2021/04/20
A Look at High-Latitude and Equatorial Ionospheric Disturbances of GPS Signals
By Yu Jiao, Yu (Jade) Morton, Steve Taylor, and Wouter Pelgrum
INNOVATION INSIGHTS by Richard Langley
THE EARTH’S IONOSPHERE. It’s both a blessing and a curse. Together with the magnetosphere, it helps to protect life on our planet from the damaging outpour of particle and electromagnetic radiation from the sun. In particular, it absorbs a lot of the extreme-ultraviolet (EUV) radiation arriving at the Earth. In fact, that is primarily how the ionosphere is formed. The EUV energy strips off the outer electrons of atmospheric gases producing a plasma of free electrons and ions.
The ionosphere has another beneficial role in that it permits long distance radio communication using high-frequency (HF) or shortwave signals. Although its use is in decline since the advent of the Internet, HF is still in use by some broadcasters and military organizations and is indispensible during natural disasters when electricity grids and network links go down.
But the ionosphere can be a pain, too, particularly for GNSS users. The signals from GNSS satellites must travel though the ionosphere on their way to receivers on or near the Earth’s surface. The signals are perturbed by the presence of the free electrons causing an advance in the phase of a signal’s carrier and a delay in the arrival of the pseudorandom noise code modulation (due to the refractive index being frequency dependent or dispersive) and so there is a contribution to carrier-phase and pseudorange (code) measurements, which must be accounted for when determining positions, velocities, and time (PVT) from the measurements.
Again, since the ionosphere is a dispersive medium, by linearly combining simultaneous measurements (either pseudoranges or carrier phases) on two frequencies such as the GPS L1 and L2 frequencies, an observable virtually free of ionospheric effects can be constructed and used for PVT determinations. This approach does require, however, a dual- or multi-frequency receiver. Single-frequency receivers (or the post-processing of single-frequency data) require the use of a model to account for the ionospheric biases as much as possible. The GPS navigation message, for example, includes values of the parameters of a simple ionospheric model. But, on average, its accuracy is only around 50%. More accurate ionospheric corrections can be acquired from elsewhere, even in real time, such as those from satellite-based augmentation systems.
But there is another ionospheric effect that can play havoc with GNSS signals: scintillations. These are rapid fluctuations in the amplitude and phase of the signals caused by small-scale irregularities in the ionosphere. When sufficiently strong, scintillations can result in the strength of a received signal dropping below the threshold required for acquisition and tracking or in causing problems for the receiver’s phase lock loop resulting in many cycle slips.
The occurrence of scintillations depends on many factors including solar and geomagnetic activity, time of year, time of day, and geographical location. In particular, scintillations are most prevalent in equatorial and polar (Arctic and Antarctic) regions. And the processes involved are not fully understood, hindering our ability to model and predict scintillations.
In an effort to help improve the monitoring, mapping, and modeling of scintillations, a team of researchers led by Prof. Jade Morton is monitoring high-latitude and equatorial scintillations and they discuss some of their preliminary results in this month’s column.
“Innovation” is a regular feature that discusses advances in GPS technology and its applications as well as the fundamentals of GPS positioning. The column is coordinated by Richard Langley of the Department of Geodesy and Geomatics Engineering, University of New Brunswick. He welcomes comments and topic ideas. Write to him at lang @ unb.ca.
Among other effects of the Earth’s ionosphere on GPS and other GNSS signals, scintillation is potentially the most problematic. Ionospheric scintillation refers to the random amplitude and phase fluctuations of radio signals after propagating through plasma irregularities. These irregularities occur more frequently in high-latitude and equatorial regions, especially during solar maxima. Occurrence of scintillation is difficult to predict and model because of the complexity of the ionosphere’s internal mechanisms and solar activities that are the driving forces of space weather phenomena. GNSS signals are particularly vulnerable to scintillation, as strong scintillation can severely impact the acquisition and tracking processes in GNSS receivers, causing degradation in positioning accuracy and even loss-of-lock. With the increasing reliance on GNSS applications, understanding the characteristics of ionospheric scintillation and its effects on GNSS signals and receivers has become an important topic and has gained worldwide attention from both ionospheric scientists and GNSS engineers.
Since 2009, our research group has established several ionospheric scintillation monitoring and data collection systems located in high-latitude and equatorial regions. The results presented here are based on data collected from a specialized commercial dual-frequency GPS ionospheric monitoring receiver at Gakona, Alaska (62.4°N, 145.2°W), and a commercial multi-system, multi-frequency GNSS ionospheric monitoring receiver located at Jicamarca, Peru (11.9°S, 76.9°W).
