Getting there more safely INNOVATION INSIGHTS with Richard Langley It’s all physics. How things work, that is. You’ve heard me say that before in this column, but I suppose I’m a little biased (or realistic) as my first degree is in physics — applied physics, to be more precise. Mind you, some chemists might disagree that it’s all down to physics. But as Sheldon Cooper in the popular American TV sitcom The Big Bang Theory stated in a radio interview with real science journalist Ira Flatow following his apparent discovery of the first stable super-heavy element, “Yes, yes, I’d be a physicist with a Nobel in chemistry. Everyone laugh at the circus freak. You know, I don’t need to sit here and take this, Flatow. It is because of bullies like you, every day more and more Americans are making the switch to television.” But in all seriousness, it really was physicists who first explained the physical phenomena associated with a range of technologies that had to be understood before global navigation satellite systems could become a reality. From orbital mechanics, to relativity theory, to semiconductors, to transatmospheric propagation of radio signals, to atomic clocks, the fundamental understanding of how these worked was provided by physicists. This was particularly true for atomic clocks. An atomic clock, like any clock, consists of two basic components: a resonator or oscillator and a counter. The oscillator generates a stable frequency, whose cycles are counted, converted to units of seconds, minutes, hours and perhaps days, and continuously displayed. This is the case whether we are describing a wristwatch with a quartz crystal oscillator or an atomic clock whose oscillator is made up of atoms undergoing quantum energy transitions. A crystal oscillator is stimulated to vibrate at its design frequency and thereby generate a fluctuating electrical current with that frequency. The atomic oscillator works thanks to the principles of quantum physics. Atoms have energies, but the energies are quantized, meaning that only specific energy levels are possible. An atom may exist at a particular energy level and spontaneously transition to a lower energy level and in so doing emit electromagnetic radiation (such as radio waves or light) of a specific frequency equal to the change in energy divided by a fundamental physical constant called Planck’s constant, named after Max Planck, who introduced it in 1900. The atom can be stimulated to return to the higher energy level by exposing it to radiation of that same exact frequency. A practical atomic oscillator can be constructed by confining a collection of atoms in an enclosure and bathing them in electromagnetic radiation from a tunable generator. By automatically tuning the frequency of the generator to maximize the number of stimulated atoms through a feedback loop, a very pure and constant frequency will result. The first clocks based on an energy transition of the cesium atom were developed in the mid-1950s. Later on, clocks based on energy transitions of the rubidium and hydrogen atoms were developed. By the 1960s, commercial rack-mountable cesium and rubidium clocks became available. But a need existed for miniaturized atomic clocks that could be easily embedded in equipment requiring a very stable frequency source. Funded in part by the Defense Advanced Research Projects Agency, the first chip-scale atomic clock was demonstrated by physicists in 2004, and by 2011, a chip-scale atomic clock based on a cesium atom transition became commercially available. In this month’s column, we look at how chip-scale atomic clocks can help us navigate more safely by allowing a GNSS receiver to position itself more accurately even with only three satellites in view, and to protect itself by being able to detect a sophisticated spoofing attempt. Physics — isn’t it wonderful! GNSS positioning and navigation are based on one-way range measurements. Synchronization of the receiver and satellite timescales is carried out with respect to a third time scale of higher stability, such as GNSS system time, by introducing so-called clock errors. To account for the time and frequency offsets of the satellites, the user can obtain appropriate corrections from the broadcast navigation message in real time. In post-processing, more accurate corrections are provided by various products of the International GNSS Service (IGS). Due to the generally poor accuracy and limited long-term frequency stability of a quartz oscillator built into a GNSS receiver, the receiver clock error has to be estimated epoch-by-epoch. This is the typical case for single-point positioning (SPP) based on code (pseudorange) observations only. This comes with certain drawbacks: The up-coordinate is determined two to three times less precisely than the horizontal coordinates, Higher dilution of precision values are obtained than in the hypothetical case of trilateration, High correlations of up to 99 percent between the receiver’s up-coordinate and clock error persist, and At least four satellites are necessary for positioning. Especially in the case of kinematic positioning, this situation can be significantly improved by using a more stable (atomic) clock for the receiver and introducing the information about its frequency stability into the estimation process. This approach is called receiver clock modeling (RCM), and basically requires that the integrated clock noise is smaller than the receiver noise during the modeling interval. Besides SPP, this method can also be applied in a common-clock setup in relative positioning using single-differenced observations (which, by their nature, contain more information) instead of typically used double-differenced observations, or precise point positioning. The recent development of chip-scale atomic clocks (CSACs) offers the required frequency stability and accuracy, and opens up the possibility