05-06-2013, 12:25 PM
WIRELESS communication
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INTRODUCTION
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.
The most common wireless technologies use electromagnetic wireless telecommunications, such as radio. With radio waves distances can be short, such as a few metres for television remote control, or as far as thousands or even millions of kilometres for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones.
Less common methods of achieving wireless communications include the use of light, sound, magnetic, or electric fields.
Wireless operations permit services, such as long-range communications, that are impossible or impractical to implement with the use of wires. The term is commonly used in the telecommunications industry to refer to telecommunications systems (e.g. radio transmitters and receivers, remote controls etc.) which use some form of energy (e.g. radio waves, acoustic energy, etc.) to transfer information without the use of wires.[1] Information is transferred in this manner over both short and long distances.
Wireless networks
Wireless networking (e.g., the various types of unlicensed 2.4 GHz WiFi devices) is used to meet many needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology:
• To span a distance beyond the capabilities of typical cabling,
• To provide a backup communications link in case of normal network failure,
• To link portable or temporary workstations,
• To overcome situations where normal cabling is difficult or financially impractical, or
• To remotely connect mobile users or networks.
Cordless
The term "wireless" should not be confused with the term "cordless", which is generally used to refer to powered electrical or electronic devices that are able to operate from a portable power source (e.g., a battery pack) without any cable or cord to limit the mobility of the cordless device through a connection to the mains power supply.
Some cordless devices, such as cordless telephones, are also wireless in the sense that information is transferred from the cordless telephone to the telephone's base unit via some type of wireless communications link. This has caused some disparity in the usage of the term "cordless", for example in Digital Enhanced Cordless Telecommunications.
WIRELESS POWER TRANSFER
Feb. 1, 2012 — A Stanford University research team has designed a high-efficiency charging system that uses magnetic fields to wirelessly transmit large electric currents between metal coils placed several feet apart. The long-term goal of the research is to develop an all-electric highway that wirelessly charges cars and trucks as they cruise down the road.
The new technology has the potential to dramatically increase the driving range of electric vehicles and eventually transform highway travel, according to the researchers. Their results are published in the journal Applied Physics Letters (APL).
"Our vision is that you'll be able to drive onto any highway and charge your car," said Shanhui Fan, an associate professor of electrical engineering. "Large-scale deployment would involve revamping the entire highway system and could even have applications beyond transportation."
Driving range
A wireless charging system would address a major drawback of plug-in electric cars -- their limited driving range. The all-electric Nissan Leaf, for example, gets less than 100 miles on a single charge, and the battery takes several hours to fully recharge.
A charge-as-you-drive system would overcome these limitations. "What makes this concept exciting is that you could potentially drive for an unlimited amount of time without having to recharge," said APLstudyco-author Richard Sassoon, the managing director of the Stanford Global Climate and Energy Project (GCEP), which funded the research. "You could actually have more energy stored in your battery at the end of your trip than you started with."
The wireless power transfer is based on a technology called magnetic resonance coupling. Two copper coils are tuned to resonate at the same natural frequency -- like two wine glasses that vibrate when a specific note is sung. The coils are placed a few feet apart. One coil is connected to an electric current, which generates a magnetic field that causes the second coil to resonate. This magnetic resonance results in the invisible transfer of electric energy through the air from the first coil to the receiving coil.
"Wireless power transfer will only occur if the two resonators are in tune," Fan noted. "Objects tuned at different frequencies will not be affected."
In 2007, researchers at the Massachusetts Institute of Technology used magnetic resonance to light a 60-watt bulb. The experiment demonstrated that power could be transferred between two stationary coils about six feet apart, even when humans and other obstacles are placed in between.
"In the MIT experiment, the magnetic field appeared to have no impact on people who stood between the coils," Fan said. "That's very important in terms of safety. "
Wireless charging
The MIT researchers have created a spinoff company that's developing a stationary charging system capable of wirelessly transferring about 3 kilowatts of electric power to a vehicle parked in a garage or on the street.
