Signal jammer legal exchange , jammer legal help now

An Answer for Precise Positioning Research By Thomas Pany, Nico Falk, Bernhard Riedl, Tobias Hartmann, Günter Stangl, and Carsten Stöber INNOVATION INSIGHTS by Richard Langley WHAT IS THE IDEAL GNSS RECEIVER? Well, that depends on what you mean by “ideal.” If we take it to mean the simplest, conceptually, yet the most capable and adaptable receiver, then we would just connect an analog-to-digital converter (ADC) to an antenna and pass the converter’s output to a digital signal processor whose software would transform the received signal into the desired result with the utmost speed and precision. There are certain technological limitations that currently preclude fully developing such a device but we are getting very close to the ideal and practical implementations already exist. Such a GNSS receiver is an example of a software-defined radio — a radio-communications architecture in which as much of the operation of a receiver (or a transmitter) as feasible is performed by software in an embedded system or on a personal computer (PC). Now, we can’t simply connect an ADC to an antenna since the strength of GNSS signals falls well below the sensitivity threshold of real ADCs and those that can directly digitize microwave radio frequencies are rather power hungry. Therefore, the front end of a real software GNSS receiver includes a low-noise preamplifier, filters, and one or more downconverters to produce an analog intermediate-frequency signal that passes to a high-speed ADC. The digitized signal is provided at the output of the front end in a convenient format, which, for processing signals on a PC, is typically USB 2.0 with its maximum signaling rate of 480 megabits per second. All baseband signal processing is then carried out in the programmable microprocessor. Software GNSS receivers offer a number of advantages over their hardware cousins. Foremost is their flexibility, which permits easy and rapid changes to accommodate new radio frequency bands, signal modulation types and bandwidths, and baseband algorithms. This flexibility is beneficial not only for multi-GNSS operation but also for prototyping algorithms for conventional hardware designs. Another advantage is their use in embedded systems such as smartphones and wireless personal digital assistants. Software GNSS receivers are also a boon for teaching, where a student can tweak a particular operating parameter and immediately see the effect. And given their remarkable flexibility, software GNSS receivers can be adapted to a variety of special scientific and engineering research applications such as reflectometry and signal analysis. In this month’s “Innovation,” we look into the development and capabilities of one modern software GNSS receiver in an effort to answer the question “What is the ideal GNSS receiver for precise positioning research?” “Innovation” is a regular feature that discusses advances in GPS technology andits 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. Personal-computer-based software receivers have found broad use as R&D tools for testing new signal processing algorithms, for analyzing received GNSS signals, and for integrating various sensors with GNSS. Software receivers also provide a consistent framework for GNSS signal samples, correlator values, pseudoranges, positions, assistance data, and sensor (inertial) data, and often act as integration platforms for prototype navigation systems. The distinctive feature of PC-based software receivers is their ability to work in post-processing mode in addition to real-time operation and the support of high-performance central processing units (CPUs). So far, software receivers are typically not used as operational receivers — neither in the mass market, nor in the professional sector, nor as a reference station where a PC would already be available. The last point can be explained by the fact that most software receivers can only process a limited number of frequency bands (sometimes just L1) and are often limited to small bandwidth signals (such as that of the L1 C/A-code signal or the L2 civil signal (L2C)). Improvements of the PC-based software receiver SX-NSR achieved at the end of 2010 and in early 2011 try to overcome these limitations. They include the first real-time implementation of P-code processing on L2, a unique method for processing the ultra-wide Galileo AltBOC signals on E5, and a method to synchronize two NavPort-4 frontends (each supporting four frequency bands of 15 MHz bandwidth) via a hardware link. The SX-NSR, which has been developed in cooperation with the Universität der Bundeswehr München in Munich, Germany, runs under the Windows operating system (XP or 7) and supports processing of GNSS signals plus sensor data (such as that from an inertial measurement unit, or IMU) in real time and in post-processing mode. It supports all the civil GPS, GLONASS, Galileo, and Compass signals. User-defined signals can be included by providing the pseudorandom noise (PRN) codes and the associated tracking parameters. The computational real-time performance can be characterized by two rules-of-thumb for acquisition and tracking. Acquisition is based on a flexible coherent and noncoherent integration and may be accelerated by a graphics card based on the Compute Unified Device Architecture (CUDA) — a parallel-computing architecture developed by Nvidia for graphics processing but also useful for accelerating non-graphics applications. Depending on the graphics card type, a few million or many millions of equivalent correlators are available to detect even the weakest signals quickly. Stable tracking is done with multiple correlators. An x86 CPU core supports around 20 channels (for a laptop) to 30 channels (for a PC) at an average CPU load below 50–60 percent. With that CPU load, the software has enough reserve (in terms of the size of the sample buffer) to cope with latencies introduced by the non-real-time Windows operating system. In post-processing, a virtually unlimited number of channels or correlators is available. The SX-NSR software typically connects to the NavPort-4 front end via a single USB 2.0 connector. One front end supports four RF paths with 15-MHz bandwidth in the L-band. One band is sampled at 40.96 MHz with 12-bit precision. Small batches of samples are transferred with 12 bits at regular intervals to the PC for increased spectral