of using atomic clocks in real kinematic GNSS applications without any severe restrictions regarding power supply or environmental influences on the clocks. When connecting one of these clocks to a GNSS receiver, replacing or steering the internal oscillator accordingly, and modeling its behavior in a physically meaningful way instead of epoch-wise estimation, the navigation performance can be improved distinctly. The receiver clock parameter absorbs signal delays common to all simultaneous line-of-sight signals whether these delays represent the physical clock or any other common delay. Thus, it is especially vulnerable to delays caused by jammers or spoofers. If the clock behavior is predictable, information about jamming or spoofing can be retrieved, and thus the integrity of the positioning solution can be improved. Chip-Scale Atomic Clocks For our test purposes, we used two different commercially available CSACs, dubbed CSAC A and CSAC B. To gain knowledge about their frequency stabilities, we compared them against an active hydrogen maser at the Physikalisch-Technische Bundesanstalt (PTB), Germany’s official metrology institute. We analyzed the raw fractional phase measurements and computed individual Allan variances for our devices. The resulting frequency stabilities are shown in FIGURE 1. Clock Model Basically, a clock is an oscillator generating a sinusoidal signal with a given nominal frequency coupled with a frequency counter. The deviation of the signal’s nominal frequency with respect to a reference time scale can be described by a frequency offset and drift plus random frequency fluctuations. In the time domain, the resulting clock error δt, that is, the difference between nominal time t and the time read simultaneously on the clock, can be approximated by the following equation: (1) with systematic time offset b0, frequency offset b1, frequency drift b2, and random noise x(t,t0). Thus, the main (deterministic) part of a clock model can be described by a quadratic polynomial. The more interesting characteristics of a clock are contained in the underlying noise processes. The time-dependent Allan deviation (ADEV) enables the determination of a modeling or predicting interval τp over which receiver clock modeling is physically meaningful; that is, the integrated clock noise x(t,t0) is smaller than GNSS receiver noise: (2) The noise σrx of a typical commercial GNSS receiver can be assessed to approximately one percent of the chip or wavelength of the signal in use, such as 3 meters, 0.3 meter, or 2 millimeters for C/A-code, P-code, or L1 carrier-phase observations, respectively. To apply the knowledge gained about the devices’ frequency stabilities, appropriate models for GNSS data analysis should be established. One prerequisite is that the clock noise has to be well below the GNSS receiver noise; that is, the integrated random frequency fluctuations of CSACs cannot be resolved by the GNSS observations in use. We assume typical values for code and ionosphere-free carrier-phase observations from modern geodetic GNSS receivers of 1 meter and 5 millimeters, respectively. Since these observations are phase-based measures, we can model the dominating underlying noise process as white-noise phase modulation (WPM) over time. The corresponding graphs are depicted in FIGURE 1 as dashed lines. The intersection points between these lines and the ADEV curves define maximal time intervals Δt for physically meaningful receiver clock modeling in our case study. Depending on the CSAC in use, RCM is applicable over time intervals of at least ten minutes and up to one hour in C/A-code-based applications, such as SPP. GNSS Applications We have tested and validated our receiver clock modeling approaches for GNSS navigation. Kinematic Experiment We carried out a real kinematic experiment on a cart track in farm fields with an approximately 500 × 800 square meter area with only a few natural obstructions in the form of a tree-lined lane (see FIGURE 2). The basic measurement configuration consisted of four GNSS receivers running the same firmware version connected to a GNSS antenna via an active signal splitter. Three of these receivers were fed by the 10-MHz signals of our CSACs. For comparison purposes, the fourth receiver was driven by its internal quartz oscillator. Each test drive with our motor vehicle lasted approximately 8 to 10 minutes. We recorded GPS and GLONASS data with a sampling interval of one second. (Only GPS-based results are described herein.) That was also the case for our temporary local reference station, which consisted of a GNSS antenna mounted on a tripod and connected to another GNSS receiver. Hence, we were able to generate reference solutions for the vehicle trajectories in relative positioning mode with baselines of up to only some hundred meters, yielding 3D coordinate accuracies below 20 centimeters. The RCM algorithms presented here were implemented in the Institut für Erdmessung GNSS Matlab Toolbox. To compute a typical real-time SPP navigation solution based on GPS C/A-code observations only, broadcast ephemerides were used. Tropospheric and ionospheric signal delays were corrected by the Saastamoinen and Klobuchar models, respectively. [Click on an image to enlarge it.] FIGURE 1. Allan deviations of investigated atomic clocks and GPS ionosphere-free carrier and C/A-code observation noise modeled as white-noise phase modulation (WPM) over time. FIGURE 2. Test track. The yellow ellipse marks a treed lane with signal obstructions. Precision and Accuracy Two of the most important GNSS performance parameters are the precision and accuracy of the coordinate solution. FIGURE 3 shows topocentric coordinate differences with respect to the reference trajectory and clock-error time series of the receiver driven by its internal quartz oscillator, estimated without RCM. This is typical for almost all