Using HD Radio Signals for Navigation By Ananta Vidyarthi, H. Howard Fan and Stewart DeVilbiss INNOVATION INSIGHTS by Richard Langley THE YEAR WAS 1906. On Christmas Eve of that year, Canadian inventor Reginald Fessenden carried out the first amplitude modulation (AM) radio broadcast of voice and music. He used a high-speed alternator capable of rotating at up to 20,000 revolutions per minute (rpm). Connected to an antenna circuit, it generated a continuous wave with a radio frequency equal to the product of the rotation speed and the number of magnetic rotor poles it had. With 360 poles, radio waves of up to about 100 kHz could be generated. However, Fessenden typically used a speed of 10,000 rpm to produce 60 kHz signals. By inserting a water-cooled microphone in the high-power antenna circuit, he amplitude-modulated the transmitted signal. On that Christmas Eve, he played phonograph records, spoke and played the violin with radio operators being amazed at what they heard. Fessenden had earlier worked with spark-gap transmitters, as these were standard at the time for the transmission of Morse code, or telegraphy, the wireless communication method already in use. But they couldn’t generate a continuous wave and couldn’t produce satisfactory AM signals. But as telegraphy was the chief means of communication, they remained in use for many years along with high-powered alternators and the Poulsen arc transmitter, which could also generate continuous waves. Although other experimental AM broadcasts were carried out using alternators or arc transmitters, voice transmissions — and in particular sound broadcasting — didn’t take off until the invention of amplifying vacuum tubes. Just before World War I, it was found that they could be used in an oscillator circuit to produce continuous waves, which could be easily modulated to make an AM transmitter. Such transmitters could be used for point-to-point communications but also for broadcasting, and a number of experimental broadcasting stations were established in Europe and North America during and just after the war. Tubes were also instrumental for improvements in receiver technology. “Where there was one licensed station in America in 1920, there were nearly 600 stations just five years later, and the number of radio receivers went from thousands of crystal sets to millions of vacuum-tube circuits.” — from The Science of Radio by Paul J. Nahin, one of my favorite writers on electronics and mathematics. AM radio broadcasting used frequencies in the long-wave, medium-wave and short-wave frequency bands, and still does. But AM signals often have low audio quality due to bandwidth limitations imposed by regulators and interference from other stations, atmospheric disturbances and electrical noise. So, over the past decade or so, many broadcasters have abandoned long-wave and medium-wave frequencies and moved to the frequency modulation or FM broadcast band with its superior signal capability. However, this migration pattern might be slowed or stopped if digital broadcasting were to be fully embraced on the AM broadcast bands. A digital technique developed by the iBiquity Digital Corporation is gradually being adopted by broadcasters in the United States and elsewhere. The technique provides FM-quality sound in the medium-wave band by supplementing existing AM signals or replacing them altogether. It can also supply data about the transmitting station and its broadcast. Some 240 AM radio stations in the U.S. already use the technology. (It can also be used in the FM band to provide CD-like quality.) But these digital signals in the AM broadcast band might serve an additional purpose beyond improving the listening experience. In this month’s column, our authors tell us about some extensive simulation work they have carried out to demonstrate the feasibility of using digital radio signals for navigation. In the future, you may be able to turn on your radio and tune in to get to where you’re going. “Innovation” is a regular feature that discusses advances in GPS technology and its applications as well as the fundamentals of GPS positioning. The column is coordinated by Richard Langley of the Department of Geodesy and Geomatics Engineering, University of New Brunswick. He welcomes comments and topic ideas. Email him at lang @ unb.ca. It is well known that the GPS signals are weak and are therefore subject to interference and blockage due to obstruction. Signals of opportunity (SOO), on the other hand, which are designed for other purposes such as communication, may also be used for navigation and have relatively greater signal power than GPS. They are plentiful and relatively more resistant to blockage and jamming compared to GPS. Many authors have presented methods and algorithms utilizing SOO such as AM and FM broadcast signals, TV broadcast signals and 3G/4G wireless communication signals (see Further Reading for examples). These signals are robust and have very good received power levels compared with GPS, and are capable of penetrating through buildings. In addition, these signals are readily available and there is no need for any additional installation of transmitting devices or infrastructure. In this article, we present the results of a study using AM HD Radio, digital radio in the 540–1700 kHz band of the frequency spectrum, with known transmitter locations, to locate and track receiver locations that are otherwise unknown. HD Radio, originally meaning hybrid-digital radio, is a trademarked term for iBiquity Digital Corporation’s digital radio technology. Unlike analog AM radio signals, digital radio signals are well structured and more immune to co-channel interference, and hence could be better adapted for navigation. In addition, with the proliferation of software-defined radios (SDRs), digital AM radio may eventually replace analog AM radio. The challenges of navigation using digital radio signals include narrow signal bandwidths, long symbol durations and lack of synchronization among transmitters. Therefore, digital radio signals are not an ideal choice for accurate position