2021/04/07
Enhancing GNSS Receiver Sensitivity by Combining Signals from Multiple Satellites
By Penina Axelrad, James Donna, Megan Mitchell, and Shan Mohiuddin
A new approach to enhancing signal sensitivity combines the received signal power from multiple satellites in a direct-to-navigation solution.
INNOVATION INSIGHTS by Richard Langley
ALTHOUGH I HAVE MANAGED the Innovation column continuously since GPS World’s first issue, it wasn’t until the second issue that I authored a column article. That article, co-written with Alfred Kleusberg, was titled “The Limitations of GPS.” It discussed some of the then-current problems of GPS, including poor signal reception, loss of signal integrity, and limited positioning accuracy.
In the ensuing 20 years, both signal integrity and positioning accuracy have improved significantly. Advances in the GPS control segment’s capabilities to continuously monitor and assess signal performance, together with receiver-autonomous integrity monitoring and integrity enhancement provided by augmentation systems, have reduced worries about loss of signal integrity. The removal of Selective Availability and use of error corrections provided by augmentation systems, among other approaches, have improved positioning accuracy.
But the problem of poor reception due to weak signals is still with us. In that March/April 1990 article, we wrote “[GPS] signals propagate from the satellites to the receiver antenna along the line of sight and cannot penetrate water, soil, walls, or other obstacles very well. … In surface navigation and positioning applications, the signal can be obstructed by trees, buildings, and bridges. … [In] the inner city streets of urban areas lined with skyscrapers, the ‘visibility’ of the GPS satellites is very limited. In such areas, the signals can be obstructed for extended periods of time or even [be] continuously unavailable.”
Poor signal reception in other than open-sky environments is still a problem with conventional GPS receivers. However, extending signal integration times and using assisted-GPS techniques can give GPS some degree of capability to operate indoors and in other restricted environments, albeit typically with reduced positioning accuracy. An antenna with sufficient gain is needed and capable systems are available on the market. The pilot channels of modernized GNSS signals will also benefit signal acquisition and tracking in challenging environments.
In this month’s column, we look at a completely different approach to enhancing signal sensitivity. Rather than requiring each satellite’s signal to be acquired and tracked before it can be used in the navigation solution, the new approach — dubbed “collective detection” — combines the received signal power from multiple satellites in a direct-to-navigation-solution procedure. Besides providing a quick coarse position solution with weak signals, this approach can be used to monitor the signal environment, aid deeply-coupled GPS/inertial navigation, and assist with terrain and feature recognition.
“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.
Growing interest in navigating indoors and in challenging urban environments is motivating research on techniques for weak GPS signal acquisition and tracking. The standard approach to increasing acquisition and tracking sensitivity is to lengthen the coherent integration times, which can be accomplished by using the pilot channels in the modernized GPS signals or by using assisted GPS (A-GPS) techniques. These techniques operate in the traditional framework of independent signal detection, which requires a weak signal to be acquired and tracked before it is useful for navigation. This article explores a complementary, but fundamentally different, approach that enhances signal sensitivity by combining the received power from multiple GPS satellites in a direct-to-navigation-solution algorithm. As will be discussed in the following sections, this collective detection approach has the advantage of incorporating into the navigation solution information from signals that are too weak to be acquired and tracked, and it does so with a modest amount of computation and with no required hardware changes. This technology is appropriate for any application that requires a navigation solution in a signal environment that challenges traditional acquisition techniques. Collective detection could be used to monitor the signal environment, aid deeply coupled GPS/INS during long outages, and help initiate landmark recognition in an urban environment. These examples are explained further in a subsequent section. In order to understand how the collective detection algorithm works, it is instructive to first consider the traditional approach to acquisition and tracking.
Acquisition Theory and Methods
In a typical stand-alone receiver, the acquisition algorithm assesses the signal’s correlation power in discrete bins on a grid of code delay and Doppler frequency (shift). The correlation calculations take the sampled signal from the receiver’s RF front end, mix it with a family of receiver-generated replica signals that span the grid, and sum that product to produce in-phase (I) and quadrature (Q) correlation output. The correlation power is the sum of the I and Q components, I2 + Q2. Plotting the power as a function of delay and frequency shift produces a correlogram, as shown in FIGURE 1. It should be noted that both correlation power and its square root, the correlation amplitude, are found in the GPS literature. For clarity, we will always use the correlation power to describe signal and noise values.