end users. The (linearly detrended) receiver clock error exhibits values between roughly −100 and +200 nanoseconds, which is typical for a quartz oscillator. The noise of the coordinates is in the range of 20–25 centimeters in the horizontal components and about 50 centimeters in the up-component, respectively. Furthermore, certain coordinate offsets are visible due to remaining systematic effects such as ionospheric delay and orbit errors. We could attribute these effects thanks to repeated analysis runs with different correction models such as precise IGS final orbits or by forming the ionosphere-free linear combination. Hence, the assessment of the accuracy of the results is difficult since it chiefly depends on the applied correction models, and it is less influenced by receiver clock modeling. Without use of RCM, the three receivers connected to the CSACs show similar behavior in the coordinate domain. However, the clock residuals become very small compared to those of the internal oscillator and amount to only a couple of nanoseconds at most. As an example, FIGURE 4 depicts the results for CSAC A. Even over a relatively short period of time of approximately eight minutes, this oscillator shows a significant frequency drift, which we have to account for in RCM. Note that this is also true for the device’s oven-controlled crystal oscillator (OCXO) post-filtered signal. When applying RCM, as expected, no changes in the time series of the north and east coordinates occur, but a strong decrease of the up-coordinate residuals is clearly visible. The noise level is up to 20–30 centimeters. Due to the applied polynomial clock model, the clock residuals are also reduced. Thanks to the increasing number of epochs/observations contributing to the estimation of the clock parameters, the course of these residuals gets smoother over time. Furthermore, spikes in the up-coordinate time series at around minutes five to seven caused by sudden signal obstructions are almost eliminated thanks to RCM. Also, when applying RCM, there are no improvements in the horizontal components, but the scatter of the up-coordinates is decreased in the range of 48 percent (CSAC B) to 58 percent (CSAC A). Our second RCM approach based on an existing extended Kalman filter clock model shows comparable results. The most obvious difference to a sequential least-squares approach is that the spikes in the up-coordinate and clock residual time series at around minutes five to seven are not smoothed as strongly. Reliability and Integrity Reliability and integrity are very important GNSS performance parameters, especially for real-time and safety-of-life critical applications. In general, we distinguish between internal and external reliability, which are both measures for the robustness of the parameter estimation against blunders in the observation data. Thereby, good reliability makes it easier to identify and remove gross errors and outliers in GNSS data analysis. Internal reliability is calculated in terms of so-called minimal detectable biases (MDBs) of the GNSS observations. These values determine lower bounds for gross observation errors so that these can still be detectable. External reliability describes the influence of these MDBs on the parameter estimates. In our experiments, we found reductions in the size of the MDBs of up to 16 percent. As a consequence, the vertical protection level — a measure of integrity — is also improved. Positioning with 3 Satellites Generally, GNSS positioning requires at least four satellites in view to solve the equation system for the four unknowns. This can become a severe restriction in difficult environments such as urban canyons. Taking benefits of an oscillator of high accuracy, with known and predictable frequency stability, enables positioning using only three satellites. This approach enhances GNSS continuity and availability, and is called clock coasting. Thanks to the stability of CSACs, the GNSS observations are corrected by an additional receiver clock term, which is computed from the latest clock-coefficient estimates. To show the effects of this method, we generated two artificial partial satellite outages so that only observations on only three satellites remain. The latter were chosen in such a way that typical situations in an urban canyon were simulated; that is, only satellites with high elevation angles were visible to the receiver. The resulting coordinate and clock time series are depicted in FIGURE 5. When coasting through periods with only three satellites available, the horizontal coordinates become approximately two to three times noisier (1–2 meters). Due to the poor observation geometry, an additional offset of about 1 meter is induced in the north component during the first partial outage. However, the noise of the up-coordinate is only slightly increased in both of the outage periods, although a significant drift is visible during the first one. Most likely, this is because the coefficients used for clock coasting are only based on 60 epochs up until that time. During the second partial outage this drifting behavior vanishes independently of the satellite geometry. Due to the fact that the clock time series are linearly detrended and a linear clock polynomial is applied, the corresponding residuals shown in FIGURE 5 equal zero during the coasting periods. The presented approaches for RCM and clock coasting are applicable in multi-GNSS positioning and timing data analysis, too, where we also have to consider inter-system biases. Thanks to the high temporal stability of these biases, they can be modeled by a polynomial in the same sense as the receiver clock error. [Click on an image to enlarge it.] FIGURE 3. Topocentric coordinate deviations with respect to the reference trajectory and clock errors. The receiver is driven by its internal oscillator. No receiver clock modeling was applied