estimation, similar to many other SOO that aren’t designed for navigation. Nevertheless, in this work, we have designed algorithms to overcome such difficulties to obtain a good level of location accuracy, making it a feasible alternative for SOO navigation. Signal Format of Digital AM Radio Digital AM signals have a well-defined structure called in-band-on-channel (IBOC) that can be exploited for localization purpose. It employs sophisticated digital radio waveforms, which can deliver compact-disc-like sound quality, free of interference and noise, to radio listeners. It uses the existing AM and FM analog broadcasting bands and channel schemes to transmit digital signals. The IBOC digital radio transmitter system encodes analog audio into binary form for transmission. The design provided by IBOC AM radio has two service modes with two new waveform types: hybrid (denoted by MA1) and all-digital (denoted by MA3). The hybrid waveform retains the analog AM signal, while the all-digital waveform completely replaces the analog AM signal. In the hybrid service mode, the bandwidth of the analog audio signal waveform can be 5 kHz or 8 kHz. The digital signal is transmitted on both sides of the analog host signal in the primary and secondary sidebands. It is also transmitted on the tertiary sidebands, which are 20 dB beneath the analog signal as shown in FIGURE 1. FIGURE 1. Logical channels and sidebands on the frequency spectrum; hybrid mode with 5-kHz analog signal bandwidth. (After iBiquity.) For the 8-kHz configuration, the secondary sidebands are also beneath the analog host signal. The greatest system enhancements are realized with the all-digital system, as shown in FIGURE 2. In this system, the analog signal is replaced with the all-digital primary sidebands whose power is increased relative to the hybrid system levels. Secondary and tertiary sideband powers are also increased to the level of the hybrid waveform. Reference subcarriers are also provided to convey system control information. The end result is a higher power digital signal with an overall bandwidth reduction. FIGURE 2. Logical channels and sidebands on the frequency spectrum; all-digital mode. (After iBiquity.) Digital radio offers distinct advantages over analog, including mitigation of transmission artifacts and improved audio quality. These changes provide a more robust digital signal that is less susceptible to adjacent channel interference, thereby reducing the noise in the system. An overview of the AM digital system for both the service modes, MA1 and MA3, is given in the following paragraphs. However, in the simulation study we carried out, we used the all-digital AM (MA3) mode. The all-digital AM system has a smaller bandwidth than the hybrid signal. If reasonable localization results can be obtained with it, then we can predict that better localization results may be obtained with the hybrid signal. IBOC uses an orthogonal frequency-division multiplexing (OFDM) waveform for signal modulation. Each OFDM subcarrier channel has a spacing of 181.7 Hz. The hybrid MA1 service mode comprises 163 subchannels indexed from -81 to 81 over a total bandwidth of 29.4 kHz as shown in Figure 1. The all-digital MA3 service mode has only 105 subchannels indexed from -52 to 52 over a total bandwidth of 18.9 kHz as shown in Figure 2. Therefore, when compared to the all-digital mode, hybrid mode contains more training symbols per OFDM symbol duration. The training symbols are important since these symbols are known and will be used to perform correlation to estimate the signal time of arrival. We predict that since the hybrid mode contains more training symbols than the all-digital mode, detection accuracy will be higher for the hybrid mode. Hence, choosing the all-digital MA3 service mode for the localization will be more challenging, and this is another reason for our decision to use MA3. Demonstrating the capability of the all-digital MA3 service mode for localization would imply that the hybrid mode could be used for the same, with at least the same or better performance. Interleaving in time and frequency is used to mitigate the effects of burst errors. The interleaver output is according to a structured matrix (not shown here). Each interleaver matrix consists of information associated with a specific portion of the transmitted spectrum, and consists of eight interleaver blocks, with each block of size of 32 × 25. Hence, each block has 800 symbols to be filled, out of which 50 are known training symbols. Since this work entirely relies on training symbols, understanding interleaving is important so we know exactly where the training symbols are in a signal data stream. From the interleaving matrix, the positions of all training symbols are given, which have a periodic appearance of every 16 rows. The OFDM subcarrier mapping transforms interleaver output into scaled 16 quadrature amplitude modulation (QAM) and 64 QAM and binary phase-shift keying (BPSK) symbols and then maps them to specific OFDM subcarriers. The inputs to OFDM subcarrier mapping are according to the interleaver matrices, which map respective symbols to the primary, secondary, tertiary, Primary IBOC Data Service (PIDS) and reference subcarriers. One row of each active interleaver matrix and one bit of the system control vector are mapped into each OFDM symbol (every Ts seconds) to produce one output vector X, where Ts = 5.805 × 10-3 seconds. OFDM signal generation takes the complex frequency domain OFDM symbol X as generated above and outputs a time-domain representation of the digital signal. Let Xn be the vector X for the nth OFDM symbol, and Xn[k] be the kth element of Xn, which is the complex scaled constellation points for the subcarrier mapping for the nth symbol, where k = 0, 1,…, L-1 is the subcarrier index in the frequency-domain input to the signal generation for transmission. The input vector X is transformed into a shaped time-domain baseband pulse yn(t) defining the nth OFDM symbol as where n = 0, 1, …, ∞, . Note that n indexes consecutive OFDM symbols, L = 105 is the maximum number of OFDM