http://hdl.handle.net/2374.MIA/265 Sun, 05 Apr 2026 13:26:02 GMT 2026-04-05T13:26:02Z http://hdl.handle.net/2374.MIA/276 Neural Network Development for the Forecasting of Upper Atmosphere Parameter Distributions Martin, Jeffrey D.; Morton, Yu T.; Zhou, Qihou This paper presents a neural network modeling approach to forecast electron concentration distributions in the 150â 600 km altitude range above Arecibo, Puerto Rico. The neural network was trained using incoherent scatter radar data collected at the Arecibo Observatory during the past two decades, as well as the Kp geomagnetic index provided by the National Space Science Data Center. The data set covered nearly two solar cycles, allowing the neural network to model daily, seasonal, and solar cycle variations of upper atmospheric parameter distributions. Two types of neural network architectures, feedforward and Elman recurrent, are used in this study. Topics discussed include the network design, training strategy, data analysis, as well as preliminary testing results of the networks on electron concentration distributions. Mon, 15 Dec 2008 22:09:24 GMT http://hdl.handle.net/2374.MIA/276 2008-12-15T22:09:24Z http://hdl.handle.net/2374.MIA/275 Interference Cancellation Using Power Minimization and Self-coherence Properties of GPS Signals Morton, Y.T. Jade; Liou, Liyeh L.; Lin, David M.; Tsui, James B.Y.; Zhou, Qihou This paper presents the performance analysis of two digital beam forming techniques used in conjunction with a software GPS receiver to mitigate interference to GPS signals in interference environment. The first method is the constrained minimum power (MOP) method. The second method is the so-called self-coherence restoral (SCORE) method. Both experimental and simulation data are used in the study. The study was performed using experiment data collected in an anechoic chamber to obtain GPS and interference signals. A two by two GPS antenna array and a four channel radio frequency front end were used to collect simulated GPS data generated using hardwarebased simulator in controlled interference environment. Three types of interference signals are deployed in the experiments: FM chirp, binary phase shift key, and broadband. The interference power levels used were +20, +30, and +40 dB above GPS signal power. A software GPS receiver was used to perform acquisition of GPS signals to evaluate the performance of the beam forming algorithms. The preliminary result showed that the MOP method can effectively mitigate all three types of interference at all power levels if a single interference source is present. Experiments using multiple broadband interference sources were also analyzed and our results shown that the effectiveness of the MOP method diminishes as the interference signal power increases and ceases to function at the +40 dB level. The SCORE method does not exhibit consistent performance for the experimental data. This is consistent with our simulation results which show that for the SCORE algorithm to generate satisfactory results, sufficient number of antenna elements is necessary even if there is no interference source present. The number of antenna element is determined by the number of satellites available, as well as the number of interference sources. The experimental and simulation results are discussed in this paper. Mon, 15 Dec 2008 22:07:33 GMT http://hdl.handle.net/2374.MIA/275 2008-12-15T22:07:33Z http://hdl.handle.net/2374.MIA/274 Software Approach to Access UWB Interference on GPS Receivers Morton, Y.T.; French, M.P.; Zhou, Qihou; Tsni, J.B.Y.; Miller, Mikel; Janning, D. Ever since the FCC approved the use of UWB devices in commercial and federal bands, various agencies whose operations and/or products rely on the integrity of signals within certain â restrictedâ radio frequency hands have voiced concerns over the potential impact of the UWB interference. GPS signals are among these â restrictedâ bands. Several groups in the GPS community have conducted experimental studies concerning the impact of UWB interference on the performance of various grades of commercial and aviation GPS receivers. In this paper, we present a software approach to simulate and evaluate UWB interference on GPS receivers. The software approach provides greater flexibility in the design of testing scenarios, such as the inclusion of a large number of aggregated UWB devices, the generation of new UWB signals and modulation schemes, and the possibility of extending the study to new GPS signals. The paper will discuss a general framework for developing algorithms to evaluate UWB and GPS interference under a wide variety of hardware and software conditions. This framework consists of three classes of components: Input, Processing, and Analysis. The input components are responsible for the generation of UWB signal waveforms and modulation schemes, and GPS signals. The processing components include a simulated model of GPS RF front end and software implementation of GPS processing blocks, such as acquisition, tracking, and post-processing. The Analysis components focus on the study of specsic receiver processing component outputs. Both real and simulated UWB signals can he used in the study. The real UWB signals are primarily used to validate the simulation procedure, whereas the simulated UWB signals are used to allow the immediate incorporation of new UWB waveforms and modulations in the evaluations. This paper will present details of the software components developed and the preliminary results achieved Mon, 15 Dec 2008 22:05:04 GMT http://hdl.handle.net/2374.MIA/274 2008-12-15T22:05:04Z http://hdl.handle.net/2374.MIA/273 Case Study of Mesospheric Gravity Wave Momentum Flux and Dynamical Instability Using the Arecibo Dual Beam Incoherent Scatter Radar Zhou, Qihou; Morton, Y.T. We report the first observation of gravity wave momentum flux in the mesosphere using the dual-beam Arecibo incoherent scatter radar (ISR). Quasimonochromatic waves were observed throughout the daytime of July 28, 2001 in the altitude range of 65â 85 km. The largest wave speed was about 100 m/s and the dominant period was about 15 min. Instability, as indicated by the Richardson number, occurred at several altitudes, most dramatically at 77 and 81 kilometers. The zonal momentum flux is found to change sign at altitudes where dynamical instability occurs. No significant gravity waves were observed in the region having an eastward background wind, while they were ubiquitous when the background wind was westward. Citation: Zhou, Q., and Y. T. Morton (2006), A case study of mesospheric gravity wave momentum flux and dynamical instability using the Arecibo dual beam incoherent scatter radar, Geophys. Res. Lett., 33, L10802, doi:10.1029/ 2005GL025608. Mon, 15 Dec 2008 21:59:56 GMT http://hdl.handle.net/2374.MIA/273 2008-12-15T21:59:56Z