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Looking Closely at Received GPS Carrier Phase By Johnathan York, Jon Little, and David Munton The stability of a received GPS signal determines how well the receiver can track the signal and the accuracy of the positioning results it provides. While the satellites use a very stable oscillator and modulation system to generate their signals, just how stable are the resulting phase-modulated carriers? In particular, do received signals always conform to the published system specifications? In this month’s column we take a look at a specially designed receiver for analyzing GPS carrier phase and some of the interesting results that have been obtained. INNOVATION INSIGHTS by Richard Langley A RADIO WAVE, OR ANY ELECTROMAGNETIC WAVE FOR THAT MATTER, may be generally characterized by four parameters: amplitude, frequency, phase, and polarization. If the values of amplitude, frequency, and polarization remain constant, then the wave is a pure oscillation or “tone” and can be represented as a sine wave. An unvarying tone doesn’t convey any information. However, the wave can be modulated by varying one or more of its characteristic parameters in a controlled fashion. In this way information, whether it be audio, images, or data, can be transmitted from one place to another. The sine wave is therefore referred to as a “carrier” (of the modulation). A continuous wave is a wave that is not interrupted. Of course, radio waves are not only used for communicating. They’re also used for navigation, radar, and many other purposes including the jamming of other radio signals. The modulating signal may either be continuously varying (analog) or have a fixed number of values of one or more of the parameters (digital) — two values in the case of binary modulation. Amplitude modulation is commonly used for broadcasting and communications. If a continuous wave is interrupted by keying the transmitter on and off using a code of some kind, such as Morse code, information can be sent. For speech and music transmission, an audio waveform is modulated onto the carrier. Frequency modulation is used for very high frequency (VHF) high-fidelity broadcasts and for communications in the VHF and ultra-high-frequency ranges of the radio spectrum. The instantaneous carrier frequency changes with the frequency and amplitude of the modulating waveform. Phase modulation is typically used for data transmissions and, as we know, this is how the pseudorandom noise codes and the navigation message modulate the signal carriers of GPS and other global navigation satellite systems. (While the polarization of a wave can be modulated to transmit information, this is not very common.) The stability of a received GPS signal — both the carrier and its modulations — determines, in part, how well the receiver can track the signal and the accuracy of the positioning results it provides. While the satellites use a very stable oscillator and modulation system to generate their signals, just how stable are the resulting phase-modulated carriers? In particular, do received signals always conform to the published system specifications? In this month’s column we take a look at a specially designed receiver for analyzing GPS carrier phase and some of the interesting results that have been obtained. “Innovation” features discussions about advances in GPS technology, its applications, and the fundamentals of GPS positioning. The column is coordinated by Richard Langley, Department of Geodesy and Geomatics Engineering, University of New Brunswick. By Johnathan York, Jon Little, and David Munton All global navigation satellite systems (GNSS) rely on well-defined data messages modulated onto stable carrier signals. The transmission of signals that adhere to published interface specifications (ISs) is what permits a GPS or GLONASS signal to be transmitted from a satellite and to be decoded at our receiver. This process is one that most of us never need to consider, and is part of the background magic that make GNSS so powerful. Still, signals are generated and received by real hardware — hardware that can be subject to the harsh space environment or a challenging ground environment. And once these signals are generated, they propagate to the user along a path through a dynamic medium that includes the ionosphere — a dilute plasma that introduces a well-known time-delay and phase change into the signal. The net result is is an effect on the signal that depends on both time and space. An interesting question is the following: How do we know that the signal we plan to send (as documented in an IS) is actually the signal that we receive? A pragmatic answer is that GNSS positioning works. If there is a difference between the IS-defined signal and the received signal, the impact is not seen by most users. Another answer is that satellite vendors test (and then test again) their equipment prior to launch, providing a high level of certainty that the ISs are being adhered too. In this article, we will describe our work in providing a third way of answering the question — by monitoring signals — motivated by our desire to see “all the bits, all the time.” We have seen some interesting effects