scholarly journals Open-loop GPS signal tracking at low elevation angles from a ground-based observation site

2017 ◽  
Vol 10 (1) ◽  
pp. 15-34 ◽  
Author(s):  
Georg Beyerle ◽  
Florian Zus
Keyword(s):  
Ground Surface ◽  
Doppler Frequency ◽  
Signal Amplitude ◽  
Open Loop ◽  
Observation Site ◽  
Data Set ◽  
Signal Tracking ◽  
Dual Channel ◽  
Setting Events ◽  
Density Ratios

Abstract. A 1-year data set of ground-based GPS signal observations aiming at geometric elevation angles below +2° is analysed. Within the "GLESER" measurement campaign about 2600 validated setting events were recorded by the "OpenGPS" open-loop tracking receiver at an observation site located at 52.3808° N, 13.0642° E between January and December 2014. The measurements confirm the feasibility of open-loop signal tracking down to geometric elevation angles of −1 to −1.5° extending the corresponding closed-loop tracking range by up to 1°. The study is based on the premise that observations of low-elevation events by a ground-based receiver may serve as test cases for space-based radio occultation measurements, even if the latter proceed at a significantly faster temporal scale. The results support the conclusion that the open-loop Doppler model has negligible influence on the derived carrier frequency profile for strong signal-to-noise density ratios above about 30 dB Hz. At lower signal levels, however, the OpenGPS receiver's dual-channel design, which tracks the same signal using two Doppler models differing by 10 Hz, uncovers a notable bias. The repeat patterns of the GPS orbit traces in terms of azimuth angle reveal characteristic signatures in both signal amplitude and Doppler frequency with respect to the topography close to the observation site. Mean vertical refractivity gradients, extracted from ECMWF meteorological fields, correlate weakly to moderately with observed signal amplitude fluctuations at geometric elevation angles between +1 and +2°. Results from multiple phase screen simulations support the interpretation that these fluctuations are at least partly produced by atmospheric multipath; at negative elevation angles diffraction at the ground surface seems to contribute.

scholarly journals Open-loop GPS signal tracking at low elevation angles from a ground-based observation site

2016 ◽  
Author(s):  
Georg Beyerle ◽  
Florian Zus
Keyword(s):  
Doppler Frequency ◽  
Signal Amplitude ◽  
Open Loop ◽  
Observation Site ◽  
Data Set ◽  
Signal Tracking ◽  
Dual Channel ◽  
Setting Events ◽  
One Year ◽  
Density Ratios

Abstract. A one-year data set of ground-based GPS signal observations aiming at geometric elevation angles below +2° is analyzed. Within the "GLESER" measurement campaign about 2600 validated setting events were recorded by the "OpenGPS" open-loop tracking receiver at an observation site located at 52.3808° N, 13.0642° E between January and December 2014. The measurements confirm the feasibility of open-loop signal tracking down to geometric elevation angles of −1° to −1.5° extending the corresponding closed-loop tracking range by up to 1°. The study is based on the premise that observations of low-elevation events by a ground-based receiver may serve as test cases for space-based radio occultation measurements, even if the latter proceed at a significantly faster temporal scale. The results support the conclusion that the open-loop Doppler model has negligible influence on the derived carrier frequency profile for strong signal-to-noise density ratios above about 30 dB Hz. At lower signal levels, however, the "OpenGPS" receiver's dual-channel design, which tracks the same signal using two Doppler models with a 10 Hz offset, uncovers a notable bias. The repeat patterns of the GPS orbit traces in terms of azimuth angle reveal characteristic signatures in both, signal amplitude and Doppler frequency with respect to the topography close to the observation site. On the other hand, vertical refractivity gradients extracted from ECMWF meteorological fields correlate moderately well with observed signal amplitude fluctuations at negative geometric elevation angles emphasizing the information content of low-elevation GPS signals with respect to the atmospheric state within the planetary boundary layer.

scholarly journals A Real-Time On-Orbit Signal Tracking Algorithm for GNSS Surface Observations

2019 ◽  
Vol 11 (16) ◽  
pp. 1858 ◽  
Author(s):  
Scott Gleason
Keyword(s):  
Time Delay ◽  
Real Time ◽  
Doppler Frequency ◽  
Open Loop ◽  
Global Navigation Satellite Systems ◽  
Sampled Data ◽  
Data Set ◽  
Signal Tracking ◽  
Satellite Systems ◽  
Phase Time

This manuscript describes real-time on-orbit instrument compatible open loop signal tracking techniques for Global Navigation Satellite Systems (GNSS) reflection observations. All GNSS-reflection (GNSS-R) satellite instruments require algorithms which run in real-time on-board the satellite, that are capable of predicting the code phase time delay and Doppler frequency of surface reflected signals. The algorithms presented here are for open loop tracking techniques in reflected GNSS signals for the purposed of making surface remote sensing observations. Initially, the algorithms are demonstrated using high resolution sampled data from the NASA Cyclone GNSS (CYGNSS) mission over ocean and land surfaces. Subsequently. the algorithm performance over ocean regions is analyzed in detail using a larger data set. As part of the analysis, the algorithm is assessed for its speed of convergence, to demonstrate general compatibility with spacecraft instrument processing limitations. Results indicate that over ocean regions is it possible to robustly predict in real time the Doppler frequency and code phase time delay of multiple reflected signal to sufficient precision to make science observations of the scattering surface. These algorithms are intended to provide a baseline technique and variations from which the scientific community can design more specialized algorithms for individual applications.