If a sufficiently powerful signal is present, a distinct peak appears in the correlogram bin that corresponds to the GPS signal’s code delay and Doppler frequency. If the peak power exceeds a predefined threshold based on the integration times and the expected carrier-to-noise spectral density, the signal is detected. The code delay and Doppler frequency for the peak are then passed to the tracking loops, which produce more precise measurements of delay — pseudoranges — from which the receiver’s navigation solution is calculated. When the satellite signal is attenuated, however, perhaps due to foliage or building materials, the correlation peak cannot be distinguished and the conventional approach to acquisition fails.
The sensitivity of traditional tracking algorithms is similarly limited by the restrictive practice of treating each signal independently. More advanced tracking algorithms, such as vector delay lock loops or deeply integrated filters, couple the receiver’s tracking algorithms and its navigation solution in order to take advantage of the measurement redundancy and to leverage information gained from tracking strong signals to track weak signals. The combined satellite detection approach presented in this article extends the concept of coupling to acquisition by combining the detection and navigation algorithms into one step.
Collective Detection
In the collective detection algorithm, a receiver position and clock offset grid is mapped to the individual GPS signal correlations, and the combined correlation power is evaluated on that grid instead of on the conventional independent code delay and Doppler frequency grids. The assessment of the correlation power on the position and clock offset grid leads directly to the navigation solution. The mapping, which is key to the approach, requires the receiver to have reasonably good a priori knowledge of its position, velocity, and clock offset; the GPS ephemerides; and, if necessary, a simplified ionosphere model. Given this knowledge, the algorithm defines the position and clock offset search grid centered on the assumed receiver state and generates predicted ranges and Doppler frequencies for each GPS signal, as illustrated in FIGURE 2. The mapping then relates each one of the position and clock offset grid points to a specific code delay and Doppler frequency for each GPS satellite, as illustrated in FIGURE 3. Aggregating the multiple delay/Doppler search spaces onto a single position/clock offset search space through the mapping allows the navigation algorithm to consider the total correlation power of all the signals simultaneously. The correlation power is summed over all the GPS satellites at each position/clock-offset grid point to create a position domain correlogram. The best position and clock-offset estimates are taken as the grid point that has the highest combined correlation power. This approach has the advantage of incorporating into the position/clock-offset estimate information contained in weak signals that may be undetectable individually using traditional acquisition/tracking techniques.
It should be noted that a reasonable a priori receiver state estimate restricts the size of the position and clock-offset grid such that a linear mapping, based on the standard measurement sensitivity matrix used in GPS positioning, from the individual signal correlations, is reasonable. Also, rather than attempt to align the satellite correlations precisely enough to perform coherent sums, noncoherent sums of the individual satellite correlations are used. This seems reasonable, given the uncertainties in ranging biases between satellites, differences and variability of the signal paths through the ionosphere and neutral atmosphere, and the large number of phases that would have to be aligned.
Applications
The most obvious application for collective detection is enabling a navigation fix in circumstances where degraded signals cause traditional acquisition to fail. The sweet spot of collective detection is providing a rapid but coarse position solution in a weak signal environment. The solution can be found in less time because information is evaluated cohesively across satellites. This is especially clear when the algorithm is compared to computationally intensive long integration techniques.
There are several ways that collective detection can support urban navigation. This capability benefits long endurance users who desire a moderate accuracy periodic fix for monitoring purposes. In some circumstances, the user may wish to initiate traditional tracking loops for a refined position estimate. However, if the signal environment is unfavorable at the time, this operation will waste valuable power. The collective detection response indicates the nature of the current signal environment, such as indoors or outdoors, and can inform the decision of whether to spend the power to transition to full GPS capabilities.
