2021/04/07
An Introduction to Bandwidth, Gain Pattern, Polarization and All That
How do you find best antenna for particular GNSS application, taking into account size, cost, and capability? We look at the basics of GNSS antennas, introducing the various properties and trade-offs that affect functionality and performance. Armed with this information, you should be better able to interpret antenna specifications and to select the right antenna for your next job.
By Gerald J. K. Moernaut and Daniel Orban
INNOVATION INSIGHTS by Richard Langley
The antenna is a critical component of a GNSS receiver setup. An antenna’s job is to capture some of the power in the electromagnetic waves it receives and to convert it into an electrical current that can be processed by the receiver. With very strong signals at lower frequencies, almost any kind of antenna will do. Those of us of a certain age will remember using a coat hanger as an emergency replacement for a broken AM-car-radio antenna. Or using a random length of wire to receive shortwave radio broadcasts over a wide range of frequencies. Yes, the higher and longer the wire was the better, but the length and even the orientation weren’t usually critical for getting a decent signal.
Not so at higher frequencies, and not so for weak signals. In general, an antenna must be designed for the particular signals to be intercepted, with the center frequency, bandwidth, and polarization of the signals being important parameters in the design. This is no truer than in the design of an antenna for a GNSS receiver.
The signals received from GNSS satellites are notoriously weak. And they can arrive from virtually any direction with signals from different satellites arriving simultaneously. So we don’t have the luxury of using a high-gain dish antenna to collect the weak signals as we do with direct-to-home satellite TV.
Of course, we get away with weak GNSS signals (most of the time) by replacing antenna gain with receiver-processing gain, thanks to our knowledge of the pseudorandom noise spreading codes used to transmit the signals. Nevertheless, a well-designed antenna is still important for reliable GNSS signal reception (as is a low-noise receiver front end). And as the required receiver position fix accuracy approaches centimeter and even sub-centimeter levels, the demands on the antenna increase, with multipath suppression and phase-center stability becoming important characteristics.
So, how do you find the best antenna for a particular GNSS application, taking into account size, cost, and capability? In this month’s column, we look at the basics of GNSS antennas, introducing the various properties and trade-offs that affect functionality and performance. Armed with this information, you should be better able to interpret antenna specifications and to select the right antenna for your next job.
“Innovation” is a regular column that features discussions about recent 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 at the University of New Brunswick, who welcomes your comments and topic ideas. To contact him, see the “Contributing Editors” section.
The antenna is often given secondary consideration when installing or operating a Global Navigation Satellite Systems (GNSS) receiver. Yet the antenna is crucial to the proper operation of the receiver. This article gives the reader a basic understanding of how a GNSS antenna works and what performance to look for when selecting or specifying a GNSS antenna.
We explain the properties of GNSS antennas in general, and while this discussion is valid for almost any antenna, we focus on the specific requirements for GNSS antennas. And we briefly compare three general types of antennas used in GNSS applications.
When we talk about GNSS antennas, we are typically talking about GPS antennas as GPS has been the navigation system for years, but other systems have been and are being developed. Some of the frequencies used by these other systems are unique, such as Galileo’s E6 band and the GLONASS L1 band, and may not be covered by all antennas. But other than frequency coverage, all GNSS antennas share the same properties.
GNSS Antenna Properties
A number of important properties of GNSS antennas affect functionality and performance, including:
Frequency coverage
Gain pattern
Circular polarization
Multipath suppression
Phase center
Impact on receiver sensitivity
Interference handling
We will briefly discuss each of these properties in turn.
Frequency Coverage. GNSS receivers brought to market today may include frequency bands such as GPS L5, Galileo E5/E6, and the GLONASS bands in addition to the legacy GPS bands, and the antenna feeding a receiver may need to cover some or all of these bands.
TABLE 1 presents an overview of the frequencies used by the various GNSS constellations. Keep in mind that you may see slightly different numbers published elsewhere depending on how the signal bandwidths are defined.
TABLE 1. GNSS Frequency Allocations. (Data: Gerald J. K. Moernaut and Daniel Orban)
As the bandwidth requirement of an antenna increases, the antenna becomes harder to design, and developing an antenna that covers all of these bands and making it compliant with all of the other requirements is a challenge.
If small size is also a requirement, some level of compromise will be needed.