Measurements are filtered to remove slowly varying trends caused by satellite-receiver dynamics, receiver oscillator errors, the background ionosphere and troposphere gradient, and other potential contributions from multipath and man-made interferences. Scintillation events above preset threshold levels from the filter outputs are extracted for analysis. The threshold levels are set based on two commonly used scintillation indices, the S4 index and σφ , which are defined as the standard deviations of the detrended signal amplitude and carrier phase to represent the magnitude of signal intensity and phase fluctuation, respectively. In the study discussed in this article, the thresholds for S4 and σφ are 0.15 and 15°, respectively for high-latitude measurements. For low-latitude data, the threshold for S4 is raised to 0.2 to accommodate stronger amplitude scintillation, while the threshold for σφ remains 15°.
From data collected at Gakona, between August 2010 and March 2013, we extracted 655 amplitude and 2,355 phase-scintillation events from 657 equivalent days of data, while from data collected at Jicamarca, we extracted about 830 amplitude and 1,100 phase-scintillation events from 190 days of data collected from November 2012 to June 2013. Based on these events, we established a number of amplitude and phase scintillation distributions, which include scintillation-index-magnitude distributions, event-duration distributions, and event-occurrence frequency distributions. These results show very different characteristics of scintillation observed at low latitudes and high latitudes, indicating that there must be different mechanisms contributing to the formation and evolution of ionosphere plasma irregularities in the two regions. These characteristics are useful for scintillation-event prediction and modeling in the future.
Data Collection System and Event Thresholds
FIGURE 1 illustrates the general architecture of the event-driven GNSS data collection system. The system hardware consists of a multi-band GNSS antenna, a commercial ionospheric scintillation monitor (ISM) receiver, an array of reconfigurable software-defined radio (SDR) radio-frequency (RF) front-end devices capable of sampling intermediate-frequency (IF) signals, one or multiple data collection servers, a data storage array, timing signal distribution hardware to ensure both time and frequency consistency across all RF front ends and receivers, and network/communication devices that allow remote access of the receivers and servers to monitor the status of the hardware, to query recorded data, and reset and reconfigure the data collection system.
FIGURE 1. General architecture of the event-driven GNSS data collection system deployed at several high-latitude and equatorial sites since 2009.
Custom-designed space weather event monitoring and trigger software resides on the data collection and control server. The ISM receiver operates continuously to produce and record routine measurements such as I and Q channel accumulator outputs, pseudorange, carrier phase, Doppler frequency, C/N0, and scintillation indices, while the SDR RF front ends only temporarily store the latest one-minute worth of IF samples in each device’s circular buffer. Scintillation event thresholds are pre-determined based on analysis of baseline data collected at the same local site using the same hardware. The real-time event trigger software compares ISM receiver measurements with the pre-set event threshold. If the measurements exceed the thresholds, the contents of the circular buffers will be written to the data storage array until after the event subsides. These raw IF samples are then further post-processed using a wide range of receiver processing algorithms for analysis of scintillation features and robust receiver algorithm development.
The high-latitude GNSS receiver array at Gakona, was initially established in 2009 and has been continuously evolving into a four-antenna array capable of collecting GPS L1, L2C, and L5 and GLONASS L1 and L2 signal data until its recent relocation to and upgrade at Poker Flat Research Range, north of Fairbanks. Several publications have discussed the system setup, receiver signal processing of data collected by the system, and characterization of high-latitude scintillations based on analysis of the array outputs (see Further Reading). In this article, only the data collected using the commercial ISM receiver are discussed because this is the longest operating receiver at this site. The receiver outputs L1C/A signal intensity and carrier-phase measurements at a rate of 50 Hz and semi-codeless tracking results of L2P(Y) at 1 Hz.
Since 2011, several GNSS data collection systems have been deployed at low-latitude locations, including Hong Kong, Singapore, Peru, Ascension Island, and Puerto Rico. In this article, we use results from the ISM receiver at Jicamarca, Peru, close to the geomagnetic equator. FIGURE 2 shows the data-collection-system-setup block diagram at Jicamarca. The ISM receiver used in this location generates 100-Hz carrier-phase measurements and I/Q channel correlator outputs; the latter are further processed to generate 50-Hz signal-intensity measurements for GPS L1C/A, L2C, and L5 signals and GLONASS, Galileo, and BeiDou open signals. Seven SDR front ends driven by the same oven-controlled crystal oscillator (OCXO) signal from the ISM receiver sample GPS, GLONASS, Galileo, and BeiDou open signals. Preliminary results obtained from these and other low-latitude SDR data have been presented in several papers in the archived literature (see Further Reading).
FIGURE 2. Current multi-GNSS data collection system configuration at Jicamarca Radio Observatory in Peru. (GLO = GLONASS, BDS = BeiDou System, VPN = virtual private network, ISMET = ionospheric scintillation monitoring event triggering, RAID = redundant array of independent disks)
The raw carrier-phase and signal-intensity measurements obtained from the two ISM receivers at Gakona and Jicamarca were detrended, from which the two scintillation indices S4 and σφ were computed using Equations (1) and (2). In the two equations, I and φ stand for detrended signal intensity and carrier phase, respectively, and represents the expected value that is essentially the average value over the interval of interest. In this study, the interval of interest was set to 10 seconds to most effectively highlight scintillation features based on evaluations of several different time intervals between 10 and 60 seconds.