in our observations, and we will discuss our attempts to detect and characterize these effects. Background For our purposes, we will be looking strictly at the L1 C/A-code signal. The reasons for this will become clear shortly. The standard textbook form of the noiseless signal is   (1) where P is the signal power, cCA(t) is the C/A-code modulation stream of plus and minus ones, nNav(t) is the navigation bitstream that is modulated onto the signal, and the cos(ωt) factor represents the fundamental carrier frequency, with ω being the angular frequency (ω=2πf). For the GPS L1 signal, f = 1575.42 MHz. The GPS receiver processes this signal (in the presence of noise) into the observables (such as range, phase, or Doppler frequency shift), or the positions and velocities that we need. One of the research problems that we find interesting is determining how to monitor the details of the signal in Equation (1) or of any other GNSS signal. Why would this be of interest? To us this is interesting because we have seen events where the signal does not behave as expected. In fact, these events were first noted by the Federal Aviation Administration’s (FAA’s) Wide Area Augmentation System (WAAS) receivers, and were later noted again in ionospheric observations. By being able to monitor the signal at a very detailed level, we can hope to gain insight into the origins of these events. We are not alone in wanting to validate that the signal and data being produced by a GNSS receiver is valid. A standard approach to monitoring the GNSS signal would be to use an autonomous receiver method, known as receiver autonomous integrity monitoring or RAIM. However, in this approach, the integrity of the navigation solution is evaluated based on the range and phase observables produced by the receiver, and we obtain no insight into the behavior of the actual signal — only the receiver’s behavior in processing the received signals. Another option is to directly observe each satellite’s signal using a high-gain antenna. This approach provides significant insight into the behavior of the signal but is expensive and is really only effective on one satellite at a time. A system, which is close in spirit to our approach, is the Ohio University GPS Anomalous Event Monitor (GAEM). GAEM consists of two high-quality commercial receivers, which serve as independent triggers for an RF capture system. When the receivers detect an anomaly, the RF capture system is able to provide 20 seconds of raw RF data for study. Using an Inexpensive Software Receiver The observations we will discuss in the rest of this paper were made using what we term the Global Navigation Satellite System Complex Ambiguity Function receiver, or GCAF. The GCAF is a prototype receiver, and is well suited to some of the detailed analysis we have described. Briefly, the GCAF receiver is a single-channel, single-frequency (L1) GPS receiver, which uses firmware installed on a field programmable gate array (FPGA) to process the incoming GPS signal. FIGURE 1 is a labeled photograph of the GCAF. RF down-conversion occurs in the module at lower left. The down-converted signal is passed to an FPGA-based software receiver, shown at lower right. All of the processing to produce the complex correlation curves is done in the software receiver. The aggregator, shown at upper right, simply provides an Ethernet interface to the outside. FIGURE 1. The GCAF receiver. The incoming signal is correlated against a replica of the expected L1 C/A-code signal, generating samples of the correlation curve. The difference between the GCAF and many standard commercial GPS receivers is that the GCAF samples the C/A-code correlation curve at 512 points (lags) at a 1-kHz rate. Each correlation sample is complex, consisting of in-phase (I) and quadrature (Q) components, with the software that processes the receiver raw data designed to maintain the signal in the I-component, and noise in the Q-component. As a result, the GCAF engine not only tracks the signal where it is expected to appear, but also at nearby offset phases and Doppler shifts simultaneously, and this ability substantially eliminates dependence on the tracking loop behavior and allows the observation of the characteristics of the received signal, rather than inferring them from observations of tracking loop behavior. See the sidebar, for more details on the receiver’s operation. Since the GCAF provides access to the high-rate complex correlation values, we can “decode” the navigation modulation sequence, nNav(t), from the incident signal by tracking the correlation peak phase and watching for phase changes. These phase changes correspond to distinct changes in the carrier phase. FIGURE 2 shows results from measurements collected with the GCAF while observing space vehicle number (SVN) 26 / pseudorandom noise code number (PRN) 26 on August 22, 2009. The top plot shows the amplitude of the in-phase component of the incident signal in blue, and that of the quadrature component in red. The amplitude is in arbitrary units, while the time along the bottom is in milliseconds–so the entire snapshot is only 0.6 seconds long. FIGURE 2. Amplitude and phase of the detrended L1 C/A-code carrier of SVN26 (PRN26) recorded