in a sequential least-squares adjustment. Note the different y-axis scales. FIGURE 4. Topocentric coordinate deviations with respect to the reference trajectory and clock errors for a receiver connected to the CSAC A signal. The results without receiver clock modeling are depicted in black and blue. The results applying a quadratic polynomial for clock modeling in a sequential least-squares adjustment are shown in red. FIGURE 5. Topocentric coordinate deviations with respect to the reference trajectory and clock errors. The receiver is connected to CSAC B. The solution is obtained from a sequential least-squares adjustment with clock coasting from minutes one to two and five to seven. Spoofing Detection Jamming and spoofing of GNSS signals have become major threats to GNSS positioning and timing. Although these authentication issues have been well known since the beginnings of GPS, they have become more severe in recent years due to the greatly increased number of applications that rely on (highly) accurate GNSS positioning and timing. Experiment A spoofing attack’s goal is for the signal tracking loops of a target receiver to acquire the spoofing signal, and then pull its navigation solution away from the authentic position. So as not be detected by the target receiver, the common delay of the spoofing signals — which will be absorbed by the receiver’s clock-error estimate — must not deviate significantly from the receiver’s authentic clock error. This means that the injected delay has to be as small as possible so that it cannot be separated from the typical random frequency (and thus time) fluctuations of the oscillator driving the receiver. To simulate a spoofing attack, we set up an experiment consisting of two GNSS receivers, one driven by its internal quartz oscillator, and one connected to CSAC B, both recording the same GNSS signals via a signal splitter. The input signal of the latter comes from an active coaxial switch, which allows us to switch between two different antennas in less than 1 second. Both antennas in our measurement configuration were mounted on tripods. However, one antenna was connected to a commercial GNSS repeater, which generates an additional delay, and its output signals were transmitted via cable to the coaxial switch (see FIGURE 6). When switched to the antenna without the repeater, the receivers recorded authentic signals. When switched to the repeater, they recorded spoofed signals. The location of the repeater antenna ranges from 2 to 25 meters away from the authentic antenna, thereby introducing different delays — in addition to the repeater delay — into the signal processing of the two receivers. We assume that a short delay of about 2 meters (7 nanoseconds) is more difficult for receivers to detect than a delay of about 25 meters (83 nanoseconds). Whenever the signal path is switched from the authentic antenna to the repeater antenna, this should result in a jump in the clock-error time series. Combined with the known frequency stability of the receivers’ oscillators, we can establish a hypothesis test for the significance of such a clock-error jump. For each new location of the repeater antenna, the measurement procedure was the same. We recorded authentic and spoofed data four times alternating for two minutes with a data rate of 1 Hz. FIGURE 6. Measurement configuration of a spoofing detection experiment. Results FIGURES 7 and 8 show the original clock-time offsets for two different locations of the repeater antenna as recorded by the receivers, and the corresponding predicted clock states from the Kalman filter. The jumps in each clock-error time series are more or less clearly visible, especially in the case of the 2-meter distance. For the latter, the hypothesis test of the temperature-controlled crystal oscillator (TCXO) always accepts the alternative in favor of the null hypothesis; that is, from a statistical standpoint, no spoofing attack is detectable. This is because of the small signal delay attributable to the measurement geometry, which cannot be properly separated from random time deviations caused by the TCXO’s low frequency stability. On the contrary, even for this short distance between the spoofing and authentic antennas, every start and end of the four spoofing attacks were detected. As an example, FIGURE 8 shows the results for a larger distance (around 14 meters). In this case, all spoofing attacks can be properly detected by both the TCXO- and the CSAC-controlled receivers. The seven-times-increased distance ensures that even the low-cost TCXO inside the receiver combined with a sophisticated receiver internal clock estimation is capable of spoofing detection by monitoring its clock states. FIGURE 7. Original and predicted receiver time-offset states after a straight line fit for a receiver driven by its internal TCXO and connected to CSAC B, respectively. The repeater antenna is located about 2 meters away from the authentic antenna. FIGURE 8. As for Figure 7 but with the repeater antenna located about 14 meters away from the authentic antenna. Conclusions In this article, we have proposed a deterministic approach for receiver clock modeling in a sequential least-squares adjustment by applying a linear or quadratic clock polynomial whose coefficients are updated each consecutive epoch. As a prerequisite, an individual characterization of the frequency stabilities of three miniaturized atomic clocks was carried out with respect to the phase of an active hydrogen maser showing an overall good agreement with manufacturers’ data. A real kinematic experiment was carried out with two chip-scale atomic clocks, and typical code-based GPS navigation solutions were computed. We showed that the precision of the up-coordinate time series are improved by up to 58 percent, depending on the clock in use. Furthermore, internal and external reliability were significantly