Radio frequency energy is the energy transmitted by sources that can generate electromagnetic fields like TV signals, radio signal, wireless networks and cell phone towers, by using specially designed circuits connected to a an antenna this electromagnetic energy can be harvested and converted into a usable DC voltage. One of the applications of this technology is in radio frequency identification tags in which harvesting device can receives an RF signal from a sensing device; this RF signal can supply enough power to let the RFID tag to send radio frequency back including identification information to any item of interest. The circuits designed for such applications can made relatively small and can convert the ambient electromagnetic waves to a usable DC voltage at distances up to 100 meters from the source of the RF signal. Depending on the environment and the power of RF signal available the power conversion circuit would be connected to a capacitor which can provide a constant required voltage to the device in question when there is not enough supply of energy available also this RF power can be used to charge batteries. Another appealing feature of harvesting available RF energy is that it can be used as a supplement to the conventional energy harvesting methods. These energy harvesting techniques can be used to charge batteries at night when solar energy is not available and they could be used as backup system if the main supply of energy fails and keep the device working or send an alarm. This technology can extend the battery lifetime and that can be done by offsetting the sleep current required by low power microcontroller.
Antenna Design and Power Management for Wireless Energy Harvesting Application:
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...ation of rectenna array configurations for enhanced RF Power harvesting”, Loughborough Antennas & Propagation Conference, 2009.
[4] U. Olgun et. al. “Efficient aembient WiFie energy harvesting technology and its applications”, IEEE, Volume:10, 2012.
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Wireless begins with a brief discussion of the 1995 centennial of the invention of radio by Marconi and a rebuttal by the British historians who oppose this claim. Using underused or previously overlooked or perhaps ignored resources the author disproves the claims against the originality and ingenuity of Marconi's 1897 patent on wireless telegraphy. While credit is given to several British scientists and engineers and their scientific discoveries and inventions, it was Marconi, a practitioner, who made the first significant breakthrough in practical wireless telegraphy when he "connected one end of the plate of the receiver, and one end of the transmitter, to the earth" (p. 20). Marconi transformed these scientific effects into wireless technologies and then exploited them for commercial purposes. The focus of British scientists and engineers on optical analogies, scientific experimentation and demonstration, and the fear of British national interests becoming monopolized (particularly by a foreigner) are the primary reasons for the dispute surrounding Marconi's patent. (By 1897 it was clear how wireless telegraphy would impact military interests.) The author shows in great detail how British scientists and engineers, namely physicist Oliver Lodge, J. J. Thomson, Minchin, Rollo Appleyard, and Campbell Swinton, deliberately constructed false scientific and social claims to discredit the originality of Marconi's patent.
According to David Shriner, a former military engineer and expert on RF technology, there are a number of different types of RF weapons, which are also referred to as High Powered Microwave (HPM) weapons. The first type is the conventional RF weapon, which sends out a concentrated band of radio waves toward a target. These radio waves act in a way similar to the waves inside a normal microwave oven; given a sufficient amount of power, they can be used to heat and damage electronic equipment operating at the same frequency. Because of this need to match frequency with the target, conventional RF weapons require prior research and intelligence before they can be deployed effectively by terrorists [3].