analysis possibilities but the continuous transfer is usually done with just 2 bits. Decimation by a factor of two (yielding a sample rate of 20.48 MHz) and/or bit reduction are options to limit the data transfer bandwidth on the USB bus. The NavPort also includes configurable notch and finite-impulse-response (FIR) filters working with 12-bit precision and 40.96-MHz data rate. The SX-NSR further supports standard output formats (such as Receiver Independent Exchange (RINEX) format or that of the Radio Technical Commission for Maritime Services (RTCM)), has a graphical user interface, and a freely user-accessible application programming interface (API) in the C programming language. A reference station was established with the SX-NSR for the International GNSS Service (IGS) Multi-GNSS Experiment (M-GEX) starting on February 1, 2012, at the Observatory Graz in Austria (marker name GRAB). The data is routinely processed by the European Reference Frame analysis center at Observatory Lustbuehel, Graz, Austria, with Bernese Software 5.0, and shows results with a quality that is virtually no different than that of commercial hardware receivers. All-in-view tracking of the four GNSS constellations on all frequencies (see TABLE 1) has been achieved with an off-the-shelf $1,000 PC, two synchronized NavPorts, and the SX-NSR software. In particular, the front end receives Compass B1, B2, and B3 signals and currently the software is tracking two of the geostationary Earth orbit (GEO) satellites, a few of the inclined geosynchronous orbit (IGSO) satellites, and the medium Earth orbit (MEO) satellites at Graz on B1 and B2. There are plans to implement tracking of the B3 signal for the M1 satellite and that of satellite-based augmentation system (SBAS) satellites on L5. Table 1. Frequency bands supported by the dual NavPort-4 receiver. Typical received carrier-to-noise-density-ratio (C/N0) values recorded at station GRAB are shown in FIGURE 1. Freely accessible GRAB data in RINEX format can be downloaded from several data archive sites (see Further Reading online). The SX-NSR software receiver provides a GNSS development and research framework with the API opening it up for user-implemented algorithms. The user may implement only small portions of new code (such as a special acquisition technique) and for the rest of the receiver rely on the well-known behavior of the SX-NSR’s framework. A number of applications are possible using the flexibility of a software receiver; some of them are described in this article. Figure 1. C/N0 values for five typical satellites, one each for GPS, GLONASS, Galileo, Compass, and the European Geostationary Navigation Overlay Service (EGNOS) SBAS as recorded at Observatory Graz. The Front End The front-end frequency plan was adjusted to have a clean spectrum free of internal interference. This is of utmost importance as software receivers are often used to detect and mitigate interference especially for the Galileo E5 and E6 frequency bands due to overlapping radio navigation services. An inter-front-end link enables synchronization of two NavPort-4 devices. It generates a synchronous reference clock for a proper phase relationship. Moreover, a trigger is used to adjust the digital data stream of both devices. One possible application of the inter-front-end link technology is to easily double the number of available GNSS frequencies. Another possible application is the building of a dual-antenna solution. For this purpose, each NavPort-4 device handles the same GNSS frequencies, but from different antennas. Whereas within each NavPort, a quad analog-to-digital converter (ADC) synchronously samples the four received GNSS signals, the synchronicity between two NavPorts is more complex. For the inter-front-end link, both devices have to use the same 10-MHz clock reference for a synchronous setup. This is reached by using the reference clock output of the master device as reference clock input of the slave device as depicted in FIGURE 2. It is also possible to connect both NavPort-4 devices to a single external clock reference. Each device generates its own 40.96-MHz sample rate from this reference. The phase difference of the 40.96-MHz sample rate is measured in the master and slave with a phase detector. The first input of the detector is the local 40.96-MHz clock. The second input is the 40.96-MHz clock from the other NavPort-4 with a different phase alignment due to ambiguities in its generation and cable delay. The phase detector measures the phase difference between both clocks. The low-pass-filtered output of this measurement is digitized with an ADC. If this measurement is within a phase range of ±7 degrees at 40.96 MHz, which corresponds to ±14 centimeters, the coarse synchronization is finished. If the value is not within this range, the synchronization algorithm repeats. After starting the data processing for both devices simultaneously with an implemented digital trigger, the phase difference between master and slave clock could be measured continuously for later fine-tuning in the SX-NSR to achieve an accuracy of much below 1 degree at 40.96 MHz, which corresponds to ±2 centimeters. The synchronization algorithm is verified by connecting two L1-capable NavPorts to the same antenna. The phase and code delay can then be determined from receiver single-differences of GPS L1 C/A-code-derived phase and code measurements. Actually, this delay estimation is part of an attitude solution (see below) and an example is shown in FIGURE 3. The code delay here is around 50 centimeters and includes the RF filter delay difference of around 40 centimeters (which can be calibrated and is stable over power cycles) in addition to the synchronization delay (here around 10 centimeters). The phase delay is naturally determined modulo one cycle and shows warm-up effects of 1.4 centimeters during the first few minutes of operation. Figure 3. Inter-front-end hardware delay variation on a GPS L1 signal. GNSS Reference Station Although the GPS modernization process is ongoing and more and more L2C-capable satellites are in orbit, tracking of the encrypted P-code signal on L2 is still a key element for any receiver to be considered as a reference station or geodetic receiver. Dual-frequency observations need to be available for the full GPS constellation. A possible option to retrieve full wavelength carrier-phase observations and code ranges