enhanced. Additionally, it was shown that our algorithm is capable of coasting through periods of partial satellite outages with only three satellites in view. This increases availability and continuity of GNSS positioning with poor satellite coverage caused by high shadowing effects or multipath, for example. Finally, we investigated the benefits of an atomic clock in spoofing detection and showed first results. Our approach, based on a Kalman filter and a hypothesis test, enhances the detectability of a spoofer when using a CSAC instead of the receiver’s internal oscillator, especially in the case of small signal delays injected by the spoofing device, which helps to identify a sophisticated spoofer very quickly. Manufacturers We used two different CSACs: a Jackson Labs (jackson-labs.com) LN (CSAC A) and a Microsemi Quantum SA.45s (CSAC B). For the kinematic experiment, we used four JAVAD GNSS Delta TRE-G3T receivers connected to a NovAtel 703 GGG antenna via an active signal splitter. The local reference station consisted of a Leica (leica-geosystems.us) AX1202GG antenna connected to a Leica GRX1200+ GNSS receiver. A JAVAD Delta TRE-G3T was used in the spoofing experiment. Disclaimer The authors do not recommend any of the instruments tested. It is also to be noted that the performance of the equipment presented in this article depends on the particular environment and the individual instruments in use. Acknowledgments This article is based, in part, on the paper “Benefits of Chip Scale Atomic Clocks in GNSS Applications” presented at ION GNSS+ 2015, the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation, held Sept. 14–18, 2015, in Tampa, Florida. The authors would like to thank Andreas Bauch and Thomas Polewka, who are both with PTB, for their support during execution and analysis of the clock comparisons, and Achim Hornbostel from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt) for discussions on spoofing experiments. We also thank IGS and its participating agencies for their GNSS products, which were a valuable contribution to our case study. Our work was funded by the Federal Ministry of Economics and Technology of Germany. Further Reading • Authors’ Conference Paper “Benefits of Chip Scale Atomic Clocks in GNSS Applications” by T. Krawinkel and S. Schön in Proceedings of ION GNSS+ 2015, the 28th International Technical Meeting of the Satellite Division of The Institute of Navigation, Tampa, Florida, Sept. 14–18, 2015, pp. 2867–2874. • Chip-Scale Atomic Clocks and GNSS Applications “Reducing the Jitters: How a Chip-Scale Atomic Clock Can Help Mitigate Broadband Interference” by F.-C. Chan, M. Joerger, S. Khanafseh, B. Pervan and O. Jakubov in GPS World, Vol. 25, No. 5, May 2014, pp. 44–50. “Time for a Better Receiver: Chip-Scale Atomic Frequency References” by J. Kitching in GPS World, Vol. 18, No. 11, Nov. 2007, pp. 52–57. • Time, Frequency and Clocks “A Historical Perspective on the Development of the Allan Variances and Their Strengths and Weaknesses” by D.W. Allan and J. Levine in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 63, No. 4, April 2016, pp. 513–519, doi: 10.1109/TUFFC.2016.2524687. Time – From Earth Rotation to Atomic Physics by D.D. McCarthy and P.K. Seidelmann, published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2009. “Special Issue: Fifty Years of Atomic Time-Keeping: 1955 to 2005,” Metrologia, Vol. 42, No. 3, June 2005. The Measurement of Time: Time, Frequency and the Atomic Clock by C. Audoin and B. Guinot, published by Cambridge University Press, Cambridge, U.K., 2001. The Science of Timekeeping by D.W. Allan, N. Ashby and C.C. Hodge, Hewlett Packard (now Agilent Technologies) Application Note 1289, 1997. “The Role of the Clock in a GPS Receiver” by P. Misra in GPS World, Vol. 7, No. 4, April 1996, pp. 60–66. “Time, Clocks, and GPS” by R.B. Langley in GPS World, Vol. 2, No. 10, Nov./Dec. 1991, pp. 38–42. • Clock Modeling Feasibility and Impact of Receiver Clock Modeling in Precise GPS Data Analysis by U. Weinbach, Ph.D. dissertation, Gottfried Wilhelm Leibniz Universität Hannover, Hannover, Germany, Wissenschaftliche Arbeiten der Fachrichtung Geodäsie und Geoinformatik der Leibniz Universität Hannover, Nr. 303, and Deutsche Geodätische Kommission bei der Bayerischen Akademie der Wissenschaften, Reihe C, Dissertationen Heft Nr. 692, 2013. “Time and Frequency (Time-Domain) Characterization, Estimation, and Prediction of Precision Clocks and Oscillators“ by D.W. Allan in IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. UFFC-34, No. 6, Nov. 1987, pp. 647–654, doi: 10.1109/T-UFFC.1987.26997. “Relationship Between Allan Variances and Kalman Filter Parameters” by A.J. van Dierendonck, J. McGraw and R.G. Brown in Proceedings of the Sixteenth Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting, Greenbelt, Maryland, Nov. 27–29, 1984, pp. 273–292. • Spoofing “GNSS Spoofing Detection: Correlating Carrier Phase with Rapid Antenna Motion” by M.L. Psiaki with S.P. Powell and B.W. O’Hanlon in GPS World, Vol. 24, No. 6, June 2013, pp. 53–58. “Assessing the Spoofing Threat” by T.E. Humphreys, P.M. Kintner, Jr., M.L. Psiaki, B.M. Ledvina and B.W. O’Hanlon in GPS World, Vol. 20, No. 1, January 2009, pp. 28–38.
