance, GaN HEMTs are a suitable choice for future wireless communication. Thus, the assumption is to further explore capabilities of this process in front-end design for future wireless communications.

No description available.

The marine atmospheric boundary layer (MABL) is the region of atmosphere that interacts with the ocean surface. The atmospheric variability (i.e. temperature and relative humidity) in this region can result in rapid changes in the refractive index with increasing height from the sea surface. The complex region can result in non-standard propagation of electromagnetic (EM) waves beyond the horizon under atmospheric ducting conditions. However, when ducting layers are not present, EM waves are limited to line-of-sight transmission. Atmospheric ducting research is typically conducted using radio frequencies in the X-band (around 8-12 GHz) due to its impact on performance of marine radars at those frequencies. Studies typically examine levels of received signal power or effects on radar returns in ducting conditions, but often ignore the time-domain effects of ducting which can also affect communications link performance. In collaboration with the Coastal Observing Research and Development Center at Scripps Institution of Oceanography (SIO), the ducting research in this thesis uses a channel sounder that consists of a X-band transmitter which transmits a coded pseudorandom sequence and a software-defined radio (SDR) receiver. Both transmitter and receiver are GPS synchronized so that the time-domain cross-correlation between the TX and RX signals can be found. In theory, if atmospheric ducting is present, there will be multipath propagation, and the TX-RX cross-correlation indicates multiple “peaks”, indicating multiple arrival times. Conversely, if little to no ducting is present, then the cross-correlation indicates a single “peak”. The channel sounding was evaluated over several over-water communications links, involving fixed-path and variable range sea tests with a moving vessel to verify if this hypothesis is true. The expected ducting conditions were determined by in-situ refractive index measurements of the atmosphere. Results from testing showed multiple peaks when strong ducting was expected, but an extensive sea test in strong ducting conditions is needed to distinguish multipath from ducting from that of terrain reflections. Further work is also needed to determine the computational model that accurately models multipath propagation through a duct, which is beyond the scope of this thesis.

International Telemetering Conference Proceedings / October 26-29, 1987 / Town and Country Hotel, San Diego, California / The three axis stabilized Indian Remote Sensing Satellite will image the earth from a 904 Km polar - sun synchronous orbit. The payload is a set of CCD cameras which collect data in four bands visible and near infra-red region. This payload data from two cameras, each at 10.4 megabits per sec is transmitted in a balanced QPSK in X Band. The payload data before transmission is formatted by adopting Major and Minor frame synchronizing codes. The formatted two streams of data are differentially encoded to take care of 4-phase ambiguity due to QPSK transmission. This paper describes the design and development aspects related to such a Data Handling System. It also highlights the environmental qualification tests that were carried out to meet the requirement of three years operational life of the satellite.

Soil moisture estimates from space on a continuous spatial domain could afford researchers with insight about agricultural productivity, flood vulnerability, and biological processes. To evaluate satellite soil moisture estimates, the SMAPVEX-16 experiment was one of a suite of verification data collection campaigns for NASA’s Soil Moisture Active Passive satellite. Soil moisture and its role in rainfall partitioning are of great interest to researchers at the Iowa Flood Center [IFC], which was founded in Iowa City, Iowa after a devastating flood event in 2008. A network of two dual-pol capable X-band radar units owned by the IFC, as well as five tipping bucket rain gauges, complemented by 15 from the USDA’s Agricultural Research Service were deployed in Central Iowa from May to August 2016 to monitor precipitation on a fine spatiotemporal domain. The data from this particular experiment was analyzed. Several radar-rainfall algorithms were assembled with a focus on assimilating multivariate radar data. Different variables allow researchers to overcome problems due to signal attenuation by X-band radars, and process radar observations into rainfall accumulations by several methods popular in the literature. Special techniques for accumulating instantaneous rainfall rates at discrete observation intervals were employed to account for the movement of storms. The rain totals between the observation points were estimated and the accumulations were compared to the rain gauge totals. Methods of rain rate calculation that assimilate many sources of data, such as radar reflectivity, differential reflectivity, and specific differential phase shift yielded the best results.

Due to the recent interest in broadband antennas a microstrip patch antenna was developed to meet the need for a cheap, low profile, broadband antenna. This antenna could be used in a wide range of applications such as in the communications industry for cell phones or satellite communication. Particle Swarm Optimization was used to design the dual-linear polarization broadband microstrip antenna and impedance matching network. This optimization method greatly reduced the time needed to find viable antenna parameters. A dual input patch antenna with over 30% bandwidth in the X-band was simulated using Ansoft's High Frequency Structural Simulator (HFSS) in conjunction with Particle Swarm Optimization. A single input and a dual input antenna was then fabricated. The fabricated antennas were composed of stacked microstrip patches over a set of bowtie apertures in the ground plane that were perpendicular to one another. A dual offset microstrip feedline was used to feed the aperture. Two different layers were used for the microstrip feedline of each polarization. The resulting measured impedance bandwidth was even wider than predicted. The antenna pattern was measured at several frequencies over the antenna bandwidth and was found to have good gain, consistent antenna patterns and low cross polarization.