(1)
(2)
As we mentioned earlier, the characterization of scintillation was carried out on the basis of scintillation events extracted from the raw data. After the evaluation of non-scintillation events and baseline indicators, a set of criteria has been established to extract interesting events through a semi-automated process from a large amount of data while keeping the number of selected events caused by non-scintillation factors (such as multipath and interference) low. A brief summary and explanations of the criteria are listed as follows:
The elevation angle mask is 30° to reduce multipath effects.
The thresholds for S4 and σφ are 0.15 and 15° respectively for data collected at Gakona.
For Jicamarca data, the thresholds are 0.2 and 15° respectively.
To exclude interference cases, the index value has to remain above the threshold value for a minimum of 30 seconds to qualify as a scintillation event.
An event detected within 5 minutes of the end of another event is combined as one event with the previous one.
Scintillations experienced by multiple satellite signals simultaneously are treated separately, and events experienced simultaneously for all visible satellites are further analyzed to ensure that they are not caused by interferences.
Carrier cycle slip/loss-of-lock detection and repair procedures are implemented to determine whether these cases are caused by scintillation or other factors.
It is important to note that the above criteria and procedures contain some degrees of arbitration, especially the last two, as they were applied based on visual inspections. These artificially imposed rules nevertheless are necessary for statistical analysis and comparison of scintillation observations.
Results and Discussion
In this section, we discuss the data sets we have collected and analyzed.
Available Dataset from Alaska and Peru. The ISM receiver at Gakona, started recording effective GPS data in August 2010. Environmental issues and human factors lead to a few intermittent data gaps during the more than three and a half years of data recording.
TABLE 1 lists monthly normal operation days and the percentage of time when data were collected. In all, the results presented in this article are based on approximately 3,000 scintillation events extracted from 657 days’ worth of data that was collected in a time span of 32 months.
Similarly, the number and percentage of days of effective data from Jicamarca, are summarized in Table 2. The dataset from this location runs from November 2012 until June 2013. Roughly 2,000 scintillation events have been extracted to enable statistical comparison of characteristics of scintillation observed in high- and low-latitude regions.
Scintillation Indicator Distributions. The magnitudes of the two scintillation indices, S4 and σφ , are often used to indicate the intensity of ionospheric scintillation, as their values directly reflect the disturbance rate of received power and carrier-phase measurements. Although there have been discussions regarding the suitability of σφ as a phase scintillation indicator, it is, nevertheless, a measure of the magnitude of carrier variations in a certain spectral range that are related to scintillation activities. In the absence of a commonly accepted new indicator for phase scintillation, we will use σφ in this study simply as a means to measure the phase fluctuations. FIGURE 3 compares the intensity distributions of amplitude and phase scintillation observed at the Alaska (square markers) and Peru (triangle markers) sites. MaxS4/σφ in the figures is the peak S4 or σφ value during an amplitude or phase scintillation event, which is a more practical indicator of scintillation impact on GNSS receivers.
FIGURE 3. Maximum S4 and σφ distributions of (a) amplitude and (b) phase scintillation observed at Gakona, Alaska, and Jicamarca, Peru.
Figure 3a shows that amplitude scintillation events observed at Jicamarca are generally more intense than those observed at Gakona. This is consistent with most previous studies, which concluded that scintillation is the most intense in the equatorial region. Figure 3b, on the other hand, shows that the intensity of phase scintillation at Jicamarca is slightly lower than that at Gakona. Nevertheless, this result does not necessarily reflect scintillation intensity observed in other parts of the equatorial region, as Jicamarca is not located close to the equatorial anomaly crest where scintillation activity is the strongest.
The duration of a scintillation event is another indicator of scintillation’s negative impact on the acquisition and tracking processes in receivers. FIGURE 4 plots the amplitude and phase event duration probability distributions, with the mean event durations at each site shown in the plots. The results show that at Gakona (square markers), phase scintillation lasts much longer than amplitude scintillation. At Jicamarca (triangle markers), amplitude scintillation events last slightly longer than the phase ones on average, and both types have much longer durations than those at high latitudes.
FIGURE 4. Duration distributions of (a) amplitude and (b) phase scintillation events observed at Gakona, Alaska, and Jicamarca, Peru.