on August 22, 2009, at 10:16:30 GPS Time. These results in Figure 2 are as we expect, with the dominant energy appearing in the I-component. Clearly visible in the I-component is the navigation bitstream, which appears as a series of 180° phase changes in the carrier signal (hence changing the sign of the amplitude). The lower plot in Figure 2 shows the results of a “squaring” detector applied to the complex signal. Effectively this doubles any phase changes, since (ejφ)2 = ej(2φ). This nicely converts the navigation bitstream transitions to 2 × 180°, or 360°, which removes them from the signal. (This is the approach pioneered by one of the first commercial GPS receivers, the Macrometer, for providing correlation-free L1 phase observations by removing both the code and navigation message phase transitions.) What the lower plot in Figure 2 conveys is the absence of any transitions other than the expected ones of 180°. However, not all of our measurements are quite this typical. In some cases we observe what we term “carrier-phase signal events” (CPSEs). FIGURE 3 shows a typical example of such a CPSE taken on SVN48 (PRN21) on March 13, 2010. In the upper plot, note the sudden change in amplitude in the quadrature component near -100 milliseconds. In the lower plot, note the sudden changes in the carrier phase that occur at the same times as the amplitude changes. In this case, the squaring detector shows clear evidence of a transition that was not anticipated, and appears to be of approximately 90° and persist for approximately 175 milliseconds. FIGURE 3. Decoded navigation bitstream on SVN45 (PRN21) taken on March 13, 2010, at 20:28:54 GPS Time. Of course, the single-channel nature of the GCAF does not permit an unambiguous identification of where in the signal chain a CPSE is introduced. The introduction of events might occur within the satellite transmission chain, or be produced within the propagation environment, or possibly be a quirk of the receiver itself. However, the types of events we observe seem a very unlikely failure mode for the GCAF. In the case of the example shown in Figure 2, the only place in the system where a signal at the exact Doppler-shifted frequency of the SV is in the numerically controlled oscillator (NCO) of the carrier-tracking loop. The GCAF tracking loop is updated at a rate slower than many of these events and manual examination of telemetry from the tracking loops in specific instances indicates no anomalous or discontinuous tracking behavior during the events examined. If events are generated by the local receiver environment, one possible mechanism would be a small multipath source at a position so as to induce a phase shift at a greater magnitude than the direct signal. This appears unlikely as events occur at many times of day (and therefore multipath geometries), and have onsets and durations that are difficult to explain with a reasonable multipath reflector. As a prototype instrument, the GCAF does have practical limitations. One of these limitations is that observations are divided into 5-minute intervals, at which point the signal is reacquired and data collected for another 5-minute interval. This is an operational limitation, which serves to improve robustness and bound individual output file sizes to 1 gigabyte each, and as a result, limits the durations of the CPSE that we can observe. Event Detection The simple squaring detector discussed above is not sufficient to provide a robust detection mechanism for the type of CPSEs we might see. In fact, we wanted a metric that would not rely on a pre-definition of what we might see in the signal, but which would flag changes in signal phase that might be interesting. To develop this metric, we borrowed ideas from the field of metrology, specifically work that characterizes noise types in oscillators. We ended up focusing on the modified Allan variance. While we will not detail the derivation of our metric here, we will discuss the results. The basic idea is to consider the phase, ϕ, of the GPS signal, averaged over sequential periods of duration τ. We choose τ to satisfy τ > 1 millisecond, since this is the basic chipping period of the L1 C/A-code signal. For the n-th period, τ, we denote this averaged phase by ϕn>. By considering the impact of noise, specifically receiver thermal noise and clock stability, we can formulate a probabilistic bound of the form:   (2) The interpretation of this result is that for a given averaging period τ the interval-to-interval variation in the average phase should never be too large. The right-hand side of Equation (2) provides a threshold for the phase variations over three consecutive periods, and is determined by the receiver thermal noise and clock stability. This bound, which is probabilistic in nature, applies with a false alarm rate of once in 10 years. If the metric exceeds this threshold, we declare that a phase event may have occurred within the three intervals. There is still the practical question of what averaging intervals τ need to be chosen. We have chosen to use a discrete set of τ that range from a few milliseconds to several seconds. This enables us to identify CPSEs that might occur rapidly (that is, at millisecond