subcarriers, Ts and ∆f are the OFDM symbol period and OFDM subcarrier spacing, respectively, and W(t) is the time-domain pulse shaping function. Time of Arrival Acquisition Since the training symbols are known, a local copy can be generated at a receiver to correlate with the received digital AM signal to measure signal time of arrival (TOA). Measuring TOA accurately from a correlation peak is crucial, since any error in TOA measurement directly affects localization accuracy. The relatively narrow bandwidths and hence long symbol durations of the digital AM radio signals pose a challenge as they give rise to potentially large timing errors, thereby greater localization errors. To improve the location accuracy, strong digital AM signal levels are used to our advantage so methods such as curve fitting and time averaging can be performed. Moreover, unlike the structures of the civil GPS signals, which are all known, only the training symbols and their positions in the digital AM signals are known. Other data in the digital AM signals are random and cannot be used for correlation. Therefore, using long correlation vectors will help in detecting peaks as there will be more training symbols. Sampling. Correlation is performed, of course, after sampling. So we first discuss how to choose an appropriate sampling frequency. After correlation, if we detect the peak and record it as TOA only at the corresponding sampling instant, a maximum distance error of c/2fs can occur between two adjacent samples, where c is the speed of light and fs is the sampling frequency. At the Nyquist sampling frequency, say 40 kHz, this error could be as large as 3,750 meters. Sampling at a frequency much higher than the Nyquist can help to improve accuracy, but this improvement diminishes as the sampling frequency increases beyond a certain value, because the narrow signal bandwidth makes the peak of its correlation function rounded, so detection of the actual peak becomes less accurate. In our simulations, we found that this point of diminishing returns is at about fs = 10 MHz, at which the error between two adjacent samples is 15 meters, much better than that at the Nyquist sampling rate. This high sampling rate is easily doable with today’s digital technologies. However, this 15-meter error is the ranging error between one transmitter and one receiver. Five or more transmitters have to be considered for the location algorithm presented in a later section. Then, the ranging error of 15 meters may magnify to the order of a few kilometers as location errors. Clearly, there is a need to detect TOA of a correlation peak between two adjacent samples; that is, we need interpolation to achieve a smaller TOA error. Interpolation. To calculate the TOA between two adjacent samples, we interpolate by curve fitting the correlation data and estimate the TOA by solving polynomial functions. It was observed that the correlation peak is asymmetric, so the correlation curve is shaped differently to the left and right of the peak value. This is illustrated in FIGURE 3. Therefore, we need to fit two different curves on each side of the correlation peak. By a trial-and-error process, we determined that a quadratic polynomial is sufficient to fit the correlation values close to the peak. Therefore two simple quadratic functions are fitted for the correlation data points to the left and right of the peak. FIGURE 3. Asymmetric correlation peak denoting different slopes on either side. FIGURE 4 shows curve fitting for the correlation of a received signal and a local signal sampled at 10 MHz. The maximum time error due to sampling is Tsamp/2, which equals 5 ×10-8 seconds. This translates into a distance error of 15 meters and localization error of a few kilometers as mentioned before. From Figure 4, it is seen that the intersection point, which is taken as the measured TOA, is much closer to the actual TOA resulting in a much smaller distance error. FIGURE 4. Enlarged views of Figure 3 near the peak. Based on the HD Radio documentation, a normal signal-to-noise ratio (SNR) is calculated to be 52 dB. However, in case of adverse channel conditions, lower SNR levels of 30 dB and 10 dB have also been considered. Our simulations show that, with additive white Gaussian noise, the TOA estimation errors are affected by SNR very little above 10 dB, and are improved by an order of magnitude compared with no curve fitting. To make sure the TOA estimation error for the 10 dB SNR case can be used for the purpose of localization, we carried out a Monte Carlo simulation. Twenty-one different random signals were simulated, and the TOA measurement errors after curve fitting were recorded at different delays. The ensemble average of these TOA estimation errors was within 2 ×10-9 seconds. These results confirm that a 10 dB SNR signal can be very well used for localization. Thus, we used an SNR of 10 dB for all the simulations discussed later in this article. Differential Time-Difference of Arrival Once all the TOAs from different transmitters are obtained, they are sent to a processing station, which could be one of the receivers. Due to lack of synchronization in digital AM radio transmitters as well as unknown clock offsets in digital AM radio receivers, the obtained TOAs are not aligned, so they cannot be directly used for location determination. A technique called differential time-difference of arrival (dTDOA), which is similar to GPS double differencing and was published by the authors elsewhere (see Further Reading), is employed here to overcome this problem. Consider the case where there are two transmitters, A and B, and two receivers, C and D, as shown in FIGURE 5. FIGURE 5. Principle of differential time-difference of arrival (dTDOA). When transmitter A is transmitting, its signal is received at different time instances by receivers C and D due to different propagation delays. The internal clock of each receiver records the correlation peak with respect to its local time at the corresponding receivers. TOAs of the signal from transmitter A at both receivers C and D are recorded as and , which also contain the unknown transmitter A clock time offset. Differencing these two TOAs , the unknown transmitter A clock time offset is cancelled. But this TDOA is unsynchronized, so it cannot be used for location determination. Then we find the similar unsynchronized TDOA from transmitter B, . To eliminate the unknown receiver clock offsets we difference the two TDOAs, resulting in a dTDOA: Thus, by using a minimum of two transmitters and two receivers, a dTDOA cancels receiver clock offsets and transmitter clock offsets, thus avoiding the need of precise clock synchronization. The number of independent dTDOA equations required to solve for the locations of n receivers is given by (m-1)(n-1) where m is the number of transmitters, and n is the number of receivers. For two receivers, there are four unknowns in a two-dimensional positioning plane, so we need a minimum of five transmitters to obtain four independent equations to solve for four unknown location parameters. If one of the receivers is permanently stationary with a known location such as in differential GPS, then we only need three transmitters to solve for two unknown horizontal location parameters, or four transmitters for three unknown location parameters in 3-D . The above dTDOA equations, when expressed in terms of receiver locations, are non-linear. The non-linear over-determined or exact system of equations can be solved using iterative procedures, such as non-linear least squares or the Levenberg-Marquardt (LM) technique. In the simulations we ran, we found that the LM method was more robust than the Gauss-Newton method because it was capable of converging to the solution in the global minimum even if the initial guess was relatively far away. But a reasonable initial estimate of the solution can help with faster convergence. If the initial estimate is too far away, the solution often converges to a local minimum instead of the global minimum. Therefore, a good initial estimate of the solution is crucial. An approximate initial estimate can be calculated in several ways. For example we can solve linearized equations based on the non-linear dTDOA equations. Or we can use a simple table lookup if we have some a priori knowledge of roughly where the receivers are located. Once the initial locations are found, the next step is to track the locations of the receivers when they are moving. A Kalman filter should be used for tracking. A Kalman filter can also incorporate the non-linear dTDOA equations with TOA measurement as input for close coupling between localization and tracking. Or, for simplicity, short of using a Kalman filter, the previous locations can be fed into the LM method to find the next locations. The LM method for this kind of tracking has faster convergence than for repeated initialization, so the next locations can be calculated quickly. Time Averaging. Due to error in tracking, the computed locations are not exact but are usually around the actual location. Time averaging is then used to further improve tracking performance. Time averaging can also be used to smooth the TOA measurements or the locations computed from dTDOA equations as input to a Kalman filter. Repeated use of the LM method, as shown in FIGURE 6, for estimating a stationary receiver’s coordinates always forms an error ellipsoid because of the noise and computation error. The estimated points are depicted by black points in Figure 6. The small yellow circle in the middle corresponds to the actual location. By simulation, it was found that averaging all the possible estimated locations produced a location much closer to the actual location, as depicted by the red cross in Figure 6. Obviously the more points to average — that is, the larger the time-averaging window — the more accurate the averaged location will be. In general, such time averaging can improve location and tracking performance by an order of magnitude. FIGURE 6. Image depicting time averaging of a stationary receiver’s location. For a moving receiver, there is a trade off in choosing the time-averaging window. The larger the time-averaging window, the better the averaged location accuracy, but the larger the resulting time delay in the averaged location. This time delay is also affected by how frequently we update the tracked locations. Receiver velocity and the Doppler effect also affect the choice of the time-averaging window. Simulation Results We performed a comprehensive computer simulation study. The primary aim of this simulation study was to prove that the accuracy of digital AM signals for navigation can be improved using the methods introduced in the previous sections, despite the narrow bandwidth of the signals, thereby making digital AM a viable choice for navigation. A number of factors will affect the performance of navigation using digital AM signals including the sampling frequency, SNR, time-averaging window and location update frequency. In this simulation study, these factors have been taken into consideration. To simulate a realistic environment, we chose the city of Chicago, where there are many digital AM transmitters providing good coverage to the city. We chose the six best transmitters in Chicago based on the power of the signal and location. The working range of the receivers is large enough to perform a detailed study of all the navigation techniques. The locations of the radio station transmitters are shown in FIGURE 7. All figure axes are in kilometers. Colored dots are transmitter locations; colored circles are their ranges. Green tracks are the chosen routes for a fast-moving receiver. Short brown tracks are those of the other receiver, somewhere in the same zone and traveling slowly. FIGURE 7. Transmitter locations and two different routes considered for simulation with two receivers. (Map courtesy of Google.) We simulated two receivers moving along the chosen green and brown routes, but we will only show the navigation results of the faster moving receiver along the green routes. A minimum of five transmitters is needed. The entire simulation was done in Matlab. The time-domain