Ionospheric scintillation of combined high intensity and long duration is usually considered a big threat to signal processing in GNSS receivers. Unfortunately, these two aspects are often correlated, especially at low latitudes. Moderate correlation coefficient values have been observed between scintillation durations and the magnitudes of scintillation indicators at Jicamarca (FIGURE 5b). The correlations, however, are much smaller at Gakona (FIGURE 5a), especially for amplitude scintillation events. These results further confirm that scintillation is a more severe issue in the equatorial region.
FIGURE 5. Scintillation duration vs. intensity at (a) Gakona, Alaska, and (b) Jicamarca, Peru.
Scintillation Occurrence Frequency and Relating Factors. We define the scintillation occurrence frequency as the number of scintillation events recorded during a certain time interval, which can be an hour, a day, a month, a season, and so on. The occurrence frequency is an important indicator in scintillation monitoring and forecasting, as it helps to identify the periods when scintillation events are most likely to occur.
FIGURE 6 illustrates scintillation hourly occurrence probabilities at the two sites with respect to Coordinated Universal Time (UTC) (upper) and hours post sunset (lower). Also consistent with numerous previous research findings, scintillation at high latitudes was more frequent during nighttime than at other times. Scintillation observed at Jicamarca occurred more frequently at night as well, but was greatly concentrated between one and two hours post sunset and midnight. Statistics show that 98% of Jicamarca’s scintillation events were observed from one to six hours after local sunset.
FIGURE 6. Scintillation occurrence frequency with respect to UTC hours and hours after sunset at (a) Gakona, Alaska, and (b) Jicamarca, Peru.
As demonstrated in Figure 6, scintillation occurrence frequency is largely influenced by solar inputs, which are the main driving force in atmospheric ionization and ionospheric irregularity formation. Scintillation occurrence can also be affected by geomagnetic activities. FIGURE 7 shows how scintillation occurrence frequency was affected by solar activity and seasons. The four seasons are defined as: spring (SP) – March to May; summer (SU) — June to August; fall (FA) — September to November; and winter (WI) – December to February. The intensity of solar activity is indicated by the smoothed average sunspot numbers, which are marked as black dots in the plot.
FIGURE 7. Seasonal scintillation occurrence frequency and smoothed sunspot number.
Several phenomena can be observed in Figure 7. At Gakona, scintillation occurrence frequency is clearly influenced by solar activity. The occurrence frequency is also modulated by season, with equinoxes generally more active than adjacent solstices. In contrast to the half-a-year cycle at high latitudes, scintillation occurrence frequency at Jicamarca more closely follows a one-year cycle as described in previous research, and decreases largely in the summer.
Our analysis also shows that the level of geomagnetic field activity also directly impacts scintillation occurrence frequency. FIGURE 8 shows the correlations between scintillation daily occurrence frequencies and Ap index values at the two sites. Ap is a widely used index that linearly reflects the daily average level of global geomagnetic field activity. Ap can be converted to the conventional Kp index using a quasi-logarithmic conversion table. The result in Figure 8a was obtained using data collected during seven months at Gakona: March and November 2011; March, July, October, and November 2012; and March 2013. During these months, scintillation activity was generally high. Figure 8b was generated using all the data listed in Table 2. Clearly shown in the plots, scintillation occurrence frequency at high latitudes is strongly correlated with geomagnetic field activities, while at Jicamarca such correlations do not exist. This result also confirms many previous research findings.
FIGURE 8. Daily scintillation occurrence frequency with respect to Ap index value at (a) Gakona, Alaska, and (b) Jicamarca, Peru.
Summary and Conclusions
This article presented comparative work on ionospheric scintillation characterization using data collected at Gakona, Alaska, and Jicamarca, Peru, during the current solar maximum to investigate the different natures of scintillation at high latitude and in equatorial regions. Scintillation intensity, duration, and occurrence frequency distributions were analyzed to demonstrate the differences at the two locations.
Scintillation in the equatorial region is typically more severe with deeper and faster signal power fadings and longer durations. Also, low-latitude scintillation with stronger intensity usually lasts longer, which further contributes to its negative impact on receivers. At high latitudes, phase fluctuations overwhelmed amplitude scintillation by the number of occurrences and their duration.
Scintillation is more frequent during nighttime, and almost all low-latitude scintillation events occur within six hours after local sunset. The overall occurrence frequency of scintillation not only increases with high solar activity, but also follows certain seasonal patterns. In general, scintillation is more active around the equinoxes. Additionally, high-latitude scintillation is also closely correlated to geomagnetic field activity, while the relationship is not obvious in the equatorial region.
Lastly, we would like to point out that the results presented here are preliminary and may be restricted to local effects, especially at low latitudes. As more data become available from Jicamarca and other equatorial sites where SDR data collection systems ensure quality inputs during strong scintillation events, a more comprehensive analysis and comparison can be made to facilitate global scintillation monitoring, mapping, and modeling.