levels) or more slowly (at second levels). FIGURE 4 provides an example of the metric response to three consecutive CPSEs that are associated with SVN48 (PRN07). The upper plot shows the results of the squaring detector applied to the phase. Clearly evident are three rapid phase changes of about 20°. The next plot shows the result of the detection metric, which shows three double peaks in the vicinity of the phase changes. The third plot shows the I- (blue) and Q- (green) signal components. The bottom plot shows the NCO offset, which is a useful diagnostic. FIGURE 4. A CPSE observed on SVN48 (PRN07) on September 15, 2010, at 19:21:42 GPS Time. (Click to enlarge.) Observations of Signal Events The examples we have shown so far reflect what we refer to as two-sided discontinuities; that is, a sudden change in phase, followed by a return to close to the original value. FIGURE 5 shows a similar type of CPSE, in which we only see one side of the change. We have seen this type of event quite commonly on SVN62 (PRN25). If there is a return to the original phase, it may be beyond our observation period. Note that the apparent slope in Figure 5 is an artifact of a linear detrending process acting across the discontinuity. FIGURE 6 shows an example of a different type of CPSE that we occasionally see, one in which a change in the slope of the phase occurs (corresponding to a change in frequency). The figure shows a single inflection in the phase rather than a rapid change in the phase value. FIGURE 5. A CPSE observed on SVN62 (PRN25) on January 16, 2011, at 16:26:03 GPS Time with a magnitude of about 40°. (Image: Authors) FIGURE 6. A CPSE observed on SVN38 (PRN08) on September 29, 2009, at 18:26:20 GPS Time. (Click to enlarge.) Over the entire GPS constellation, we see events with rapid phase changes most frequently associated with the signals from three SVNs: 45 (an original Block IIR satellite), 48 (a Block IIR-M satellite), and 62 (a Block IIF satellite). This is most clearly shown in FIGURE 7, which contains a histogram of the number of events with rapid phase changes we have seen, broken out by SVN. For this histogram, we have chosen to count only those events that have well-defined phase discontinuities. Other SVNs, for example SVN34 (a Block IIA satellite), will show CPSEs on occasion, but the signals from this set of three SVNs are the ones that we have come to observe most closely. Until recently, SVN62 was the newest SV, and so we have been heavily weighting our observations on this SV. FIGURE 7. Histogram of event counts for SVNs 45, 48, and 62 (PRNs 21, 07, and 25) covering the periods from mid-2009 until mid-August 2011. (Data: Authors) Is There an Impact on Users? To conclude, it is worth assessing what the potential impact of signal events on user equipment might be. We first began to investigate the detailed carrier-phase structure when we learned that the FAA WAAS system found that the carrier phase from SVN45 behaved differently than the rest of the GPS constellation, and that similar effects were seen in SVN34 (PRN04) and SVN35 (PRN05). What was observed were short-duration irregularities ( But what about more standard user equipment? Given the types of events that we have observed, particularly those in which the phase changes suddenly and by a large amount, it is natural to ask how this might impact position and navigation users. A momentary 90-degree phase shift that lasts tens to hundreds of milliseconds might have varying effects on receivers depending on the duration of the event, the design of the carrier tracking loop in the receiver, and the instantaneous noise environment at each receiver. If the CPSE is shorter than the inverse of the receiver carrier tracking loop bandwidth, then the receiver might perceive the CPSE as a very brief loss of signal since the tracking loop will not be able to respond quickly enough. Observables formed from a second or more of raw values are likely to experience a small reduction in signal strength. As a result, short events are likely to go undetected by a traditional receiver that is primarily performing navigation. However, CPSEs that persist longer than the inverse of the receiver carrier-tracking-loop bandwidth could be interpreted by the receiver in a variety of ways, including a combination of cycle slip(s), navigation bit polarity inversion, or rapid carrier-phase changes. Summary We have been engaged in a detailed examination of the GPS L1 C/A-code signal for several years. In examining the signals, we have found that there are times when the signal exhibits an unexpected transition in phase. Looking across the GPS constellation, we find that these events tend to vary by satellite, both in rate and in behavior. While the impact from these events on most user equipment is small, the fact that the behavior is unique by SV is interesting. The type of detailed signal monitoring we have described is useful in two ways: it provides a means of observing effects that might otherwise pass unnoticed, and it gives us the capability to look for events in the future that might have a more obvious impact. Acknowledgment This article was stimulated by our research paper “A Non-Traditional Approach to Analysis of Signal