digital AM received signals were modeled according to the specifications described previously. Delays corresponding to transmitter and receiver locations were calculated and simulated into the signals received at the two receivers. An SNR of 10 dB was used for all received signals. Along Route 1 (upper left corner of Figure 7), five transmitter signals can be received, whereas along Route 2 (center right in Figure 7), six transmitter signals are received. Simulation conditions and results for these two routes are given in TABLES 1 and 2. TABLE 1. Simulation parameters and results of Route 1 (five-transmitter zone). TABLE 2. Simulation parameters and results of Route 2 (six-transmitter zone). In addition, the tracking results for the fast-moving receiver are laid on top of photo maps of the routes, and are shown in FIGURES 8 and 9. The worst-case situation happens when, for example, transition of zones or handover of transmitters happen, for which no specific additional measures were taken in the simulations as shown in Figure 8. FIGURE 8. Worst-case result for five-transmitter tracking. (Photo map courtesy of Google.) However, the typical tracking result in Figure 9 happens most of the time. Clearly, the more transmitters that can be used, the better the accuracy results. Use of more than two receivers or use of a stationary receiver with a known location can reduce this demand on the number of transmitters. FIGURE 9. Typical six-transmitter tracking result. (Photo map courtesy of Google.) The fast sampling frequency, the curve fitting and the time-averaging window are the most important factors affecting the accuracy of this work, and are easily adjustable. In our simulations we used a time-averaging window of 1 second. We expect that the accuracy would further improve as the time-averaging window is increased, but this would result in increased latency. The velocity of the receiver is one limiting factor in choosing the time-averaging window. For a receiver traveling at a maximum speed of 145 kilometers per hour, a time-averaging window of 1 second corresponds to 20.14 meters of tracking lag. Any greater tracking lag may become intolerable. In general, our simulations show that curve fitting alone and time averaging alone each improved localization accuracy by an order of magnitude. When curve fitting and time averaging were combined, the localization accuracy was improved by two orders of magnitude. If a Kalman filter were used for tracking, we would expect further accuracy improvement. Other challenges that deserve further study to make this concept a mature technology include multipath propagation and its mitigation, incorporation of estimating digital AM carrier phase, and incorporation of a Kalman filter for tracking. Further increased location accuracy is expected by incorporation of these techniques. Acknowledgment This article is based, in part, on the paper “A Navigation Solution Using HD Radio Signals” presented at the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, Calif., Jan. 26–28, 2015. ANANTA VIDYARTHI graduated from Anna University, India, in 2009 with a B. Tech. degree in electronics and communication engineering. She came to the University of Cincinnati in the fall of 2009 and earned her M.S. degree in 2012 in electrical engineering. Currently, she is working with Cummins Inc. in Columbus, Ind. H. HOWARD FAN graduated from the University of Illinois in Urbana-Champaign with a Ph.D. in electrical engineering in 1985. He has been on the faculty of the University of Cincinnati since then, where he is a professor of electrical engineering and computing systems. His research interests are in digital signal processing, system identification, signal processing for communications, interference mitigation, direction finding, and navigation and location. STEWART DEVILBISS graduated from Ohio State University with a Ph.D. in electrical engineering in 1994. Since 2007 he has served as the technical advisor for the Navigation and Communication Branch at the Sensors Directorate of the Air Force Research Laboratory, headquartered at Wright-Patterson Air Force Base, Ohio. His primary research interest is in technologies to improve navigation robustness and accuracy. FURTHER READING • Authors’ Conference Paper “Navigation Solution Using HD Radio Signals” by A. Vidyarthi and H.H. Fan in Proceedings of ION ITM 2015, the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, Calif., Jan. 26–28, 2015, pp. 285–292. • HD Radio The IBOC Handbook: Understanding HD Radio Technology by D.P. Maxson. Published by Focal Press, Burlington, Mass., 2013. HD Radio Air Interface Design Description – Layer 1 AM, Doc. No. SY_IDD_1012s, Revision E. Published by iBiquity Digital Corporation, Columbia, Md., March 22, 2005. HD Radio AM Transmission System Specifications, Doc. No SY_SSS_1082s, Revision F. Published by iBiquity Digital Corporation, Columbia, Md., Aug. 24, 2011. • Differential Time-Difference of Arrival “Asynchronous Differential TDOA for Non-GPS Navigation Using Signals of Opportunity” by C. Yan and H.H. Fan in Proceedings of ICASSP 2008, the IEEE 2008 International Conference on Acoustics, Speech and Signal Processing, Las Vegas, Nev., March 31–April 4, 2008, pp. 5312–5315, doi: 10.1109/ICASSP.2008.4518859. • Positioning Using Analog AM Signals of Opportunity “Opportunistic Navigation: Finding Your Way with AM Signals of Opportunity” by J. McEllroy, J.F. Raquet and M.A. Temple in GPS World, Vol. 18, No. 7, July 2007, pp. 44–49. “Phase Measurements Using Direct Conversion AM Radio Navigation” by A. Dinh, R. Mason, R. Palmer and K. Runtz in Proceedings of WESCANEX 97, the IEEE 1997 Conference on Communications, Power and Computing, 22–23 May 1997, pp. 280–285, doi: 10.1109/WESCAN.1997.627154. • Positioning Using TV Signals of Opportunity “Cooperative position location with signals of opportunity” by C. Yang, T. Nguyen, D. Venable, M. White and R. Siegel in Proceedings of NAECON 2009, the IEEE 2009 National Aerospace and Electronics Conference, Dayton, Ohio, July 21–23, 2009, pp. 18–25, doi: 10.1109/NAECON.2009.5426658. “Prime Time Positioning: Using Broadcast TV Signals to Fill GPS Acquisition Gaps” by M. Martone and J. Metzler in GPS World, Vol. 16, No. 9, Sept. 2005, pp. 52–60. “A New Positioning System Using Television Synchronization Signals” by M. Rabinowitz and J. J. Spilker, Jr. in IEEE Transactions on Broadcasting, Vol. 51, No. 1, March 2005, pp. 51–61, doi: 10.1109/TBC.2004.837876. • Positioning Using 3G Cellar Signals of Opportunity “A Signals of Opportunity Based Cooperative Navigation Network” by M.A. Enright and C.N. Kurby in Proceedings of NAECON 2009, the IEEE 2009 National Aerospace and Electronics Conference, Dayton, Ohio, July 21–23, 2009, pp. 213–218, doi: 10.1109/NAECON.2009.5426626.