on L2 is cross-correlation tracking of the encrypted P-code signal. The receiver computes the cross-correlation function between the raw L1 and L2 samples over a long coherent interval as shown in FIGURE 4. The encrypted P-code stream, identical on L1 and L2, is represented by c(tµ). Figure 4. Cross-correlation block diagram. A receiver internal complex carrier is generated (see frequency compensation in Figure 4), whose frequency equals the Doppler shift frequency plus the intermediate-frequency difference between L1 and L2. This frequency is generally different for each satellite. The L1 signal is delayed to compute the cross-correlation function for several code-phase taps. The cross-correlation function is computed using the predicted Doppler difference based on the Doppler frequency estimated from L1 with complex-valued baseband samples. A number of batches are collected and a post-correlation fast Fourier transform is applied. The parameter values shown in TABLE 2 result in a total coherent integration time of 6.4 seconds. Table 2. SX-NSR cross-correlation parameter values. The result is the cross-correlation function as a function of code phase and Doppler. Using interpolation techniques, the position of the peak is determined, which then gives the delay and Doppler shift of the L2 signal with respect to the L1 signal. The complex argument of the peak value gives the L2-L1 carrier-phase differences. Those differences are filtered and are then added to the L1 parameters to give the L2P code estimates. We use two first-order Kalman filters (one for the code, one for the phase) to smooth the cross-correlation estimates. The code filter is updated with the estimated delay and the Doppler; the phase filter is updated with the estimated Doppler and phase. Cycle slips are detected if the L1-L2 phase changes are too high. Loss-of-lock is detected by comparing the estimated L2 C/N0 value against a threshold. After several Kalman filter tuning steps, the L2P signal is tracked down to low elevation angles. For example, the GPS Block IIF satellite PRN1 was tracked over a whole pass without cycle slips as shown in the code-minus-carrier plot in FIGURE 5.  Figure 5. Code minus carrier-phase measurements for GPS PRN1 at site GRAB on day of year 106, 2012. One of the key applications of a professional GNSS receiver is its use as a GNSS reference station. Using a software receiver for this purpose would also provide increased monitoring capabilities to detect (un)intentional inference via RF spectral analysis or to detect signal anomalies due to satellite failures or multipath. Furthermore, it is useful for a number of scientific experiments and research topics such as scintillation monitoring or atmospheric occultation studies. Other GNSS Signals The inclusion of new GNSS signals in a software receiver is typically straightforward. The PRN codes need to be loaded and the tracking parameters (such as carrier frequency, integration time, error correction scheme, phase relation of signal components data/pilot, correlator positions, and discriminator type) can be selected without source code modification. If a hand-over from a different signal is performed (such as from GPS L1 to GPS L5) and if the first signal has already been synchronized to the transmit time by decoding the time-of-week, then it is possible to directly resolve the code ambiguity of the new signal. If this is not possible, a navigation message decoder has to be implemented to retrieve the time-of-week, which mostly has to be in the source code. Galileo AltBOC. An important exception to this rule is the Galileo AltBOC signal due to its high bandwidth. A conventional view on the AltBOC signal processing would require a sample rate of at least two times the total signal bandwidth. Depending on how many outer AltBOC side lobes are considered, this results in a sampling rate of 102 megasamples per second or more. This is undesirable for a cost-efficient software receiver solution, regarding the data transfer and the CPU load. The AltBOC processing inside the SX-NSR relies on the fact that both frequency bands E5a and E5b are sampled coherently and this coherency can be exploited to reconstruct the full AltBOC signal. The accuracy of the AltBOC navigation signal is concentrated in the main BOC sidelobes itself. More specifically, the thermal noise and multipath performance are dependent on the Gabor bandwidth, which represents the curvature of the correlation function at the tracking point. Thus a similar Gabor bandwidth can be obtained by sampling the E5a and the E5b band separately. This is the key idea of the resulting AltBOC processing scheme. The E5a and E5b signal samples are generated synchronously inside the same ADC chip and are transferred via the USB bus to the PC running the SX-NSR. The SX-NSR first acquires and tracks the signal separately on E5a and E5b. As it is quite efficient to run the E5a and E5b tracking on separate threads (and on separate CPU cores), the combination of E5a and E5b correlation values to E5 correlation values is done at the post-correlation level. There is no feedback from the E5 channel to the E5a/b channels. The channel maintains its own numerically controlled oscillator (NCO). A dedicated transformation is used to account for NCO differences between the E5a/b NCO values and the E5 NCO values. It is basically a sinc-interpolation in the code-phase direction and accounts for Doppler and carrier-phase differences. The transformed correlation values are added and yield an approximation to the AltBOC correlation function. The E5 correlation values are used to compute the discriminator values to update the E5 tracking loops. The E5 NCO values are used to compute the code pseudoranges and carrier-phase measurements, the Doppler frequency, and the C/N0 values, which are the primary outputs of the E5 receiver. Although the E5 receiver is a somehow a virtual receiver (that is, without correlators), it has the same user interface including most of the configuration parameters, output (for example, multi-correlator), and API. With AltBOC tracking, the Galileo satellites deliver code and phase measurements on five different carrier frequencies. A code-minus-carrier plot is shown in FIGURE 6. The code accuracy of the AltBOC signal is striking. The E6 signal is severely impacted by the present interference, and phase tracking is only possible for higher elevation