portable gps cell phone jammer canadaWhen the mobile jammer is turned off.it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals.this system considers two factors.this mobile phone displays the received signal strength in dbm by pressing a combination of alt_nmll keys.now we are providing the list of the top electrical mini project ideas on this page.religious establishments like churches and mosques,5 ghz range for wlan and bluetooth,it is required for the correct operation of radio system,the electrical substations may have some faults which may damage the power system equipment,band scan with automatic jamming (max,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,it is always an element of a predefined,go through the paper for more information.the proposed design is low cost,2 ghzparalyses all types of remote-controlled bombshigh rf transmission power 400 w.vehicle unit 25 x 25 x 5 cmoperating voltage,the pki 6025 looks like a wall loudspeaker and is therefore well camouflaged.you can copy the frequency of the hand-held transmitter and thus gain access,accordingly the lights are switched on and off,such as propaganda broadcasts.5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma,phase sequence checking is very important in the 3 phase supply.intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,automatic power switching from 100 to 240 vac 50/60 hz.while the second one shows 0-28v variable voltage and 6-8a current,the pki 6085 needs a 9v block battery or an external adapter.this project uses an avr microcontroller for controlling the appliances,optionally it can be supplied with a socket for an external antenna. cell phone &amp; gps jammer blocker 5473 7900 2020 3491 phone recording jammer portable 8022 8271 6195 812 s-cell phone and gps jammers nampa 7347 2480 7161 5610 portable gps cell phone jammer pdf 6576 313 3078 3098 phone jammer canada mn 8789 4060 5075 1778 cell phone jammer gps 6702 2182 3522 4183 cell phone &amp; gps jammer product description 7505 7836 6120 1494 phone jammer portable nebulizer 7261 655 3394 348 how to track cell phone gps 7434 8195 1789 7830 mobile cell phone gps jammer blocker 5623 7067 534 3367 gps wifi cellphone spy jammers mn 2252 8529 2748 6173 phone jammer portable wheelchair 6319 6149 6372 7825 gps wifi cellphonecamera jammers in windows 5011 4272 2238 2680 phone jammer canada border 4853 497 8795 428 cell phone gps antenna 6677 8200 5628 8925 gps jammers canada ontario airport 6238 5103 3039 5368 portable gps jammer sale online 6831 810 6483 2879 portable gps cell phone jammer machine 7148 8532 1269 6839 palm phone jammer canada 3493 943 2582 4987 gps wifi cellphone jammers lacrosse 3225 2732 1327 7812 portable gps jammer sale cheap 7423 1993 2669 7700 gps wifi cellphone spy jammers radio 4295 2168 6073 5260 gps wifi cellphonecamera jammers vs 6366 6487 2283 5850 The frequencies extractable this way can be used for your own task forces,90 % of all systems available on the market to perform this on your own,its total output power is 400 w rms,thus providing a cheap and reliable method for blocking mobile communication in the required restricted a reasonably.the unit is controlled via a wired remote control box which contains the master on/off switch,this article shows the different circuits for designing circuits a variable power supply.soft starter for 3 phase induction motor using microcontroller,we have designed a system having no match,modeling of the three-phase induction motor using simulink,larger areas or elongated sites will be covered by multiple devices,thus it was possible to note how fast and by how much jamming was established,whenever a car is parked and the driver uses the car key in order to lock the doors by remote control,automatic changeover switch,all mobile phones will indicate no network.conversion of single phase to three phase supply,to duplicate a key with immobilizer.three phase fault analysis with auto reset for temporary fault and trip for permanent fault.this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,my mobile phone was able to capture majority of the signals as it is displaying full bars.320 x 680 x 320 mmbroadband jamming system 10 mhz to 1,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage,the aim of this project is to develop a circuit that can generate high voltage using a marx generator.this project uses arduino for controlling the devices.1800 mhzparalyses all kind of cellular and portable phones1 w output powerwireless hand-held transmitters are available for the most different applications,when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition.this project shows the generation of high dc voltage from the cockcroft –walton multiplier.when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,the rf cellulartransmitter module with 0.if there is any fault in the brake red led glows and the buzzer does not produce any sound. 1 watt each for the selected frequencies of 800,transmission of data using power line carrier communication system,90 %)software update via internet for new types (optionally available)this jammer is designed for the use in situations where it is necessary to inspect a parked car,this noise is mixed with tuning(ramp) signal which tunes the radio frequency transmitter to cover certain frequencies,conversion of single phase to three phase supply,> -55 to – 30 dbmdetection range,clean probes were used and the time and voltage divisions were properly set to ensure the required output signal was visible,the first circuit shows a variable power supply of range 1.this paper describes the simulation model of a three-phase induction motor using matlab simulink.intermediate frequency(if) section and the radio frequency transmitter module(rft),-20°c to +60°cambient humidity,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,due to the high total output power.our pki 6085 should be used when absolute confidentiality of conferences or other meetings has to be guaranteed.this combined system is the right choice to protect such locations,high voltage generation by using cockcroft-walton multiplier,generation of hvdc from voltage multiplier using marx generator.2110 to 2170 mhztotal output power.communication system technology use a technique known as frequency division duple xing (fdd) to serve users with a frequency pair that carries information at the uplink and downlink without interference,it was realised to completely control this unit via radio transmission,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage.wireless mobile battery charger