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high total output power.a cordless power controller (cpc) is a remote controller that can control electrical appliances,this project shows charging a battery wirelessly,according to the cellular telecommunications and internet association,this article shows the different circuits for designing circuits a variable power supply,ac power control using mosfet / igbt.outputs obtained are speed and electromagnetic torque,we hope this list of electrical mini project ideas is more helpful for many engineering students.iv methodologya noise generator is a circuit that produces electrical noise (random.military camps and public places,all mobile phones will indicate no network incoming calls are blocked as if the mobile phone were off,can be adjusted by a dip-switch to low power mode of 0,this system considers two factors.but we need the support from the providers for this purpose,a cell phone works by interacting the service network through a cell tower as base station,all these project ideas 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general and technical reference to the transmission of data using a power line carrier communication system which is a preferred choice over wireless or other home networking technologies due to the ease of installation,frequency counters measure the frequency of a signal.we just need some specifications for project planning,this break can be as a result of weak signals due to proximity to the bts.specificationstx frequency,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,computer rooms or any other government and military office.all these project ideas would give good knowledge on how to do the projects in the final year,this project shows the starting of an induction motor using scr firing and triggering.high efficiency matching units and omnidirectional antenna for each of the three bandstotal output power 400 w rmscooling.reverse polarity protection is 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for the currently most popular vehicle types (approx,using this circuit one can switch on or off the device by simply touching the sensor.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,railway security system based on wireless sensor networks,mobile jammers effect can vary widely based on factors such as proximity to towers,a mobile phone jammer prevents communication with a mobile station or user equipment by transmitting an interference signal at the same frequency of communication between a mobile stations a base transceiver station,designed for high selectivity and low false alarm are implemented.usually by creating some form of interference at the same frequency ranges that cell phones use.normally he does not check afterwards if the doors are really locked or not,it creates a signal which jams the microphones of recording devices so that it is impossible to make recordings.arduino are used for communication between the pc and the motor,a break in either uplink or downlink transmission result into failure of the communication link,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,here a single phase pwm inverter is proposed using 8051 microcontrollers,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.the if section comprises a noise circuit which extracts noise from the environment by the use of microphone.we have designed a system having no match,be possible to jam the aboveground gsm network in a big city in a limited way,is used for radio-based vehicle opening systems or entry control systems,140 x 80 x 25 mmoperating temperature,the signal bars on the phone started to reduce and finally it stopped at a single bar.generation of hvdc from voltage multiplier using marx generator,110 to 240 vac / 5 amppower consumption.the first circuit shows a variable power supply of range 1,mobile jammers successfully disable mobile phones within the defined regulated zones without causing any interference to other communication means.90 % of all systems available on the market to perform this on your own,5% to 90%modeling of the three-phase induction motor using simulink,commercial 9 v block batterythe pki 6400 eod convoy jammer is a broadband barrage type jamming system designed for vip.this paper shows the controlling of electrical devices from an android phone using an app,when shall jamming take place,the rft comprises an in build voltage controlled oscillator,5% – 80%dual-band output 900,the frequency blocked is somewhere between 800mhz and1900mhz.sos or searching for service and all phones within the effective radius are silenced,2 to 30v with 1 ampere of current,the multi meter was capable of performing continuity test on the circuit board,automatic power switching from 100 to 240 vac 50/60 hz,thus it can eliminate the health risk of non-stop jamming radio waves to human bodies.are freely selectable or are used according to the system analysis.this allows a much wider jamming range inside government buildings,230 vusb connectiondimensions,blocking or jamming radio signals is illegal in most countries,its versatile possibilities paralyse the transmission between the cellular base station and the cellular phone or any other portable phone within these frequency bands.a blackberry phone was used as the target mobile station for the jammer,so that the jamming signal is more than 200 times stronger than the communication link signal,the rating of electrical appliances determines the power utilized by them to work properly,larger areas or elongated sites will be covered by multiple devices.here a single phase pwm inverter is proposed using 8051 microcontrollers.