Wire time (or panghantar such as an antenna) conducts alternating current, electromagnetic radiation is propagated at the same frequency as the electric current. Depending on the situation, electromagnetic waves can be waves or like particles. As a wave, characterized by speed (speed of light), wavelength, and frequency. When considered as particles, they are known as photons, and each has an energy associated with the frequency of the waveform shown by the Planck relationship E = Hν, where E is the photon energy, h is the Planck constant - 6.626 × 10 -34 J · s - and ν is the frequency of the
"The Future of the Wireless Art," Wireless Telegraphy and Telephony, 1908, pg. 67–71, Nikola Tesla
The simplest of task have been made simpler, yet not only is this the future but it’s the now. Radio Frequency identification technology is technology that was created from Identification friend or foe or other wise known as (IFF). This later brought to life RFID, (Radio-Frequency Identification). The purpose of RFID varies has multiple purpose and multiple looks, but the results are all the same. There are multiple looks and shapes to these tags, some come in stickers, plastic, and even chips that would be implanted. Originally During World War 2 a British engineer Watson-Watt, developed the first active identify friend or foe (IFF). The purpose was to identify aircrafts that where returning to base. According to rfidjournal.com, IFF either reflects back a signal or broadcasts a signal. Thus creating RFID the modern tracker. The sizes of the transmitters varied from plane to plane, but ground troops had special readers that allowed them to identify the aircrafts. The implications of these modern methods of tracking later led to develop RFID tags. During the 50’s and 60’s the worlds scientist begun to research how advancements in radio frequency could be harnessed, it became emanate that this advancement would be used to track packages for consumers world wide. The first patents for RFID was America Mario W. Cardullo, he claims to have the first United States patent for an RFID tag with rewritable memory during 1973. That same year, a man named Charles Walton, received a patent for a RFID tag to unlock a door without a key. The RFID tag had an embedded transponder, which communicated a signal to a reader near the door. When the reader picked up a valid identity, the reader unlocked the door. Ultimately this advancement is soon t...
[3] S. Srisathit, M. Chongcheawchamnan, and A. Worapishet,“Design and realization of a dual-band 3-dB power divider based on a two-section transmission-line topology,” Electron. Lett., Vol. 39, pp. 723–724, May2003.
For physically small antennas, the Wheeler cap method is highly preferred for measuring the radiation efficiency. According to this method, if a radiation shield is placed around the antenna so as to enclose the near fields of the antenna, the radiation resistance of the antenna is reduced to zero while the loss resistance and the stored energy remain the same as for the unshielded antenna. When covering the antenna with a metal cap, the radiation is suppressed and the input power (proportional to the input resistance) is equal to the power loss (proportional to the loss resistance). Without the cap, the input power is equal to the radiated power plus the power loss (input resistance + loss resistance). The radiation efficiency of the antenna can be obtained from these two parameters.
MTC ONLINE, " Reports of Current Experimentation with Microwave and EM Weapons," <http://www.heart7.net/mcf/1.html> (10 August 2003)
L. Ophir "802.11 Over Coax - A Hybrid Coax - Wireless Home Network Using 802.11Technology", Consumer Communications and Networking Conference, pp.13 -18
Microstrip patch antennas radiate primarily because of the fringing fields between the patch edge and the ground plane. For good antenna performance, a thick dielectric substrate having a low dielectric constant is desirable since this provides better efficiency, larger bandwidth and better radiation [4]. However, such a configuration leads to a larger antenna size.
Tong, K. F., K. M. Luk, and K. F. Lee, “Wideband II-shaped aperture-coupled U-slot patch antenna,” Microwave and Optical Technology Letters, Vol. 28, 70–72, Jan. 2001.
A wireless sensor network (WSN) consists of distributed sensors to monitor environmental conditions such as temperature, sound, vibration, pressure, motion or detect dimensions, to pass their data through the network to a base station for processing. Advantages of WSN over a wired system considered in elimination of wiring cost, sensors can be installed in harsh environments. Each sensor node is a combination of Radio transceiver with an internal antenna or connection to an external antenna micro-controller, electronic circuit for interfacing with the sensors, energy source, usually a battery or an embedded form of energy harvesting. Drawback of using sensors is having limited power to consume, a memory that is capable of performing limited computations, in addition to probability of communication failures between nodes.
FM Radio waves also go horizontally along the ground and skyward. However, due to the higher frequency of the carrier w...
Barcodes are used everywhere around us. They are used to track products through shipment, track products at a store and speed up and enhance the checkout process, as well as allowing faster access to information. Barcodes began to be used heavily in the 1970’s. This began a great movement in the consumer industry, speeding up the checkout process and allowing easier inventory tracking. However, just like all technologies, barcodes have been enhanced many times over and are being replaced by better, more efficient systems (Bonsor).