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Global positioning system report and ppt
Post: #16

.docx  Imamul Report.docx (Size: 478.38 KB / Downloads: 64)
This is a new technique for the protection of transmission systems by using the global positioning system (GPS) and fault generated transients. In this scheme the relay contains a fault transient detection system together with a communication unit, which is connected to the power line through the high voltage coupling capacitors of the CVT. Relays are installed at each bus bar in a transmission network. These detect the fault generated high frequency voltage transient signals and record the time instant corresponding to when the initial traveling wave generated by the fault arrives at the busbar.
The decision to trip is based on the components as they propagate through the system extensive simulation studies of the technique were carried out to examine the response to different power system and fault condition. The communication unit is used to transmit and receive coded digital signals of the local information to and from associated relays in the system.
At each substation relay determine the location of the fault by comparing the GPS time stay measured locally with those received from the adjacent substations, extensive simulation studies presented here demonstrate feasibility of the scheme.

Accurate location of faults on power transmission systems can save time and resources for the electric utility industry. Line searches for faults are costly and can be inconclusive. Accurate information needs to be acquired quickly in a form most useful to the power system operator communicating to field personnel.
To achieve this accuracy, a complete system of fault location technology, hardware, communications, and software systems can be designed. Technology is available which can help determine fault location to within a transmission span of 300 meters. Reliable self monitoring hardware can be configured for installation sites with varying geographic and environmental conditions. Communications systems can retrieve fault location information from substations and quickly provide that information to system operators. Other communication systems, such as Supervisory Control and Data Acquisition (SCADA), operate fault sectionalizing circuit breakers and switches remotely and provide a means of fast restoration. Data from SCADA, such as sequence of events, relays, and oscillographs, can be used for fault location selection and verification. Software in a central computer can collect fault information and reduce operator response time by providing only the concise information required for field personnel communications. Fault location systems usually determine “distance to fault” from a transmission line end. Field personnel can use this data to find fault locations from transmission line maps and drawings. Some utilities have automated this process by placing the information in a fault location Geographical Information System (GIS) computer. Since adding transmission line data to the computer can be a large effort, some utilities have further shortened the process by utilizing a transmission structures location database. Several utilities have recently created these databases for transmission inventory using GPS location technology and handheld computers.
The inventory database probably contains more information than needed for a fault location system, and a reduced version would save the large data-collection effort. Using this data, the power system operator could provide field personnel direct location information.
Field personnel could use online information to help them avoid spending valuable time looking for maps and drawings and possibly even reduce their travel time. With precise information available, crews can prepare for the geography, climatic conditions, and means of transport to the faulted location. Repair time and resources would be optimized by the collected data before departure. Accurate fault location can also aid in fast restoration of power, particularly on transmission lines with distributed loads. Power system operators can identify and isolate faulted sections on tap-loaded lines and remove them by opening circuit breakers or switches remotely along the line, restoring power to the tap loads serviced by the unfaulted transmission sections.

Electric power transmission, a process in the delivery of electricity to consumers, is the bulk transfer of electrical power. Typically, power transmission is between the power plant and a substation near a populated area. Electricity distribution is the delivery from the substation to the consumers. Electric power transmission allows distant energy sources (such as hydroelectric power plants) to be connected to consumers in population centers, and may allow exploitation of low-grade fuel resources that would otherwise be too costly to transport to generating facilities. Due to the large amount of power involved, transmission normally takes place at high voltage (110 kV or above). Electricity is usually transmitted over long distance through overhead power transmission lines. Underground power transmission is used only in densely populated areas due to its high cost of installation and maintenance, and because the high reactive power produces large charging currents and difficulties in voltage management. A power transmission system is sometimes referred to colloquially as a "grid"; however, for reasons of economy, the network is not a mathematical grid. Redundant paths and lines are provided so that power can be routed from any power plant to any load center, through a variety of routes, based on the economics of the transmission path and the cost of power. Much analysis is done by transmission companies to determine the maximum reliable capacity of each line, which, due to system stability considerations, may be less than the physical or thermal limit of the line.

