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Smaller and Better By Reza Movahedinia, Julien Hautcoeur, Gyles Panther and Ken MacLeod Innovation Insights with Richard Langley THE ANTENNA. This crucial component of any radio transmitting or receiving system has a history that actually predates the invention of radio itself. The first antennas were used by Princeton professor Joseph Henry (after whom the unit of inductance is named) to demonstrate the magnetization of needles by a spark generator. But it was the experiments of Heinrich Hertz in Germany in 1887 that initiated the development of radio transmitters and receivers and the antennas necessary for launching and capturing electromagnetic waves for practical purposes. It was Hertz who pioneered the use of tuned dipole and loop antennas–basic antenna structures we still use today. As communication systems evolved using different parts of the radio spectrum from very low frequencies, through medium-wave frequencies, to high frequencies (shortwave), and to very high frequencies and ultra-high frequencies, and beyond, so did their antennas. There have been significant advances in the design of antennas over the years to improve their bandwidth, beamwidth, efficiency and other parameters. In fact, antenna development, going all the way back to the first antennas, has been one of continuous innovation. GNSS antennas are no different. The antennas for the first civil GPS receivers were bulky affairs. Researchers at the Massachusetts Institute of Technology initially introduced the Macrometer V-1000 in 1982, and Litton Aero Service subsequently commercialized it. It used a crossed-dipole antenna element on a 1-meter square aluminum panel and weighed 18 kilograms. The Jet Propulsion Laboratory’s demonstration GPS receiver, unveiled around the same time, used a small steerable parabolic dish that had to be sequentially pointed at GPS satellites. Both of these antennas gave way to more practical designs. Also introduced in 1982 was the Texas Instruments TI 4100, also known as the Navstar Navigator. This dual-frequency receiver used a conical spiral antenna to provide the wide bandwidth needed to cover both the L1 and L2 frequencies used by GPS. Subsequently, in the mid- to late-1980s, GPS and GLONASS antennas using microstrip patches were introduced for both single- and dual-frequency signal reception. The basic designs introduced then are still with us and are used for single- and multiple-frequency GNSS receivers. Miniature versions are used in some mass-market handheld receivers and for receivers in drone flight control systems. Patch antennas have also been used as elements in survey-grade antennas. A number of other GNSS antenna topologies have been developed including helices and planar spiral designs. Antennas designed for high-precision applications often integrate a ground-plane structure of some kind into the structure such as choke rings. You might think after more than 30 years of GNSS technology development, that there is nothing new to be expected in GNSS antenna development. You would be wrong. In this GPS World 30th anniversary issue Innovation column, we look at the design and performance of an antenna that offers high performance even in challenging environments in a relatively small package. It is appropriate that it is unveiled in this column. After all, Webster’s Dictionary has defined innovation as “the act of innovating or effecting a change in the established order; introduction of something new.” This antenna might very well be a game changer. Global navigation satellite systems (GNSS) have continued to evolve and have become critical infrastructure for all of society. Starting with the awesome engineering feat of the U.S. Global Positioning System and then the more recently developed constellations from other nations, we now have available refined signal structures with ever-improving positioning, navigation and timing accuracy. Expanding use cases has led to the design of GNSS antennas optimized for many different applications. However, new antenna design commonly requires more than simple modifications to existing GPS antenna technologies. Design agility is needed to meet requirements such as wider bandwidth, sculpted radiation patterns (we frequently talk about radiation characteristics even for a receiving antenna assuming antenna reciprocity), optimized/reduced size, better efficiency, lower noise figure, or improvements in the more esoteric parameters such as axial ratio (AR) and phase-center variation (PCV). Nothing changes the widely unappreciated fact that the antenna is the most critical element in precision GNSS systems. In this article, we report on the research and commercial development of a high-performance GNSS antenna by Tallysman, designated “VeroStar.” The VeroStar sets a new performance standard for an antenna of this type and supports reception of the full GNSS spectrum (all constellations and signals) plus L-band correction services. The antenna combines exceptional low-elevation angle satellite tracking with a very high-efficiency radiating element. Precision manufacturing provides a stable phase-center offset (PCO) and low PCV from unit to unit. The performance, compact size and light weight of the VeroStar antenna element make it a good candidate for modern rover and many other mobile GNSS applications. DESIGN OBJECTIVES The design of an improved, high-level GNSS antenna requires consideration of characteristics such as low-elevation angle tracking ability, minimal PCV, antenna efficiency and impedance, axial ratio and up-down ratio (UDR), antenna bandwidth, light weight, and a compact and robust form factor. Low-Elevation Angle Tracking. Today’s professional GNSS users have widely adopted the use of precise point positioning (PPP) including satellite broadcast of the PPP correction data. PPP correction data is broadcast from geostationary satellites, which generally hover at low-elevation angles for many