Structure Anomalies Observed in PRN 21” presented at ION GNSS 2010, the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation in Portland, Oregon, September 21–24, 2010. Manufacturer The GCAF receiver uses a Xilinx, Inc., Spartan-3 FPGA. The Global Navigation Satellite System Complex Ambiguity Function Receiver The signal from the GCAF’s antenna passes through an amplifier stage, and then to an analog front end, where the signal is downconverted from the L1 frequency, 1575.42 MHz, directly to in-phase and quadrature IF signals. The signal is then passed to a Flexible Low-power Wideband Receiver (FLWR). The FLWR is a low-cost FPGA-based digitizing receiver designed and built by the Applied Research Laboratories at the University of Texas. Notably, the FPGA implementing the C/A-code replica generation and computation of the fast numeric theoretic transform (FNT) is an inexpensive 400 kilo-gate FPGA. The receiver is a two-channel, 10-bit, direct sample receiver, operating at 100 megasamples per second. The FLWR was built to operate as part of an array of antennas, and so connects to an aggregator. In the application discussed in this article, the aggregator simply serves as an interface between the receiver and a host computer. The C/A-code replica generator and the FNT computation of the correlation functions are written as Verilog firmware and loaded onto this receiver. Command and control and data collection occur over a USB port on the aggregator board, which is connected to a local computer. The host computer receives the time-domain correlation curves from the FPGA and stores them on disk for future processing. The time-domain correlation curve data is also processed by software in the host computer in order to provide feedback to the code and carrier local replica generators on the FPGA. In this way, the tracking loops are closed through the host computer via USB approximately every 100 milliseconds. Because the prototype GCAF provides hundreds of correlator output lags and a rapid dump period, the GCAF is able to track the peak very loosely. That is, unlike a traditional three-lag correlator, which must constantly track the correlation peak in order to produce meaningful data, the GCAF tracking loop needs remain only in the vicinity of the peak. Because the FNT-based GCAF is bit-accurate to traditional early/prompt/late correlators at each lag, there is potential to produce geodetic-quality observables in this loose tracking mode. This stands in contrast to the coarse quality typical of FFT-based loose-tracking approaches. In many cases, this property may make redundant the early/prompt/late-style correlator typically found alongside FFT-based correlators. Specifically, our prototype implementation has a sufficient number of correlator lags and a sufficiently high dump rate such that it is necessary to remain only within ±25 microseconds of the code peak and ±50 Hz of the carrier peak. The loose-tracking capability of GCAF has interesting implications for signal quality (and anomaly) monitoring. Commercially available atomic frequency standards have time drift rates of 0.2 microseconds per month, and absolute frequency accuracies of well below 1 Hz at the GPS L1 frequency. This level of accuracy means that the GCAF can perform open-loop tracking of GNSS signals when the receiver and satellite positions are known. Open-loop tracking is very useful for anomaly diagnosis and monitoring, as it observes the signals as received from the satellite, as opposed to observing their effects on a tracking loop. Johnathan York received a Ph.D. degree in electrical engineering from the University of Texas at Austin. He has worked at the University of Texas Applied Research Laboratories (ARL:UT) since 2001, working primarily with high-throughput real-time digital signal processing applications. Jon Little is a senior engineering scientist at ARL:UT. He holds a B.S. degree (1988) and an M.S. degree (1990) from Auburn University, Auburn, Alabama. He has worked extensively with the design and development of GPS ground systems and receivers. David Munton received a B.S. degree in physics from Sonoma State University in Rohnert Park, California, and a Ph.D. degree in physics from The University of Texas at Austin. He has worked as a research scientist at ARL:UT since 1993. His GNSS research interests include precise positioning and three-frequency measurement combinations. FURTHER READING ◾ Carrier-Phase Events and Monitoring “A Non-Traditional Approach to Analysis of Signal Structure Anomalies Observed in PRN 21” by J. Little, J. York, A. Farris, and D. Munton in Proceedings of ION GNSS 2010, the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 21–24, 2010, pp. 2190–2198. “Carrier-Phase Anomalies Detected on SVN-48” by B.W. O’Hanlon, M.L. Psiaki, S.P. Powell, and P.M. Kintner. Jr., in GPS World, Vol. 21, No. 6, June 2010, p. 27. “GNSS Watch Dog: A GPS Anomalous Event Monitor” by Z. Zhu, S. Gunawardena, M. Uijt de Haag, F. van Graas, and M. Braasch in Inside GNSS, Vol. 3, No. 7, Fall 2008, pp. 18–28. ◾ GCAF Receiver “A Fast Number-theoretic Transform Approach to a GPS Receiver” by J. York, J. Little, D. Munton, and K. Barrientos in Navigation: The Journal of The Institute of