Faults on the power transmission system cause transients that propagate along the transmission line as waves. Each wave is a composite of frequencies, ranging from a few kilohertz to several megahertz, having a fast rising front and a slower decaying tail. Composite waves have a propagation velocity and characteristic impedance and travel near the speed of light away from the fault location toward line ends. They continue to travel throughout the power system until they diminish due to impedance and reflection waves and new power system equilibrium is reached. The location of faults is accomplished by precisely time-tagging wave fronts as they cross a known point typically in substations at line ends. With waves time tagged to sub microsecond resolution of 30 m, fault location accuracy of 300 m can be obtained. Fault location can then be obtained by multiplying the wave velocity by the time difference in line ends. This collection and calculation of time data is usually done at a master station. Master station information polling time should be fast enough for system operator needs.

Early fault locators used pulsed radar. This technique uses reflected radar energy to determine the fault location. Radar equipment is typically mobile or located at substations and requires manual operation. This technique is popular for location of permanent faults on cable sections when the cable is de-energized. Impedance-based fault locators are a popular means of transmission line fault locating. They provide algorithm advances that correct for fault resistance and load current inaccuracies. Line length accuracies of ±5% are typical for single-ended locators and 1-2% for two-ended locator systems. Traveling wave fault locators are becoming popular where higher accuracy is important. Long lines, difficult accessibility lines, high voltage direct current (HVDC), and series-compensated lines are popular applications. Accuracies of <300 meters have been achieved on 500 kV transmission lines with this technique. Hewlett-Packard has developed a GPS-based sub microsecond timing system that has proven reliable in several utility traveling wave projects. This low-cost system can also be used as the substation master clock.
Post: #17

.doc  Global Positioning System.doc (Size: 205.5 KB / Downloads: 64)
A review as a communication systems application

The last decade saw the emergence of yet another satellite-based navigational system called the GLOBAL POSITIONING SYSTEM, which is today capable of providing accuracy levels of less than a centimeter. The GLOBAL POSITIONING SYSTEM is a radio-based navigation system that gives 3-D coverage of the earth 24 hours a day in all weather conditions. Using a commercial GLOBAL POSITIONING SYSTEM locator, the user can determine his position on the earth .Out of 24 NAVSTAR satellites 21 are operational satellites and the other three are standby satellites. The control segment comprises five monitoring stations that are capable of transmitting data to the satellite. The user segment consists of receivers, which could be handheld or installed on aircrafts, ships, tanks, submarines, etc. Receivers detect, decode and process GLOBAL POSITIONING SYSTEM satellite signals and convert them into position, velocity and time estimates.