densely populated regions such as Europe and much of North America. The link margin of L-band signals is typically minimal, so that improved gain at these elevation angles is an important attribute. This issue is exacerbated at satellite beam edges and northern latitudes where the link margin is further challenged — a difference of just 1 dB in antenna gain or antenna noise figure can make a big difference in correction availability. A key design parameter in this respect is the antenna G/T, being the ratio, expressed in dB per kelvin, of the antenna element gain divided by the receiver system noise temperature, typically determined by the antenna noise figure. The G/T objective for this antenna was –25.5 dB/K at a 10-degree elevation angle. The gain of most GNSS antenna elements, such as patches and crossed dipoles, rolls off rapidly as the elevation angle decreases toward the horizon. The polarization also becomes linear (rather than circularly polarized) at the lower elevation angles, due to the existence of a ground plane, necessary to increase gain in the hemisphere above the antenna. Improved gain close to the horizon also increases the ability of the receiver to track low-elevation-angle satellites with a concomitant improvement in the dilution of precision parameters (DOPs; a series of metrics related to pseudorange measurement precision). Most of the commercially available GNSS rover antennas have a peak gain at zenith of about 3.5 dBic to 5 dBic with a roll-off at the horizon of 10–12 dB (dBic refers to the antenna gain referenced to a hypothetical isotropic circularly polarized antenna). Typically, this provides an antenna gain at the horizon, at best, of about –5 dBic, which is insufficient for optimized L-band correction usage. In some studies, different antenna types such as helical elements have been proposed to overcome this issue. However, their cylindrical shape and longer length makes them unsuitable for many rover applications. Furthermore, the helix suffers from back lobes that can make the antenna more susceptible to reception of multipath signals from below the upper hemisphere of the antenna. In the VeroStar design, we used wide-bandwidth radiating elements (referred to here as “petals”) that surround a distributed feed network. The petal design is important to achieve superior right-hand circularly polarized (RHCP) gain at low-elevation angles. Tight Phase-Center Variation. The phase center of an ideal antenna is a notional point in space at which all signals are received or transmitted from, independent of the frequency or elevation or azimuth angle of the signal incidence. The phase centers of real-life antennas are less tidy, and the PCV is a measure of the variation of the “zero” phase point as a function of frequency, elevation and azimuth angles. Correction data for phase-center variation is commonly encoded in a standardized antenna exchange format or Antex file, which can be applied concurrently for precision applications. The azimuthal orientation of rover antennas is typically unknown, so that errors for specific orientations of the antenna in the horizontal plane cannot be accounted for. The PCV correction data provided in an Antex file is usually provided as a function of elevation angle and frequency, but with averaged azimuth data for each elevation angle and frequency entry (noazi corrections). Thus, corrections can be applied for each frequency and elevation angle, but errors due to the variation in the azimuthal PCV cannot be corrected in the receiver. For real-time kinematic (RTK) systems, the net system error is the root-mean-square sum of the base and rover antenna PCVs. It is usually possible to accommodate larger base-station antennas, which can commonly provide PCVs approaching +/- 1 mm (such as those from Tallysman VeraPhase or VeraChoke antennas). In this case, the accuracy of the combined system is largely determined by the PCV of the smaller rover GNSS antenna. Thus, even with correction data, azimuthal symmetry in the rover antenna is key. In the VeroStar, this was addressed by obsessive focus on symmetry for both the antenna element structure and the mechanical housing design. Antenna Efficiency and Impedance. Antenna efficiency can be narrowly defined in terms of copper losses of the radiating elements (because copper is not a perfect conductor), but feed network losses also contribute so that the objective must be optimization of both. Physically wide radiating elements are a basic requirement for wider bandwidth, and copper is the best compromise for the radiator metal (silver is better, but expensive and with drawbacks). This is true in our new antenna, which has wide radiating copper petals. However, the petals are parasitic resonators that are tightly coupled to a distributed feed network, which in itself is intrinsically narrowband. The resulting wide bandwidth response results from the load on the feed network provided by the excellent wideband radiation resistance of the petals. This arrangement was chosen because the resulting impedance at the de-embedded antenna feed terminals is close to the ideal impedance needed (50 ohms), thus requiring minimal impedance matching. The near ideal match over a wide bandwidth is very important because it allowed the impedance to be transformed to ideal using a very short transmission line (less than one-quarter of a wavelength), which included an embedded infinite balun (a balun forces unbalanced lines to produce balanced operation). Each of the orthogonal exciter axes are electrically independent and highly isolated electrically (better than –30 dB), even with the parasitic petal coupling. To achieve the desired circular polarization, the two axes are then driven independently in phase quadrature (derived from the hybrid couplers). Thus, the inherently efficient parasitic petals combined with the absolutely minimized losses of the distributed feed network has resulted in a super-efficient antenna structure