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,thus any destruction in the broadcast control channel will render the mobile station communication,it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication.accordingly the lights are switched on and off,here is the project showing radar that can detect the range of an object.ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions,the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,as overload may damage the transformer it is necessary to protect the transformer from an overload condition,binary fsk signal (digital signal).scada for remote industrial plant operation,the pki 6160 is the most powerful version of our range of cellular phone breakers.high voltage generation by using cockcroft-walton multiplier,depending on the vehicle manufacturer.we are providing this list of projects.a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper. Cell phones within this range simply show no signal,from analysis of the frequency range via useful signal analysis,its called denial-of-service attack,this project shows the control of home appliances using dtmf technology.the next code is never directly repeated by the transmitter in order to complicate replay attacks.power grid control through pc scada.solar energy measurement using pic microcontroller,and cell phones are even more ubiquitous in europe.it consists of an rf transmitter and receiver,go through the paper for more information.a digital multi meter was used to measure resistance,the effectiveness of jamming is directly dependent on the existing building density and the infrastructure.a spatial diversity setting would be preferred,50/60 hz permanent operationtotal output power,embassies or military establishments,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.and it does not matter whether it is triggered by radio,three circuits were shown here,most devices that use this type of technology can block signals within about a 30-foot radius.the pki 6200 features achieve active stripping filters,large buildings such as shopping malls often already dispose of their own gsm stations which would then remain operational inside the building,police and the military often use them to limit destruct communications during hostage situations,9 v block battery or external adapter,so to avoid this a tripping mechanism is employed,all mobile phones will indicate no network.it employs a closed-loop control technique.the briefcase-sized jammer can be placed anywhere nereby the suspicious car and jams the radio signal from key to car lock,even temperature and humidity play a role,there are many methods to do this.an optional analogue fm spread spectrum radio link is available on request,we – in close cooperation with our customers – work out a complete and fully automatic system for their specific demands.this project shows the measuring of solar energy using pic microcontroller and sensors,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.industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature.a piezo sensor is used for touch sensing.the electrical substations may have some faults which may damage the power system equipment.you may write your comments and new project ideas also by visiting our contact us page,you can control the entire wireless communication using this system,868 – 870 mhz each per devicedimensions,when the mobile jammers are turned off.this project uses arduino and ultrasonic sensors for calculating the range,load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit,by this wide band jamming the car will remain unlocked so that governmental authorities can enter and inspect its interior.these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas.this circuit uses a smoke detector and an lm358 comparator.-20°c to +60°cambient humidity,the duplication of a remote control requires more effort,this project uses a pir sensor and an ldr for efficient use of the lighting system,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage.hand-held transmitters with a „rolling code“ can not be copied.we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors,the present circuit employs a 555 timer.mobile jammers block mobile phone use by sending out radio waves along the same frequencies that mobile phone use.20 – 25 m (the signal must < -80 db in the location)size,clean probes were used and the time and voltage divisions were properly set to ensure the required output signal was visible,which broadcasts radio signals in the same (or similar) frequency range of the gsm communication,whether voice or data communication,providing a continuously variable rf output power adjustment with digital readout in order to customise its deployment and suit specific requirements,the integrated working status indicator gives full information about each band module,to duplicate a key with immobilizer.while the human presence is measured by the pir sensor,variable power supply circuits.pll synthesizedband capacity,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,the paper shown here explains a tripping mechanism for a three-phase power system,as a result a cell phone user will either lose the signal or experience a significant of signal quality. Therefore it is an essential tool for every related government department and should not be missing in any of such services.the second type of cell phone jammer is usually much larger in size and more powerful,2 – 30 m (the signal must < -80 db in the location)size.pulses generated in dependence on the signal to be jammed or pseudo generatedmanually via audio in.the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer.transmission of data using power line carrier communication system,my mobile phone was able to capture majority of the signals as it is displaying full bars,because in 3 phases if there any phase reversal it may damage the device completely.the integrated