It is new generation of universal navigational aid based on satellite. In GLOBAL POSITIONING SYSTEM, radio signals from number of orbiting satellites are received by an aircraft or ships, as the case may be the GLOBAL POSITIONING SYSTEM is most cost effective and versatile universal navigational aid for the coming years.
It is a second generation satellite navigational based on the measurement of the times of arrival of time signal received from three or more orbiting satellite, whose positional co-ordinates in the space are also transmitted. There are now 21 GLOBAL POSITIONING SYSTEM satellites including three spares, in 12 hours circular orbits inclined at an angle of 55 0 to the altitude of 20,200 Km. This altitude is about half way lower then geostationary satellite. This will ensure that, at least 4 satellites will be visible at a time from any location round the world for position determination from the aircraft and the ship. Signals from up to 10 number of GLOBAL POSITIONING SYSTEM satellite may be received in a GLOBAL POSITIONING SYSTEM receiver and typically up to 7 satellites are involved at a time for position determination of GLOBAL POSITIONING SYSTEM station. The timing pulses are sent out by each satellite in the L band using spread spectrum modulation and received by the GLOBAL POSITIONING SYSTEM receiver in aircraft or ships, as the case may be processed by match filter which is required to be increased the precision of arrival time measurement of the pulse. The onboard GLOBAL POSITIONING SYSTEM receivers are however much simpler then required for Doppler Navigations and they are excepted to determine the position of an aircraft or ships with precision of 16 meter as better in 3-dimension. It is planned by International Civil Aviation Organization (ICAO), to install GLOBAL POSITIONING SYSTEM round the world and eventually renders the conventional navigational aid for airport and ships.
GLOBAL POSITIONING SYSTEM for navigations use to determine the positional coordinator of user weaker which may be aircraft or ship or land mobile vehicle by measuring its distance by range from 3 or more satellites, whose positional coordinates are telemeter to the user by radio links using a coed. If the delay of the received code relative to the locally generated identical Reference code at the users location be T1, T2 , T3 for the satellite transmission from SV1,SV2,SV3 respectively. Then respective ranges are given by
* R1=C T1
* R2=C T2
* R3=C T3
The point of intersection of this three lines representing the ranges R1,R2 and R3 defines the special coordinates of the user vehicle and then it can be converted into latitude, longitude and altitude, by transformation of coordinates using computers. In an GLOBAL POSITIONING SYSTEM navigation system the information about time is required for which the signal from the fourth GLOBAL POSITIONING SYSTEM satellite at a range R4 has also to be utilized to obtain 4 equations relating R1, R2 ,R3 and R4 to t1, t2, t3 and t4 respectively. Three of these equations will allow us to determine the positional coordinates, while the fourth is used to derive the time information. Another way of looking at the problem would be consider that we must have at least four equations to solve for the four unknowns X, Y, Z and T .To measure the value of time delay for wave propagation between satellite transmitter and users receiver phase modulated radio signals in L-band are first received by the GLOBAL POSITIONING SYSTEM receiver from the GLOBAL POSITIONING SYSTEM satellites. The received signals are then demodulated by phase demodulator and resulting pseudo noise code is compared by locally generated code to measure the delay between the envelope delay the range of satellite is determine.
RF front end of GLOBAL POSITIONING SYSTEM receiver converts the equencythe signal received by the helical antenna to an intermediate frequency by double
Super heterodyne technique to process the data digitally for determining the users geographic position.
Low noise pre amplification is done either by: -
1). Low noise bipolar transistor OR
2). Low noise High electron mobility Transistor OR
3). Pseudomorphic High electron mobility Transistor OR
4). Ga As MOSET OR
5). Silicon MMICS OR
6). Schottky diodes.
Silicon MMICS or PIN attenuators diodes are used for AGC.Bipolar transistor provides a low phase noise for the local oscillator Phase. Locked to the crystal reference oscillator. The signal processing circuit is comprised of coherent clocked Detector for the C/A code and/or P-code, estimate for latitude, longitude &altitude of the GLOBAL POSITIONING SYSTEM station together with their errors X Y, Z. And time error T.
GLOBAL POSITIONING SYSTEM is comprised of three distinct segments.
1) Space segment.
2) Control segment.
3) User segment.
It comprises of 18 satellites orbiting in a circular orbits at an altitude of 20,200 Km at an inclination of 55 Degree with a period of 12 hours. The relative position is arrange in such a way that at least four satellites will be visible to any user at a given instant of time thus, ensuring a GLOBAL coverage.(A broad beam antenna used in GLOBAL POSITIONING SYSTEM receiving system ,up to 10 satellite signals can be received.) Each satellite is design to transmit radio signals at two L-band frequencies for commercial services 1575.42 MHz , and for military purpose 1277.6 MHz is used.
The radiation pattern of L-band transmitting antenna at the GLOBAL POSITIONING SYSTEM satellite are specially designed to produce uniform signal strength at earth surface independent of
Position of user. Besides this for allowing control and telemetry function by ground station, the satellite has S-band antenna operating on a down link frequency of 22 to 27.5 MHz and up link frequency is 1783.74 MHz.
Post: #18

.ppt  13_GPS.PPT (Size: 4.18 MB / Downloads: 53)
Global Positioning System (GPS)

The current global positioning system (GPS) is the culmination of years of research and unknown millions of dollars.
Navigational systems have been and continue to be developed and funded by the U.S. government.
The current system is managed by the U.S Air Force for the Department of Defense (DOD).
The current system became fully operational June 26, 1993 when the 24th satellite was lunched.
While there are millions of civil users of GPS worldwide, the system was designed for and is operated by the U. S. military.