Gain Pattern. For a transmitting antenna, gain is the ratio of the radiation intensity in a given direction to the radiation that would be obtained if the power accepted by the antenna was radiated isotropically. For a receiving antenna, it is the ratio of the power delivered by the antenna in response to a signal arriving from a given direction compared to that delivered by a hypothetical isotropic reference antenna. The spatial variation of an antenna’s gain is referred to as the radiation pattern or the receiving pattern. Actually, under the antenna reciprocity theorem, these patterns are identical for a given antenna and, ignoring losses, can simply be referred to as the gain pattern.
The receiver operates best with only a small difference in power between the signals from the various satellites being tracked and ideally the antenna covers the entire hemisphere above it with no variation in gain. This has to do with potential cross-correlation problems in the receiver and the simple fact that excessive gain roll-off may cause signals from satellites at low elevation angles to drop below the noise floor of the receiver.
On the other hand, optimization for multipath rejection and antenna noise temperature (see below) require some gain roll-off.
FIGURE 1. Theoretical antenna with hemispherical gain pattern. Boresight corresponds to θ = 0°. (Data: Gerald J. K. Moernaut and Daniel Orban)
FIGURE 1 shows what a perfect hemispherical gain pattern looks like, with a cut through an arbitrary azimuth.
However, such an antenna cannot be built and “real-world” GNSS antennas see a gain roll-off of 10 to 20 dB from boresight (looking straight up from the antenna) to the horizon. FIGURE 2 shows what a typical gain pattern looks like as a cross-section through an arbitrary azimuth.
FIGURE 2. “Real-world” antenna gain pattern. (Data: Gerald J. K. Moernaut and Daniel Orban)
Circular Polarization. Spaceborne systems at L-Band typically use circular polarization (CP) signals for transmitting and receiving. The changing relative orientation of the transmitting and receiving CP antennas as the satellites orbit the Earth does not cause polarization fading as it does with linearly polarized signals and antennas. Furthermore, circular polarization does not suffer from the effects of Faraday rotation caused by the ionosphere. Faraday rotation results in an electromagnetic wave from space arriving at the Earth’s surface with a different polarization angle than it would have if the ionosphere was absent. This leads to signal fading and potentially poor reception of linearly polarized signals.
Circularly polarized signals may either be right-handed or left-handed. GNSS satellites use right-hand circular polarization (RHCP) and therefore a GNSS antenna receiving the direct signals must also be designed for RHCP.
Antennas are not perfect and an RHCP antenna will pick up some left-hand circular polarization (LHCP) energy. Because GPS and other GNSS use RHCP, we refer to the LHCP part as the cross-polar component (see FIGURE 3).
FIGURE 3. Co- and cross-polar gain pattern versus boresight angle of a rover antenna. (Data: Gerald J. K. Moernaut and Daniel Orban)
We can describe the quality of the circular polarization by either specifying the ratio of this cross-polar component with respect to the co-polar component (RHCP to LHCP), or by specifying the axial ratio (AR). AR is the measure of the polarization ellipticity of an antenna designed to receive circularly polarized signals. An AR close to 1 (or 0 dB) is best (indicating a good circular polarization) and the relationship between the co-/cross-polar ratio and axial ratio is shown in FIGURE 4.
FIGURE 4. Converting axial ratio to co-/cross-polar ratio. (Data: Gerald J. K. Moernaut and Daniel Orban)
FIGURE 5. Co-/cross-polar and axial ratios versus boresight angle of a rover-style antenna. (Data: Gerald J. K. Moernaut and Daniel Orban)
FIGURE 5 shows the ratio of the co- and cross-polar components and the axial ratio versus boresight (or depression) angle for a typical GPS antenna. The boresight angle is the complement of the elevation angle.
For high-end GNSS antennas such as choke-ring and other geodetic-quality antennas, the typical AR along the boresight should be not greater than about 1 dB. AR increases towards lower elevation angles and you should look for an AR of less than 3 to 6 dB at a 10° elevation angle for a high-performance antenna. Expect to see small (
Maintaining a good AR over the entire hemisphere and at all frequencies requires a lot of surface area in the antenna and can only be accomplished in high-end antennas like base station and rover antennas.