angles. Figure 6. Code minus carrier-phase measurements for Galileo PRN12 at site GRAB on day of year 104, 2012. Polyfit and Vector Tracking A software receiver should provide a transparent way to retrieve pseudorange measurements that is well understood and can be well modeled. It should also provide a flexible input to control tracking NCO values. Both points are important if the receiver is part of larger navigation system (such as an integrated GNSS/INS system). Conventional delay-lock loop (DLL) / frequency-lock loop (FLL) / phase-lock loop (PLL) configuration is one option and is well understood by all GNSS researchers and engineers. It has, however, two major drawbacks. The loops introduce time correlations that cannot be easily modeled in a positioning Kalman filter, especially if low bandwidths (carrier aiding) are used. Second, the internal parameters of a DLL are difficult to match to a deeply coupled GPS/INS system. One way to overcome this is a method called polyfit tracking based on a rather old Jet Propulsion Laboratory patent (U.S. Patent No. 4821294). The idea behind this is to decouple pseudorange determination from the NCO counters. This is accomplished by forming the pseudoranges at the integrate-and-dump rate (such as 50 Hz) and to add the discriminator values to them. The resulting pseudorange is then obtained via a polyfit over the measurement interval. The time correlation of the measurements is solely determined by the discriminator values, and they compensate for the NCO correlations. A nice example is the application of this method to vector tracking. In vector tracking the NCO values are determined via a line-of-sight projection of the last position, velocity, and time (PVT) estimate and this estimate is usually slightly delayed. Furthermore, the line-of-sight projection is not perfect due to inevitable modeling errors (such as atmospheric delay errors). Thus the NCO does not follow the received signal as well as for DLL/FLL/PLL tracking. This is not a problem as the difference is captured in the discriminator values. FIGURE 7 shows the output of the method for a measurement interval of 0.5 second, one GPS C/A-code signal and for a dynamic user. The PVT update happens with a delay of about 100 milliseconds, changing the Doppler frequency. This resulting phase slope discontinuity is nicely compensated by the phase discriminator. The actual measurements are marked as brown stars in Figure 7. The method can also be applied to slave a channel to a master channel. This is useful for reflectometry, for example, where the master channel locks onto a line-of-sight signal and the slave channel tracks the reflected signal from sea surface. Figure 7. NCO-based phases (green) plus discriminator values (yellow) and polyfit for carrier-phase, code, and Doppler tracking (dynamic user, GPS C/A-code tracking). With multiple correlators (for example, nine correlators equally spaced from -0.5 to 0.3 chip for GPS C/A-code tracking), the polyfit method can be extended in a natural way to estimate and mitigate multipath. Using the polyfit carrier estimate, the multi-correlator values are coherently combined over the measurement interval and then a correlation function model is fitted to it. An eventually presented data bit is estimated and wiped off. The correlator fit starts with the assumption that only the line-of-sight signal is present. If the chi-squared value is above a certain threshold, the correlator fit is repeated assuming additionally one multipath signal. Up to two multipath signals can be estimated. The performance of this method can be tested with an RF signal generator. The scenario includes the line-of-sight signal (GPS C/A-code) and one multipath signal. The initial multipath delay is 0 meters and increases slowly (5.7 millimeters per second). The standard tracking method uses a multipath-mitigating double-delta code discriminator formed from four correlators (-0.2, -0.1, 0.1, 0.2) and an arctan carrier discriminator. Standard tracking is used to control the NCO values. FIGURE 8 shows that multipath is detected for delays larger than 15 meters. The detection performance depends on the carrier-phase difference of the line-of-sight and multipath signal, but for delays larger than 32 meters, multipath is always detected. If multipath is detected, the corrected ranges and C/N0 values are significantly improved. Figure 8. SX-NSR real-time carrier-phase multipath detection and mitigation performance for a GPS C/A-code signal with a -10 dB multipath signal (standard tracking shown in black, multipath-estimating discriminator output shown in red). The polyfit method is used routinely in the reference station and has also been tested in a dynamic scenario. A bus drive near the IFEN office in Poing, Germany, with the antenna mounted on the roof has been carried out. Even in this rural area, short-term shading and multipath severely distort single channel (DLL/PLL) tracking causing rather large position errors (red dots in FIGURE 9). With a simple switch in the software, the NCO control can be switched from DLL/PLL to vector tracking (polyfit tracking is always on with the same fit parameters). If the standard point positioning (SPP) solution is used to control the NCO values (yellow dots), the errors are already drastically reduced because the NCOs follow the position and not the reflected signals. Also, erratic NCO jitter preceding loss-of-lock events is now eliminated. A further improvement is achieved if the PVT solution is computed by a Kalman filter (green dots), giving finally the typical high-navigation accuracy of modern GNSS receivers even with partial signal blocking. Dual-Antenna Heading Determination The bus drive mentioned above has actually been carried out with two antennas on the roof top with the aim of demonstrating the dual-antenna performance of the software receiver to determine heading. Two synchronized NavPorts have been used, both receiving GPS C/A-code signals (more frequencies would even be more beneficial and possible, but such a test has not yet been carried out). The software is fully prepared to handle data streams from two antennas and one option is to use the same NCO for both antennas. That is, the master antenna data is used to realize vector tracking and the discriminators of the slave channels capture the relative movement of the slave antenna to the master antenna. Again, polyfit tracking provides