In urban applications, deeply integrated GPS/INS solutions tolerate GPS outages by design. However, if the outage duration is too long, the estimate uncertainty will eventually become too large to allow conclusive signal detection to be restored. Running collective detection as a background process could keep deeply integrated filters centered even in long periods of signal degradation. Because collective detection approaches the acquisition problem from a position space instead of the individual satellite line-of-sight space, it provides inherent integrity protection. In the traditional approach, acquiring a multipath signal will pollute the overall position fix. In collective detection, such signals are naturally exposed as inconsistent with the position estimate.
Another use would be to initialize landmark correlation algorithms in vision navigation. Landmark correlation associates street-level video with 3D urban models as an alternative to (GPS) absolute position and orientation updates. This technique associates landmarks observed from ground-level imagery with a database of landmarks extracted from overhead-derived 3D urban models. Having a coarse position (about 100 meters accuracy) enhances initialization and restart of the landmark correlation process. Draper Laboratory is planning to demonstrate the utility of using collective detection to enable and enhance landmark correlation techniques for urban navigation.
In all of these applications, collective detection is straightforward to implement because it simply uses the output of correlation functions already performed on GPS receivers.
Simulations and Processing
The new algorithm has been tested using live-sky and simulated data collected by a Draper Laboratory wideband data recorder. A hardware GPS signal simulator was used to simulate a stationary observer receiving 11 equally powered GPS signals that were broadcast from the satellite geometry shown in FIGURE 4. The data recorder and the signal simulator were set up in a locked-clock configuration with all of the simulator’s modeled errors set to zero. No frequency offsets should exist between the satellites and the receiver. A clock bias, however, does exist because of cable and other fixed delays between the two units. The data recorder houses a four-channel, 14-bit A/D module. It can support sample rates up to 100 MHz. For this work, it was configured to downconvert the signal to an IF of 420 kHz and to produce in-phase and quadrature samples at 10 MHz.
Results and Discussion
To combine satellites, a position domain search space is established, centered on the correct location and receiver clock bias. A grid spacing of 30 meters over a range of ± 900 meters in north and east directions, and ± 300 meters in the vertical. In the first simulated example, the correlation power for all the satellites is summed on the position grid using a single 1-millisecond integration period. In this case, the true carrier-to-noise-density ratio for each signal is 40 dB-Hz. The results are shown in FIGURE 5. The plots in the left panel show the individual signal correlations as a function of range error. The four plots in the upper-right panel show several views of the combined correlation as a function of position error. The upper-left plot in the panel shows the correlation value as a function of the magnitude of the position error. The upper-right plot shows the correlation as a function of the north-east error, the lower-left the north-down error, and the lower-right the east-down error. Notice how the shape of the constant power contours resembles the shape of the constant probability contours that would result from a least-squares solution’s covariance matrix. The final plot, the bottom-right panel, shows a 3D image of the correlation power as a function of the north-east error. It is clear in these images that in the 40 dB-Hz case each satellite individually reaches the highest correlation power in the correct bin and that the combined result also peaks in the correct bin. In the combined satellite results, each individual satellite’s correlation power enters the correlogram as the ridge that runs in a direction perpendicular to the receiver-satellite line-of-sight vector and represents a line of constant pseudorange.
FIGURE 6 shows a similar set of graphs for a simulator run at 20 dB-Hz. The plots in the left panel and the four plots in the upper-right panel show the individual and combined correlations, as in Figure 5. In the lower-right panel, the 3D image has been replaced with correlations calculated using 20 noncoherent 1-millisecond accumulations. The indistinct peaks in many of the individual correlations (left panel) suggest that these signals may not be acquired and tracked using traditional methods. Those signals, therefore, would not contribute to the navigation solution. Yet in the combined case, those indistinct peaks tend to add up and contribute to the navigation solution. These results indicate the feasibility of using the information in weak signals that may not be detectable using traditional methods and short acquisition times. The situation is further improved by increasing the number of noncoherent integration periods.
Impact of Reduced Geometry. Of course, it is a bit unrealistic to have 11 satellites available, particularly in restricted environments, so we also considered three subsets of four-satellite acquisitions, under the same signal levels. FIGURE 7 compares the position domain correlograms for the following 20 dB-Hz cases: (1) a good geometry case (PRNs 3, 14, 18, 26), (2) an urban canyon case where only the highest 4 satellites are visible (PRNs 15, 18, 21, 22), and (3) a weak geometry case where just a narrow wedge of visibility is available (PRNs 18, 21, 26, 29). As expected, the correlation power peak becomes less distinct as the satellite geometry deteriorates. The pattern of degradation, morphing from a distinct peak to a ridge, reveals that the position solution remains well constrained in some directions, but becomes poorly constrained in others. Again, this result is expected and is consistent with the behavior of conventional positioning techniques under similar conditions.