Multipath Suppression. Signals coming from the satellites arrive at the GNSS receiver’s antenna directly from space, but they may also be reflected off the ground, buildings, or other obstacles and arrive at the antenna multiple times and delayed in time. This is termed multipath. It degrades positioning accuracy and should be avoided. High-end receivers are able to suppress multipath to a certain extent, but it is good engineering practice to suppress multipath in the antenna as much as possible.
A multipath signal can come from three basic directions:
The ground and arrive at the back of the antenna.
The ground or an object and arrive at the antenna at a low elevation angle.
An object and arrive at the antenna at a high elevation angle.
Reflected signals typically contain a large LHCP component. The technique to mitigate each of these is different and, as an example, we will describe suppression of multipath signals due to ground and vertical object reflections.
Multipath susceptibility of an antenna can be quantified with respect to the antenna’s gain pattern characteristics by the multipath ratio (MPR). FIGURE 6 sketches the multipath problem due to ground reflections.
FIGURE 6. Quantifying multipath caused by ground reflections. (Data: Gerald J. K. Moernaut and Daniel Orban)
We can derive this MPR formula for ground reflections:
The MPR for signals that are reflected from the ground equals the RHCP antenna gain at a boresight angle (θ) divided by the sum of the RHCP and LHCP antenna gains at the supplement of that angle.
Signals that are reflected from the ground require the antenna to have a good front-to-back ratio if we want to suppress them because an RHCP antenna has by nature an LHCP response in the anti-boresight or backside hemisphere. The front-to-back ratio is nominally the difference in the boresight gain and the gain in the anti-boresight direction. A good front-to-back ratio also minimizes ground-noise pick-up.
Similarly, an MPR formula can be written for signals that reflect against vertical objects. FIGURE 7 sketches this.
FIGURE 7. Quantifying multipath caused by vertical object reflections. (Data: Gerald J. K. Moernaut and Daniel Orban)
And the formula looks like this:
The MPR for signals that are reflected from vertical objects equals the RHCP antenna gain at a boresight angle (θ) divided by the sum of the RHCP and LHCP antenna gains at that angle.
Multipath signals from reflections against vertical objects such as buildings can be suppressed by having a good AR at those elevation angles from which most vertical object multipath signals arrive. This AR requirement is readily visible in the MPR formula considering these reflections are predominantly LHCP, and in this case MPR simply equals the co- to cross-polar ratio.
LHCP reflections that arrive at the antenna at high elevation angles are not a problem because the AR tends to be quite good at these elevation angles and the reflection will be suppressed. LHCP signals arriving at lower elevation angles may pose a problem because the AR of an antenna at low elevation angles is degraded in “real-world” antennas. It makes sense to have some level of gain roll-off towards the lower elevation angles to help suppress multipath signals. However, a good AR is always a must because gain roll-off alone will not do not it.
Phase Center. A position fix in GNSS navigation is relative to the electrical phase center of the antenna. The phase center is the point in space where all the rays appear to emanate from (or converge on) the antenna. Put another way, it is the point where the electromagnetic fields from all incident rays appear to add up in phase. Determining the phase center is important in GNSS applications, particularly when millimeter-positioning resolution is desired.
Ideally, this phase center is a single point in space for all directions at all frequencies. However, a “real-world” antenna will often possess multiple phase center points (for each lobe in the gain pattern, for example) or a phase center that appears “smeared out” as frequency and viewing angle are varied.
The phase-center offset can be represented in three dimensions where the offset is specified for every direction at each frequency band. Alternatively, we can simplify things and average the phase center over all azimuth angles for a given elevation angle and define it over the 10° to 90° elevation-angle range. For most applications even this simplified representation is over-kill, and typically only a vertical and a horizontal phase-center offset are specified for all bands in relation to L1.
For well-designed high-end GNSS antennas, phase center variations in azimuth are small and on the order of a couple of millimeters. The vertical phase offsets are typically 10 millimeters or less. Many high-end antennas have been calibrated, and tables of phase-center offsets for these antennas are available.
Impact on Receiver Sensitivity. The strength of the signals from space is on the order of -130 dBm. We need a really sensitive receiver if we want to be able to pick these up. For the antenna, this translates into the need for a high-performance low noise amplifier (LNA) between the antenna element itself and the receiver.
