Space-time Characteristics and Experimental Analysis of Broadening First-order Sea Clutter in HF Hybrid Sky-surface Wave Radar

In high frequency (HF) hybrid sky-surface wave radar, the first-order sea clutter broadening is very complex and serious under the influence of ionosphere and bistatic angle, which affects the detection of ship target. This paper analyzes the space-time characteristics based on the HF sky-surface wave experimental system. We first introduce the basic structure, working principle and position principle based on our experimental system. Also analyzed is the influence of ionosphere and bistatic angle on the space-time coupling characteristics of broadening first-order sea clutter and the performance of space-time adaptive processing (STAP). Finally, the results of theoretic analysis are examined with the experimental data. Simulation results show that the results of experiment consist with that of theoretic analysis

Scenedesmus biomass productivity and nutrient removal from wet market wastewater, a bio-kinetic study

The current study aims to investigate the production of microalgae biomass as a function for different wet market wastewater ratios (10, 25, 50, 75 and 100%) and Scenedesmus sp. initial concentrations (104 , 105 , 106 , 107 cells/mL) through the phycoremediation process. The biomass production, total nitrogen (TN), total phosphorus (TP) and total organic compounds (TOC) were determined daily. The pseudo-first order kinetic model was used to measure the potential of Scendesmus sp. in removing nutrients while the Verhulst logistic kinetic model was used to study the growth kinetic. The study revealed that the maximum productivity of Scenedesmus sp. biomass was recorded with 106 cells/mL of the initial concentration in 50% wet market wastewater (98.54 mg/L/day), and the highest removal of TP, TN, and TOC was obtained (85, 90 and 65% respectively). Total protein and lipid contents in the biomass yield produced in the wet market wastewater were more than that in the biomass produced in the BBM (41.7 vs. 37.4 and 23.2 vs. 19.2%, respectively). The results of GC–MS confirmed detection of 44 compounds in the biomass from the wet market wastewater compared to four compounds in the BBM. These compounds have several applications in pharmaceutical and personal care products, chemical industry and antimicrobial activity. These findings indicated the applicability of wet market wastewater as a production medium for microalgae biomass

Conceptual Architecture to Measure the Effects of Subauroral Polarization Streams on Radar Operations

This thesis provides the initial conceptual development of taking into account subauroral polarization streams when preparing for a radar operation. The DoDAF views created to portray the architecture consisted of operational, capabilities, data and information, and finally system views to ensure consistency and realistic outcomes. OV-2 was the significant view because it set the baseline for required actions necessary for the proposed results the Flow Integration of Ionospheric Activity and Radar Evaluation (FIIARE) system would produce. FIIARE is a computer based system concept that performs consolidations and produce predictions using algorithms from the International Reference Ionosphere (IRI). The data portrayed in the views would come from National Oceanic Atmospheric Administration and Super Dual Auroral Radar Network (SuperDARN). Data from both agencies would then be utilized in the FIIARE system to prepare the radar operators for calibrating the radar to perform in any area of responsibility (AOR). The overall purpose of this thesis is to develop the initial concept of deciding whether SAPS cause clutter during radar operations. There is a negative impact on the mission due to clutter that SAPS could cause in a 24-hour period. To get better data and estimate how much SAPS effects radar operations, the execution of over the horizon radars and documentation of clutter should use the high-level architecture as a baseline