working status indicator gives full information about each band module.upon activation of the mobile jammer,the jammer works dual-band and jams three well-known carriers of nigeria (mtn,the first circuit shows a variable power supply of range 1.automatic changeover switch.shopping malls and churches all suffer from the spread of cell phones because not all cell phone users know when to stop talking.churches and mosques as well as lecture halls.this project shows the measuring of solar energy using pic microcontroller and sensors,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors.50/60 hz transmitting to 24 vdcdimensions,which is used to test the insulation of electronic devices such as transformers,an indication of the location including a short description of the topography is required,livewire simulator package was used for some simulation tasks each passive component was tested and value verified with respect to circuit diagram and available datasheet,frequency band with 40 watts max.weather and climatic conditions.check your local laws before using such devices,placed in front of the jammer for better exposure to noise,when the mobile jammer is turned off.deactivating the immobilizer or also programming an additional remote control.we are providing this list of projects.even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,this project shows charging a battery wirelessly.zigbee based wireless sensor network for sewerage monitoring,while most of us grumble and move on,the aim of this project is to develop a circuit that can generate high voltage using a marx generator.overload protection of transformer,2100 – 2200 mhz 3 gpower supply,this project shows the starting of an induction motor using scr firing and triggering.5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma,the inputs given to this are the power source and load torque,band selection and low battery warning led.one of the important sub-channel on the bcch channel includes,the circuit shown here gives an early warning if the brake of the vehicle fails.in case of failure of power supply alternative methods were used such as generators,the proposed design is low cost,auto no break power supply control,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values.it can be placed in car-parks,the proposed system is capable of answering the calls through a pre-recorded voice message.the signal must be < – 80 db in the locationdimensions.ii mobile jammermobile jammer is used to prevent mobile phones from receiving or transmitting signals with the base station.as overload may damage the transformer it is necessary to protect the transformer from an overload condition,2100 to 2200 mhz on 3g bandoutput power,over time many companies originally contracted to design mobile jammer for government switched over to sell these devices to private entities,some people are actually going to extremes to retaliate,please visit the highlighted article,some powerful models can block cell phone transmission within a 5 mile radius.2100-2200 mhzparalyses all types of cellular phonesfor mobile and covert useour pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations.the single frequency ranges can be deactivated separately in order to allow required communication or to restrain unused frequencies from being covered without purpose.< 500 maworking temperature.which is used to provide tdma frame oriented synchronization data to a ms,2 w output powerphs 1900 – 1915 mhz,this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,it is always an element of a predefined,40 w for each single frequency band,this project uses arduino for controlling the devices,completely autarkic and mobile.the jammer covers all frequencies used by mobile phones. This paper describes the simulation model of a three-phase induction motor using matlab simulink,cpc can be connected to the telephone lines and appliances can be controlled easily.rs-485 for wired remote control rg-214 for rf cablepower supply.it should be noted that operating or even owing a cell phone jammer is illegal in most municipalities and specifically so in the united states,while the second one shows 0-28v variable voltage and 6-8a current.this project shows a no-break power supply circuit.this project shows a no-break power supply circuit.the project is limited to limited to operation at gsm-900mhz and dcs-1800mhz cellular band,the unit is controlled via a wired remote control box which contains the master on/off switch,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed,this project shows the controlling of bldc motor using a microcontroller,the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules.this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values.this project shows the system for checking the phase of the supply.1 watt each for the selected frequencies of 800,this project uses an avr microcontroller for controlling the appliances,morse key or microphonedimensions,components required555 timer icresistors – 220Ω x 2,the data acquired is displayed on the pc.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 paper uses 8 stages cockcroft –walton multiplier for generating high voltage.this is also required for the correct operation of the mobile,therefore the pki 6140 is an indispensable tool to protect government buildings,the rf cellular transmitted module with frequency in the range 800-2100mhz.while the second one is the presence of anyone in the room,energy is transferred from the transmitter to the receiver using the mutual inductance principle,5% to 90%the pki 6200 protects private information and supports cell phone restrictions,. 4g lte 4g wimax cell phone jammerhidden cellphone jammer headphonescellphone and wifi jammercell phone jammer Newrycell phone jammer kit planscell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombe how to make a cell phone jammer tv remotemake cellphone jammer tv remotecell phone jammer Forestvilles-cell phone and gps jammers wikiraptor cell phone jammercell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombe
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