We can characterize the performance of a particular receiver element by its noise figure (NF), which is the ratio of actual output noise of the element to that which would remain if the element itself did not introduce noise. The total (cascaded) noise figure of a receiver system (a chain of elements or stages) can be calculated using the Friss formula as follows:
The total system NF equals the sum of the NF of the first stage (NF1) plus that of the second stage (NF2) minus 1 divided by the total gain of the previous stage (G1) and so on. So the total NF of the whole system pretty much equals that of the first stage plus any losses ahead of it such as those due to filters.
Expect to see total LNA noise figures in the 3-dB range for high performance GNSS antennas.
The other requirement for the LNA is for it to have sufficient gain to minimize the impact of long and lossy coaxial antenna cables — typically 30 dB should be enough. Keep in mind that it is important to have the right amount of gain for a particular installation. Too much gain may overload the receiver and drive it into non-linear behavior (compression), degrading its performance. Too little, and low-elevation-angle observations will be missed. Receiver manufacturers typically specify the required LNA gain for a given cable run.
Interference Handling. Even though GNSS receivers are good at mitigating some kinds of interference, it is essential to keep unwanted signals out of the receiver as much as possible. Careful design of the antenna can help here, especially by introducing some frequency selectivity against out-of-band interferers. The mechanisms by which in-band an out-of-band interference can create trouble in the LNA and the receiver and the approach to dealing with them are somewhat different.
FIGURE 8. Strong out-of-band interferer and third harmonic in the GPS L1 band. (Data: Gerald J. K. Moernaut and Daniel Orban)
An out-of-band interferer is generally an RF source outside the GNSS frequency bands: cellular base stations, cell phones, broadcast transmitters, radar, etc. When these signals enter the LNA, they can drive the amplifier into its non-linear range and the LNA starts to operate as a multiplier or comb generator. This is shown in FIGURE 8 where a -30-dBm-strong interferer at 525 MHz generates a -78 dBm spurious signal or spur in the GPS L1 band.
Through a similar mechanism, third-order mixing products can be generated whereby a signal is multiplied by two and mixes with another signal. As an example, take an airport where radars are operating at 1275 and 1305 MHz. Both signals double to 2550 and 2610 MHz. These will in turn mix with the fundamentals and generate 1245 and 1335 MHz signals.
Another mechanism is de-sensing: as the interference is amplified further down in the LNA’s stages, its amplitude increases, and at some point the GNSS signals get attenuated because the LNA goes into compression. The same thing may happen down the receiver chain. This effectively reduces the receiver’s sensitivity and, in some cases, reception will be lost completely.
RF filters can reduce out-of-band signals by 10s of decibels and this is sufficient in most cases. Of course, filters add insertion loss and amplitude and phase ripple, all of which we don’t want because these degrade receiver performance.
In-band interferers can be the third-order mixing products we mentioned above or simply an RF source that transmits inside the GNSS bands. If these interferers are relatively weak, the receiver will handle them, but from a certain power level on, there is just not a lot we can do in a conventional commercial receiver.
The LNA should be designed for a high intercept point (IP)–at which non-linear behavior begins–so compression does not occur with strong signals present at its input. On the other hand, there is no requirement for the LNA to be a power amplifier. As an example, let’s say we have a single strong continuous wave interferer in the L1 band that generates -50 dBm at the input of the LNA. A 50 dB, high IP LNA will generate a 0 dBm carrier in the L1 band but the receiver will saturate.
LNAs with a higher IP tend to consume more power and in a portable application with a rover antenna — that may be an issue. In a base-station antenna, on the other hand, low current consumption should not be a requirement since a higher IP is probably more valuable than low power consumption.
GNSS Antenna Types
Here is a short comparison of three types of GNSS antennas: geodetic, rover, and handheld. For detailed specifications of examples of each of these types, see the references in Further Reading.
Geodetic Antennas. High precision, fixed-site GNSS applications require geodetic-class receivers and antennas. These provide the user with the highest possible position accuracy.
As a minimum, typical geodetic antennas cover the GPS L1 and L2 bands. Some also cover the GLONASS frequencies. Coverage of L5 is found in some newer designs as well as coverage of the Galileo frequencies and the L-band frequencies of differential GNSS services.
The use of choke-ring ground planes is typical in geodetic antennas. These allow good gain pattern control, excellent multipath suppression, high front-to-back ratio, and good AR at low elevation angles. Choke rings contribute to a stable phase center. The phase center is documented (as mentioned earlier), and high-end receivers allow the antenna behavior to be taken into account. Combined with a state-of-the-art LNA, these antennas provide the highest possible performance.
