International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Telemetry propagation channel is modeled to predict PCM/FM telemetry receiving signal level at APG(Anheung Proving Ground), ADD(Agency for Defense Development). Channel model is composed of direct wave and reflected wave in sea surface, so-called 2-ray model. Our 2-ray model includes transmitting antenna radiation pattern, auto-tracking antenna radiation pattern, sea surface reflection coefficient and phase depending on incident angle. Vertical and horizontal polarized receiving signal strength is obtained from pre-calculated flight trajectory of transmitter. Calculated results are compared with measured data in real flight test. 2-ray channel model can predict almost identical receiving signal level and calculate starting point of multi-path fading effect. Using these results, receiving system can be moved to more proper position before flight test.

Modeling of electromagnetic wave propagation in terms of Gaussian beams (GBs) has been considered in recent years. The incident radiation is expanded in terms of GBs by means of the point matching method. The simultaneous equations can be solved directly to produce excitation coefficients that generate the approximate pattern of a known antenna. Two different types of antenna patterns have been approximated in terms of GBs: a truncated antenna pattern and a hyperbolic antenna pattern. The influence of the Gaussian beam parameters on the approximation process is clarified.

Numerical dispersion resulting from using the second-order central-difference operation to approximate the differential operation is the main error source of the FDTD method. The effect of numerical dispersion can be minimized if the spatial grid size is small than£f/10. It is difficultly to analyze the modeling of electrically large structures since a huge amount of computer memory will be needed if using a very fine grid to discretize the structure. Using higher-order FDTD is the effective alternative to reduce the effect of numerical dispersion. In this paper will discuss the handling of the discontinuous PEC boundary condition in four-order FDTD and its applications to antenna pattern analysis. Using the fourth-order FDTD can enlarge the spatial grid size and reduce the requirement of computer¡¦s memory. The far field range of small size antenna operating at higher frequency is shorter enough to directly derive the far field pattern by enlarging the spatial size of fourth-order FDTD. It will compare the far field pattern derived by four-order FDTD with near-to-far field transformation and analyze their characteristic individually.

RapidScat is a pencil-beam wind scatterometer which operated from September 2014 to August 2016. Mounted aboard the International Space Station (ISS), RapidScat experiences significant altitude and attitude variations over its dataset. These variations need to be properly accounted for to ensure accurate calibration and to produce high resolution scatterometer images. Both the antenna pose and the one-way antenna pattern need to be validated. The spatial response function (SRF) is the two-way antenna pattern for a scatterometer combined with the processing and filtering done in the radar system electronics, and is dominated by the two-way pattern. To verify the pointing of the RapidScat antenna, the RapidScat SRF is estimated using on-orbit data. A rank reduced least squares estimate is used, which was developed previously for the Oceansat-2 (OSCAT) scatterometer [1]. This algorithm uses a small, isolated island as a delta function to sample the SRF. The island used is Rarotonga Island of the Cook Islands. The previously developed algorithm is updated to estimate the SRF in terms of beam azimuth and elevation angle rather than in kilometers on the ground. The angle-based coordinate system promotes greater understanding of how the SRF responds to biases and errors in antenna geometry. The estimation process is simulated to verify its accuracy by calculating the SRF for several thousand measurements in the region of Rarotonga. The calculated SRFs are multiplied by a corresponding synthetically created surface and integrated to yield simulated backscatter measurements, with added white noise. The SRF estimation algorithm is then performed. The results of the simulation show that the SRF estimation process yields a close estimate of the original SRF. The antenna pointing is validated by introducing a fixed offset in azimuth angle into the simulation and observing that the SRF is correspondingly shifted in the azimuth-elevation grid. The SRF computed from real data shows that there is an azimuth rotation angle bias of about 0.263 degrees for the inner beam and about 0.244 degrees for the outer beam. Since the SRF is dominated by the two-way antenna pattern, it can be modeled as the product of two identical one-way antenna patterns which are slightly offset from each other due to antenna rotation during the transmit/receive cycle. A method is developed based on this model to derive the one-way antenna pattern from the estimated SRF. Using a Taylor series expansion the one-way antenna pattern is computed from the SRF. The derived pattern recovers the SRF with small error, but there is significant error in the inferred one-way pattern when compared to the pre-launch estimated RapidScat one-way antenna pattern.

ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada / This paper presents the dynamic RF link estimation result for telemetry system of KSLV (Korea Space Launch Vehicle)-I. In particular, it utilizes the parameters of the instantaneous vehicle antenna gain pattern in three dimensions, the improvement by polarization diversity combiner at the ground receiver, and the free space propagation loss. The structural transformation and discontinuity of ground plane after the separation events of nose fairing, stage, and spacecraft, are also included in this analysis. As a consequence, the prediction of link variation has been performed in accordance with ARDP (Antenna Radiation Distribution Plot) and look angle trace of vehicle. In addition, the optimum position of onboard antennas has been investigated to provide better RF link margin in the nominal trajectory.

The work presented herein explores the ability of Ultra High Frequency Radio Frequency (UHF RF) devices, specifically (Radio Frequency Identification) RFID passive tags and Bluetooth Low Energy (BLE) to be used as tools to locate items of interest inside a building. Localization Systems based on these technologies are commercially available, but have failed to be widely adopted due to significant drawbacks in the accuracy and reliability of state of the art systems. It is the goal of this work to address that issue by identifying and potentially improving upon localization algorithms. The work presented here breaks the process of localization into distance estimations and trilateration algorithms to use those estimations to determine a 2D location. Distance estimations are the largest error source in trilateration. Several methods are proposed to improve speed and accuracy of measurements using additional information from frequency variations and phase angle information. Adding information from the characteristic signature of multipath signals allowed for a significant reduction in distance estimation error for both BLE and RFID which was quantified using neural network optimization techniques. The resulting error reduction algorithm was generalizable to completely new environments with very different multipath behavior and was a significant contribution of this work. Another significant contribution of this work is the experimental comparison of trilateration algorithms, which tested new and existing methods of trilateration for accuracy in a controlled environment using the same data sets. Several new or improved methods of triangulation are presented as well as traditional methods from the literature in the analysis. The Antenna Pattern Method represents a new way of compensating for the antenna radiation pattern and its potential impact on signal strength, which is also an important contribution of this effort. The performance of each algorithm for multiple types of inputs are compared and the resulting error matrix allows a potential system designer to select the best option given the particular system constraints.