GPS provides specially coded satellite signals that can be processed with a GPS receiver, enabling the receiver to compute position, velocity and time.
A minimum of four GPS satellite signals are required to compute positions in three dimensions and the time offset in the receiver clock.
Accuracy and precision of data increases with more satellites.
Three Parts
Space segment
Control segment
User segment
Space Segment
The Air force insures that at least 24 satellites are operational at all times.
There are six orbital planes (with nominally four space vehicles (SVs) in each), equally spaced (60 degrees apart), and inclined at about fifty-five degrees with respect to the equatorial plane.
The satellite orbits are controlled so that at least six should be available, unobstructed location, at all times.
Each satellite circles the earth twice a day.
Control Segment
The Master Control facility is located at Schriever Air Force Base (formerly Falcon AFB) in Colorado.
Control Segment--cont.
User Segment
The primary use of GPS is navigation.
Navigation receivers are made for aircraft, ships, ground vehicles, surveying, and for hand carrying by individuals.
The accuracy of a receiver depends on the number of channels, compatibility with other navigational systems (WAAS, GLONAS, etc.) and design of the receiver (cost).
User Segment--cont.
The GPS User Segment consists of all GPS receivers.
GPS receivers convert satellite signals into position, velocity, and time estimates.
Four satellites are required to compute the four dimensions of X, Y, Z (position) and Time.
User Segment--cont.
Time and frequency dissemination, based on the precise clocks on board the SVs and controlled by the monitor stations, is another use for GPS.
Astronomical observatories, telecommunications facilities, and laboratory standards can be set to precise time signals or controlled to accurate frequencies by special purpose GPS receivers.
The GPS signals are available to everyone, and there is no limit to the number and types of applications that use them.
The GPS system operates on the principles of trilateration, determining positions from distance measurements.
This can be explained using the velocity equation.
Trilateration Example
The signals from the GPS satellites travel at the speed of light--186,000 feet/second.
How far apart are the sender and the receiver if the signal travel time was 0.23 seconds?
Satellite Signals
Each satellite has its own unique signal.
It continuously broadcasts its signal and also sends out a time stamp every time it starts.
The receiver has a copy of each satellite signal and determines the distance by recording the time between when the satellite says it starts its signal and when the signal reaches the receiver.
GPS Trilateration
Each satellite knows its position and its distance from the center of the earth.
Each satellite constantly broadcasts this information.
With this information the receiver tries to calculate its position.
Just knowing the distance to one satellite doesn’t provide enough information.
GPS Trilateration--cont.
When the receiver knows its distance from only one satellite, its location could be anywhere on the earths surface that is an equal distance from the satellite.
All the receiver can determine is that it is some where on the perimeter of a circle that is an equal distance from the satellite.
The receiver must have additional information.
GPS Trilateration--cont.
With signals from two satellites, the receiver can narrow down its location to just two points on the earths surface.
GPS Trilateration--cont.
Knowing its distance from three satellites, the receiver can determine its location because there is only two possible combinations and one of them is out in space.
In this example, the receiver is located at b.
Most receivers actually require four to insure the receiver has full information on time, and satellite positions.
The more satellite positions that are used, the greater the potential accuracy of the position location.
Factors Influencing Position Accuracy
The number of satellites (channels) the receiver can track.
The number of channels a receiver has is part of it’s design.
The higher the number of channels---the greater the potential accuracy.
The higher the number of channels---the greater the cost.
The number of satellites that are available at the time.
Because of the way the satellites orbit, the same number are not available at all times.
When planning precise GPS measurements it is important to check for satellite availability for the location and time of measurement.
If a larger number of channels are required (6-10), and at the time of measurement the number available was less than that, the data will be less accurate.
Factors Influencing Position Accuracy--cont.
The system errors that are occurring during the time the receiver is operating.
The GPS system has several errors that have the potential to reduce the accuracy.
To achieve high levels of precision, differential GPS must be used.
Differential GPS uses one unit at a known location and a rover.
The stationary unit compares its calculated GPS location with the actual location and computes the error.
The rover data is adjusted for the error.
Real Time Kinematic (RTK)
Post processing
Once the GPS receiver has located its position it is usually displayed in one of two common formats:
Latitude and longitude
Universal transverse mercator (UTM).
Latitude and Longitude
Latitudes and longitudes are angles.
Latitude gives the location of a place on the Earth north or south of the Equator.
Latitude is an angular measurement in degrees (marked with °) ranging from 0° at the Equator to 90° at the poles (90° N for the North Pole or 90° S for the South Pole)
The equator divides the planet into a Northern Hemisphere and a Southern Hemisphere.
The latitude of the equator is, by definition, 0°.
Four lines of latitude are named because of the role they play in the geometrical relationship with the Earth and the Sun.
The circumference of the earth at the equator is approximately 24,901.55 miles.
There is an important difference between latitude and longitude.
The circumference of the earth declines as the latitude increase away from the equator.
This means the miles per degree of longitude changes with the latitude.
This makes determining the distance between two points identified by longitude more difficult.
Mercator Projection
A Mercator projection is a ‘pseudocylindrical’ conformal projection (it preserves shape).
Points on the earth are transferred, on an angle from the center of the earth, to the surface of the cylinder.
What you often see on poster-size maps of the world is an equatorial mercator projection that has relatively little distortion along the equator, but quite a bit of distortion toward the poles.
Mercator Projection
What a transverse mercator projection does, in effect, is orient the ‘equator’ north-south (through the poles), thus providing a north-south oriented swath of little distortion.
By changing slightly the orientation of the cylinder onto which the map is projected, successive swaths of relatively undistorted regions can be created.
UTM Zones
These zones begin at 180o longitude and are numbered consecutively eastward.
UTM Zones--cont.
The conterminous United States is covered by 10 UTM grid zones.
In the Northern Hemisphere each zone's northing coordinate begins at the equator as 0,000,000 and is numbered north in meters.
The UTM system uses a different grid for the polar regions.
These areas are covered by a different conformal projection called the Polar Stereographic.
Since compass directions have little meaning at the poles, one direction on the grid is arbitrarily designated "north-south" and the other "east-west" regardless of the actual compass direction.
The UTM coordinates are called "false northing" and "false easting.”
Using Location Information
Determining UTM Zone