Fan and his colleagues wondered if the MIT system could be modified to transfer 10 kilowatts of electric power over a distance of 6.5 feet -- enough to charge a car moving at highway speeds. The car battery would provide an additional boost for acceleration or uphill driving.
HOW IT WORKS
Wireless energy transfer (WET) is the process where electrical energy is transmitted from a power source to an electrical load, without interconnecting wires. There are two main methods of wireless electricity transmission, mutual induction and evanescent wave coupling.
Mutual induction is the production of voltage across a conductor situated in a changing magnetic field or a conductor moving through a stationary magnetic field. This allows for the wireless transmission of electricity over a very close proximity and is already in use in items such as electric toothbrushes
The “Splash pad”, a brand of wireless charging pads based on mutual induction technology.
This technology has currently expanded and is being marketed by a number of companies who have created “charging pads”—areas on which electronic devices can simply be placed and receive a charge. However, while this is effective for powering devices such as cell phones or laptops, this method of wireless electricity requires too close a proximity for any sort of medium- to long-range power transmission. Another means of wireless energy transfer, Evanescent Wave Coupling, hopes to change that.
Evanescent Wave Coupling (EWC), or non-radiative energy transfer, introduces a concept called “resonance” to the wireless energy equation. Similar to mutual induction, wherein electricity traveling along an electromagnetic wave moves between coils on the same frequency, EWC functions on the concept that if you make both coils resonate at the same frequency, electricity can be passed between them at farther distances and without health dangers. According to this theory, one can even send electricity to multiple devices at once, as long as they all share the same resonance frequency. While this technology is yet to come to market, in 2007, researchers at MIT published a detailed report describing a working prototype they had built which powered a light bulb from two metres away.
[attachment=54799]
INTRODUCTION
Wireless communication is the transfer of information between two or more points that are not connected by an electrical conductor.
The most common wireless technologies use electromagnetic wireless telecommunications, such as radio. With radio waves distances can be short, such as a few metres for television remote control, or as far as thousands or even millions of kilometres for deep-space radio communications. It encompasses various types of fixed, mobile, and portable applications, including two-way radios, cellular telephones, personal digital assistants (PDAs), and wireless networking. Other examples of applications of radio wireless technology include GPS units, garage door openers, wireless mice, keyboards and headsets, headphones, radio receivers, satellite television, broadcast television and cordless telephones.
Less common methods of achieving wireless communications include the use of light, sound, magnetic, or electric fields.
Wireless operations permit services, such as long-range communications, that are impossible or impractical to implement with the use of wires. The term is commonly used in the telecommunications industry to refer to telecommunications systems (e.g. radio transmitters and receivers, remote controls etc.) which use some form of energy (e.g. radio waves, acoustic energy, etc.) to transfer information without the use of wires.[1] Information is transferred in this manner over both short and long distances.
Wireless networks
Wireless networking (e.g., the various types of unlicensed 2.4 GHz WiFi devices) is used to meet many needs. Perhaps the most common use is to connect laptop users who travel from location to location. Another common use is for mobile networks that connect via satellite. A wireless transmission method is a logical choice to network a LAN segment that must frequently change locations. The following situations justify the use of wireless technology:
• To span a distance beyond the capabilities of typical cabling,
• To provide a backup communications link in case of normal network failure,
• To link portable or temporary workstations,
• To overcome situations where normal cabling is difficult or financially impractical, or
• To remotely connect mobile users or networks.
Cordless
The term "wireless" should not be confused with the term "cordless", which is generally used to refer to powered electrical or electronic devices that are able to operate from a portable power source (e.g., a battery pack) without any cable or cord to limit the mobility of the cordless device through a connection to the mains power supply.
Some cordless devices, such as cordless telephones, are also wireless in the sense that information is transferred from the cordless telephone to the telephone's base unit via some type of wireless communications link. This has caused some disparity in the usage of the term "cordless", for example in Digital Enhanced Cordless Telecommunications.