Este trabalho apresenta o projeto de uma portadora que opera na frequência de 8.300 MHz para ser utilizado em moduladores vetoriais diretos com aplicação em sistemas embarcados de satélites. Foram realizados estudos sistêmicos de arquiteturas que operam nesta faixa de frequência com as características necessárias para atender as especificações da European Cooperation for Space Standardization, ECSS - Space Engineering Radio Frequency and Modulation da agência espacial europeia -ESA, que regulamenta as frequências e características para sistemas de transmissão para enlace de descida. A partir dos conhecimentos adquiridos nos estudos, é apresentada uma metodologia de projeto visando o atendimento das especificações definidas pela ECSS e a escolha de uma topologia de projeto. Foram realizadas simulações a nível sistêmico, utilizando o software Advanced Design System-ADS da fabricante Keysight Technologies, para definir as especificações de projeto dos circuitos que compõem o sistema de geração da portadora na banda X. O circuito da malha de sincronismo de fase - PLL opera na frequência de 2.075 MHz, onde seu sinal é amplificado e filtrado pela cadeia de amplificação na banda S cuja função é aumentar a isolação para minimizar os efeitos de pulling do oscilador controlado por tensão - VCO, devido à alta velocidade nas transições de tempo de subida e de descida dos sinais digitais I e Q. O filtro também é responsável por aumentar a rejeição de espúrios e harmônicos gerados pelos efeitos não lineares dos amplificadores. O sinal é enviado ao circuito multiplicador de frequências que gera o sinal na banda X e é filtrado por um filtro passa-faixas de linhas acopladas, rejeitando os sinais espúrios provenientes da saída do multiplicador de frequência. Na saída, o sinal passa por uma cadeia de amplificação na banda X para adequar o nível de potência à entrada dos moduladores vetoriais. Os circuitos projetados foram desenvolvidos utilizando tecnologia de microfita de linha. Os protótipos foram caracterizados, apresentando boa concordância com os resultados simulados, comprovando experimentalmente a metodologia de projeto utilizada neste trabalho assim como o atendimento das especificações sugeridas pela ECSS. / This work presents the project of an carrier that works in the frequency of 8,300 MHz to be used in direct vector modulator for embedded system application in satellites. It were realized system level studies of PLL topologies that work in this frequency range with the necessary features to provide the requirements from European Cooperation for Space Standardization, ECSS - Space Engineering Radio Frequency and Modulation of the European Space Agency - ESA, which is responsible for the frequencies and features regulation for downlink transmission system. With the knowledge acquired from the studies, it is presented a project method intending to the meet the requirements defined by the ECSS and the definition of a topology to the project. It were performed system level simulation, using the Advanced Design System - ADS tool, from Keysight Technologies, in order to define the design specifications in the project of the circuits of the X band carrier generator developed. The PLL circuit works in the frequency of 2,075 MHz, in which its signal is amplified and filtered for amplifier chain in S band, increasing the isolation to reduce the pulling effects in the voltage controlled oscillator, due to the high-speed transitions in the rise time and fall time of the digital signal I and Q. The filter is also responsible for increasing the rejection of spurious and harmonics generated by non-linear amplifiers effects. The signal is conducted to the frequency multiplier circuit that generates the X band signal and it is filtered by a coupled line bandpass filter, rejecting the spurious from the frequency multiplier output. At the output stage, the signal passes through a X band amplification chain in order to adequate the power level of the vector modulators input level. The specified circuits were designed and developed using microstrip line technology. The prototypes were characterized, presenting adequate results according to the data obtained by the simulations, experimentally reinforcing the project method used in this work as well as the meeting of the requirements suggested by the ECSS.

Networks of small, often mobile, polarimetric radars are gaining popularity in the hydrometeorology community due to their rainfall observing capabilities and relative low purchase cost. In recent years, a number of installations have become operational around the globe. The problem of signal attenuation by intervening rainfall has been recognized as the major source of error in rainfall estimation by short-wavelength (C-, X, K-band) radars. The simultaneous observation of precipitation by multiple radars creates new prospects for better and more robust attenuation correction algorithms and, consequently, yields more accurate rainfall estimation. The University of Iowa hydrometeorology group's acquisition of a network of four mobile, polarimetric, X-band radars has resulted in the need for a thoughtful evaluation of the instrument. In this work, we use computer simulations and the data collected by The University of Iowa Polarimetric Radar Network to study the performance of attenuation correction methods in single-radar and network-based arrangements. To support the computer simulations, we developed a comprehensive polarimetric radar network simulator, which replicates the essential aspects of the radar network rainfall observing process. The simulations are based on a series of physics- and stochastic-based simulated rainfall events occurring over the area of interest. The characteristics of the simulated radars are those of The University of Iowa Polarimetric Radar Network. We assess the correction methods by analyzing the errors in reflectivity and rainfall rate over the area of interest covered by the network's radars. To enable the implementation of the attenuation correction methods to the data collected by The University of Iowa Polarimetric Radar Network, we first developed a set of utilities to assist with efficient data collection and analysis. Next, we conducted a series of calibration tests to evaluate the relative calibration and channel balance of the 2 network's radars. Finally, in an attempt to verify the results obtained via computer simulations, we applied the set of attenuation correction algorithms to the data collected by The University of Iowa Polarimetric Radar Network.