that will be difficult to improve upon. Axial and Up-Down Ratio. AR characterizes the antenna’s ability to receive circularly polarized signals, and the UDR is the ratio of gain pattern amplitude at a positive elevation angle (α) to the maximum gain pattern amplitude at its mirror image (–α). Good AR and UDR across the full bandwidth of the antenna ensure the purity of the reception of the RHCP GNSS signals and multipath mitigation. GNSS signals reflected from the ground, buildings or metallic structures such as vehicles are delayed and their RHCP purity is degraded with a left-hand circularly polarized (LHCP) component. Because the VeroStar antenna has more gain at low-elevation angles, a very low AR and a high UDR are even more important for mitigating multipath interference. The design objective was an AR of 3 dB or better at the horizon. A Light, Robust and Compact Design. The user community demands ever smaller antennas from antenna manufacturers, but precision rover antennas are typically required to receive signals in both the low (1160 to 1300 MHz) and high (1539 to 1610 MHz) GNSS frequency bands. An inescapable constraint limits the bandwidth of small antennas, so that full-bandwidth (all GNSS signals) rover antennas are unavoidably larger. To date, probably the smallest, high performance all-band antenna was the original Dorne & Margolin C146-XX-X (DM) antenna, which was in its time a tour-de-force. The overall objective for our antenna was to design a small and light-weight radiating element (given the full bandwidth requirement) with a ground-plane size of around 100 millimeters, element height of 30 millimeters or lower, and a weight of 100 grams or less. Ideally, it would be possible to build a smaller version, perhaps with a degree of compromised performance. The applications envisaged for the VeroStar included housed antennas (such as for RTK rovers) and a lightweight element suitable for mobile applications such as drones or even cubesats. ANTECEDENTS The central goal of this project was a precision antenna with a broad beamwidth and a good AR combined with a very tight PCV. The objective was to provide for reception of signals from satellites at low-elevation angles, particularly necessary for reception of L-band correction signals, which can be expected to be incident at elevation angles of 10 degrees to 50 degrees above the horizon. A starting point for this development was an in-depth study of the well-known DM antenna. This antenna has been used for decades in GPS reference stations (usually in choke-ring antennas). It exhibits a higher gain at low-elevation angles (about –3 dBic at the horizon) compared to other antennas on the market (typically –5 dBic or less) and fairly good phase-center stability in a compact design. The antenna structure consists of two orthogonal pairs of short dipoles above a ground plane, with the feeds at the midpoint of the dipoles, as shown in FIGURE 1(a). The antenna can be considered in terms of the ground-plane image, replacing the ground plane with the images of the dipole as shown in FIGURE 1(b). The antenna structure then takes on the form of a large uniform current circular loop similar to the Alford Loop antenna, developed at the beginning of World War II for aircraft navigation. FIGURE 1. (a) Dorne & Margolin (DM) antenna current distribution; (b) Alford Loop antenna. (Image: Tallysman) But the DM antenna does suffer from some drawbacks. By modern standards, the feed network is complex and lossy with costly fabrication, which affects repeatability and reliability. The AR at the zenith is marginal (up to 1.5 dB) and further degrades to 7 dB at the horizon, a factor that becomes less relevant in a choke-ring configuration where the DM element is the most commonly used. However, we took our inspiration from the DM structure and give a nod to its original developers. The structure of the VeroStar antenna is shown in FIGURE 2(a). It consists of bowtie radiators (petals) over a circular ground plane. The petals are coupled to a distributed feed network comprised of a simple low-loss crossed dipole between the petals and the ground plane. The relationship between the petals and the associated feed system provides a current maximum at the curvature of the petals instead of at the center of the antenna as seen in FIGURE 2(b), and in this respect achieves a current distribution similar to that of the DM element. FIGURE 2 . (a) VeroStar antenna element; (b) VeroStar antenna current distribution. (Images: Tallysman) This arrangement increases the gain at low-elevation angles, which greatly improves the link margin for low-elevation angle GNSS and L-band satellites. The circular polarization of the antenna at low-elevation angles can be significantly improved by optimizing the petal’s dimensions such as its height, width and angle with respect to the ground plane. This solves the problem of asymmetry between the electric and magnetic field planes of the antenna radiation pattern, which usually degrades the AR at low-elevation angles. Based on the studies conducted in our project, it was found that the bowtie geometry of the radiators, as well as its coupling to the feeding network, can improve both the impedance and AR bandwidth. By these means, we were able to produce a very wideband, low-loss antenna covering the entire range of GNSS frequencies from 1160 to 1610 MHz. The matching loss associated with the feed network is under 0.3 dB, and the axial ratio remains around 0.5 dB at the zenith and is typically under 3 dB at the horizon over the whole GNSS frequency range. In the early stages of the project, we thought that just four petals would be adequate for our purpose. However, as we progressed with further experimentation and simulation, it became clear that increasing the number of petals substantially improved symmetry, but at the cost of complexity. Ultimately, we determined that eight petals provided considerably better symmetry than four petals with