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An antenna is a device that sends or accepts electromagnetic waves. It changes electromagnetic waves into electric currents, and electric currents to electromagnetic waves. Antennas are used to send and receive waves from the radio frequency of the electromagnetic spectrum. Antennas are used in radio and television broadcasting, spacecraft communication, point-to-point radio communication like walkie-talkie system, hand phones, radar, and wireless LAN.
An antenna is a setup of one or more electrical conductors, also called elements. In the transmission of an antenna, a voltage is applied at the antenna terminals to produce an alternating current (A.C) in the elements, thus causing the elements to produce an electromagnetic field as an effect. In reception, the reverse happens: an electromagnetic wave from an external source induces an alternating current in the elements and a matching voltage at the antenna’s terminals. Some receiving antennas use shaped reflective surfaces to collect the radio waves hitting them and direct or focus them onto the elements.
Heinrich Hertz (1857-1894) built some of the first primitive antennas in 1888 in his experiments to prove that electromagnetic waves exist as inferred by the James Clerk Maxwell’s theory. One of the antennas he built was the dipole antenna, which will be explained in detail in the Supporting Theory section of this report. He published his work and installation design in Annalen der Physik und Chemie (vol. 36, 1889).
In 1919, J Hettinger was granted a patent for the concept of a plasma antenna. A plasma antenna is a type of antenna that is currently in development in which plasma is used to replace the metal elements of a normal antenna. A plasma antenna can be used for transmission and reception, just like normal radio antennas. Plasma antennas have only become practical in recent years, where high speed internet connection is an important necessity to all.
Currently, Plasma Antennas (a company) in Winchester of the United Kingdoms have developed a plasma antenna which they named Plasma Silicon Antenna or PSiAN.
2.1 – SUPPORTING THEORY
Here is an explanation of how a traditional antenna works. There are many types of antennas that have been designed by humans over the years but for simplicity’s sake, the explanation here will describe how a dipole antenna works. A dipole antenna is an antenna that can be built using a simple wire with a driven element in the centre. It consists of two metal conductors of rod or wire, arranged parallel and in line with each other, with a small space between them. The radio frequency voltage is applied to the driven element at the center, between the two conductors. These antennas are the most primitive practical antennas. They are used mostly in traditional “rabbit ears” television antennas.
How the antenna transmits signals:
First, a voltage is applied to the antenna terminal (in this case, the driven element in the centre) to produce a potential difference in between the opposite ends of the two conducting wires. When a potential difference exists, there will be a flow of electrons, which in turn produces a current. Say that the electrons from end A are moving towards end B at maximum speed. When they reach end B, they will stop instantaneously. End B is now negatively charged whereas end A is positively charged. The electrons are attracted to the positive charges at end A and move back towards A at maximum speed. Now, the charges at both ends are reversed. This back and forth movement of the electrons produces an alternating current in the conducting wires. When there is an alternating current in the metal conductors, electromagnetic waves are produced. These waves are the signals being transmitted by the antenna.
How the antenna receives signals:
On the other hand, the entire process is reversed for the antenna to receive signals. Electromagnetic waves from an external source reach the conducting wires. The electromagnetic field is cut by the conducting wires, causing an alternating current to flow in the conducting wires. Consequently, when there is a current flowing in the wires, a voltage will exist too. The antenna receives the alternating current as its signal.
2.1.2 â€¢ PLASMA
Contrary to popular belief, there are actually four states of matter in existence: solid, liquid, gas and plasma. Plasma contains fields, charged particles like ions and electrons, and also neutral particles. Plasma is capable of conducting electricity and generating magnetic fields.
2.1.3 â€¢ PLASMA ANTENNA
In the plasma antenna, the traditional metal conductor of the normal antenna is replaced with plasma. This technology employs the electrical conductivity of the substance, plasma, to conduct the electrical currents and so generate the electromagnetic waves necessary to transmit the signal. There are two types of plasma antennas, the gas antenna and the semi-conductor antenna.
The gas antenna is an antenna with ionised gas enclosed in a tube as the conductor.A wide assortment of gases can be used to produce the plasma, such as Group 18 elements like neon, argon, xenon, krypton and other gases like mercury vapour and helium. When the gases are ionised, they will be a composition of positive ions and electrons, which provides us with plasma.