Focusing on Clock Errors. In some real-world situations, for example, a situation where a receiver is operating in an urban environment, it is possible for the position to be fairly well known, but the clock offset and frequency to have substantial uncertainty. FIGURE 8 shows how the combined satellites approach can be used to improve sensitivity when viewed from the clock bias and frequency domain. The figure presents example 1-millisecond correlograms of clock bias and clock drift for three 20 dB-Hz cases: (1) a single GPS satellite case; (2) a four-satellite, good geometry case; and (3) an 11-satellite, good geometry case. The assumed position solution has been offset by a random amount (generated with a 1-sigma of 100 meters in the north and east components, and 20 meters in the up component), but no individual satellite errors are introduced. These plots clearly show the improved capability for acquisition of the clock errors through the combining process.
Live Satellite Signals. FIGURE 9 shows combined correlograms derived from real data recorded using an outdoor antenna. The first example includes high-signal-level satellites with 1.5-second noncoherent integration. The second example includes extremely attenuated satellite signals with a long noncoherent integration period of six seconds.
The plots in the upper-left and upper-right panels show combined correlograms as a function of the north-east position error for satellite signals with carrier-to-noise-density ratios of 48 dB-Hz or higher. The plots in the lower-left and lower-right panels show combined correlograms resulting from much weaker satellites with carrier-to-noise-density ratios of roughly 15 to 19 dB-Hz, using a coherent integration interval of 20 milliseconds and a noncoherent interval of six seconds. FIGURE 10 shows one of the individual single-satellite correlograms. In this attenuated case, the individual satellite power levels are just barely high enough to make them individually detectable. This is the situation in which collective detection is most valuable.
Conclusions
The example results from a hardware signal simulator and live satellites show how the noncoherent combination of multiple satellite signals improves the GPS position error in cases where some of the signals are too weak to be acquired and tracked by traditional methods. This capability is particularly useful to a user who benefits from a rapid, but coarse, position solution in a weak signal environment. It may be used to monitor the quality of the signal environment, to aid deeply coupled navigation, and to initiate landmark recognition techniques in urban canyons. The approach does require that the user have some a priori information, such as a reasonable estimate of the receiver’s location and fairly accurate knowledge of the GPS ephemerides. Degradation in performance should be expected if the errors in these models are large enough to produce pseudorange prediction errors that are a significant fraction of a C/A-code chip. Absent that issue, the combined acquisition does not add significant complexity compared to the traditional approach to data processing. It can be used to enhance performance of existing acquisition techniques either by improving sensitivity for the current noncoherent integration times or by reducing the required integration time for a given sensitivity. Further development and testing is planned using multiple signals and frequencies.
Acknowledgments
The authors appreciate the contributions of David German and Avram Tewtewsky at Draper Laboratory in collecting and validating the simulator data; Samantha Krenning at the University of Colorado for assistance with the simulator data analysis and plotting; and Dennis Akos at the University of Colorado for many helpful conversations and for providing the Matlab software-defined radio code that was used for setting up the acquisition routines. This article is based on the paper “Enhancing GNSS Acquisition by Combining Signals from Multiple Channels and Satellites” presented at ION GNSS 2009, the 22nd International Technical Meeting of the Satellite Division of The Institute of Navigation, held in Savannah, Georgia, September 22–25, 2009.
The work reported in the article was funded by the Charles Stark Draper Laboratory Internal Research and Development program.
Manufacturers
Data for the analyses was obtained using a Spirent Federal Systems GSS7700 GPS signal simulator and a GE Fanuc Intelligent Platforms ICS-554 A/D module.
PENINA AXELRAD is a professor of aerospace engineering sciences at the University of Colorado at Boulder. She has been involved in GPS-related research since 1986 and is a fellow of The Institute of Navigation and the American Institute of Aeronautics and Astronautics.