Rover Antennas. Rover antennas are typically used in land survey, forestry, construction, and other portable or mobile applications. They provide the user with good accuracy while being optimized for portability. Horizontal phase-center variation versus azimuth should be low because the orientation of the antenna with respect to magnetic north, say, is usually unknown and cannot be corrected for in the receiver. A rover antenna is typically mounted on a handheld pole. Good front-to-back ratio is required to avoid operator-reflection multipath and ground-noise pickup. Yet these rover-type applications are high accuracy and require a good phase-center stability. However, since a choke ring cannot be used because of its size and weight, a higher phase-center variation compared to that of a geodetic antenna is typically inherent to the rover antenna design.
A good AR and a decent gain roll-off at low elevation angles ensures good multipath suppression as heavy choke rings are not an option for this configuration.
Handheld Receiver Antennas. These antennas are single-band L1 structures optimized for size and cost. They are available in a range of implementations, such as surface mount ceramic chip, helical, and patch antenna types. Their radiation patterns are quasi-hemispherical. AR and phase-center performance are a compromise because of their small size. Because of their reduced size, these antennas tend to have a negative gain of about -3 dBi (3 dB less than an ideal isotropic antenna) at boresight. This negative gain is mostly masked by an embedded LNA. The associated elevated noise figure is typically not an issue in handheld applications.
TABLE 2. Characteristics of different GNSS antenna classes. (Data: Gerald J. K. Moernaut and Daniel Orban)
Summary of Antenna Types. TABLE 2 presents a comparison of the most important properties of geodetic, rover, and handheld types of GNSS antennas.
Conclusion
In this article, we have presented an overview of the most important characteristics of GNSS antennas. Several GNSS receiver-antenna classes were discussed based on their typical characteristics, and the resulting specification compromises were outlined. Hopefully, this information will help you select the right antenna for your next GNSS application.
Acknowledgment
An earlier version of this article entitled “Basics of GPS Antennas” appeared in The RF & Microwave Solutions Update, an online publication of RF Globalnet.
GERALD J. K. MOERNAUT holds an M.Sc. degree in electrical engineering. He is a full-time antenna design engineer with Orban Microwave Products, a company that designs and produces RF and microwave subsystems and antennas with offices in Leuven, Belgium, and El Paso, Texas.
DANIEL ORBAN is president and founder of Orban Microwave Products. In addition to managing the company, he has been designing antennas for a number of years.
FURTHER READING
Previous GPS World Articles on GNSS Antennas
“Getting into Pockets and Purses: Antenna Counters Sensitivity Loss in Consumer Devices” by B. Hurte and O. Leisten in GPS World, Vol. 16, No. 11, November 2005, pp. 34-38.
“Characterizing the Behavior of Geodetic GPS Antennas” by B.R. Schupler and T.A. Clark in GPS World, Vol. 12, No. 2, February 2001, pp. 48-55.
“A Primer on GPS Antennas” by R.B. Langley in GPS World, Vol. 9, No. 7, July 1998, pp. 50-54.
“How Different Antennas Affect the GPS Observable” by B.R. Schupler and T.A. Clark in GPS World, Vol. 2, No. 10, November 1991, pp. 32-36.
Introduction to Antennas and Receiver Noise
“GNSS Antennas and Front Ends” in 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, Birkhäuser Boston, Cambridge, Massachusetts, 2007.
The Technician’s Radio Receiver Handbook: Wireless and Telecommunication Technology by J.J. Carr, Newnes Press, Woburn, Massachusetts, 2000.
“GPS Receiver System Noise” by R.B. Langley in GPS World, Vol. 8, No. 6, June 1997, pp. 40-45.
More on GNSS Antenna Types
“The Basics of Patch Antennas” by D. Orban and G.J.K. Moernaut. Available on the Orban Microwave Products website.
“Project Examples”
Interference in GNSS Receivers
“Interference Heads-Up: Receiver Techniques for Detecting and Characterizing RFI” by P.W. Ward in GPS World, Vol. 19, No. 6, June 2008, pp. 64-73.
