Satellite communications represent one of the most significant applications of space technology. Satellites provide a vital communication link for radio, telephone and television traffic in addition to other forms of data communication. Satellite communication systems are useful alternatives to conventional terrestrial communication systems, such as land lines, fiber optic, and microwave. A satellite communication system can cover a broad area, it is used for not only communications between fixed stations (earth stations), but also mobile communications. The satellite network system provides the capability for mobile earth terminals to access one or more multiple beam satellites located in geostationary orbit for the purposes of providing mobile communications services.
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Saturday, 09 December 2006 |
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Satellite navigation systems provide an attractive service for their global coverage and accuracy. Receivers for receiving satellite navigation signals comprise a receiving unit for receiving navigation signals emitted by satellites, the receiving unit is connected with a computer unit for processing the signals and data for navigation purposes. Satellite navigation receivers provide the user with position, time, and velocity information. A satellite navigation receiver receives and processes radio signals broadcasted by satellites. The satellite signals comprise carrier signals which are modulated by pseudo-random binary codes, which are then used to measure the delay relative to local reference clock or oscillator. A global positioning system (GPS) employs a constellation of satellites in circular orbits. |
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Sunday, 03 December 2006 |
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Satellite receivers enable the position of an object to be determined by using the signals transmitted by global navigation satellite systems. Digital satellite receivers comprise a receiving unit for receiving navigation signals, the receiving unit is connected with a processor for processing and forwarding said signals and data for navigation purposes. Global positioning system (GPS) receivers determine position by computing time delays between transmission and reception of signals transmitted from satellites and received by the receiver. GPS receivers receive GPS signals transmitted from orbiting GPS satellites containing unique pseudo-random noise (PN) codes. The PN codes provide a mechanism to precisely determine the signal transmission time from each satellite. |
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Saturday, 18 November 2006 |
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Satellite based GPS systems use a constellation of satellites orbit the earth while relaying bi-directional communications signals between mobile terminals and earth stations. The GPS receiver is used to measure the distances to the satellites. Then the location expressed as latitude, longitude and elevation are derived. Most personal navigation systems exist as handheld devices which report position in terms of latitude, longitude, and altitude. In a position measuring system using a GPS, a map centered on the measured position is displayed on the screen of the GPS terminal, thereby allowing the user recognize the current position of the GPS terminal. GPS mapping systems have map data stored in memory and a display for showing the device position with reference to the map data. |
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Sunday, 12 November 2006 |
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Satellite telephone systems provide ubiquitous coverage of large areas of the earth without the construction of many small terrestrial cells. They utilize many individual circuits routed through one satellite or a constellation of many satellites to provide communications for terrestrial terminals. Satellite phones are typically handheld devices and allow a given user to establish a telephone conversation via a satellite link. The satellite typically communicates with phones over a bidirectional communications pathway, with phone communication signals being communicated from the satellite to the phone over a downlink or forward link, and from the phone to the satellite over an uplink or return link. A signal transmitted from a phone terminal to a satellite is referred to as a satellite uplink signal or frequency. |
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Friday, 27 October 2006 |
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Global positioning system (GPS) is a space-based positioning and velocity system permitting users of GPS receivers to determine their respective positions to a high degree of accuracy. A GPS receiver is composed of an antenna unit for receiving high frequency satellite signals and a processing unit for processing the signals to compute positional coordinates of the GPS receiver. Signals sent from GPS satellites may be used by location measuring applications to determine latitude and longitude of a receiver. Cellular phones are commonly used together with GPS receivers for communicating the location of the receiver. The GPS system requires a GPS antenna for receiving radio wave transmitted from satellites. Antennas for GPS receivers are divided into a ceramic patch antenna and a helix antenna. |
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Friday, 20 October 2006 |
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The global positioning system (GPS) is a satellite-based navigation system that continuously transmits timing, frequency and satellite position information to potential users. A typical global positioning satellite signal comprises a high frequency carrier signal which is modulated by one or more pseudo-random number sequences of lower frequency. In the GPS tracking system, transmitters are positioned on orbiting satellites. The receiver is synchronized with the data stream by matching an identical suedo-random data stream albeit with a time offset. The signals from several satellites allow the receiver to compute its position, velocity and time parameters through known triangulation techniques. The global positioning system (GPS) navigation system has come to a wide application in tracking systems. |