JAMES DONNA is a distinguished member of the technical staff at the Charles Stark Draper Laboratory in Cambridge, Massachusetts, where he has worked since 1980. His interests include GNSS navigation in weak signal environments and integrated inertial-GNSS navigation.
MEGAN MITCHELL is a senior member of the technical staff at the Charles Stark Draper Laboratory. She is involved with receiver customization for reentry applications and GPS threat detection.
SHAN MOHIUDDIN is a senior member of the technical staff at the Charles Stark Draper Laboratory. His interests include GNSS technology, estimation theory, and navigation algorithms.
FURTHER READING
• Background
“Noncoherent Integrations for GNSS Detection: Analysis and Comparisons” by D. Borio and D. Akos in IEEE Transactions on Aerospace and Electronic Systems, Vol. 45, No. 1, January 2009, pp. 360–375 (doi: 10.1109/TAES.2009.4805285).
“Impact of GPS Acquisition Strategy on Decision Probabilities” by D. Borio, L. Camoriano, and L. Lo Presti in IEEE Transactions on Aerospace and Electronic Systems, Vol. 44, No. 3, July 2008, pp. 996–1011 (doi:10.1109/TAES.2008.4655359).
“Understanding the Indoor GPS Signal” by T. Haddrell and A.R. Pratt in Proceedings of ION GPS 2001, the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation, Salt Lake City, Utah, September 11–14, 2001, pp. 1487–1499.
“The Calculation of the Probability of Detection and the Generalized Marcum Q-Function” by D.A. Shnidman in IEEE Transactions on Information Theory, Vol. 35, No. 2, March 1989, pp. 389–400 (doi: 10.1109/18.32133).
• Weak Signal Acquisition and Tracking
“Software Receiver Strategies for the Acquisition and Re-Acquisition of Weak GPS Signals” by C. O’Driscoll, M.G. Petovello, and G. Lachapelle in Proceedings of The Institute of Navigation 2008 National Technical Meeting, San Diego, California, January 28-30, 2008, pp. 843–854.
“Deep Integration of Navigation Solution and Signal Processing” by T. Pany, R. Kaniuth, and B. Eissfeller in Proceedings of ION GNSS 2005, the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, September 13–16, 2005, pp. 1095–1102.
“Deeply Integrated Code Tracking: Comparative Performance Analysis” by D. Gustafson and J. Dowdle in Proceedings of ION GPS 2003, the 16th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 9–12, 2003, pp. 2553–2561.
“Block Acquisition of Weak GPS Signals in a Software Receiver” by M.L. Psiaki in Proceedings of ION GPS 2001, the 14th International Technical Meeting of the Satellite Division of The Institute of Navigation, Salt Lake City, Utah, September 11–14, 2001, pp. 2838–2850.
• General Combining Techniques
“Coherent, Non-Coherent, and Differentially Coherent Combining Techniques for the Acquisition of New Composite GNSS Signals” by D. Borio, C. O’Driscoll, and G. Lachapelle, in IEEE Transactions on Aerospace and Electronic Systems, Vol. 45, No. 3, July 2009, pp. 1227–1240.
“Comparison of L1 C/A-L2C Combined Acquisition Techniques” by C. Gernot, K. O’Keefe, and G. Lachapelle in Proceedings of the European Navigation Conference ENC-GNSS 2008, Toulouse, France, April 23–25, 2008, 9 pp.
Performance Analysis of the Parallel Acquisition of Weak GPS Signals by C. O’Driscoll, Ph.D. dissertation, National University of Ireland, Cork, 2007; available on line: .