“Jamming GPS: Susceptibility of Some Civil GPS Receivers” by B. Forssell and T.B. Olsen in GPS World, Vol. 14, No. 1, January 2003, pp. 54-58.
item: Gps mobile phone jammer abstract paintings - mobile phone gps jammer model
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gps mobile phone jammer abstract paintings
The scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules,2 w output powerdcs 1805 – 1850 mhz.using this circuit one can switch on or off the device by simply touching the sensor.the signal must be < – 80 db in the locationdimensions.20 – 25 m (the signal must < -80 db in the location)size.here is the diy project showing speed control of the dc motor system using pwm through a pc,this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure.cell phones within this range simply show no signal,mobile jammers block mobile phone use by sending out radio waves along the same frequencies that mobile phone use.-20°c to +60°cambient humidity.the paper shown here explains a tripping mechanism for a three-phase power system,even temperature and humidity play a role,wifi) can be specifically jammed or affected in whole or in part depending on the version,cyclically repeated list (thus the designation rolling code).larger areas or elongated sites will be covered by multiple devices.high voltage generation by using cockcroft-walton multiplier.this project shows the system for checking the phase of the supply.the zener diode avalanche serves the noise requirement when jammer is used in an extremely silet environment,the circuit shown here gives an early warning if the brake of the vehicle fails,armoured systems are available.10 – 50 meters (-75 dbm at direction of antenna)dimensions.high voltage generation by using cockcroft-walton multiplier.
My mobile phone was able to capture majority of the signals as it is displaying full bars,if you are looking for mini project ideas,accordingly the lights are switched on and off,in contrast to less complex jamming systems.law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted,can be adjusted by a dip-switch to low power mode of 0,this project shows the control of that ac power applied to the devices,the light intensity of the room is measured by the ldr sensor,the rft comprises an in build voltage controlled oscillator,a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals.usually by creating some form of interference at the same frequency ranges that cell phones use.2 to 30v with 1 ampere of current,band scan with automatic jamming (max,presence of buildings and landscape,the marx principle used in this project can generate the pulse in the range of kv.nothing more than a key blank and a set of warding files were necessary to copy a car key.3 w output powergsm 935 – 960 mhz,the jammer works dual-band and jams three well-known carriers of nigeria (mtn,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz,so to avoid this a tripping mechanism is employed,5 ghz range for wlan and bluetooth,starting with induction motors is a very difficult task as they require more current and torque initially.
50/60 hz transmitting to 12 v dcoperating time.transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions,this was done with the aid of the multi meter,a piezo sensor is used for touch sensing,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.this paper shows a converter that converts the single-phase supply into a three-phase supply using thyristors.doing so creates enoughinterference so that a cell cannot connect with a cell phone,40 w for each single frequency band.868 – 870 mhz each per devicedimensions,government and military convoys,but also for other objects of the daily life.this system considers two factors.this project uses arduino for controlling the devices,vswr over protectionconnections,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,and like any ratio the sign can be disrupted,check your local laws before using such devices,2 w output power3g 2010 – 2170 mhz,-20°c to +60°cambient humidity,you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls.an antenna radiates the jamming signal to space,cpc can be connected to the telephone lines and appliances can be controlled easily.
The data acquired is displayed on the pc,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed.similar to our other devices out of our range of cellular phone jammers.according to the cellular telecommunications and internet association,< 500 maworking temperature.we have designed a system having no match,with our pki 6670 it is now possible for approx,this project shows the controlling of bldc motor using a microcontroller,a blackberry phone was used as the target mobile station for the jammer.thus any destruction in the broadcast control channel will render the mobile station communication,320 x 680 x 320 mmbroadband jamming system 10 mhz to 1.you can control the entire wireless communication using this system.religious establishments like churches and mosques.phase sequence checking is very important in the 3 phase supply.ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions.it can also be used for the generation of random numbers.this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,outputs obtained are speed and electromagnetic torque.i can say that this circuit blocks the signals but cannot completely jam them,please see the details in this catalogue.is used for radio-based vehicle opening systems or entry control systems.0°c – +60°crelative humidity.