Another type of plasma antenna is known as the semi-conductor antenna. These plasma antennas rely on silicon chips through which electricity is passed though to release a cloud of electrons, which then serves as the plasma.
Silicon chips in the semiconductor antenna
Similar to the way a normal antenna functions, the plasma antenna basically transmits and receives signals the same way. Both the transmission and reception processes involve the movement of electrons and the production of electromagnetic waves. The only difference between the normal antenna and the plasma antenna is the conducting element. That said, the plasma antenna entails more advantages and benefits as compared to the traditional antenna.
2.2.1 â€¢ ADVANTAGES OF THE PLASMA ANTENNA
1. Plasma antennas are invisible to radar. When the plasma antenna is not turned on, radar will find it difficult to detect the antenna. Even if the plasma antenna is turned on, it is invisible to signals above the plasma frequency. This makes it hard for the plasma antenna signals to be intercepted or detected by anyone other than the intended recipient. Clearly, this particular aspect of the plasma antenna makes it ideal for use by the military to transmit and receive secret instructions and information.
2. The plasma antenna allows for extremely short pulses, unlike a normal metal antenna. When electricity is passed through a metal conductor, an effect known as “ringing” occurs, that is an extra burst of electricity flow through the conductor for an extremely short while when there is a sudden change of input (like when the pulse is short). This wastes energy and causes unwanted electromagnetic waves to be produced. With the plasma antenna, ringing is totally eliminated.
3. Plasma antenna technology allows for the design of antennas that are efficient, light, and smaller than traditional antennas. With the metal conductors replaced with either silicon chips or gas, the plasma antenna is lighter and more portable than the metal antenna.
4. The plasma antenna is dynamically reconfigurable, which means that the handlers of the antenna can freely change the frequency, gain, polarization, power, directionality and beamwidth of the signal. The implications of this advantage is that instead of needing multiple normal antennas, we can just use a single plasma antenna, reducing cost and saving space.
5. The plasma antenna is capable of transmitting signals at an extremely fast speed. In the plasma semiconductor antenna, by selectively activating certain diodes, the handler is able to focus the electromagnetic waves produced into a beam, which travels faster than a wave.
2.2.2 â€¢ DISADVANTAGES OF THE PLASMA ANTENNA AND SOLUTIONS
1. According to a scientist who is involved in the development of the plasma antenna, Ted Handerson, Haleakala R&D, Brookfield, Massachusetts, the semi-conductor version of the plasma antenna is limited to high frequencies, which makes certain applications difficult. For example, Wi-Gig routers operating at 60Ghz cannot penetrate walls.
Solution: The signals can be reflected off surfaces to reach their destination instead. For example, Wi-Gig routers will emit the signals, which will then reflect off the physical surfaces of the walls to reach the computer or device.
2. The ionizer increases power consumption. More energy is required to ionize the gases or to make the silicon chips release electrons. Therefore, plasma antennas actually use more power than normal antennas.
Solution: Other technologies to reduce power consumption of plasma antennas can be considered or developed in the future. One current example is the Antenna Integrated Radio Solution developed by the partnership between Ericsson and Kathrein-Werke KG. In this design, the antenna is built into the radio unit to cut installation time and power consumption greatly. This design has the potential to be tailored so that it works for plasma antennas as well.
3. Plasma volumes must be stable and repeatable. When a gas is ionised, not all 100% of the gas will ionise to become plasma. With silicon chips, it is reasonable to say that the amount of electrons released by the silicon when heated or charged will vary from time to time. Thus it is imperative that the volume of plasma generated each time should be the same. The amount of plasma existing during a transmission or reception should also be the stable and not fluctuate. Only then will the electromagnetic waves transmitted be stable.
Solution: Perhaps one way of controlling plasma emission by the ionised gases and silicon chips would be to keep the current flowing through it constant, thereby exciting only a certain amount of particles, and producing a fixed volume of plasma.
2.2.3 â€¢ APPLICATIONS OF THE PLASMA ANTENNA
The plasma antenna has high potential to be used in the military sector, as it is hard to be detected by radar. This is good for the military to send and receive top secret documents or instructions. As signals radiated by a plasma antenna is hard to intercept and therefore hard to be blocked, the plasma antenna is said to be resistant to electronic warfare, a strategy commonly employed by enemy countries.