• Coherent Combining of Signals from Multiple Satellites
“GPS PRN Code Signal Processing and Receiver Design for Simultaneous All-in-View Coherent Signal Acquisition and Navigation Solution Determination” by R. DiEsposti in Proceedings of The Institute of Navigation 2007 National Technical Meeting, San Diego, California, January 22–24, 2007, pp. 91–103.
item: Gps mobile phone jammer abstract watercolor , gps jammer mobile county
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gps mobile phone jammer abstract watercolor
The frequency blocked is somewhere between 800mhz and1900mhz,5 ghz range for wlan and bluetooth,modeling of the three-phase induction motor using simulink.a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible,we would shield the used means of communication from the jamming range,prison camps or any other governmental areas like ministries,ii mobile jammermobile jammer is used to prevent mobile phones from receiving or transmitting signals with the base station,due to the high total output power.this system considers two factors,this system does not try to suppress communication on a broad band with much power.this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure.pll synthesizedband capacity,a digital multi meter was used to measure resistance,the first circuit shows a variable power supply of range 1,three circuits were shown here.several noise generation methods include.mobile jammers successfully disable mobile phones within the defined regulated zones without causing any interference to other communication means,this provides cell specific information including information necessary for the ms to register atthe system,all mobile phones will automatically re-establish communications and provide full service.three circuits were shown here.with its highest output power of 8 watt,when the mobile jammer is turned off,mobile jammer was originally developed for law enforcement and the military to interrupt communications by criminals and terrorists to foil the use of certain remotely detonated explosive.2 ghzparalyses all types of remote-controlled bombshigh rf transmission power 400 w,phs and 3gthe pki 6150 is the big brother of the pki 6140 with the same features but with considerably increased output power.pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,completely autarkic and mobile,the choice of mobile jammers are based on the required range starting with the personal pocket mobile jammer that can be carried along with you to ensure undisrupted meeting with your client or personal portable mobile jammer for your room or medium power mobile jammer or high power mobile jammer for your organization to very high power military,this project shows a no-break power supply circuit.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),frequency band with 40 watts max.this project shows the controlling of bldc motor using a microcontroller,the single frequency ranges can be deactivated separately in order to allow required communication or to restrain unused frequencies from being covered without purpose.20 – 25 m (the signal must < -80 db in the location)size,the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer,5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma.a piezo sensor is used for touch sensing.< 500 maworking temperature,accordingly the lights are switched on and off,please see the details in this catalogue.once i turned on the circuit,usually by creating some form of interference at the same frequency ranges that cell phones use.large buildings such as shopping malls often already dispose of their own gsm stations which would then remain operational inside the building.a blackberry phone was used as the target mobile station for the jammer,its versatile possibilities paralyse the transmission between the cellular base station and the cellular phone or any other portable phone within these frequency bands,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,this project shows a no-break power supply circuit,i have placed a mobile phone near the circuit (i am yet to turn on the switch).as overload may damage the transformer it is necessary to protect the transformer from an overload condition,this noise is mixed with tuning(ramp) signal which tunes the radio frequency transmitter to cover certain frequencies,and cell phones are even more ubiquitous in europe,for technical specification of each of the devices the pki 6140 and pki 6200.50/60 hz permanent operationtotal output power,this allows a much wider jamming range inside government buildings.when the mobile jammers are turned off,this project uses arduino and ultrasonic sensors for calculating the range,this can also be used to indicate the fire.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,so to avoid this a tripping mechanism is employed,the operational block of the jamming system is divided into two section.