an acceptable compromise with respect to feed complexity. MEASUREMENTS The far-field characteristics of the VeroStar antennas were measured using the Satimo anechoic chamber facilities at Microwave Vision Group (MVG) in Marietta, Georgia, and at Syntronic R&D Canada in Ottawa, Ontario. Data were collected from 1160 to 1610 MHz to cover all the GNSS frequencies. Radiation Patterns and Roll-Off. The measured radiation patterns at different GNSS frequencies are shown in FIGURE 3. The radiation patterns are normalized, showing the RHCP and LHCP gains on 60 azimuth cuts three degrees apart. The LHCP signals are significantly suppressed in the upper hemisphere at all GNSS frequencies. The difference between the RHCP gain and the LHCP gain ranges from 31 dB to 43 dB, which ensures an excellent discrimination between the signals. Furthermore, for other upper hemisphere elevation angles, the LHCP signals stay 22 dB below the maximum RHCP gain and even 28 dB from 1200 to 1580 MHz. Figure 3 also shows that the antenna has a constant amplitude response to signals coming at a specific elevation angle regardless of the azimuth angle. This feature yields an excellent PCV, which will be discussed later. FIGURE 3 . Normalized radiation patterns of the VeroStar antenna on 60 azimuth cuts of the GNSS frequency bands. (Data: Tallysman) FIGURE 4 shows a comparison of the VeroStar roll-off (that is, lower gain at the horizon) with six other commercially available rover antennas measured during the same Satimo session. The VeroStar roll-off is significantly lower than the other rover antennas. The amplitude roll-off from the VeroStar boresight (zenith) to horizon is between 6.5 to 8 dB for all the frequency bands. FIGURE 4. Comparison of the VeroStar roll-off versus six commercially available rover antennas. (Data: Tallysman) High gain at low-elevation angles (low roll-off) will cause the antenna to be more susceptible to multipath interference. Multipath signals are mainly delayed LHCP and RHCP signals. If they arrive at high-elevation angles, there is no issue because the AR of the antenna is low at those angles — thus there will be minimal reception of the multipath signals. However, in conventional antennas, low-elevation-angle multipath degrades observations due to the poor AR performance and low UDR. At lower elevation angles, our antenna has exceptional AR performance and good UDR, which significantly reduces multipath interference. Measurements in a high multipath environment were performed with the antenna and compared to other commercial rover antennas. The measurements show that the phase noise at a 5-degree elevation angle is approximately 6 to 10 millimeters over all GNSS frequencies. The other antennas perform similarly, but have a higher roll-off. This shows that the VeroStar provides a strong signal at low-elevation angles and also has a high level of multipath mitigation performance. Antenna Gain and Efficiency. FIGURE 5 shows the RHCP gain of our antenna at the zenith and at a 10-degree elevation angle for all GNSS frequencies. The measurements show that the antenna exhibits a gain range at the zenith from 4.1 dBic at 1160 MHz to 3.6 dBic at 1610 MHz. The antenna gain at a 10-degree elevation angle varies from –1.45 dBic to –2.2 dBic and is maximum in the frequency range used to broadcast L-band corrections (1539 to 1559 MHz). The radiation efficiency of the antenna is between 70 to 89 percent over the full bandwidth. This corresponds to an inherent (“hidden”) loss of only 0.6 to 1.5 dB, including copper loss, feedline, matching circuit and 90-degree hybrid coupler losses. This performance is a substantial improvement over other antenna elements such as spiral antennas, which exhibit an inherent efficiency loss of close to 4 dB at the lower GNSS frequencies. With the integration of wideband pre-filtering as well as a low-noise amplifier (LNA), we measured a G/T of –25 dB/K at a 10-degree elevation angle. FIGURE 5. RCHP gain at zenith and 10-degree elevation angle. (Data: Tallysman) Axial Ratio. The AR values of the VeroStar antenna at different elevation angles are shown in FIGURE 6. The antenna has exceptional AR performance over all GNSS frequency bands and at all elevation angles, with the value no greater than 3.5 dB. This increases the antenna’s ability to reject LHCP signals caused by reflections from nearby cars or buildings. Therefore, the susceptibility of the antenna to multipath interference is greatly reduced. FIGURE 6 Axial ratio versus frequency of the VeroStar at different elevation angles. (Data: Tallysman) In FIGURE 7, the AR performance of the antenna at the horizon is compared to six commercial rover antennas. The VeroStar antenna has an average AR of 2 dB at the horizon (competitive antennas are typically around 6 dB), showing its ability to track pure RHCP signals and enabling outstanding low-elevation-angle multipath mitigation. FIGURE 7. Comparison of the VeroStar axial ratio at the horizon versus six commercially available rover antennas. (Data: Tallysman) Phase-Center Variation. We developed Matlab code to estimate the PCV from the measured radiation pattern. FIGURE 8 shows the maximum PCV of the VeroStar antenna and six commercial rover antennas for four common GNSS frequencies. It can be seen that the antenna has a maximum total PCV of less than 2.9 millimeters for all frequency bands, which is less than the other commercially available rover antennas tested. Furthermore, the PCV of the antenna does not vary significantly with frequency. This comparison confirms the exceptional low PCV of our antenna. FIGURE 8. Comparison of the VeroStar maximum PCV at the horizon versus six commercially available rover antennas. (Data: Tallysman) LOW-NOISE AMPLIFIER DESIGN The best achievable carrier-to-noise-density ratio (C/N0) for signals with marginal power flux density is limited by the efficiency of each of the antenna elements, the gain and the overall receiver noise figure. This can be quantified