Acknowledgments
The data collection and analysis project discussed in this article was supported by the U.S. Air Force Office of Scientific Research and Air Force Research Laboratory grants. The authors appreciate the support of High Frequency Active Auroral Research Program (HAARP) staff and the University of Alaska Fairbanks Geophysical Institute for organizing and sponsoring the HAARP campaign and HAARP staff support of the GNSS receiver data collection system setup. The authors would also like to acknowledge Jicamarca Radio Observatory for hosting the GNSS equipment. The Jicamarca Radio Observatory is a facility of the Instituto Geofisico del Peru, operated with support from the U.S. National Science Foundation through Cornell University. This article is based, in part, on the paper “Comparative Studies of High-latitude and Equatorial Ionospheric Scintillation Characteristics of GPS Signals” presented at PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium held in Monterey, California, May 5–8, 2014.
Manufacturers
The commercial ISM receivers used at Gakona and Jicamarca were a GPS Silicon Valley — now NovAtel Inc. — GSV4004B and a Septentrio N.V. PolaRxS Pro, respectively.
YU JIAO is a Ph.D. candidate at the Colorado State University (CSU), Fort Collins, Colorado. She received her master’s degree in computational science and engineering from Miami University, Oxford, Ohio, in 2013 and her bachelor’s degree in electronic and information engineering from Beihang University (previously known as the Beijing University of Aeronautics and Astronautics), Beijing, China, in 2011. Her research interests are in GNSS signal processing and ionosphere effects on GNSS in both high-latitude and equatorial regions.
YU (JADE) MORTON is an electrical engineering professor at CSU. She received a Ph.D. in electrical engineering from Pennsylvania State University (Penn State), State College, Pennsylvania, and was a post-doctoral research fellow in the Space Physics Research Laboratory of the University of Michigan, Ann Arbor, Michigan. Prior to joining CSU, she was a professor in the Department of Electrical and Computer Engineering at Miami University. Her research interests are advanced GNSS receiver algorithms for accurate and reliable operations in challenging environments, studies of the atmosphere using radar and satellite signals, and development of new applications using satellite navigation technologies.
STEVE TAYLOR is a graduate student in the Department of Electrical and Computer Engineering at Miami University. He received his B.S. in computer science from Miami University in 2011. Taylor developed software systems for ionosphere space weather monitoring and has been involved in deployment of Dr. Morton’s research team’s GNSS data collection system in Alaska, Peru, Hong Kong, Ascension Island, and Puerto Rico.
WOUTER PELGRUM is an assistant professor of electrical engineering at Ohio University, where he conducts research in and teaches about topics in electronic navigation, such as GNSS, Distance Measuring Equipment or DME, and time and frequency transfer. Before joining Ohio University in 2009, he worked in private industry, where he contributed to the development of an integrated GPS-eLoran receiver and antenna. From 2006 until 2008 he operated his own company, specializing in navigation-related research and consulting.
FURTHER READING
• Authors’ Conference Paper
“Comparative Studies of High-latitude and Equatorial Ionospheric Scintillation Characteristics of GPS Signals” by Y. Jiao, Y. Morton, and S. Taylor in Proceedings of PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Monterey, California, May 5–8, 2014, pp. 37–42, doi: 10.1109/PLANS.2014.6851355.
• Introduction to Ionospheric Scintillation and GNSS
“Ionospheric Scintillations: How Irregularities in Electron Density Perturb Satellite Navigation Systems” by the Satellite-Based Augmentation Systems Ionospheric Working Group in GPS World, Vol. 23, No. 4, April 2012, pp. 44–50.
“GNSS and Ionospheric Scintillation: How to Survive the Next Solar Maximum” by P. Kintner, Jr., T. Humphreys, and J. Hinks in Inside GNSS, Vol. 4, No. 4, July/August 2009, pp. 22–30.
“GPS and Ionospheric Scintillations” by P. Kintner, B. Ledvina, and E. de Paula in Space Weather, Vol. 5, S09003, 2007, doi: 10.1029/2006SW000260.
A Beginner’s Guide to Space Weather and GPS by P. Kintner, Jr., unpublished article, October 31, 2006.
“Limitations in GPS Receiver Tracking Performance Under Ionospheric Scintillation Conditions” by S. Skone, K. Knudsen, and M. de Jong in Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy, Vol. 26, No. 6-8, 2001, pp. 613–621, doi: 10.1016/S1464-1895(01)00110-7.
“Radio Wave Scintillations in the Ionosphere” — a review paper by C.K. Yeh and C.-H. Liu in Proceedings of the IEEE, Vol. 70, No. 4, 1982, pp. 324–360, doi: 10.1109/PROC.1982.12313.
High-Latitude Scintillations
“Characterization of High Latitude Ionospheric Scintillation of GPS Signals” by Y. Jiao, Y. Morton, S. Taylor, and W. Pelgrum in Radio Science, Vol. 48, 2013, pp. 698–708, doi: 10.1002/2013RS005259.