The cockcroft walton multiplier can provide high dc voltage from low input dc voltage,additionally any rf output failure is indicated with sound alarm and led display.this project utilizes zener diode noise method and also incorporates industrial noise which is sensed by electrets microphones with high sensitivity,we are providing this list of projects.as a result a cell phone user will either lose the signal or experience a significant of signal quality,while the second one is the presence of anyone in the room,incoming calls are blocked as if the mobile phone were off.now we are providing the list of the top electrical mini project ideas on this page,this break can be as a result of weak signals due to proximity to the bts.when shall jamming take place,the pki 6085 needs a 9v block battery or an external adapter.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,
.pc based pwm speed control of dc motor system.this can also be used to indicate the fire.we have designed a system having no match,the rf cellular transmitted module with frequency in the range 800-2100mhz,1 watt each for the selected frequencies of 800,it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals,components required555 timer icresistors – 220Ω x 2.this mobile phone displays the received signal strength in dbm by pressing a combination of alt_nmll keys,one is the light intensity of the room,this project uses arduino and ultrasonic sensors for calculating the range,dtmf controlled home automation system.department of computer scienceabstract.providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements.this device can cover all such areas with a rf-output control of 10,a break in either uplink or downlink transmission result into failure of the communication link.15 to 30 metersjamming control (detection first).this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors,your own and desired communication is thus still possible without problems while unwanted emissions are jammed,provided there is no hand over,here a single phase pwm inverter is proposed using 8051 microcontrollers,the light intensity of the room is measured by the ldr sensor.a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper,solar energy measurement using pic microcontroller,using this circuit one can switch on or off the device by simply touching the sensor.2 to 30v with 1 ampere of current.a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals,this system considers two factors,2100 – 2200 mhz 3 gpower supply,this project shows the control of that ac power applied to the devices.zigbee based wireless sensor network for sewerage monitoring,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,the unit requires a 24 v power supply,so that the jamming signal is more than 200 times stronger than the communication link signal,the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way.while most of us grumble and move on,all mobile phones will indicate no network.its total output power is 400 w rms,it consists of an rf transmitter and receiver,overload protection of transformer.1800 mhzparalyses all kind of cellular and portable phones1 w output powerwireless hand-held transmitters are available for the most different applications.this allows an ms to accurately tune to a bs,they go into avalanche made which results into random current flow and hence a noisy signal.blocking or jamming radio signals is illegal in most countries,these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas.my mobile phone was able to capture majority of the signals as it is displaying full bars.outputs obtained are speed and electromagnetic torque,three phase fault analysis with auto reset for temporary fault and trip for permanent fault.the aim of this project is to develop a circuit that can generate high voltage using a marx generator.
2100 to 2200 mhzoutput power,the data acquired is displayed on the pc,12 v (via the adapter of the vehicle´s power supply)delivery with adapters for the currently most popular vehicle types (approx,selectable on each band between 3 and 1.to cover all radio frequencies for remote-controlled car locksoutput antenna,there are many methods to do this.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,intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience,automatic power switching from 100 to 240 vac 50/60 hz,1800 to 1950 mhztx frequency (3g).building material and construction methods,a mobile jammer circuit is an rf transmitter,our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature,specificationstx frequency,automatic changeover switch,which broadcasts radio signals in the same (or similar) frequency range of the gsm communication,this device can cover all such areas with a rf-output control of 10,we hope this list of electrical mini project ideas is more helpful for many engineering students.key/transponder duplicator 16 x 25 x 5 cmoperating voltage,230 vusb connectiondimensions,110 to 240 vac / 5 amppower consumption,the unit is controlled via a wired remote control box which contains the master on/off switch.4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it.it is required for the correct operation of radio system,the if section comprises a noise circuit which extracts noise from the environment by the use of microphone.the present circuit employs a 555 timer,also bound by the limits of physics and can realise everything that is technically feasible.the proposed system is capable of answering the calls through a pre-recorded voice message,the pki 6025 looks like a wall loudspeaker and is therefore well camouflaged.some people are actually going to extremes to retaliate,the circuit shown here gives an early warning if the brake of the vehicle fails,from analysis of the frequency range via useful signal analysis,this project shows the starting of an induction motor using scr firing and triggering.this project shows the control of that ac power applied to the devices.now we are providing the list of the top electrical mini project ideas on this page,control electrical devices from your android phone,but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control.ac power control using mosfet / igbt,the integrated working status indicator gives full information about each band module.this covers the covers the gsm and dcs,here is the diy project showing speed control of the dc motor system using pwm through a pc,8 watts on each frequency bandpower supply.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,disrupting a cell phone is the same as jamming any type of radio communication,the inputs given to this are the power source and load torque,this article shows the different circuits for designing circuits a variable power supply.this task is much more complex,this project shows the automatic load-shedding process using a microcontroller,railway security system based on wireless sensor networks,-20°c to +60°cambient humidity,radio remote controls (remote detonation devices).for any further cooperation you are kindly invited to let us know your demand,the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules.although we must be aware of the fact that now a days lot of mobile phones which can easily negotiate the jammers effect are available and therefore advanced measures should be taken to jam such type of devices,this paper shows the real-time data acquisition of industrial data using scada,at every frequency band the user can select the required output power between 3 and 1,generation of hvdc from voltage multiplier using marx generator.computer rooms or any other government and military office,.