scholarly journals Mountain Top-Based Atmospheric Radio Occultation Observations with Open/Closed Loop Tracking: Experiment and Validation

2020 ◽  
Vol 12 (24) ◽  
pp. 4078
Author(s):  
Fenghui Li ◽  
Chunping Hou ◽  
Liang Kan ◽  
Naifeng Fu ◽  
Meng Wang ◽  
...  
Keyword(s):  
Closed Loop ◽  
Radio Occultation ◽  
Rapid Change ◽  
Doppler Frequency ◽  
Signal Amplitude ◽  
Open Loop ◽  
Lower Atmosphere ◽  
Refractive Index Gradient ◽  
Receiver System ◽  
Occultation Data

Through Global Navigation Satellite System (GNSS) occultation measurement, the global ionosphere and atmosphere can be observed. When the navigation satellites’ signal passes through the lower atmosphere, the rapid change of the atmospheric refractive index gradient will cause serious multipath phenomena in radio wave propagation. Atmospheric doppler frequency shift and amplitude signal fluctuations increase drastically. Due to the attenuation of signal amplitude and the rapid change of the Doppler frequency, the general phase locked loop (PLL) cannot work properly. Hence, a more stable tracking technology is needed to track the occultation signal passing through the lower atmosphere. In this paper, a mountain-top based radio occultation experiment is performed, where we employ an open-loop receiver and remove the navigation bits by the internal demodulation. In the process of the experiment, we adopt the open-loop tracking technique and there is no feedback between the observed signal and the control model. Specifically, taking the pseudo-range and doppler information from models as input, three key parameters, i.e., accurate code phase, carrier doppler and code doppler, can be obtained, and furthermore, the accurate accumulation is determined by them. For the full open-loop occultation data, a closed-loop observation assisted strategy is presented to compare the tracking results between open-loop and closed-loop occultation data. Through the compared results, we can determine whether the initial phase has been reversed or not, and obtain the high consistency corrected open-loop data that can be directly used for subsequent atmospheric parameters inversion. To verify the effect of open-loop tracking and open-loop inversion, we used the company’s self-developed occult receiver system for verification. The company’s self-developed occult receiver system supports Global Position System (GPS)/Beidou satellites constellation (BD, the 2nd and 3rd generations) dual systems. We have verified GPS and BD open-loop tracking and inversion, carried out in a three-week mountain-based experiment. We used closed-loop and open-loop strategies to track and capture the same navigation star to detect its acquisition effect. Finally, we counted the results of a week (we only listed the GPS data; BD’s effect is similar). The experimental results show that the open-loop has expanded the signal-cut-off angle by nearly 20% under the condition of counting all angles, while the open-loop has increased the signal-cut-off angle value by nearly 89% when only calculating the negative angle. Finally, the atmosphere profiles retrieved from observations in open-loop tracking mode are evaluated with the local observations of temperature, humidity and pressure provided by the Beijing Meteorological Bureau, and it is concluded that the error of open-loop tracking method is within ~4% in MSER (mean square error of relative error), which meets the accuracy of its applications (<5%, in MSER).

scholarly journals ESTIMATION OF LONG-RANGE CORRELATION SCALES BY SEISMOACOUSTIC EMISSION SIGNALS OF NEAR-SURFACE SEDIMENTARY ROCKS IN KAMCHATKA

2019 ◽  
pp. 190-200
Author(s):  
В.Н. Сычёв ◽  
М.А. Мищенко ◽  
С.А. Имашев ◽  
М.Е. Чешев
Keyword(s):  
Long Range ◽  
Ground Surface ◽  
Frequency Range ◽  
Self Similarity ◽  
Observation Site ◽  
Near Surface ◽  
Long Range Correlations ◽  
Seismic Receiver ◽  
Range Correlation ◽  
Geophysical Observation

На Камчатке в пункте комплексных геофизических наблюдений ИКИР ДВО РАН Карымшина для регистрации сигналов сейсмоакустической эмиссии на поверхности земли установлен измерительный комплекс. В качестве датчика сигналов используется трехкомпонентный пьезокерамический сейсмоприемник, который регистрирует колебательное ускорение в частотном диапазоне 0.5-400 Гц. Рассмотрен сейсмоакустический отклик на несколько региональных землетрясений с энергетическим классом Ks 11:0 в период 2017-2018 гг. При помощи статистических методов установлено самоподобие их структуры на ограниченном интервале временных масштабов. Это, в свою очередь, указывает на наличие дальних корреляций в рассматриваемой системе и позволяет получить оценку масштабов корреляций. A measurement complex is installed on the ground surface at Karymshina complex geophysical observation site of IKIR FEB RAS (Kamchatka) to record seismoacoustic emission signals. A three-component piezoceramic seismic receiver, which records oscillatory acceleration in the frequency range from 0.2 to 400 Hz, is used as the signal sensor. A series of seismoacoustic responses on regional earthquakes of 2017-2018 with the energy class Ks 11:0 has been considered. Self-similarity of their structures has been established in a limited interval of time scales by statistical methods. That, in its turn, indicates the presence of long-range correlations in the system under consideration and allows one to estimate correlation scales.