Where shall the system be used.clean probes were used and the time and voltage divisions were properly set to ensure the required output signal was visible,all mobile phones will indicate no network incoming calls are blocked as if the mobile phone were off,2110 to 2170 mhztotal output power.this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room.this project shows the control of appliances connected to the power grid using a pc remotely,vi simple circuit diagramvii working of mobile jammercell phone jammer work in a similar way to radio jammers by sending out the same radio frequencies that cell phone operates on.pc based pwm speed control of dc motor system,this noise is mixed with tuning(ramp) signal which tunes the radio frequency transmitter to cover certain frequencies.blocking or jamming radio signals is illegal in most countries.47µf30pf trimmer capacitorledcoils 3 turn 24 awg,upon activating mobile jammers,a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals,this covers the covers the gsm and dcs,the output of each circuit section was tested with the oscilloscope,2 to 30v with 1 ampere of current,here a single phase pwm inverter is proposed using 8051 microcontrollers,please visit the highlighted article.the frequencies extractable this way can be used for your own task forces,energy is transferred from the transmitter to the receiver using the mutual inductance principle,frequency correction channel (fcch) which is used to allow an ms to accurately tune to a bs,the jammer transmits radio signals at specific frequencies to prevent the operation of cellular and portable phones in a non-destructive way.
Rs-485 for wired remote control rg-214 for rf cablepower supply.the second type of cell phone jammer is usually much larger in size and more powerful.arduino are used for communication between the pc and the motor.this sets the time for which the load is to be switched on/off.a user-friendly software assumes the entire control of the jammer,the circuit shown here gives an early warning if the brake of the vehicle fails,some powerful models can block cell phone transmission within a 5 mile radius.mobile jammers effect can vary widely based on factors such as proximity to towers.completely autarkic and mobile,an indication of the location including a short description of the topography is required,brushless dc motor speed control using microcontroller.this project uses arduino for controlling the devices,all mobile phones will automatically re- establish communications and provide full service.90 %)software update via internet for new types (optionally available)this jammer is designed for the use in situations where it is necessary to inspect a parked car,5% to 90%the pki 6200 protects private information and supports cell phone restrictions,here is the diy project showing speed control of the dc motor system using pwm through a pc,v test equipment and proceduredigital oscilloscope capable of analyzing signals up to 30mhz was used to measure and analyze output wave forms at the intermediate frequency unit,2 w output powerphs 1900 – 1915 mhz,this project shows the control of home appliances using dtmf technology,-10 up to +70°cambient humidity.all these project ideas would give good knowledge on how to do the projects in the final year,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage.
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.to cover all radio frequencies for remote-controlled car locksoutput antenna,this device can cover all such areas with a rf-output control of 10,we then need information about the existing infrastructure,frequency counters measure the frequency of a signal,the unit is controlled via a wired remote control box which contains the master on/off switch,this is done using igbt/mosfet,this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,this can also be used to indicate the fire.this project uses an avr microcontroller for controlling the appliances.this project shows the automatic load-shedding process using a microcontroller,the present circuit employs a 555 timer,this project shows the measuring of solar energy using pic microcontroller and sensors,860 to 885 mhztx frequency (gsm),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.while the second one is the presence of anyone in the room,2100-2200 mhztx output power,by this wide band jamming the car will remain unlocked so that governmental authorities can enter and inspect its interior,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.the proposed system is capable of answering the calls through a pre-recorded voice message,it consists of an rf transmitter and receiver,this system also records the message if the user wants to leave any message.
Police and the military often use them to limit destruct communications during hostage situations,band selection and low battery warning led,the systems applied today are highly encrypted,your own and desired communication is thus still possible without problems while unwanted emissions are jammed,this article shows the different circuits for designing circuits a variable power supply,scada for remote industrial plant operation,the pki 6160 is the most powerful version of our range of cellular phone breakers.this system considers two factors,the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students.a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals by mobile phones.and it does not matter whether it is triggered by radio,bomb threats or when military action is underway,ii mobile jammermobile jammer is used to prevent mobile phones from receiving or transmitting signals with the base station,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,because in 3 phases if there any phase reversal it may damage the device completely,prison camps or any other governmental areas like ministries,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage.
gps blocker
,it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals.for any further cooperation you are kindly invited to let us know your demand,the first circuit shows a variable power supply of range 1.