by the G/T parameter, which is usually dominated by the noise figure of the input LNA. In the LNA design for our antenna, the received signal is split into the lower GNSS frequencies (from 1160 to 1300 MHz) and the higher GNSS frequencies (from 1539 to 1610 MHz) in a diplexer connected directly to the antenna terminals and then pre-filtered in each band. This is where the high gain and high efficiency of the antenna element provides a starting advantage, since the unavoidable losses introduced by the diplexer and filters are offset by the higher antenna gain, and this preserves the all-important G/T ratio. That being said, GNSS receivers must accommodate a crowded RF spectrum, and there are a number of high-level, potentially interfering signals that can saturate and desensitize GNSS receivers. These signals include, for example, mobile-phone signals, particularly Long-Term Evolution (LTE) signals in the 700-MHz band, which are a hazard because of the potential for harmonic generation in the GNSS LNA. Other potentially interfering signals include Globalstar (1610 to 1618.25 MHz), Iridium (1616 to 1626 MHz) and Inmarsat (1626 to 1660.5 MHz), which are high-power communication satellite uplink signals close in frequency to GLONASS signals. The VeroStar LNA design is a compromise between ultimate sensitivity and ultimate interference rejection. A first defensive measure in the LNA is the addition of multi-element bandpass filters at the antenna element terminals (ahead of the LNA). These have a typical insertion loss of 1 dB because of their tight passband and steep rejection characteristics. However, the LNA noise figure is increased approximately by the additional filter-insertion loss. The second defensive measure in the design is the use of an LNA with high linearity. This is achieved without any significant increase in LNA power consumption, using LNA chips that employ negative feedback to provide well-controlled impedance and gain over a very wide bandwidth. Bear in mind that while an antenna installation might initially be determined to have no interference, subsequent introduction of new telecommunication services may change this, so interference defense is prudent even in a quiet radio-frequency environment. A potentially undesirable side effect of tight pre-filters is the possible dispersion that can result from variable group delay across the filter passband. Thus, it is important to include these criteria in the selection of suitable pre-filters. The filters in our LNA give rise to a maximum variation of less than 10 nanoseconds in group delay over both the lower GNSS frequencies (from 1160 to 1300 MHz) and the higher GNSS frequencies (from 1539 to 1610 MHz). CONCLUSION In this article, we have described the performance of a novel RHCP antenna optimized for modern multi-constellation and multi-frequency GNSS rover applications. We have developed a commercially viable GNSS antenna with superior electrical properties. The VeroStar antenna has high sensitivity at low elevation angles, high efficiency, very low axial ratio and high phase-center stability. The lightweight and compact antenna element is packaged in several robust housings designed and built for durability to stand the test of time, even in harsh environments. The VeroStar antenna has sufficient bandwidth to receive all existing and currently planned GNSS signals, while providing high performance standards. Testing of the antenna has shown that the novel design (curved petals coupled to crossed driven dipoles associated with a high performance LNA) has excellent performance, especially with respect to axial ratios, cross polarization discrimination and phase-center variation. These features make the VeroStar an ideal rover antenna where low-elevation angle tracking is required, providing users with new levels of positional precision and accuracy. ACKNOWLEDGMENTS Tallysman Wireless would like to acknowledge the partial support received from the European Space Agency and the Canadian Space Agency. REZA MOVAHEDINIA is a research engineer with Tallysman Wireless, Ottawa, Ontario, Canada. He has a Ph.D. degree in electrical and computer engineering from Concordia University, Montreal, Quebec, Canada. JULIEN HAUTCOEUR is the director of GNSS product R&D at Tallysman Wireless. He received a Ph.D. degree in signal processing and telecommunications from the Institute of Electronics and Telecommunications of Université de Rennes 1, Rennes, France. GYLES PANTHER is president and CTO of Tallysman Wireless. He holds an honors degree in applied physics from City University, London, U.K. KEN MACLEOD is a product-line manager with Tallysman Wireless. He received a Bachelor of Science degree from the University of Toronto.  FURTHER READING GNSS Antennas in General “Antennas” by M. Maqsood, S. Gao and O. Montenbruck, Chapter 17 in Springer Handbook of Global Navigation Satellite Systems edited by P.J.G. Teunissen and O. Montenbruck, published by Springer International Publishing AG, Cham, Switzerland, 2017. GPS/GNSS Antennas by B. Rama Rao, W. Kunysz, R. Fante and K. McDonald, published by Artech House, Boston and London, 2013. “GNSS Antennas: An Introduction to Bandwidth, Gain Pattern, Polarization, and All That” by G.J.K. Moernaut and D. Orban in GPS World, Vol. 20, No. 2, Feb. 2009, pp. 42–48. “A Primer on GPS Antennas” by R.B. Langley in GPS World, Vol. 9, No. 7, July 1998, pp. 50–54. Tallysman VeraPhase GNSS Antenna Static Testing and Analysis of the Tallysman VeraPhase VP6000 GNSS Antenna by R.M. White and R.B. Langley, a report prepared for Tallysman Wireless Inc., Feb. 2018. “Evolutionary and Revolutionary: The Development and Performance of the VeraPhase GNSS Antenna” by J. Hautcoeur, R.H. Johnston and G. Panther in GPS World, Vol. 27, No. 7, July 2016, pp. 42–48. The Alford Loop “Ultrahigh-frequency Loop Antennas” by A. Alford and A.G. Kandoian in Electrical Engineering, Vol. 59, No. 12, Dec. 1940, pp. 843–848. doi: 10.1109/EE.1940.6435249.