WIRELESS POWER TRANSFER
Feb. 1, 2012 — A Stanford University research team has designed a high-efficiency charging system that uses magnetic fields to wirelessly transmit large electric currents between metal coils placed several feet apart. The long-term goal of the research is to develop an all-electric highway that wirelessly charges cars and trucks as they cruise down the road.
The new technology has the potential to dramatically increase the driving range of electric vehicles and eventually transform highway travel, according to the researchers. Their results are published in the journal Applied Physics Letters (APL).
"Our vision is that you'll be able to drive onto any highway and charge your car," said Shanhui Fan, an associate professor of electrical engineering. "Large-scale deployment would involve revamping the entire highway system and could even have applications beyond transportation."
Driving range
A wireless charging system would address a major drawback of plug-in electric cars -- their limited driving range. The all-electric Nissan Leaf, for example, gets less than 100 miles on a single charge, and the battery takes several hours to fully recharge.
A charge-as-you-drive system would overcome these limitations. "What makes this concept exciting is that you could potentially drive for an unlimited amount of time without having to recharge," said APLstudyco-author Richard Sassoon, the managing director of the Stanford Global Climate and Energy Project (GCEP), which funded the research. "You could actually have more energy stored in your battery at the end of your trip than you started with."
The wireless power transfer is based on a technology called magnetic resonance coupling. Two copper coils are tuned to resonate at the same natural frequency -- like two wine glasses that vibrate when a specific note is sung. The coils are placed a few feet apart. One coil is connected to an electric current, which generates a magnetic field that causes the second coil to resonate. This magnetic resonance results in the invisible transfer of electric energy through the air from the first coil to the receiving coil.
"Wireless power transfer will only occur if the two resonators are in tune," Fan noted. "Objects tuned at different frequencies will not be affected."
In 2007, researchers at the Massachusetts Institute of Technology used magnetic resonance to light a 60-watt bulb. The experiment demonstrated that power could be transferred between two stationary coils about six feet apart, even when humans and other obstacles are placed in between.
"In the MIT experiment, the magnetic field appeared to have no impact on people who stood between the coils," Fan said. "That's very important in terms of safety. "
Wireless charging
The MIT researchers have created a spinoff company that's developing a stationary charging system capable of wirelessly transferring about 3 kilowatts of electric power to a vehicle parked in a garage or on the street.
Fan and his colleagues wondered if the MIT system could be modified to transfer 10 kilowatts of electric power over a distance of 6.5 feet -- enough to charge a car moving at highway speeds. The car battery would provide an additional boost for acceleration or uphill driving.
HOW IT WORKS
Wireless energy transfer (WET) is the process where electrical energy is transmitted from a power source to an electrical load, without interconnecting wires. There are two main methods of wireless electricity transmission, mutual induction and evanescent wave coupling.
Mutual induction is the production of voltage across a conductor situated in a changing magnetic field or a conductor moving through a stationary magnetic field. This allows for the wireless transmission of electricity over a very close proximity and is already in use in items such as electric toothbrushes
The “Splash pad”, a brand of wireless charging pads based on mutual induction technology.
This technology has currently expanded and is being marketed by a number of companies who have created “charging pads”—areas on which electronic devices can simply be placed and receive a charge. However, while this is effective for powering devices such as cell phones or laptops, this method of wireless electricity requires too close a proximity for any sort of medium- to long-range power transmission. Another means of wireless energy transfer, Evanescent Wave Coupling, hopes to change that.
Evanescent Wave Coupling (EWC), or non-radiative energy transfer, introduces a concept called “resonance” to the wireless energy equation. Similar to mutual induction, wherein electricity traveling along an electromagnetic wave moves between coils on the same frequency, EWC functions on the concept that if you make both coils resonate at the same frequency, electricity can be passed between them at farther distances and without health dangers. According to this theory, one can even send electricity to multiple devices at once, as long as they all share the same resonance frequency. While this technology is yet to come to market, in 2007, researchers at MIT published a detailed report describing a working prototype they had built which powered a light bulb from two metres away.