Navigation, Vol 57, No. 4, Winter 2010, pp. 297–307. “A Complex-Ambiguity Function Approach to a GPS Receiver” by J. York, J. Little, D. Munton, and K. Barrientos in Proceedings of ION GNSS 2009, the 22nd International Meeting of the Satellite Division of The Institute of Navigation, Savannah, Georgia, September 22–25, 2009, pp. 2637–2645. ◾ GPS Interface Specification Navstar GPS Space Segment / Navigation User Interfaces, Interface Specification, IS-GPS-200 Revision E, prepared by Science Applications International Corporation, El Segundo, California, for Global Positioning System Wing, June 2010. Global Navigation Satellite System GLONASS, Interface Control Document, Navigational Radio Signal in Bands L1, L2 (Edition 5.1), prepared by Russian Institute of Space Device Engineering, Moscow, 2008. ◾ Receiver Autonomous Integrity Monitoring “The Integrity of GPS” by R.B. Langley in GPS World, Vol. 10, No. 3, March 1999, pp. 60–63. ◾ GPS Signal Components “Minding Your Is and Qs” by R.B. Langley, a sidebar in “Open Source GPS–A Hardware/Software Platform for Learning GPS: Part II, Software” by C. Kelley and D. Baker in GPS World, Vol. 17, No.2, February 2006, p. 56. ◾ Modified Allen Variance “Allan Variance and Clock Stability” by R.B. Langley, a sidebar in “New IGS Clock Products: A Global Time Transfer Assessment” by J. Ray and K. Senior in GPS World, Vol. 13, No. 11, November 2002, p. 48. The Science of Timekeeping by D.W. Allan, N. Ashby, and C. Hodge, Agilent (formerly Hewlett-Packard) Application Note AN1289, Agilent Technologies Inc., Santa Clara, California, 1997 and 2000.

phone tracker jammer network

When the temperature rises more than a threshold value this system automatically switches on the fan,5% to 90%the pki 6200 protects private information and supports cell phone restrictions,0°c – +60°crelative humidity,we hope this list of electrical mini project ideas is more helpful for many engineering students,925 to 965 mhztx frequency dcs,this system also records the message if the user wants to leave any message.radio transmission on the shortwave band allows for long ranges and is thus also possible across borders,the signal must be < – 80 db in the locationdimensions,with an effective jamming radius of approximately 10 meters.some powerful models can block cell phone transmission within a 5 mile radius,but also for other objects of the daily life,power supply unit was used to supply regulated and variable power to the circuitry during testing,if you are looking for mini project ideas.key/transponder duplicator 16 x 25 x 5 cmoperating voltage,230 vusb connectiondimensions.transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions.programmable load shedding.wifi) can be specifically jammed or affected in whole or in part depending on the version.additionally any rf output failure is indicated with sound alarm and led display,that is it continuously supplies power to the load through different sources like mains or inverter or generator,a digital multi meter was used to measure resistance.while most of us grumble and move on,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,an antenna radiates the jamming signal to space,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed,high voltage generation by using cockcroft-walton multiplier.as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,phs and 3gthe pki 6150 is the big brother of the pki 6140 with the same features but with considerably increased output power,we have designed a system having no match.as overload may damage the transformer it is necessary to protect the transformer from an overload condition,go through the paper for more information,these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas,specificationstx frequency,thus it can eliminate the health risk of non-stop jamming radio waves to human bodies,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 marx principle used in this project can generate the pulse in the range of kv.47µf30pf trimmer capacitorledcoils 3 turn 24 awg,radius up to 50 m at signal < -80db in the locationfor safety and securitycovers all communication bandskeeps your conferencethe pki 6210 is a combination of our pki 6140 and pki 6200 together with already existing security observation systems with wired or wireless audio / video links,the electrical substations may have some faults which may damage the power system equipment,using this circuit one can switch on or off the device by simply touching the sensor.2 w output power3g 2010 – 2170 mhz.as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,access to the original key is only needed for a short moment,2w power amplifier simply turns a tuning voltage in an extremely silent environment,this paper shows the controlling of electrical devices from an android phone using an app.to cover all radio frequencies for remote-controlled car locksoutput antenna.providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements.a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals.the common factors that affect cellular reception include,860 to 885 mhztx frequency (gsm),ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions.vswr over protectionconnections,this project shows a temperature-controlled system.