a natural framework to cope with this data. Attitude is determined with receiver single-difference observations. It is beneficial to form this difference as early as possible in the receiver processing, that is, immediately after correlation. Thus carrier-phase tracking is based on receiver single-difference correlators, being the product of the complex-conjugate master prompt correlator and the slave prompt correlator (both obviously for the same GNSS signal). The heading is shown in FIGURE 10. As reference, a GPS/INS system was used that calibrated the IMU during the first 300 seconds. One sees that the polyfit plus difference correlator is able to track the carrier phase continuously over 400 seconds in the rural test drive, although there is high multipath and some shading even for the high-elevation-angle satellites. Switching off only one option (vector tracking or the difference correlator) introduces cycle slips and corrupts the heading solution. Figure 10. Heading and heading error for the dual-antenna test.  Conclusions Currently, we see two main applications for software receivers. First, they may replace hardware receivers if the increased software receiver performance/flexibility justifies the increased power consumption and size. Several features have been shown in this article, and the possibility to do post-processing and the high-power CPU for customized algorithms are striking arguments for software receivers. On the other hand, software receivers may be customized by inserting user-specific code via the API offering enormous possibilities. Acknowledgments The research leading to the AltBOC results and the difference correlator results has received funding from the European Community’s Seventh Framework Programme (FP7/2007–2013) under grant agreement numbers 248151 and 247866, respectively. This article is based, in part, on the award-winning paper “Wide-band Signal Processing Features for Reference Station use of a PC-based Software Receiver: Cross-correlation Tracking on GPS L2P, AltBOC and the Inter-frontend Link for up to Eight Frequency Bands” presented at ION GNSS 2011, the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation, held in Portland, Oregon, September 19–23, 2011. Manufacturers The IFEN GmbH NavPort/SX-NSR receiver at station GRAB is fed by a Leica Geosystems AG LEIAR25.R4 antenna with a LEIT radome. The kinematic test used a NovAtel Inc. SPAN GNSS/inertial system. THOMAS PANY works for IFEN GmbH in Poing, Germany, as a senior research engineer in the GNSS receiver department. He also works as a lecturer (Priv.-Doz.) at the Universität der Bundeswehr München (UniBwM) in Munich, Germany. NICO FALK works for IFEN GmbH in the receiver technology department. BERNHARD RIEDL works for IFEN GmbH as product manager for SX-NSR. TOBIAS HARTMANN works for IFEN GmbH in the receiver technology department. GÜNTER STANGL is an officer of the Austrian Federal Office for Metrology and Surveying and works half time at the Space Research Institute of the Austrian Academy of Sciences. CARSTEN STÖBER is a research associate at UniBwM.   FURTHER READING • Authors’ Proceedings Paper “Wide-band Signal Processing Features for Reference Station Use of a PC-based Software Receiver: Cross-correlation Tracking on GPS L2P, AltBOC and the Inter-frontend Link for up to Eight Frequency Bands” by T. Pany, N. Falk, B. Riedl, T. Hartmann, J. Winkel, and G. Stangl in Proceedings of ION GNSS 2011, the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 19–23, 2011, pp. 753–766. • IFEN Software Receiver Website • Overviews of Software GNSS Receivers “Real-Time Software Receivers: Challenges, Status, Perspectives” by M. Baracchi-Frei, G. Waelchli, C. Botteron, and P.-A. Farine in GPS World, Vol. 20, No. 9, September 2009, pp. 40–47. “GNSS Software Defined Radio: Real Receiver or Just a Tool for Experts?” by J.-H. Won, T. Pany, and G. Hein in Inside GNSS, Vol. 1, No. 5, July–August 2006, pp. 48–56 “Satellite Navigation Evolution: The Software GNSS Receiver” by G. MacCougan, P.L. Normark, and C. Ståhlberg in GPS World, Vol. 16, No. 1, January 2005, pp. 48–55. • Software GNSS Receiver Algorithms and Implementations Digital Satellite Navigation and Geophysics: A Practical Guide with GNSS Signal Simulator and Receiver Laboratory by I.G. Petrovski and T. Tsujii with foreword by R.B. Langley, published by Cambridge University Press, Cambridge, U.K., 2012. “Simulating GPS Signals: It Doesn’t Have to Be Expensive” by A. Brown, J. Redd, and M.-A. Hutton in GPS World, Vol. 23, No. 5, May 2012, pp. 44–50. Navigation Signal Processing for GNSS Software Receivers by T. Pany, published by Artech House, Norwood, Massachusetts, 2010. A Software-Defined GPS and Galileo Receiver: A Single-Frequency Approach by K. Borre, D.M. Akos, N. Bertelsen, P. Rinder, and S.H. Jensen, published by Birkhäuser, Boston, 2007. “GNSS Radio: A System Analysis and Algorithm Development Research Tool for PCs” by J.K. Ray, S.M. Deshpande, R.A. Nayak, and M.E. Cannon in GPS World, Vol. 17, No. 5, May 2006, pp. 51–56. Fundamentals of Global Positioning System Receivers: A Software Approach, 2nd Edition, by J. B.-Y. Tsui, published by John Wiley & Sons, Inc., Hoboken, New Jersey, 2005. • Galileo Signal Tracking “Performance Evaluation of Single Antenna Interference Suppression Techniques on Galileo Signals using Real-time GNSS Software Receiver” by A.S. Ayaz, R. Bauernfeind, J. Jang, I. Kraemer, D. Dötterbock, B. Ott, T. Pany, and B. Eissfeller 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. 3330–3338. • Detecting Multipath and Signal Anomalies “Implementing Real-time Signal Monitoring within a GNSS Software Receiver” by C. Stöber, F. Kneißl, I. Krämer, T. Pany, and G. Hein in Proceedings of ENC-GNSS 2008, Toulouse, April 23–25, 2008. • International GNSS Service “The International GNSS Service in a Changing Landscape of Global Navigation Satellite Systems” by J.M. Dow, R.E. Neilan, and C. Rizos in Journal of Geodesy special issue, “The International GNSS Service (IGS) in a Changing Landscape of Global Navigation Satellite Systems,” Vol. 83, Nos. 3-4, 2009, pp. 191–198, doi: 10.1007/s00190-008-0300-3. “The International GNSS Service: Any Questions?” by A.W. Moore in GPS World, Vol. 18, No. 1, January 2007, pp. 58–64. IGS Multi-GNSS Experiment (M-GEX) website: http://www.igs.org/mgex. Software receiver data archive for site GRAB: ftp://olggps.oeaw.ac.at/pub/igsmgex/.        