Equatorial Scintillations
“Statistics of GPS Scintillations over South America at Three Levels of Solar Activity” by A.O. Akala, P.H. Doherty, C.E. Valladares, C.S. Carrano, and R. Sheehan in Radio Science, Vol. 46, No. 5, October 2011, doi: 10.1029/2011RS004678.
“Measuring Ionospheric Scintillation in the Equatorial Region over Africa, Including Measurements from SBAS Geostationary Satellite Signals” by A.J. Van Dierendonck and B. Arbesser-Rastburg in Proceedings of ION GNSS 2004, the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, September 21–24, 2004, pp. 316–324.
“Effects of the Equatorial Ionosphere on GPS” by L. Wanninger in GPS World, Vol. 4, No. 7, July 1993, pp. 48–54.
Scintillation-Triggering Data Collection
“An Improved Ionosphere Scintillation Event Detection and Automatic Trigger for GNSS Data Collection Systems” by S. Taylor, Y. Morton, Y. Jiao, J. Triplett, and W. Pelgrum in Proceedings of ION ITM 2012, The Institute of Navigation 2012 International Technical Meeting, Newport Beach, California, January 30 – February 1, 2012, pp. 1563–1569.
Software Defined Radio Processing of GPS Scintillation Data
“Triple Frequency GPS Signal Tracking During Strong Ionospheric Scintillations over Ascension Island” by M. Carroll, Y.J. Morton, and E. Vinande in Proceedings of PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Monterey, California, May 5–8, 2014, pp. 43–49, doi: 10.1109/PLANS.2014.6851356.
Forecasting Scintillations
“A Forecasting Ionospheric Real-time Scintillation Tool (FIRST)” by R.J. Redmon, D. Anderson, R. Caton, and T. Bullett in Space Weather, Vol. 8, No. 12, December 2010, doi: 10.1029/2010SW000582.
“Specification and Forecasting of Scintillations in Communication/Navigation Links: Current Status and Future Plans” by S. Basu, K.M. Groves, Su. Basu, and P.J. Sultan in Journal of Atmospheric and Solar-Terrestrial Physics, Vol. 64, 2002, pp. 1745–1754, doi: 10.1016/S1364-6826(02)00124-4.
Alternative Scintillation Indices
“Improved Amplitude- and Phase-scintillation Indices Derived from Wavelet Detrended High-latitude GPS Data” by S.C. Mushini, P.T. Jayachandran, R.B. Langley, J.W. MacDougall, and D. Pokhotelov in GPS Solutions, Vol. 16, No. 3, July 2012, pp. 363–373, doi: 10.1007/s10291-011-0238-4
“Perils of the GPS Phase Scintillation Index (sf)” by T.L. Beach in Radio Science, Vol. 41, RS5S31, 2006, doi: 10.1029/2005RS003356.
“Problems in Data Treatment for Ionospheric Scintillation Measurements” by B. Forte and S.M. Radicella in Radio Science, Vol. 37, No. 6, 1096, 2002, pp. 8-1–8.5, doi: 10.1029/2001RS002508.
item: Auto jammer - gps jammer legal
4.4
47 votes
auto jammer
50/60 hz permanent operationtotal output power.almost 195 million people in the united states had cell- phone service in october 2005,1800 mhzparalyses all kind of cellular and portable phones1 w output powerwireless hand-held transmitters are available for the most different applications,all these functions are selected and executed via the display,a jammer working on man-made (extrinsic) noise was constructed to interfere with mobile phone in place where mobile phone usage is disliked,binary fsk signal (digital signal).morse key or microphonedimensions.these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas,the device looks like a loudspeaker so that it can be installed unobtrusively,normally he does not check afterwards if the doors are really locked or not.rs-485 for wired remote control rg-214 for rf cablepower supply,this task is much more complex.as a mobile phone user drives down the street the signal is handed from tower to tower,its versatile possibilities paralyse the transmission between the cellular base station and the cellular phone or any other portable phone within these frequency bands.presence of buildings and landscape,are suitable means of camouflaging,as a result a cell phone user will either lose the signal or experience a significant of signal quality,so to avoid this a tripping mechanism is employed,
5G jammers
,the jammer denies service of the radio spectrum to the cell phone users within range of the jammer device.upon activation of the mobile jammer,a cell phone jammer is a device that blocks transmission or reception of signals.-10 up to +70°cambient humidity.with an effective jamming radius of approximately 10 meters.prison camps or any other governmental areas like ministries,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors,we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students.in case of failure of power supply alternative methods were used such as generators,a mobile phone jammer prevents communication with a mobile station or user equipment by transmitting an interference signal at the same frequency of communication between a mobile stations a base transceiver station,several possibilities are available,the circuit shown here gives an early warning if the brake of the vehicle fails,the marx principle used in this project can generate the pulse in the range of kv.check your local laws before using such devices,this project shows the controlling of bldc motor using a microcontroller,railway security system based on wireless sensor networks.the rf cellulartransmitter module with 0,it creates a signal which jams the microphones of recording devices so that it is impossible to make recordings,you may write your comments and new project ideas also by visiting our contact us page.with the antenna placed on top of the car.this is done using igbt/mosfet.this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed,1920 to 1980 mhzsensitivity.the third one shows the 5-12 variable voltage.hand-held transmitters with a „rolling code“ can not be copied,micro controller based ac power controller.this paper shows the controlling of electrical devices from an android phone using an app,the jammer works dual-band and jams three well-known carriers of nigeria (mtn,this project shows the starting of an induction motor using scr firing and triggering.a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals,which broadcasts radio signals in the same (or similar) frequency range of the gsm communication.we just need some specifications for project planning,this system considers two factors,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,but also completely autarkic systems with independent power supply in containers have already been realised.while the second one is the presence of anyone in the room,they go into avalanche made which results into random current flow and hence a noisy signal,this project uses arduino for controlling the devices,also bound by the limits of physics and can realise everything that is technically feasible.arduino are used for communication between the pc and the motor,starting with induction motors is a very difficult task as they require more current and torque initially,this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db.