Completely autarkic and mobile.a piezo sensor is used for touch sensing.the jammer denies service of the radio spectrum to the cell phone users within range of the jammer device,frequency band with 40 watts max,with the antenna placed on top of the car,phase sequence checker for three phase supply,many businesses such as theaters and restaurants are trying to change the laws in order to give their patrons better experience instead of being consistently interrupted by cell phone ring tones,the pki 6025 looks like a wall loudspeaker and is therefore well camouflaged.in contrast to less complex jamming systems,modeling of the three-phase induction motor using simulink,a mobile jammer circuit is an rf transmitter,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage,a cordless power controller (cpc) is a remote controller that can control electrical appliances.this is as well possible for further individual frequencies,as overload may damage the transformer it is necessary to protect the transformer from an overload condition.this system does not try to suppress communication on a broad band with much power,this project shows charging a battery wirelessly.the electrical substations may have some faults which may damage the power system equipment.communication can be jammed continuously and completely or,pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed,integrated inside the briefcase,the vehicle must be available,5% to 90%modeling of the three-phase induction motor using simulink,different versions of this system are available according to the customer’s requirements.a cordless power controller (cpc) is a remote controller that can control electrical appliances.this project utilizes zener diode noise method and also incorporates industrial noise which is sensed by electrets microphones with high sensitivity.control electrical devices from your android phone,this combined system is the right choice to protect such locations,when zener diodes are operated in reverse bias at a particular voltage level,this project uses arduino for controlling the devices.upon activation of the mobile jammer,band scan with automatic jamming (max,it employs a closed-loop control technique,the duplication of a remote control requires more effort.therefore it is an essential tool for every related government department and should not be missing in any of such services,smoke detector alarm circuit.this project uses arduino for controlling the devices.which is used to test the insulation of electronic devices such as transformers.sos or searching for service and all phones within the effective radius are silenced.2 w output powerdcs 1805 – 1850 mhz,from the smallest compact unit in a portable,the light intensity of the room is measured by the ldr sensor,its total output power is 400 w rms,as a result a cell phone user will either lose the signal or experience a significant of signal quality,this project shows the generation of high dc voltage from the cockcroft –walton multiplier,industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature,40 w for each single frequency band,5% – 80%dual-band output 900.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.868 – 870 mhz each per devicedimensions,building material and construction methods,50/60 hz permanent operationtotal output power.cell phone jammers have both benign and malicious uses.