Not only that, but the plasma antenna can be used in radio and television broadcasting. The signals emitted by the plasma antenna tend to be stronger than the signals emitted by the normal metal antenna, thus causing the radio waves to last longer without damping and being extinguished. The consequence of this implication is that radio broadcasting companies no longer need to build so many relay stations and towers to relay the signal to further areas. As a result, the plot of land can be used for industrial or residential purposes, or preserved to save nature.
44thSignalTower.jpg A signal relay tower
Another market application for the plasma antenna is to be installed on ships and submarines. Submarines require stealth to complete the mission of its crew, and so having a plasma antenna would be of great benefit. For fishing ships that require echolocation to locate the position of fish in deep sea, the plasma antenna will also be advantageous. The signals emitted by the plasma antenna can be adjusted to high frequency, thus able to penetrate miles and miles of seawater.
One very relevant application of the plasma antenna is in wireless Internet, like Wi-Gig. Wi-Gig provides faster Internet connection to users than is provided by Wi-Fi. A faster Internet connection means that users will be more productive and save time. The economy of the country can be improved as more work can be done in a shorter time. Activities like downloading podcasts, movies and music at fast speeds can be done even using wireless Internet connection. This is clearly an advantage for mobile users.
Another application of the plasma antenna is its role in improving public safety networks. Devices like CCTVs around a neighbourhood or city are usually connected in a video surveillance network. These devices are used to prevent crimes from happening, or as video evidence in court. Clearly, these devices are also important in tracking down criminals who are escaping. If any of the devices are malfunctioning or have suffered malevolent damage by terrorists, it is possible for a handler from the public safety department to reroute traffic through backhaul networks using plasma antennas.
It is also possible that plasma antennas can be used in space communication. Plasma antennas which prove to be lighter than normal antennas can serve as communication devices on jet planes, commercial planes, and even space shuttles. For example, scientists and researchers working at the NASA Glenn Research Centre have filed and received a patent for a slotted antenna waveguide plasma source.
After doing all this research on the plasma antenna, this section will be about my recommendations on how the plasma antenna can benefit Malaysians in particular.
As mentioned before this, the plasma antenna is crucial in the development of Wi-Gig, wireless Internet connection faster than the Wi-Fi. In Malaysia, Wi-Fi is actually considered very slow if compared to other countries like the US and Korea. If the Internet providers if our country can upgrade their antennas with plasma antennas, our wireless Internet connection will no doubt speed up by 10 times. Malaysians will be able to download their favourite songs and movies while on the move.
The plasma antenna can also be used by the TV broadcasting companies of our nation. ASTRO, for example, would certainly improve its service by upgrading to plasma antennas. Currently, Malaysians complain that whenever it rains, their reception of ASTRO faces problems. Often, they cannot receive a connection when the weather is bad. According to ASTRO, the radio waves that their satellites emit cannot penetrate through the thick layer of clouds and rain to reach the consumers’ home.
In my opinion, if they switch to plasma antennas, they can use the electromagnetic wave focussing ability of the plasma antenna to send out beams instead of waves. Beams would certainly have higher penetration power and can penetrate through cloud and rain to reach the customers’ homes.
In conclusion, the plasma antenna works according to the same principles and physics laws as the normal antenna, with plasma replacing the metal conductors of the normal antenna. But because the conducting material used is plasma, it affords some advantages over a normal antenna. The most notable advantage of the plasma antenna is the fact that it is practically invisible to radar and can release short pulses of signals. Therefore, the military of US is currently racing to implement the plasma antenna into their existing systems.
Also, another advantage of the plasma antenna is that it can pave the way towards faster wireless Internet, which is certainly needed by most users nowadays, whether it be for entertainment or business purposes.
Although the plasma antenna has some disadvantages, these can be overcome using the problems’ respective solutions. Who knows, in the future somebody may design and manufacture plasma antennas after solving all disadvantages of the plasma antenna. What is certain though is the fact that plasma antennas are commercially viable and are expected to enter the market in 2011 or 2012.
Because the manufacturing price of plasma antenna is quite low compared to normal antennas, it would be best if Malaysia can manufacture plasma antennas as a way to widen the jobs available.
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