Effusion Cooled Combustor Liner Tiles With Modern Cooling Concepts: A Comparative Experimental Study

2016 ◽  
Author(s):  
Thomas Jackowski ◽  
Achmed Schulz ◽  
Hans-Jörg Bauer ◽  
Miklós Gerendás ◽  
Thomas Behrendt
Keyword(s):  
Pressure Difference ◽  
Open Loop ◽  
Test Rig ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Cooling Hole ◽  
Manufacturing Techniques ◽  
Aero Engines ◽  
Density Ratios ◽  
Combustor Liner

Advanced combustion techniques in aero engines require highly effective cooling schemes of combustor liners. One parameter affecting the cooling performance is the geometry of the cooling holes themselves. So far, the freedom in the design of cooling holes was limited due to the manufacturing techniques. With emerging additive manufacturing methods, e.g. Direct Metal Laser Sintering, however, the geometry of the cooling holes is virtually unlimited. Especially the entrance and the curvature of the cooling holes determines the through-flow of the hole and consequently the cooling performance of the ejected cooling film. In this study a set of combustor liner tiles with two innovative and four traditional cooling hole geometries will be analyzed and compared to each other in terms of cooling performance. The innovative geometries have bent cooling holes with a nearly horizontal outlet. All specimens have the same cooling hole pattern. The cooling performance is determined by comparing the total cooling effectiveness for a given pressure difference across the combustor liner tiles. The coolant mass flow rate is gained from experimentally determined discharge coefficients for the respective pressure difference. The first set of measurements is conducted in an atmospheric open-loop test rig at reduced temperatures but realistic density ratios between hot gas and coolant. The specimen with the best cooling performance has been selected for an investigation in a high pressure test rig at realistic combustor conditions (pressure, temperature) including fluctuations of the cooling air to simulate combustion instabilities. The cooling performance again is determined by the total cooling effectiveness for a given pressure difference across the combustor liner tiles.

scholarly journals Research on Acquisition and Tracking Algorithm of Global Satellite Positioning Receiver Based on UWB

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Li Yang ◽  
Danshi Sun ◽  
Haote Ruan
Keyword(s):  
Influence Factor ◽  
Three Dimensional ◽  
Doppler Frequency ◽  
Pulse Generation ◽  
Tracking Algorithm ◽  
Tracking Accuracy ◽  
Signal Tracking ◽  
Satellite Positioning ◽  
Working Principle ◽  
Satellite Signal

In order to overcome the problems of the traditional algorithm, such as the time-consuming execution of acquisition instructions, low signal tracking accuracy, and low signal capture accuracy, a global satellite positioning receiver acquisition and tracking algorithm based on UWB technology is designed in this study. On the basis of expounding the pulse generation method and working principle in UWB technology, this paper analyzes in detail the characteristics of UWB technology, such as antimultipath, low power consumption, and strong penetration. Then, on the basis of window function filtering, in the process of three-dimensional search of global satellite positioning signal, firstly, the satellite signal entering the GPS software receiver is processed by RF front-end mixing and AD sampling, and then, the signal tracking and navigation message solving are completed according to the relationship between the influence factor and Doppler frequency offset. The experimental results show that the execution time of the acquisition instruction of the proposed algorithm varies between 1129 ms and 1617 ms; the signal tracking accuracy ranges between 0.931 and 0.951, and the signal capture accuracy ranges between 93.3% and 95.6%, which proves that the proposed algorithm has achieved the design expectation.

New Microstrip Diplexer for Recent Wireless Applications

2018 ◽  
Vol 7 (3.4) ◽  
pp. 96 ◽  
Author(s):  
Yaqeen S. Mezaal ◽  
Seham A. Hashim ◽  
Aqeel H.Al-fatlawi ◽  
Hussein A. Hussein
Keyword(s):  
Insertion Loss ◽  
Return Loss ◽  
Design Method ◽  
Open Loop ◽  
Coupled Resonators ◽  
Wireless Applications ◽  
Frequency Responses ◽  
Operating Band ◽  
Dual Channel ◽  
Better Than

In this study, dual-channel diplexer using microstrip open loop coupled resonators has been designed and simulated; each channel has two operating band frequencies. This microstrip diplexer is designed for (1.424/1.732GHz) for first channel and (2.014/2.318GHz) for second channel. The simulated results for this device have insertion loss (1.8 and 1 dB) at load 1, and (1.5 and 3 dB) at load 2. Additionally, it has reasonable return loss magnitudes better than 10 dB and effective isolation between channels of35 dB. The proposed design has shown an uncomplicated topology, an effectual design method, small circuit size and narrowband frequency responses that are fitting for multi service wireless schemes.  

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