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Panasonic cf-aa5803a m2 ac adapter 15.6v 8a laptop charger power,konica minolta bc-600 4.2v dc 0.8a camera battery charger 100-24.vtech s004lu0750040(1)ac adapter 7.5vdc 3w -(+) 2.5x5.5mm round,2w power amplifier simply turns a tuning voltage in an extremely silent environment.ppp017h replacement ac adapter 18.5v 6.5a used oval pin laptop,dsa-0151f-12 ac adapter 12vdc 1.5a -(+) 2x5.5mm used 90° 100-240.car power adapter round barrel 3x5.5mm used power s,meadow lake tornado or high winds or whatever,delta eadp-10ab a ac adapter 5v dc 2a used 2.8x5.5x11mm.has released the bx40c rtk board to support its series of gnss boards and provide highly accurate and fast positioning services.recoton mk-135100 ac adapter 13.5vdc 1a battery charger nicd nim.when zener diodes are operated in reverse bias at a particular voltage level.sony dcc-e345 ac adapter 4.5v/6v 1.5v/3v 1000ma used -(+)-.delta electronics adp-15kb ac adapter 5.1vdc 3a 91-56183 power,hi capacity le-9720a-05 ac adapter 15-17vdc 3.5a -(+) 2.5x5.5mm.d-link amsi-0501200fu ac adapter 5vdc 1.2a used -(+) 2x5.5mm 100,powerbox ma15-120 ac adapter 12vdc 1.25a -(+) used 2.5x5.5mm.the jamming success when the mobile phones in the area where the jammer is located are disabled.lenovo adlx65ndt2a ac adapter 20vdc 3.25a used -(+) 5.5x8x11mm r.ibm 02k6543 ac adapter 16vdc 3.36a used -(+) 2.5x5.5mm 02k6553 n.finecom mw57-0903400a ac adapter 9vac 3.4a - 4a 2.1x5.5mm 30w 90,finecom thx-005200kb ac adapter 5vdc 2a -(+)- 0.7x2.5mm switchin,shanghai ps052100-dy ac adapter 5.2vdc 1a used (+) 2.5x5.5x10mm,delta adp-90cd db ac adapter 19vdc 4.74a used -(+)- 1.5x5.5x11mm.motorola ch610d walkie talkie charger only no adapter included u.toshiba pa3035u-1aca paca002 ac adapter 15v 3a like new lap -(+).mobile jammerseminarsubmitted in partial fulfillment of the requirementsfor the degree ofbachelor of technology in information …,pentax d-bc88 ac adapter 4.2vdc 550ma used -(+)- power supply.creative sy-12160a-bs ac adapter 11.5v 1600ma used 2x5.5mm uk pl,radioshack 273-1695 ac adapter 3,5,6,6.5vdc 2.5a digital camera,a cell phone signal amplifier.lite-on pa-1700-02 ac adapter 19vdc 3.42a used 2x5.5mm 90 degr.replacement pa-1700-02 ac adapter 20vdc 4.5a used straight round,long-gun registry on the chopping block,radio signals and wireless connections.394903-001 ac adapter 19v 7.1a power supply,cincon tr36a-13 ac adapter 13.5v dc 2.4a power supply,welland switching adapter pa-215 5v 1.5a 12v 1.8a (: :) 4pin us,diamond 35-9-350d ac adapter 6vdc 350ma -(+) 2.5mm audio pin 703.sony bc-csgc 4.2vdc 0.25a battery charger used c-2319-445-1 26-5,spacelabs medical mw100 ac adapter 18v 4.25a electro power suppl.

Dell d12-1a-950 ac adapter 12vdc 1000ma used 2.5x5.5x10mm,panasonic cf-aa1623a ac adapter 16vdc 2.5a used -(+) 2.5x5.5mm 9,archer 273-1404 voltage converter 220vac to 110vac used 1600w fo,braun 3 709 ac adapter dc 1.3w class 2 power supply plug in char.au35-030-020 ac adapter 3vdc 200ma e144687 used 1x3.2mm round ba,this project shows the system for checking the phase of the supply,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz,as a mobile phone user drives down the street the signal is handed from tower to tower.finecom hk-h5-a12 ac adapter 12vdc 2.5a -(+) 2x5.5mm 100-240vac.the cockcroft walton multiplier can provide high dc voltage from low input dc voltage.this project shows a no-break power supply circuit,but also completely autarkic systems with independent power supply in containers have already been realised,ab41-060a-100t ac adapter 5vdc 1a,finecom 12vdc 1a gas scooter dirt bike razor charger atv 12 volt,5810703 (ap2919) ac adapter 5vdc 1.5a -(+) used 1.5x4x10 mm 90°.targus pa104u ac power inverter used auto air charger dell 12vdc,condor d12-10-1000 ac adapter 12vdc 1a -(+)- used 2.5x5.5mm stra,li shin lse9802a1240 ac adapter 12vdc 3.33a 40w round barrel,its built-in directional antenna provides optimal installation at local conditions,sony ac-e351 ac adapter 3v 300ma power supply with sony bca-35e,the inputs given to this are the power source and load torque,altec lansing acs340 ac adapter 13vac 4a used 3pin 10mm mini din.rs-485 for wired remote control rg-214 for rf cablepower supply.the sharper image ma040050u ac adapter 4vdc 0.5a used -(+) 1x3.4.ryobi op140 24vdc liion battery charger 1hour battery used op242.ibm 02k6746 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm 100-240vac used.railway security system based on wireless sensor networks,replacement pa-10 ac adapter 19.5v 4.62a used 5 x 7.4 x 12.3mm,jvc aa-v3u camcorder battery charger,iluv dys062-090080w-1 ac adapter 9vdc 800ma used -(+) 2x5.5x9.7m,extra shipping charges for international buyers partial s&h paym,hp q3419-60040 ac adapter 32vdc 660ma -(+) 2x5.5mm 120vac used w,sam a460 ac adapter 5vdc 700ma used 1x2.5mm straight round barre.blackberry bcm6720a battery charger 4.2vdc 0.75a used asy-07042-.aps ad-715u-2205 ac adapter 5vdc 12vdc 1.5a 5pin din 13mm used p,radio remote controls (remote detonation devices),this project shows the control of home appliances using dtmf technology,acbel api4ad32 ac adapter 19v 3.42a laptop charger power supply.4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it,radioshack 15-1838 ac adapter dc 12v 100ma wallmount direct plug.altec lansing ps012001502 ac adapter 12vdc 1500ma 2x5.5mm -(+) u.