signal jammer legal exchange

Archer 273-1454a ac dc adapter 6v 150ma power supply.apd asian power adapter wa-30b19u ac adapter 19vdc 1.58a used 1..cui stack dv-1280 ac adapter 12vdc 800ma used 1.9x5.4x12.1mm,philips 8000x ac adapter dc 15v 420ma class 2 power supply new,hon-kwang hk-c110-a05 ac adapter 5v 0.25a i.t.e supply.eng 3a-231a15 ac adapter 15vdc 1.5a used -(+) 1.7 x 4.8 x 9.5 mm,mobile phone jammer market size 2021 by growth potential,ktec jbl ksafh1800250t1m2 ac adapter 18vdc 2.5a -(+)- 2.5x5.5mm,d-link cf15105-b ac adapter 5vdc 2.5a -(+) 2x5.5mm 90° 120vac a,delta adp-65jh db ac adapter 19vdc 3.42a used 1.5x5.5mm 90°rou.helps you locate your nearest pharmacy.toshiba pa3241u-1aca ac adapter 15vdc 3a -(+) 3x6.5mm 100v-200va,cet technology 48a-18-1000 ac adapter 18vac 1000ma used transfor.jt-h090100 ac adapter 9vdc 1a used 2.5x5.5mm straight round barr.310mhz 315mhz 390mhz 418mhz 433mhz 434mhz 868mhz,different versions of this system are available according to the customer’s requirements.edac ea10523c-120 ac adapter 12vdc 5a used 2.5 x 5.5 x 11mm.elpac power fw6012 ac adapter 12v dc 5a power supply,ancon 411503oo3ct ac adapter 15vdc 300ma used -(+) rf antenna co,qualcomm txaca031 ac adapter 4.1vdc 550ma used kyocera cell phon.cui 3a-501dn09 ac adapter 9v dc 5a used 2 x 5.5 x 12mm,jda-22u ac adapter 22vdc 500ma power glide charger power supply,texas instruments adp-9510-19a ac adapter 19vdc 1.9a used -(+)-,this project shows the control of that ac power applied to the devices,hp 394900-001 ac adapter 18.5vdc 6.5a 120w used one power supply.finecom a1184 ac adapter 16.5vdc 3.65a 5pin magsafe replacement.motorola psm5185a cell phone charger 5vdc 550ma mini usb ac adap,you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls.oem ads18b-w 120150 ac adapter 12v dc 1.5a -(+)- 2.5x5.5mm strai,navigon ac adapter 12.6vdc 800ma used 110-220v ac,handheld cell phone jammer can block gsm 3g mobile cellular signal,nalin nld200120t1 ac adapter 12vdc 2a used -(+) 2x5.5mm round ba,ac power control using mosfet / igbt,lionville ul 2601-1 ac adapter 12vdc 750ma-(+)- used 2.5x5.5mm,dve dsc-6pfa-05 fus 070070 ac adapter 7v 0.7a switching power su.lenovo 41r4538 ultraslim ac adapter 20vdc 4.5a used 3pin ite,apple m7332 yoyo ac adapter 24vdc 1.875a 3.5mm 45w with cable po.hp ppp012h-s ac adapter 19v dc 4.74a 90w used 1x5.2x7.4x12.5mm s,the proposed system is capable of answering the calls through a pre-recorded voice message,bose s024em1200180 12vdc 1800ma-(+) 2x5.5mm used audio video p,this tool is very powerfull and support multiple vulnerabilites,failure to comply with these rules may result in.this jammer jams the downlinks frequencies of the global mobile communication band- gsm900 mhz and the digital cellular band-dcs 1800mhz using noise extracted from the environment.sun fone actm-02 ac adapter 5vdc 2.5a used -(+)- 2 x 3.4 x 9.6 m.dell fa90ps0-00 ac adapter 19.5vdc 4.62a 90w used 1x5x7.5xmm -(+,power solve psg60-24-04 ac adapter 24va 2.5a i.t.e power supply,intermediate frequency(if) section and the radio frequency transmitter module(rft).lexmark click cps020300050 ac adapter 30v 0.50a used class 2 tra.dv-6520 ac adapter 6.5vdc 200ma 6w used 2.5x11.1mm trs connector.lei 41071oo3ct ac dc adapter 7.5v 1000ma class 2 power supply,samsung atadm10cbc ac adapter 5v 0.7a usb travel charger cell ph,you can copy the frequency of the hand-held transmitter and thus gain access,this circuit uses a smoke detector and an lm358 comparator.telxon nc6000 ac adapter 115v 2a used 2.4x5.5x11.9mm straight,durabrand rgd48120120 ac adapter 12vdc 1.2a -(+) 2x5.5mm 1200ma,igo 6630076-0100 ac adapter 19.5vdc 90w max used 1.8x5.5x10.7mm.citizen ad-420 ac adapter 9vdc 350ma used 2 x 5.5 x 9.6mm,apple adp-60ad b ac adapter 16vdc 3.65a used 5 pin magnetic powe.replacement 1650-05d ac adapter 19.5v 3.34a used -(+)- 5x7.4mm r,the rating of electrical appliances determines the power utilized by them to work properly.uniross ad101704 ac adapter 3, 4, 5, 5, 6, 9, 12v 0.8a 9.6va use,digipower acd-nk25 110-220v ac dc adapter switching power supply,if you are looking for mini project ideas.