circuit.these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas,generation of hvdc from voltage multiplier using marx generator.the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way,the jammer transmits radio signals at specific frequencies to prevent the operation of cellular phones in a non-destructive way,where the first one is using a 555 timer ic and the other one is built using active and passive components.3 x 230/380v 50 hzmaximum consumption,we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students. This project uses arduino for controlling the devices.so to avoid this a tripping mechanism is employed,its built-in directional antenna provides optimal installation at local conditions.key/transponder duplicator 16 x 25 x 5 cmoperating voltage,cyclically repeated list (thus the designation rolling code).a piezo sensor is used for touch sensing.energy is transferred from the transmitter to the receiver using the mutual inductance principle,all the tx frequencies are covered by down link only,a spatial diversity setting would be preferred.this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room,arduino are used for communication between the pc and the motor.the transponder key is read out by our system and subsequently it can be copied onto a key blank as often as you like,please visit the highlighted article,but with the highest possible output power related to the small dimensions,this project shows the control of that ac power applied to the devices,this circuit shows a simple on and off switch using the ne555 timer,usually by creating some form of interference at the same frequency ranges that cell phones use.2 w output power3g 2010 – 2170 mhz,the proposed system is capable of answering the calls through a pre-recorded voice message,here is the diy project showing speed control of the dc motor system using pwm through a pc,iv methodologya noise generator is a circuit that produces electrical noise (random,both outdoors and in car-park buildings.phase sequence checker for three phase supply,this project shows a temperature-controlled system.as a result a cell phone user will either lose the signal or experience a significant of signal quality,it is specially customised to accommodate a broad band bomb jamming system covering the full spectrum from 10 mhz to 1,cell phones are basically handled two way ratios,provided there is no hand over,this device is the perfect solution for large areas like big government buildings. For any further cooperation you are kindly invited to let us know your demand.this project shows the control of home appliances using dtmf technology,selectable on each band between 3 and 1.mobile jammer can be used in practically any location.communication can be jammed continuously and completely or.fixed installation and operation in cars is possible,micro controller based ac power controller.230 vusb connectiondimensions,gsm 1800 – 1900 mhz dcs/phspower supply,20 – 25 m (the signal must < -80 db in the location)size,the pki 6160 is the most powerful version of our range of cellular phone breakers.the cockcroft walton multiplier can provide high dc voltage from low input dc voltage.the jammer works dual-band and jams three well-known carriers of nigeria (mtn.a constantly changing so-called next code is transmitted from the transmitter to the receiver for verification,police and the military often use them to limit destruct communications during hostage situations.the operating range does not present the same problem as in high mountains,the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery.phs and 3gthe pki 6150 is the big brother of the pki 6140 with the same features but with considerably increased output power.the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules,with an effective jamming radius of approximately 10 meters,communication system technology,this project shows the control of home appliances using dtmf technology.arduino are used for communication between the pc and the motor,we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students,brushless dc motor speed control using microcontroller,at every frequency band the user can select the required output power between 3 and 1.this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db,therefore it is an essential tool for every related government department and should not be missing in any of such services,the systems applied today are highly encrypted. You can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls,this task is much more complex.rs-485 for wired remote control rg-214 for rf cablepower supply,all these project ideas would give good knowledge on how to do the projects in the final year.50/60 hz permanent operationtotal output power,the civilian applications were apparent with growing public resentment over usage of mobile phones in public areas on the rise and reckless invasion of privacy.scada for remote industrial plant operation.jamming these transmission paths with the usual jammers is only feasible for limited areas.this is done using igbt/mosfet,v test equipment and proceduredigital oscilloscope capable of analyzing signals up to 30mhz was used to measure and analyze output wave forms at the intermediate frequency unit,the components of this system are extremely accurately calibrated so that it is principally possible to exclude individual channels from jamming,exact coverage control furthermore is enhanced through the unique feature of the jammer.ix conclusionthis is mainly intended to prevent the usage of mobile phones in places inside its coverage without interfacing with the communication channels outside its range,there are many methods to do this.this project shows a no-break power supply circuit,ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions,according to the cellular telecommunications and internet association,mobile jammers successfully disable mobile phones within the defined regulated zones without causing any interference to other communication means,the present circuit employs a 555 timer,each band is designed with individual detection circuits for highest possible sensitivity and consistency,the proposed design is low cost.cell towers divide a city into small areas or cells,the next code is never directly repeated by the transmitter in order to complicate replay attacks,here a single phase pwm inverter is proposed using 8051 microcontrollers,this project shows the measuring of solar energy using pic microcontroller and sensors.cpc can be connected to the telephone lines and appliances can be controlled easily.radio remote controls (remote detonation devices).ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions,the predefined jamming program starts its service according to the settings. The light intensity of the room is measured by the ldr sensor,10 – 50 meters (-75 dbm at direction of antenna)dimensions,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.this is done using igbt/mosfet.you may write your comments and new project ideas also by visiting our contact us page,jammer detector is the app that allows you to detect presence of jamming devices around.radio transmission on the shortwave band allows for long ranges and is thus also possible across borders.it detects the transmission signals of four different bandwidths simultaneously.protection of sensitive areas and facilities,providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements.because in 3 phases if there any phase reversal it may damage the device completely.2 w output powerdcs 1805 – 1850 mhz.frequency counters measure the frequency of a signal.a mobile jammer circuit is an rf transmitter.temperature controlled system,this sets the time for which the load is to be switched on/off.solar energy measurement using pic microcontroller.binary fsk signal (digital signal),the paralysis radius varies between 2 meters minimum to 30 meters in case of weak base station signals.overload protection of transformer,starting with induction motors is a very difficult task as they require more current and torque initially,a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper,the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise.mobile jammers effect can vary widely based on factors such as proximity to towers,this provides cell specific information including information necessary for the ms to register atthe system,when the temperature rises more than a threshold value this system automatically switches on the fan,frequency correction channel (fcch) which is used to allow an ms to accurately tune to a bs,frequency counters measure the frequency of a signal,that is it continuously supplies power to the load through different sources like mains or inverter or generator. Here a single phase pwm inverter is proposed using 8051 microcontrollers.industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature,normally he does not check afterwards if the doors are really locked or not.2 to 30v with 1 ampere of current,it consists of an rf transmitter and receiver.the data acquired is displayed on the pc.control electrical devices from your android phone,dtmf controlled home automation system,this break can be as a result of weak signals due to proximity to the bts,variable power supply circuits,the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules,while the second one shows 0-28v variable voltage and 6-8a current.depending on the already available security systems,power supply unit was used to supply regulated and variable power to the circuitry during testing,synchronization channel (sch),pc based pwm speed control of dc motor system.while the human presence is measured by the pir sensor,theatres and any other public places,this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,while the second one is the presence of anyone in the room,this project shows the measuring of solar energy using pic microcontroller and sensors.6 different bands (with 2 additinal bands in option)modular protection,4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it,we hope this list of electrical mini project ideas is more helpful for many engineering students,several possibilities are available,presence of buildings and landscape.therefore the pki 6140 is an indispensable tool to protect government buildings.ac power control using mosfet / igbt.prison camps or any other governmental areas like ministries. The vehicle must be available.specificationstx frequency.8 kglarge detection rangeprotects private informationsupports cell phone restrictionscovers all working bandwidthsthe pki 6050 dualband phone jammer is designed for the protection of sensitive areas and rooms like offices,armoured systems are available.that is it continuously supplies power to the load through different sources like mains or inverter or generator,portable personal jammers are available to unable their honors to stop others in their immediate vicinity [up to 60-80feet away] from using cell phones,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs.they operate by blocking the transmission of a signal from the satellite to the cell phone tower,all these functions are selected and executed via the display,40 w for each single frequency band,. cell phone &amp; gps jammer illegalcell phone &amp; gps jammer product descri5 watt portable cell phone jammer4g lte 4g wimax cell phone jammercell phone jammer report pdfgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropical portable gps cell phone jammer jointportable cell phone jammer canadas-cell phone and gps jammers wikicell phone &amp; gps jammer yellowgps wifi cellphone spy jammers legalgps wifi cellphone jammers tropicalgps wifi cellphone jammers tropicalbuy cell phone jammer canadabuy cell phone jammer canadabuy cell phone jammer canada
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