This thesis presents methods for modeling the pattern of large axisymmetric paraboloidal focus-fed reflector antenna systems. The intended application of these methods is to improve the performance of time-domain interference canceling (TDC) in radio astronomy. The first method yields a closed-form expression for the antenna pattern with parameters accounting for the focal ratio and feed pattern. In subsequent adaptive methods, parameters of this model are calculated using measurements of interference signals. The corrected pattern model improves the prediction of the change in the true pattern for future times. The methods are compared by (1) comparing the error in the pattern model with respect to the true pattern and (2) comparing the pattern value update period required to achieve a specified level of residual interference when used in TDC. The efficacy of the pattern modeling methods is demonstrated by showing that the error in the pattern model decreases and the pattern value needs to be updated at a much slower rate for effective TDC. / Master of Science / Radio astronomy is the study of astronomical objects at radio frequencies. Radio telescopes, employing large reflector antennas, are often used to detect and measure extremely weak signals received from distant astronomical bodies. A growing problem for radio astronomy is that human-made communication satellites, orbiting around the earth, interfere with the radio signals. A satellite traversing the antenna pattern interferes with the signal of interest and contaminates it. Presently, this interference is managed by scheduling (avoidance) or by deleting the afflicted data. However, satellite interference is expected to become worse in the future with the increase in the number of satellites in orbit. Therefore, it will become increasingly difficult to avoid the interference by scheduling observations, and there may be too much afflicted data to delete. Hence, more sophisticated techniques may soon be required. One possible method for interference mitigation is Time Domain Canceling (TDC), which is the method addressed in this thesis. This method involves generating an estimate of the interference signal from the interfering satellite. This estimated interference signal is then subtracted from the measured signal contaminated with the interference signal. Ideally, this process should completely remove the interference while preserving the signal of interest and the noise (important in radio astronomy). To improve the accuracy of estimation of the interference signal, we require precise knowledge of the antenna pattern because the interference signal is seen through the antenna pattern. However, the pattern for large reflector antennas employed in radio telescopes is not precisely known and is often difficult to measure or analyze. In this work, we address this problem of lack of pattern knowledge by developing methods for modeling the pattern of large axisymmetric paraboloidal focus-fed reflector antenna systems. We have shown that the pattern model can be significantly improved using measurements of the interference signal in real time. We have also demonstrated that the performance of TDC improves with the incorporation of the developed pattern models.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Automating Telemetry Tracking Systems Operational Readiness Tests is a concept that was introduced at White Sands Missile Range in the early 1980’s. The idea was to determine the condition of a Telemetry Tracking System in a reliable manner in a short time as possible. A series of RF and Servo Tests designed to determine the condition of a Telemetry Tracking System was implemented using HP BASIC. The latest personal computers are faster and have more storage capacity plus the capability to be programmed in higher level languages such as C/C++ and LabView. This technology makes it easier to automate system tests. Many of these tests need to be conducted just prior to supporting a mission. Some tests are required to be performed on mobile systems after moving the system from one location to another, especially if the move was over long distances and rugged terrain. Tests such as G/T are conducted before each mission because it yields accurate information on the Figure of Merit, or, System Sensitivity. Noise Figure Measurements are more difficult to perform to determine the System Sensitivity since modern RF Subsystems have pre-amplifiers with Noise Figures of less than 1.0 dB. The “down-sizing” of personnel increases the possibility of failure in mission support scenarios due to the many critical readiness tests needed to assess the Telemetry Tracking Systems. Also, conventional test methods can be time consuming and are subject to human error. This paper describes four critical tests that have been automated to improve reliability of the test data and decrease the amount of time required to conduct the tests. The “C/C++” language was used to write the automation programs. More tests will be automated later.

Beam scanning Microstrip (BSMS) antenna is designed to work at center frequency of 10 GHz for using in the scanning applications of 9 GHz to 11 GHz band. The design parameters are defined and by using an Electromagnetic Simulation software program, the parameters are optimized. A Beam Scanning Microstrip Antenna is produced as a prototype and the measurement&rsquo / s results are compared with theoretical results. In conclusion, the values of deviation between theoretical and experimental results are discussed.

In satellite applications, a circularly polarized satellite antenna is desirable with a pattern that results in constant received power while the distance between the transmitter and the receiver is changing. The Circular Disk - Annular Ring (CDAR) antenna satisfies these requirements along with other requirements for the satellite antenna. The CDAR antenna is a combination of a Circular Disk and an Annular Ring patch antennas. In this thesis, a circularly polarized CDAR antenna that is fed from a single point is designed at the center frequency of 8.2 GHz. This antenna is investigated and optimized to ease the fabrication process. The design parameters are defined on this report and optimized by using an Electromagnetic Simulation software program. In order to verify the theoretical results, Circular Disk - Annular Ring Antenna is produced as a prototype. Measurements of antenna parameters, electromagnetic field and circuit properties are interpreted to show compliance with theoretical and simulation results. The values of deviation between theoretical and experimental results are also discussed.