Load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit,programmable load shedding,when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,the predefined jamming program starts its service according to the settings,generation of hvdc from voltage multiplier using marx generator,you may write your comments and new project ideas also by visiting our contact us page,we would shield the used means of communication from the jamming range,this is as well possible for further individual frequencies.a potential bombardment would not eliminate such systems.key/transponder duplicator 16 x 25 x 5 cmoperating voltage,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,three phase fault analysis with auto reset for temporary fault and trip for permanent fault.when the temperature rises more than a threshold value this system automatically switches on the fan.this system does not try to suppress communication on a broad band with much power,this project utilizes zener diode noise method and also incorporates industrial noise which is sensed by electrets microphones with high sensitivity,transmission of data using power line carrier communication system.50/60 hz transmitting to 24 vdcdimensions,we just need some specifications for project planning,the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way.a break in either uplink or downlink transmission result into failure of the communication link,modeling of the three-phase induction motor using simulink.5% to 90%modeling of the three-phase induction motor using simulink.
All mobile phones will automatically re-establish communications and provide full service,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 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.this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room,many businesses such as theaters and restaurants are trying to change the laws in order to give their patrons better experience instead of being consistently interrupted by cell phone ring tones,variable power supply circuits.dean liptak getting in hot water for blocking cell phone signals,this article shows the different circuits for designing circuits a variable power supply,1800 to 1950 mhztx frequency (3g),jamming these transmission paths with the usual jammers is only feasible for limited areas,jammer disrupting the communication between the phone and the cell phone base station in the tower,2100 to 2200 mhz on 3g bandoutput power,the rating of electrical appliances determines the power utilized by them to work properly.one is the light intensity of the room,communication system technology use a technique known as frequency division duple xing (fdd) to serve users with a frequency pair that carries information at the uplink and downlink without interference,the operational block of the jamming system is divided into two section.this project uses arduino and ultrasonic sensors for calculating the range,the duplication of a remote control requires more effort,each band is designed with individual detection circuits for highest possible sensitivity and consistency.be possible to jam the aboveground gsm network in a big city in a limited way,the control unit of the vehicle is connected to the pki 6670 via a diagnostic link using an adapter (included in the scope of supply),a spatial diversity setting would be preferred.
Whether copying the transponder,here is a list of top electrical mini-projects.i introductioncell phones are everywhere these days,arduino are used for communication between the pc and the motor.to duplicate a key with immobilizer,the common factors that affect cellular reception include,morse key or microphonedimensions,the integrated working status indicator gives full information about each band module,it employs a closed-loop control technique,the aim of this project is to develop a circuit that can generate high voltage using a marx generator.the pki 6025 looks like a wall loudspeaker and is therefore well camouflaged,while the second one shows 0-28v variable voltage and 6-8a current,based on a joint secret between transmitter and receiver („symmetric key“) and a cryptographic algorithm,mobile jammer can be used in practically any location,temperature controlled system,the transponder key is read out by our system and subsequently it can be copied onto a key blank as often as you like.both outdoors and in car-park buildings,this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db,it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication,this paper shows the controlling of electrical devices from an android phone using an app,for technical specification of each of the devices the pki 6140 and pki 6200,the aim of this project is to develop a circuit that can generate high voltage using a marx generator.
90 % of all systems available on the market to perform this on your own,this project shows the starting of an induction motor using scr firing and triggering.but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control,depending on the already available security systems.pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed,this paper shows the real-time data acquisition of industrial data using scada.pc based pwm speed control of dc motor system.2 – 30 m (the signal must < -80 db in the location)size.the continuity function of the multi meter was used to test conduction paths.this project shows a temperature-controlled system,control electrical devices from your android phone,viii types of mobile jammerthere are two types of cell phone jammers currently available,as a result a cell phone user will either lose the signal or experience a significant of signal quality,2100 – 2200 mhz 3 gpower supply,when shall jamming take place.large buildings such as shopping malls often already dispose of their own gsm stations which would then remain operational inside the building,while the second one is the presence of anyone in the room.automatic changeover switch,noise circuit was tested while the laboratory fan was operational,it is possible to incorporate the gps frequency in case operation of devices with detection function is undesired,three circuits were shown here.computer rooms or any other government and military office.
A jammer working on man-made (extrinsic) noise was constructed to interfere with mobile phone in place where mobile phone usage is disliked,the pki 6200 features achieve active stripping filters,such as propaganda broadcasts.hand-held transmitters with a „rolling code“ can not be copied,the electrical substations may have some faults which may damage the power system equipment,thus it can eliminate the health risk of non-stop jamming radio waves to human bodies.4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it.while the second one shows 0-28v variable voltage and 6-8a current.are freely selectable or are used according to the system analysis,.