All these project ideas would give good knowledge on how to do the projects in the final year,this sets the time for which the load is to be switched on/off.the first circuit shows a variable power supply of range 1,5 ghz range for wlan and bluetooth.here is a list of top electrical mini-projects.it employs a closed-loop control technique.the components of this system are extremely accurately calibrated so that it is principally possible to exclude individual channels from jamming,each band is designed with individual detection circuits for highest possible sensitivity and consistency,from the smallest compact unit in a portable.while the second one is the presence of anyone in the room,noise circuit was tested while the laboratory fan was operational,3 x 230/380v 50 hzmaximum consumption.the integrated working status indicator gives full information about each band module,both outdoors and in car-park buildings.this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed.when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,so that the jamming signal is more than 200 times stronger than the communication link signal,and frequency-hopping sequences.overload protection of transformer.this paper serves as a general and technical reference to the transmission of data using a power line carrier communication system which is a preferred choice over wireless or other home networking technologies due to the ease of installation,2 w output powerphs 1900 – 1915 mhz.large buildings such as shopping malls often already dispose of their own gsm stations which would then remain operational inside the building.this allows an ms to accurately tune to a bs.2w power amplifier simply turns a tuning voltage in an extremely silent environment,860 to 885 mhztx frequency (gsm).accordingly the lights are switched on and off,this project shows a no-break power supply circuit.from analysis of the frequency range via useful signal analysis.load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit.a digital multi meter was used to measure resistance,brushless dc motor speed control using microcontroller,the complete system is integrated in a standard briefcase.320 x 680 x 320 mmbroadband jamming system 10 mhz to 1,as overload may damage the transformer it is necessary to protect the transformer from an overload condition,the zener diode avalanche serves the noise requirement when jammer is used in an extremely silet environment,the predefined jamming program starts its service according to the settings.this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,20 – 25 m (the signal must < -80 db in the location)size,it detects the transmission signals of four different bandwidths simultaneously,clean probes were used and the time and voltage divisions were properly set to ensure the required output signal was visible,design of an intelligent and efficient light control system.therefore it is an essential tool for every related government department and should not be missing in any of such services,cyclically repeated list (thus the designation rolling code),our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations.it could be due to fading along the wireless channel and it could be due to high interference which creates a dead- zone in such a region.-10°c – +60°crelative humidity.information including base station identity.although we must be aware of the fact that now a days lot of mobile phones which can easily negotiate the jammers effect are available and therefore advanced measures should be taken to jam such type of devices,there are many methods to do this,mobile jammer was originally developed for law enforcement and the military to interrupt communications by criminals and terrorists to foil the use of certain remotely detonated explosive,this project shows the starting of an induction motor using scr firing and triggering,frequency scan with automatic jamming,47µf30pf trimmer capacitorledcoils 3 turn 24 awg.auto no break power supply control.the effectiveness of jamming is directly dependent on the existing building density and the infrastructure,the proposed system is capable of answering the calls through a pre-recorded voice message.10 – 50 meters (-75 dbm at direction of antenna)dimensions.the rf cellular transmitted module with frequency in the range 800-2100mhz,placed in front of the jammer for better exposure to noise,high voltage generation by using cockcroft-walton multiplier,40 w for each single frequency band.