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Tuesday, 10 October 2006 |
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A car navigation system locates a present position of a vehicle, sets a route plan and gives route guidance to a driver. Modern navigational systems utilize global positioning systems (GPS) to constantly calculate a vehicle's direction and use this calculated direction as the top of the display. The global positioning system is a satellite-based radio navigation, positioning and time transfer system based on an earth-orbiting constellation of twenty-four satellites, each broadcasting its precise location and ranging information. GPS provides highly accurate navigational information on a continuous global basis to an unlimited number of properly-equipped users. GPS receivers for receiving satellite-based navigation signals comprise a receiving unit for receiving navigation signals emitted by satellites. |
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Saturday, 23 September 2006 |
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In order to receive a satellite broadcast signal from broadcasting satellite or communications satellite, it is necessary to install a satellite receiver and a satellite dish antenna. A typical satellite receive antenna uses a parabolic reflector dish to reflect and concentrate signals to a focal point. The parabolic reflector antenna is a high gain antenna with orientation that is mostly used in radar systems, microwave systems and satellite systems. The reflector gathers radio or microwave frequency energy transmitted from the feed horn or through the ambient environment from an external transmitter. Satellite dishes require careful alignment in order to achieve a good reception performance because a parabolic dish antenna has very strong directivity. Antenna dish systems vary in their size. |
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Saturday, 16 September 2006 |
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Satellite digital audio radio service (SDARS) is a satellite-based service that broadcasts audio entertainment to fixed and mobile receivers. In a satellite radio broadcasting system, signals transmitted from a satellite can be received in a wide area on the earth. In satellite radio systems, a broadcast studio generates analog audio signals much the same as a conventional radio station studio does. Satellite broadcasting has become very popular throughout the world. The use of satellites to broadcast radio programs for reception in automobiles, trucks, and vans has been widely implemented. In order to receive satellite broadcasts, vehicles must be equipped with proper antennas and receivers. Satellite radio signals in satellite radio systems are transmitted with circular polarization. |
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Monday, 04 September 2006 |
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The global positioning system (GPS) is a satellite based navigation system having a constellation of 24 earth orbiting satellites. Global positioning system receivers determine location, velocity, and time by receiving and processing information in GPS signals received from GPS satellites. Global positioning system (GPS) receivers provide accurate location, velocity and time information based on specially coded data broadcast from orbiting satellites. A GPS signal contains timing information that allows a user to determine the time elapsed for the GPS signal to transverse the distance between the GPS satellite and a receiver receiving the signal. Global position system receivers and related apparatus have become widely used for determining geographical location and time in commercial applications. |
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Saturday, 12 August 2006 |
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Direct broadcast satellite service (DSS or DBS) refers to satellite transmission of television signals directly for use by individual households or subscribers having the proper signal receiving equipment. Satellite television systems use a satellite positioned at several hundred kilometers high above the earth, and are capable of transmitting a broadcast signal to much wider area than other broadcasting systems. A satellite television broadcasting receiver is used for the purpose of receiving pictures and television broadcasting programs offered by utilizing satellites. Satellite receiver tunes, demodulates and otherwise processes the received television signals to provide video and audio signals. The use of satellite antennas to receive satellite television transmissions has provided these households with access to hundreds of television channels. |
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Saturday, 12 August 2006 |
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The Internet is a collection of independent computer networks, which communicate with each other using standard communication protocols. The Internet has a plurality of computer systems which are generally interconnected to each other using local area networks and dedicated transmission lines to form a wide area network of computers. Internets may employ a variety of electronic transport media, such as telephone lines, optical fiber, satellite systems, local area networks, etc. With the advent of satellite-based communications systems, access to computer networks such as the Internet and in particular the worldwide web, can now readily be achieved by mobile users through the use of lap top computers or other portable terminals such as cell phones. Satellite data systems provide a solution to the consumer seeking broadband Internet connectivity where no terrestrial alternatives such as cable or telephone line based broadband service are available. |
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Satellite Communications