Treat west longitude as negative and east as positive.
Add 180 degrees; this converts the longitude to a number between zero and 360 degrees.
Divide by 6 and round up to the next higher number.
The location of the intersection of Hall of Fame and Virginia on OSU campus is 56 7 23.71 N and 97 05 16.079 W.
Determining a UTM Grid Value for a Map Point
The UTM grid is shown on all quadrangle maps prepared by the U.S. Geological Survey (USGS).
On 7.5-minute quadrangle maps (1:24,000 and 1:25,000 scale) and 15-minute quadrangle maps (1:50,000, 1:62,500, and standard-edition 1:63,360 scales), the UTM grid lines are indicated at intervals of 1,000 meters, either by blue ticks in the margins of the map or with full grid lines.
The 1,000-meter value of the ticks is shown for every tick or grid line.
Determining a UTM Grid Value for a Map Point--cont.
To use the UTM grid, you can place a transparent grid overlay on the map to subdivide the grid, or you can draw lines on the map connecting corresponding ticks on opposite edges.
The distances can be measured in meters at the map scale between any map point and the nearest grid lines to the south and west.
The northing of the point is the value of the nearest grid line south of it plus its distance north of that line; its easting is the value of the nearest grid line west of it plus its distance east of that line.
Determining Distance Using UTM
In the illustration the UTM coordinates for two points are given.
The distance can be determined using Pythagorean Theorem because UTM is a grid system.
UTM Example--cont.
Subtracting the easting proved the length of the horizontal side: 208,000 meters.
Subtracting the northing proves the length of the vertical side: 535,000 meters.
The distance between the two points is:
GPS Errors
Noise Error
Noise errors are the combined effect of code noise (around 1 meter) and noise within the receiver noise (around 1 meter).
Bias Error
Selective Availability (SA)
SA is the intentional degradation of the SPS signals by a time varying bias. SA is controlled by the DOD to limit accuracy for non-U. S. military and government users.
Selective availability is turned off.
Ephemeris data errors: 1 meter
Satellite orbits are constantly changing. Any error in satellite position will result in an error for the receiver position.
SV clock errors uncorrected by Control Segment can result in one meter errors.
Tropospheric delays: 1 meter.
The troposphere is the lower part (ground level to from 8 to 13 km) of the atmosphere that experiences the changes in temperature, pressure, and humidity associated with weather changes.
Complex models of tropospheric delay require estimates or measurements of these parameters.
Bias Error--cont.
Unmodeled ionosphere delays: 10 meters.
The ionosphere is the layer of the atmosphere from 50 to 500 km that consists of ionized air. The transmitted model can only remove about half of the possible 70 ns of delay leaving a ten meter un-modeled residual.
Multipath: 0.5 meters.
Multipath is caused by reflected signals from surfaces near the receiver that can either interfere with or be mistaken for the signal that follows the straight line path from the satellite.
Blunders can result in errors of hundred of kilometers.
Control segment mistakes due to computer or human error can cause errors from one meter to hundreds of kilometers.
User mistakes, including incorrect geodetic datum selection, can cause errors from 1 to hundreds of meters.
Receiver errors from software or hardware failures can cause blunder errors of any size.
Post: #19