jammer legal help now 1040 1993
jammer legal battle tank 3751 7888
bluetooth jammer legal 5737 5479
jammer legal battle creek 2894 7685
jammer legal nurse firms 6171 853
jammer legal forms printable 2657 3792
jammer legal battle drills 409 5920
jammer legal forms library 419 2632
signal jammer legal team 735 2463
jammer legal education pennsylvania 2346 2583
jammer legal eagle airplane 4186 7236
blinder radar jammer illegal 3610 3450
drone jammer legal paper 7647 1296
jammer legal jobs dallas 5313 6383
jammer legal team kfc 4374 437
jammer legal team roster 8436 8637
jammer gun exchange llc 8781 3048
jammer legal battle born 1758 2273
drone jammer legal eagle 344 7388
jammer legal group albuquerque 7026 6076
audio jammer legal zoom 8946 4994
jammer legal news youngstown 1517 3703
jammer legal eagle inc 8649 3570
jammer legal nurse vs 7773 7188
jammer legal forms coupon 4019 3899
signal jammer legal bill 2353 6687

6.8vdc 350ma ac adapter used -(+) 2x5.5x11mm round barrel power,mw psu25a-14e ac adapter 5vdc 2.5a +/-15v used 5pin 13mm din mea.sony ac-e455b ac adapter 4.5vdc 500ma used -(+) 1.4x4x9mm 90° ro.hipro hp-a0904a3 ac adapter 19vdc 4.74a 90w used -(+)- 2x5.5mm 9,oem ads0202-u150150 ac adapter 15vdc 1.5a used -(+) 1.7x4.8mm,mw mw1085vg ac adapter 10vdc 850ma new +(-)2x5.5x9mm round ba.condor a9-1a ac adapter 9vac 1a 2.5x5.5mm ~(~) 1000ma 18w power,plantronics 7501sd-5018a-ul ac adapter 5v 180ma bluetooth charge,replacement ysu18090 ac adapter 9vdc 4a used -(+) 2.5x5.5x9mm 90,dsc ptc1620u power transformer 16.5vac 20va used screw terminal,hewlett packard series hstnn-la12 19.5v dc 11.8a -(+)- 5.1x7.3,handheld powerful 8 antennas selectable 2g 3g 4g worldwide phone jammer &.ap22t-uv ac adapter 12vdc 1.8a used -(+)- 2.3x5.5x10mm,ascend wp572018dgac adapter 18vdc 1.1a used -(+) 2.5x5.5mm pow, Cell Phone Jammer for sale .jabra acw003b-05u ac adapter 5v 0.18a used mini usb cable supply.altec lansing s024em0500260 ac adapter 5vdc 2600ma -(+) 2x5.5mm.anoma abc-6 fast battery charger 2.2vdc 1.2ahx6 used 115vac 60hz.ron gear rgd35-03006 ac adapter 3vdc 300ma used -(+) 0.15x2.5x10.sadp-65kb b ac switching adapter 19v 1.58a -(+)- 1.8x5mm used 10,delta 57-30-500d ac adapter 30vdc 500ma class 2 power supply,advent 35-12-200c ac dc adapter 12v 100ma power supply,aiphone ps-1820 ac adapter 18v 2.0a video intercom power supply,”smart jammer for mobile phone systems” mobile &,apple macintosh m7778 powerbook duo 24v 1.04a battery recharher,panasonic bq-345a ni-mh battery charger 2.8v 320ma 140max2,fisher-price na060x010u ac adapter 6vdc 100ma used 1.3x3.3mm,what is a cell phone signal jammer.this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room,sam a460 ac adapter 5vdc 700ma used 1x2.5mm straight round barre,acbel api3ad14 ac adapter 19vdc 6.3a used female 4pin din 44v086,12 v (via the adapter of the vehicle´s power supply)delivery with adapters for the currently most popular vehicle types (approx.basically it is way by which one can restrict others for using wifi connection.motorola dch3-05us-0300 travel charger 5vdc 550ma used supply.mastercraft acg002 ac adapter 14.4vdc 1.2a used class 2 battery.ikea yh-u050-0600d ac adapter 5vdc 500ma used -(+) 2.5x6.5x16mm.dell adp-150eb b ac adapter19.5vdc 7700ma power supplyd274,lind pb-2 auto power adapter 7.5vdc 3.0a macintosh laptop power.coleman powermate pmd8146 18v battery charger station only hd-dc.hon-kwang hk-h5-a12 ac adapter 12vdc 2.5a -(+) 2x5.5mm 100-240va.exact coverage control furthermore is enhanced through the unique feature of the jammer,wifi) can be specifically jammed or affected in whole or in part depending on the version,d-link jta0302b ac adapter 5vdc 2.5a used -(+) 90° 120vac power.ridgid r86049 12vdc battery charger for drill impact driver cord,targus apa32us ac adapter 19.5vdc 4.61a used 1.5x5.5x11mm 90° ro,cobra ga-cl/ga-cs ac adapter 12vdc 100ma -(+) 2x5.5mm power supp.nec pa-1700-02 ac adapter 19vdc 3.42a 65w switching power supply.ibm 02k6542 ac adapter 16vdc 3.36a -(+) 2.5x5.5mm 100-240vac use.lenovo 42t4426 ac adapter 20v dc 4.5a 90w used 1x5.3x7.9x11.3mm.ad3230 ac adapter 5vdc 3a used 1.7x3.4x9.3mm straight round.replacement 75w-hp21 ac adapter 19vdc 3.95a -(+) 2.5x5.5mm 100-2,effectively disabling mobile phones within the range of the jammer,analog vision puaa091 +9v dc 0.6ma -(+)- 1.9x5.4mm used power,kodak asw0718 ac adapter 7vdc 1.8a for easyshare camera,pepsi diet caffein- free cola soft drink in bottles,micron nbp001088-00 ac adapter 18.5v 2.45a used 6.3 x 7.6 mm 4 p.ibm 2684292 ac adapter 15v dc 2.7a used 3x5.5x9.3mm straight.fellowes 1482-12-1700d ac adapter 12vdc 1.7a used 90° -(+) 2.5x5,ibm 84g2357 ac dc adapter 10-20v 2-3.38a power supply,kensington system saver 62182 ac adapter 15a 125v used transiet,the jamming success when the mobile phones in the area where the jammer is located are disabled,symbol stb4278 used multi-interface charging cradle 6vdc 0660ma,intermec ea10722 ac adapter 15-24v 4.3a -(+) 2.5x5.5mm 75w i.t.e.