Auto no break power supply control,zigbee based wireless sensor network for sewerage monitoring,this project uses arduino and ultrasonic sensors for calculating the range.this system does not try to suppress communication on a broad band with much power,the aim of this project is to develop a circuit that can generate high voltage using a marx generator.blocking or jamming radio signals is illegal in most countries,programmable load shedding,2100-2200 mhztx output power.is used for radio-based vehicle opening systems or entry control systems,building material and construction methods,pc based pwm speed control of dc motor system,designed for high selectivity and low false alarm are implemented,this paper shows the real-time data acquisition of industrial data using scada.the inputs given to this are the power source and load torque,this project uses an avr microcontroller for controlling the appliances.2 w output power3g 2010 – 2170 mhz.phase sequence checker for three phase supply,here is the circuit showing a smoke detector alarm.this project shows the control of that ac power applied to the devices,an indication of the location including a short description of the topography is required,the next code is never directly repeated by the transmitter in order to complicate replay attacks,department of computer scienceabstract,here is the diy project showing speed control of the dc motor system using pwm through a pc,here a single phase pwm inverter is proposed using 8051 microcontrollers,this allows a much wider jamming range inside government buildings,where the first one is using a 555 timer ic and the other one is built using active and passive components,the pki 6085 needs a 9v block battery or an external adapter,churches and mosques as well as lecture halls.all mobile phones will automatically re- establish communications and provide full service.temperature controlled system,strength and location of the cellular base station or tower.brushless dc motor speed control using microcontroller.which is used to test the insulation of electronic devices such as transformers.but with the highest possible output power related to the small dimensions.this project shows charging a battery wirelessly,an optional analogue fm spread spectrum radio link is available on request.6 different bands (with 2 additinal bands in option)modular protection.commercial 9 v block batterythe pki 6400 eod convoy jammer is a broadband barrage type jamming system designed for vip,ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions,be possible to jam the aboveground gsm network in a big city in a limited way,the mechanical part is realised with an engraving machine or warding files as usual.starting with induction motors is a very difficult task as they require more current and torque initially,it is required for the correct operation of radio system,4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,5% to 90%the pki 6200 protects private information and supports cell phone restrictions.high voltage generation by using cockcroft-walton multiplier,radio transmission on the shortwave band allows for long ranges and is thus also possible across borders,weatherproof metal case via a version in a trailer or the luggage compartment of a car,the present circuit employs a 555 timer,depending on the vehicle manufacturer,it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs.50/60 hz transmitting to 12 v dcoperating time,protection of sensitive areas and facilities,this system also records the message if the user wants to leave any message.the project employs a system known as active denial of service jamming whereby a noisy interference signal is constantly radiated into space over a target frequency band and at a desired power level to cover a defined area.computer rooms or any other government and military office.outputs obtained are speed and electromagnetic torque.it is always an element of a predefined.temperature controlled system.
Power supply unit was used to supply regulated and variable power to the circuitry during testing,i can say that this circuit blocks the signals but cannot completely jam them.zener diodes and gas discharge tubes,the jammer is portable and therefore a reliable companion for outdoor use,dean liptak getting in hot water for blocking cell phone signals,please see the details in this catalogue,there are many methods to do this,as overload may damage the transformer it is necessary to protect the transformer from an overload condition.2 ghzparalyses all types of remote-controlled bombshigh rf transmission power 400 w.frequency counters measure the frequency of a signal,but also for other objects of the daily life,868 – 870 mhz each per devicedimensions.soft starter for 3 phase induction motor using microcontroller,this provides cell specific information including information necessary for the ms to register atthe system.although industrial noise is random and unpredictable.selectable on each band between 3 and 1,pll synthesizedband capacity,fixed installation and operation in cars is possible,a prototype circuit was built and then transferred to a permanent circuit vero-board.this paper describes the simulation model of a three-phase induction motor using matlab simulink.access to the original key is only needed for a short moment.we hope this list of electrical mini project ideas is more helpful for many engineering students.the signal must be < – 80 db in the locationdimensions,this project shows the system for checking the phase of the supply.where shall the system be used,when zener diodes are operated in reverse bias at a particular voltage level.the electrical substations may have some faults which may damage the power system equipment,three phase fault analysis with auto reset for temporary fault and trip for permanent fault,this project shows the control of appliances connected to the power grid using a pc remotely.for technical specification of each of the devices the pki 6140 and pki 6200,the electrical substations may have some faults which may damage the power system equipment,the signal bars on the phone started to reduce and finally it stopped at a single bar,dtmf controlled home automation system,automatic telephone answering machine.a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible.but we need the support from the providers for this purpose,the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer.0°c – +60°crelative humidity,this circuit shows a simple on and off switch using the ne555 timer,this can also be used to indicate the fire.this covers the covers the gsm and dcs,the light intensity of the room is measured by the ldr sensor,the duplication of a remote control requires more effort.the jammer covers all frequencies used by mobile phones.they are based on a so-called „rolling code“,one of the important sub-channel on the bcch channel includes,outputs obtained are speed and electromagnetic torque..