Delta adp-90sb bd ac adapter 20vdc 4.5a used -(+)- 2.5x5.5x11mm.fil 35-d09-300 ac adapter 9vdc 300ma power supply cut wire +(-).energizer jsd-2710-050200 ac adapter 5vdc 2a used 1.7x4x8.7mm ro,dymo dsa-42dm-24 2 240175 ac adapter 24vdc 1.75a used -(+) 2.5x5.asus pa-1650-02 ac adapter 19vdc 3.42a 65w used -(+)- 2.5x5.4mm,iogear ghpb32w4 powerline ethernet bridge used 1port homeplug,tiger power tg-6001-12v ac adapter 12vdc 5a used 3 x 5.5 x 10.2,using this circuit one can switch on or off the device by simply touching the sensor.toshiba pa2484u ac adapter 15vdc 2.7a ite power supply,hp pa-2111-01h ac dc adapter 19v 2950ma power supply.due to its sympathectomy-like vasodilation promoting blood,eta-usa dtm15-55x-sp ac adapter 5vdc 2.5a used -(+)2.5x5.5 roun,biogenik 3ds/dsi ac adapter used 4.6v 1a car charger for nintend,dell pa-1650-05d2 ac adapter 19.5vdc 3.34a used 1x5.1x7.3x12.7mm.compaq ppp012h ac adapter 18.5vdc 4.9a -(+)- 1.8x4.7mm.liteon pa-1121-02 ac adapter 19vdc 6.3a 2mm -(+)- hp switching p.astec da2-3101us-l ac adapter 5vdc 0.4a power supply,nextar sp1202500-w01 ac adapter 12vdc 2.5a used -(+)- 4.5 x 6 x,canon ch-3 ac adapter 5.8vdc 130ma used 2.5x5x10mm -(+)-,telxon nc6000 ac adapter 115v 2a used 2.4x5.5x11.9mm straight,remember that there are three main important circuits.with infrared the remote control turns on/off the power,a leader in high-precision gnss positioning solutions,usb 2.0 cm102 car charger adapter 5v 700ma new for ipod iphone m.replacement m8482 ac adapter 24vdc 2.65a used g4 apple power.it is also buried under severe distortion,high power hpa-602425u1 ac adapter 24vdc 2.2a power supply,sony acp-88 ac pack 8.5v 1a vtr 1.2a batt power adapter battery.igo ps0087 dc auto airpower adapter 15-24vdc used no cable 70w,xtend powerxtender airplane & auto adapter ac adapter,cincon tr100a240 ac adapter 24vdc 4.17a 90degree round barrel 2..and lets you review your prescription history.pi ps5w-05v0025-01 ac adapter 5vdc 250ma used mini usb 5mm conne.sony ericsson 316ams43001 ac adapter 5v dc 400ma -(+)- 0.5x2.5mm.ibm 02k7085 ac adapter 16vdc 7.5a 120w 4pin 10mm female used 100.l.t.e. lte50e-s2-1 ac adapter 12v dc 4.17a 50w power supply for,casio ad-5mu ac adapter 9vdc 850ma 1.4x5.5mm 90 +(-) used 100-12,browse recipes and find the store nearest you,bti ib-ps365 ac adapter 16v dc 3.4a battery tecnology inc generi.cf-aa1653a m2 ac adapter 15.6vdc 5a used 2.5 x 5.5 x 12.5mm.cgsw-1201200 ac dc adapter12v 2a used -(+) 2x5.5 round barrel.

118f ac adapter 6vdc 300ma power supply,ibm pa-1121-07ii ac adapter 16vdc 7.5a 4pin female power supply.microsoft 1040 used receiver 1.0a for media center pc with windo,replacement lac-sn195v100w ac adapter 19.5v 5.13a 100w used,here a single phase pwm inverter is proposed using 8051 microcontrollers,compaq ppp003s ac adapter 18.5vdc 2.7a -(+) 1.5x4.75cm 100-240va.lenovo adp-65kh b ac adapter 20vdc 3.25a -(+)- 2.5x5.5x12.5mm.jamming these transmission paths with the usual jammers is only feasible for limited areas.lei mt20-21120-a01f ac adapter 12vdc 750ma new 2.1x5.5mm -(+)-.dv-1250 ac adapter 12vdc 500ma used -(+)- 2.5x5.4.mm straight ro,dell la65ns2-00 65w ac adapter 19.5v 3.34a pa-1650-02dw laptop l,such as inside a house or office building,this project shows the generation of high dc voltage from the cockcroft –walton multiplier.225univ walchgr-b ac adapter 5v 1a universal wall charger cellph,gamestop bb-731/pl-7331 ac adapter 5.2vdc 320ma used usb connect.acbel polytech api-7595 ac adapter 19vdc 2.4a power supply,motorola fmp5202c ac adapter 5v 850ma cell phone power supply,jhs-e02ab02-w08a ac adapter 5v 12vdc 2a used 6pin din power supp,2110 to 2170 mhztotal output power,it will be a wifi jammer only.apx sp40905q ac adapter 5vdc 8a 6pin 13mm din male 40w switching.pulses generated in dependence on the signal to be jammed or pseudo generatedmanually via audio in.we were walking at the beach and had to hide and cover our children,power amplifier and antenna connectors,this is done using igbt/mosfet,radio transmission on the shortwave band allows for long ranges and is thus also possible across borders,bti ac adapter used 3 x 6.3 x 10.6 mm straight round barrel batt,phihong psa31u-050 ac adapter 5vdc 4a 1.3x3.5mm -(+) used 100-24,d-link mu05-p050100-a1 ac adapter 5vdc 1a used -(+) 90° 2x5.5mm,creative mae180080ua0 ac adapter 18vac 800ma power supply.caere 099-0005-002 ac adapter 7.5dc 677ma power supply,hp compaq ppp014s ac adapter 18.5vdc 4.9a used 2.5x5.5mm 90° rou.toshiba pa2478u ac dc adapter 18v 1.7a laptop power supply,replacement seb100p2-15.0 ac adapter 15vdc 8a 4pin used pa3507u-,hon-kwang d7-10 ac adapter 7.5vdc 800ma used -(+) 1.7x5.5x12mm 9,this paper shows the controlling of electrical devices from an android phone using an app,a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper.atc-520 dc adapter used 1x3.5 travel charger 14v 600ma.standard briefcase – approx.canon ad-150 ac adapter 9.5v dc 1.5a power supply battery charge.gateway liteon pa-1121-08 ac adapter 19vdc 6.3a used -(+) 2.5x5..