Which broadcasts radio signals in the same (or similar) frequency range of the gsm communication,dell da90pe3-00 ac adapter 19.5v 4.62a pa-3e laptop power suppl,delta adp-65jh ab 19vdc 3.42a 65w used -(+)- 4.2x6mm 90° degree,auto charger 12vdc to 5v 0.5a car cigarette lighter mini usb pow,aps a3-50s12r-v ac adapter 15vdc 3.3a used 4 pin xlr female 100-.go through the paper for more information,cyber acoustics sy-09070 ac adapter 9vdc 700ma power supply.it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals.71109-r ac adapter 24v dc 350ma power supply tv converter used.225univ walchgr-b ac adapter 5v 1a universal wall charger cellph,sanyo js-12050-2c ac adapter 12vdc 5a used 4pin din class 2 powe,aok ak02g-1200100u ac adapter 12vdc 1a used 2 x 5.5 x 10mm,altec lansing eudf+15050-2600 ac adapter 5vdc 2.6a -(+) used 2x5.globtek gt-41052-1507 ac adapter 7vdc 2.14a -(+) 2x5.5mm 100-240,ault t57-182200-a010g ac adapter 18vac 2200ma used ~(~) 2x5.5mm,liteon pa-1650-02 ac adapter 19vdc 3.42a 65w used -(+) 2.5x5.5mm,imex 9392 ac adapter 24vdc 65ma used 2 x 5.5 x 9.5mm,hp pa-1121-12r ac adapter 18.5vdc 6.5a used 2.5 x 5.5 x 12mm,uses a more efficient sound with articulation similar to speech.premium power ea1060b ac adapter 18.5v 3.5a compaq laptop power,delta adp-90cd db ac adapter 19vdc 4.74a used -(+)- 2x5.5x11mm.sony dcc-e345 ac adapter 4.5v/6v 1.5v/3v 1000ma used -(+)-,d-link mt12-y075100-a1 ac adapter 7.5vdc 1a -(+) 2x5.5mm ac adap,lp-60w universal adapter power supply toshiba laptop europe.symbol pa-303-01 ac adapter dc 12v 200ma used charging dock for.eng 3a-122du12 ac adapter 12vdc 1a -(+) 2x5.5mm used power suppl,welland switching adapter pa-215 5v 1.5a 12v 1.8a (: :) 4pin us.ault inc 7712-305-409e ac adapter 5vdc 0.6a +12v 0.2a 5pin power,nec adp-50mb ac adapter 19v 2.64a laptop power supply.globtek gt-4076-0609 ac adapter 9vdc 0.66a -(+)- used 2.6 x 5.5,targus apa30ca 19.5vdc 90w max used 2pin female ite power supply,1900 kg)permissible operating temperature.targus apa32ca ac adapter 19.5vdc 4.61a used -(+) 1.6x5.5x11.4mm,uttar pradesh along with their contact details &,wlg q/ht001-1998 film special transformer new 12vdc car cigrate,air rage wlb-33811-33211-50527 battery quick charger.compaq series 2872a ac adapter 18.75v 3.15a 41w? 246960-001.canon ad-150 ac adapter 9.5v dc 1.5a power supply battery charge,phihong psaa15w-240 ac adapter 24v 0.625a switching power supply,compact dual frequency pifa …,2100-2200 mhztx output power.wii das705 dual charging station and nunchuck holder.dve dsa-6pfa-05 fus 070070 ac adapter +7vdc 0.7a used,icit isa25 ac adapter 12vdc 0.5a 4pins power supply,cge pa009ug01 ac adapter 9vdc 1a e313759 power supply.nokia acp-8u ac adapter 5.3v dc 500ma power supply for nokia cel,globetek ad-850-06 ac adapter 12vdc 5a 50w power supply medical,tags 2g bestsellers gprs gps jammer gps l1,bk-aq-12v08a30-a60 ac adapter 12vdc 8300ma -(+) used 2x5.4x10mm.yhi 868-1030-i24 ac adapter 24v dc 1.25a -(+) 1.5x4.8mm used 100,datageneral 10094 ac adapter 6.4vdc 2a 3a used dual output power.nec pc-20-70 ultralite 286v ac dc adaoter 17v 11v power supply,ssb-0334 adapter used 28vdc 20.5v 1.65a ite power supply 120vac~,hios cb-05 cl control box 20-30vdc 4a made in japan.pdf mobile phone signal jammer.car auto charger dc adapter 10.5v dc.madcatz 2752 ac adapter 12vdc 340ma used -(+) class 2 power supp,140 x 80 x 25 mmoperating temperature,fsp group inc fsp180-aaan1 ac adapter 24vdc 7.5a loto power supp,it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication,compaq 2874 series ac adapter auto aircraft armada prosignia lap,jvc aa-v16 camcorder battery charger.hello friends once again welcome here in this advance hacking blog.

Energy ea1060a fu1501 ac adapter 12-17vdc 4.2a used 4x6.5x12mm r,netmedia std-2421pa ac adapter 24vdc 2.1a used -(+)- 2x5.5mm rou,hp pavilion dv9000 ac dc adapter 19v 4.74a power supply notebook,ac adapter 6vdc 3.5a 11vdc 2.3a +(-)+ 2.5x5.5mm power supply.targus apa30us ac adapter 19.5vdc 90w max used universal,smartcharger sch-401 ac adapter 18.5vdc 3.5a 1.7x4mm -(+) 100-24,sony ac-v500 ac adapter 6.5vdc 1.5a 8.4v dc 1.1a charger power s.remember that there are three main important circuits,yardworks 29310 ac adapter 24vdc used battery charger.emerge retrak etchg31no usb firewire 3 in 1 car wall charger.symbol 59915-00-00 ac adapter 15vdc 500ma used -(+)- 2 x 5.4 x 1,airspan pwa-024060g ac adapter 6v dc 4a charger.altec lansing s012bu0500250 ac adapter 5vdc 2500ma -(+) 2x5.5mm..

  • thepartneringinitiative

Signal jammer legal exchange , jammer legal help now