.doc  gps.doc (Size: 441 KB / Downloads: 72)
Where am I? Where am I going? Where are you? What is the best way to get there? When will I get there? GPS technology can answer all these questions. GPS satellite can show you exact position on the earth any time, in any weather, no matter where you are! GPS technology has made an impact
On navigation and positioning needs with the use of satellites and ground stations the ability to track aircrafts, cars, cell phones, boats and even individuals has become a reality.
This paper describes the Global positioning system (GPS) satellite. It depicts what GPS satellite is, how it works and its tracking features. This paper also gives how
the GPS satellite has been used to compute position and time, gives the details of various
segments in which the GPS system is useful. The paper gives the benefits of GPS satellite such as ability to track an object, due to reduced cost it is more affordable for everyone and helps you to find out where you are and how to get to your destination,
where ever you are going on land or sea.,
Applications such as military, car alarms, home security and home monitoring
Trying to figure out where you are and where you're going is probably one of man's oldest pastimes. Navigation and positioning are crucial to so many activities and yet the process has always been quite cumbersome. Over the years all kinds of technologies have tried to simplify the task but everyone has had some disadvantages. Finally, the U.S. Department of Defense decided that the military had to have a super precise form of worldwide positioning. And fortunately they had the kind of money ($12 billion!) it took to build something really good. The result is the Global Positioning System, a system that's changed navigation forever.
GPS initially created by the U.S Defense Department for the military has later been made available to the public. GPS technology is not just a handheld “help-me-find-my-way-home” operation anymore. GPS is finding its way into cars, boats, planes, construction equipment, moviemaking gear, farm machinery, even laptop computers. Move over Mr. Bell, it won’t be long until GPS will become as basic as the telephone.
A constellation of 24 satellites
A system of satellites, computers, and receivers that is able to determine the latitude and longitude of a receiver on Earth by calculating the time difference for signals from The Global Positioning different satellites to reach the receiver. System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations. GPS uses these "man-made stars" as reference points to calculate positions accurate to a matter of meters. In fact, with advanced forms of GPS you can make measurements to better than a centimeter! In a sense it's like giving every square meter on the planet a unique address. GPS receivers have been miniaturized to just a few integrated circuits and so are becoming very economical. And that makes the technology accessible to virtually everyone.
Technical description
The system consists of a "constellation" of at least 24 satellites in 6 orbital planes. The GPS satellites were initially manufactured by Rockwell; the first was launched in February 1978, and the most recent was launched November 6 2004. Each satellite circles the Earth twice every day at an altitude of 20,200 kilometers (12,600 miles). The satellites carry atomic clocks and constantly broadcast the precise time according to their own clock, along with administrative information including the Orbital elements of their own motion, as determined by a set of ground-based observatories.
The receiver does not need a precise clock, but does need to have a clock with good short-term stability and receive signals from four satellites in order to find its own latitude, longitude, elevation, and the precise time. The receiver computes the distance to each of the four satellites from the difference between local time and the time the satellite signals were sent (this distance is called a pseudo range). It then decodes the satellites' locations from their radio signals and an internal database. The receiver should now be located at the intersection of four spheres, one around each satellite, with a radius equal to the time delay between the satellite and the receiver multiplied by the speed of the radio signals. The receiver does not have a very precise clock and thus cannot know the time delays. However, it can measure with high precision the differences between the times when the various messages were received. This yields 3 hyperboloids of revolution of two sheets, whose intersection point gives the precise location of the receiver. This is why at least four satellites are needed: fewer than 4 satellites yield 2 hyperboloids, whose intersection is a curve; it is impossible to know where the receiver is located along the curve without supplemental information, such as elevation. If elevation information is already known, only signals from three satellites are needed (the point is then defined as the intersection of two hyperboloids and an ellipsoid representing the Earth at this altitude). The receiver contains a mathematical model to account for these influences, and the satellites also broadcast some related information, which helps the receiver in estimating the correct speed of propagation. High-end receiver /antenna systems make use of both L1 and L2 frequencies to aid in the determination of atmospheric delays.
Post: #20
to get information about the topic Global Positioning System full report,ppt and related topic refer the link bellow