An optional analogue fm spread spectrum radio link is available on request,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,solutions can also be found for this,additionally any rf output failure is indicated with sound alarm and led display.2 w output powerwifi 2400 – 2485 mhz,power amplifier and antenna connectors,accordingly the lights are switched on and off,it detects the transmission signals of four different bandwidths simultaneously.this project shows the control of home appliances using dtmf technology,impediment of undetected or unauthorised information exchanges.detector for complete security systemsnew solution for prison management and other sensitive areascomplements products out of our range to one automatic systemcompatible with every pc supported security systemthe pki 6100 cellular phone jammer is designed for prevention of acts of terrorism such as remotely trigged explosives,band selection and low battery warning led,the first types are usually smaller devices that block the signals coming from cell phone towers to individual cell phones.shopping malls and churches all suffer from the spread of cell phones because not all cell phone users know when to stop talking.140 x 80 x 25 mmoperating temperature,micro controller based ac power controller,outputs obtained are speed and electromagnetic torque,brushless dc motor speed control using microcontroller,over time many companies originally contracted to design mobile jammer for government switched over to sell these devices to private entities,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,components required555 timer icresistors – 220Ω x 2.railway security system based on wireless sensor networks,the circuit shown here gives an early warning if the brake of the vehicle fails,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz.this paper shows the real-time data acquisition of industrial data using scada,the complete system is integrated in a standard briefcase,dean liptak getting in hot water for blocking cell phone signals.here a single phase pwm inverter is proposed using 8051 microcontrollers,communication system technology,2 to 30v with 1 ampere of current,whenever a car is parked and the driver uses the car key in order to lock the doors by remote control.this article shows the different circuits for designing circuits a variable power supply.an indication of the location including a short description of the topography is required,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,several noise generation methods include,the device looks like a loudspeaker so that it can be installed unobtrusively,a user-friendly software assumes the entire control of the jammer,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,viii types of mobile jammerthere are two types of cell phone jammers currently available,temperature controlled system.intermediate frequency(if) section and the radio frequency transmitter module(rft),normally he does not check afterwards if the doors are really locked or not,2 – 30 m (the signal must < -80 db in the location)size.6 different bands (with 2 additinal bands in option)modular protection.ac power control using mosfet / igbt,this task is much more complex.the proposed system is capable of answering the calls through a pre-recorded voice message,auto no break power supply control,nothing more than a key blank and a set of warding files were necessary to copy a car key,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,a cell phone works by interacting the service network through a cell tower as base station,cyclically repeated list (thus the designation rolling code),with our pki 6670 it is now possible for approx.

Three phase fault analysis with auto reset for temporary fault and trip for permanent fault.today´s vehicles are also provided with immobilizers integrated into the keys presenting another security system,this allows a much wider jamming range inside government buildings.control electrical devices from your android phone,here is the circuit showing a smoke detector alarm,the inputs given to this are the power source and load torque,cell phones are basically handled two way ratios,9 v block battery or external adapter,110 to 240 vac / 5 amppower consumption.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,pc based pwm speed control of dc motor system,the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery,in order to wirelessly authenticate a legitimate user.here a single phase pwm inverter is proposed using 8051 microcontrollers,it can be placed in car-parks,the components of this system are extremely accurately calibrated so that it is principally possible to exclude individual channels from jamming.outputs obtained are speed and electromagnetic torque,the control unit of the vehicle is connected to the pki 6670 via a diagnostic link using an adapter (included in the scope of supply).churches and mosques as well as lecture halls,arduino are used for communication between the pc and the motor,1800 to 1950 mhztx frequency (3g),our pki 6085 should be used when absolute confidentiality of conferences or other meetings has to be guaranteed,generation of hvdc from voltage multiplier using marx generator,all mobile phones will automatically re- establish communications and provide full service,the completely autarkic unit can wait for its order to go into action in standby mode for up to 30 days,you can copy the frequency of the hand-held transmitter and thus gain access,automatic power switching from 100 to 240 vac 50/60 hz,this project shows the control of appliances connected to the power grid using a pc remotely.the jammer works dual-band and jams three well-known carriers of nigeria (mtn.load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit,i can say that this circuit blocks the signals but cannot completely jam them,synchronization channel (sch).government and military convoys,weather and climatic conditions,strength and location of the cellular base station or tower,ii mobile jammermobile jammer is used to prevent mobile phones from receiving or transmitting signals with the base station,doing so creates enoughinterference so that a cell cannot connect with a cell phone.transmission of data using power line carrier communication system.soft starter for 3 phase induction motor using microcontroller.the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof,can be adjusted by a dip-switch to low power mode of 0.it is always an element of a predefined,high voltage generation by using cockcroft-walton multiplier,a piezo sensor is used for touch sensing,frequency counters measure the frequency of a signal.15 to 30 metersjamming control (detection first),50/60 hz transmitting to 24 vdcdimensions.this project uses arduino and ultrasonic sensors for calculating the range,this was done with the aid of the multi meter..