Sinkronisasi Gelombang Pembawa untuk Sistem Komunikasi HF Berbasis USRP

Kinerja sistem komunikasi HF pada frekuensi 3-30 MHz akan berkurang dengan berbagai parameter, seperti adanya noise yang mengganggu, panjang lintasan propagasi, dan variasi kanal terhadap waktu. Sistem komunikasi HF memanfaatkan ionosfer sebagai lintasan propagasi gelombang radio, sehingga dapat menyebabkan terjadinya kesalahan pendeteksian gelombang pembawa, seperti pergeseran atau perubahan informasi pada sisi penerima. Hal ini terjadi karena adanya efek multipath dan doppler yang menyebabkan terjadinya pergeseran frekuensi dan fasa saat proses transmisi. Dengan memanfaatkan Phase-Locked Loop (PLL) yang merupakan pusat dari metode sinkronisasi gelombang pembawa, pergeseran frekuensi dan fasa saat proses transmisi dapat dikompensasi. Oleh karena itu, pada penelitian tugas akhir ini, dilakukan perancangan desain PLL pada sistem komunikasi HF menggunakan perangkat keras USRP N210 melalui perangkat lunak LabVIEW. Dengan daya pancar ± 7 Watt, modulasi BPSK, dan beberapa parameter lainnya, telah berhasil diuji untuk komunikasi menggunakan antena dipol untuk pemancar dan penerima yang berjarak ± 35 meter. Dari hasil pengujian sebanyak 25 kali, sistem PLL menghasilkan waktu dengan rata-rata 14,2. =============================================================================================================================== Performance of the HF communication system at 3-30 MHz frequency will be reduced with various parameters, such as the presence of disturbing noise, the length of the propagation path, and channel variation towards time. HF communication system utilizes the ionosphere as a radio wave propagation path, so it can cause an error at carrier wave detection, such as a shift or change in information on the receiving side. It happens because of the multipath and doppler effects which cause a frequency and phase shift during the transmission process. By utilizing Phase-Locked Loop (PLL) which is the center of the carrier wave synchronizing method, frequency and phase shift can be compensated. Therefore, in this final project, design of the PLL have been done on the for HF communication system using USRP N210 through LabVIEW software. With ± 7 Watt transmit power, BPSK modulation, and other parameters, it has been successfully tested for communication using dipole antennas on the transmitter and receiver within ± 35 meter. From the results of test 25 times, PLL system produces a time with an average of 14,

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Propagation management for no-acknowledge HF communications links

The problems in the engineering of no-acknowledge HF links are reviewed with particular application to naval applications. Models for predicting the performance of the ionospheric path and techniques for measurement of channel quality are considered. Manual methods of propagation management are found to be limited by speed and accuracy in conducting measurements. Automation of the channel quality measurement process allowed observation of short term behaviour of the link for comparison with predictions. Long term behaviour tends toward the prediction but large deviations are found in the short term. Techniques for improving the estimates of the remote ionosphere were investigated. Updating predictions using a derived ionospheric index and the use of a backscatter sounder were attempted with limited success. Concepts for improvement in no-acknowledge links include networking between transmitting stations, modulation diversity and coding techniques, and development of 'intelligent receiving terminals with facilities for rapid selection of operating channels and overcoming unwanted signal interference. Recommendations for further work to investigate these concepts is presented

On the variability of doppler spectra in hf groundwave radar remote sensing over the ocean surface: an investigation based on pulsed and frequency modulated sources

An examination of the fluctuations of the Bragg peaks in high frequency (HF) radar received backscatter spectra from the ocean surface is considered in the light of recent cross section models. It is well known that there are likely several factors giving rise to this phenomenon. In the first part of the research work, the effect that is purely caused by the use of a pulsed Doppler radar waveform is examined. The radar received signal is assumed to be scattered from a time-varying random rough surface represented as a zero-mean, Gaussian random process. Numerical examinations of the existence and distribution of Bragg fluctuations are carried out first. Various radar operating frequencies and pulse widths are selected to simulate the time series for different conditions. Doppler spectra (power spectral density, PSD) are estimated as periodograms. The centroids of the Bragg peaks are obtained and compared with theoretical values and the Bragg fluctuations from time to time are observed. The statistical properties of the centroid positions are indicated and compared with resolutions of the fast Fourier transform (FFT) algorithm to reveal their significance. Then the physical processes which underlie the observed variability of the HF sea echo over short time periods are examined. It will be seen that, by implementing both numerical and analytical techniques, interrogation of such a surface via a pulsed signal inherently leads to temporal variation of echo power at every frequency position of the Doppler spectrum. -- The second part of the research work is an investigation of the Bragg fluctuations when HF radar uses the frequency modulated waveforms, which include frequency modulated continuous wave (FMCW) and frequency modulated interrupted continuous wave (FMICW) sources. Such waveforms are often employed in practical radar systems. The mathematical expressions of the cross sections for the FMCW and FMICW waveforms are worked out and their properties are addressed. Then, similar to the previous analysis for the pulsed waveform, time series of the radar received electric field signals are simulated and the PSDs are calculated. Centroid positions of the Bragg peak regions are located and compared to the theoretical values. Statistical properties of the Bragg fluctuations are investigated and comparison with respect to that for the pulsed waveform is carried out. Field data from the Wellen Radar (WERA) are used to verify the simulation results and the fluctuations of the Bragg peaks for the FMCW waveform

Technical approaches, chapter 3, part E

Radar altimeters, scatterometers, and imaging radar are described in terms of their functions, future developments, constraints, and applications