Post: #21
GLOBAL Positioning System

.pdf  GLOBAL Positioning System.pdf (Size: 378.36 KB / Downloads: 19)


GLOBAL Positioning System (GPS) receivers for the consumer
market require solutions that are compact, cheap, and low power.
Manufacturers of cellular telephones, portable computers, watches, and other
mobile devices are looking for ways to embed GPS into their products. Thus,
there is a strong motivation to provide highly integrated solutions at the lowest
possible power consumption. GPS radios consist of a front-end and a digital
baseband section incorporating a digital processor. While for the baseband
processor, cost-reduction reasons dictate the use of the most dense digital
CMOS technology, for the front-end, the best option in terms of power
consumption is a SiGe BiCMOS technology.


The GPS signal code is a direct-sequence spread spectrum, and the type
of spread spectrum employed by GPS is known as binary phase-shift keying
direct-sequence spread spectrum (BPSK DSSS). In a spread-spectrum system,
data are modulated onto the carrier such that the transmitted signal has a larger
bandwidth than the information rate of the data. The term “direct sequence” is
used when the spreading of the spectrum is accomplished by phase modulation
of the carrier.


As stated, the overall design has been geared to a high level of
integration and reduction of silicon area at the lowest possible power
consumption. Below, the detailed design choices in the various sections are
RF Section
The LNA has been designed to have a very low noise since it sets a lower
bound for the total receiver sensitivity. A high voltage gain is necessary to
sufficiently reduce the noise contribution of the following mixers.
A common source configuration with inductive degeneration provides
high voltage gain and low NF, as shown in Fig. 3. In fact, in a narrow band,
this structure allows achieving a noise factor close to the theoretical minimum.
Post: #22

to get information about the topic Global Positioning System full report,ppt and related topic refer the link bellow

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