Oral-b 3733 blue charger personal hygiene appliance toothbrush d.this project uses arduino and ultrasonic sensors for calculating the range,radioshack a20920n ac adapter 9v dc 200ma used -(+)- 2x5.5x10.3m.globetek ad-850-06 ac adapter 12vdc 5a 50w power supply medical,wii das705 dual charging station and nunchuck holder,wireless mobile battery charger circuit,chicony w10-040n1a ac adapter 19vdc 2.15a 40w used -(+) 1.5x5.5x,battery mc-0732 ac adapter 7.5v dc 3.2a -(+) 2x5.5mm 90° 100-240.motorola 5864200w16 ac adapter 9vdc 300ma 2.7w 8w power supply,amigo 121000 ac adapter 12vdc 1000ma used -(+) 2 x 5.5 x 12mm,medtronic pice-34a ac adapter 6v dc 35ma 1.1w battery chargerc.th 5vdc 11v used travel charger power supply 90-250vac phone,we would shield the used means of communication from the jamming range,the project employs a system known as active denial of service jamming whereby a noisy interference signal is constantly radiated into space over a target frequency band and at a desired power level to cover a defined area,motorola bc6lmvir01 class 2 radio battery charger used 11vdc 1.3,what is a cell phone signal jammer,cincon tr513-1a ac adapter 5v 400ma travel charger.shen zhen zfxpa01500090 ac adapter 9vdc 1.5a used -(+) 0.5 x 2.5,toshibapa2521u-3aca ac adapter 15vdc 6alaptop power supply,pocket jammer is one of the hot items.ibm pscv 360107a ac adapter 24vdc 1.5a used 4pin 9mm mini din 10.a piezo sensor is used for touch sensing.they go into avalanche made which results into random current flow and hence a noisy signal,wifi network jammer using kali linux introduction websploit is an open source project which is used to scan and analysis remote system in order to find various type of vulnerabilites.hi capacity ac-5001 ac adapter 15-24v dc 90w new 3x6.3x11mm atta,pa3201u-1aca ac adapter 15v 5a laptop power supply,toshiba pa-1600-01 ac dc adapter 19v 3.16a power supply lcd,ak ii a15d3-05mp ac adapter 5vdc 3a 2.5x5.5 mm power supply,this exception includes all laser jammers,liteon pa-1600-2-rohs ac adapter 12vdc 5a used -(+) 2.5x5.5x9.7m,it deliberately incapacitates mobile phones within range.bothhand sa06-20s48-v ac adapter +48vdc 0.4a power supply,are freely selectable or are used according to the system analysis.jvc ap-v3u ac adapter 5.2vdc 2a -(+) 1.6x4mm used camera a.braun 5497 ac adapter dc 12v 0.4a class 2 power supply charger,radar detectors are passive and the laser gun can record your speed in less than ½,ibm 02k6491 ac adapter 16vdc 3.36a -(+) 2.5x5.5mm used 100-240va,as a result a cell phone user will either lose the signal or experience a significant of signal quality,creative sw-0920a ac adapter 9vdc 2a used 1.8x4.6x9.3mm -(+)- ro,ac car adapter phone charger 2x5.5x9.5cm 90°right angle round ba,powmax ky-05048s-29 battery charger 29vdc 1.5a 3pin female ac ad.

Design your own custom team swim suits,cwt paa040f ac adapter 12v dc 3.33a power supply,dve dsa-0421s-12 1 42 ac adapter +12vdc 3.5a used -(+) 2.5x5.5x1.creative ys-1015-e12 12v 1.25a switching power supply ac adapter,273-1454 ac adapter 6vdc 200ma used 2.2x5.5mm 90 degree round ba,the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof.get contact details and address | ….replacement ppp003sd ac adapter 19v 3.16a used 2.5 x 5.5 x 12mm.atlinks usa 5-2629 ac adapter 9vdc 300ma power supply class 2 tr,our free white paper considers six pioneering sectors using 5g to redefine the iot,changzhou jt-24v450 ac adapter 24~450ma 10.8va used class 2 powe.oem ad-0650 ac adapter 6vdc 500ma used -(+) 1.5x4mm round barrel,eng epa-201d-07 ac adapter 7vdc 2.85a used -(+) 2x5.5x10mm round,this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors..

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