Abstarct: In this paper we get an overview of the dielectric resonator antenna which replaced the simple form of antennas that were being used for the past ten years. These dielectric antenna have been of a great importance to the research work in antenna field as these have a great dielectric constant and higher Q factor than the other isotropic or directive antennas. Earlier these antennas were considered to be energy storage devices but in this paper we have made use of the DRA antennas as radiators. These antennas have been described with their features which separates them from ordinary antennas, the features include small size, high efficiency etc. The DRA are compared to micro strip antennas in this review paper. Basically this paper gives an idea about the evolution of directive resonator antennas and their applications and the different DRA antennas are compared.
Introduction
From the time of origination of dielectric resonator antennas, they were being used in microwave circuits like filters or oscillators and were being used as energy storage devices until a paper was published in 1983 which made people accepted that these could be used as antennas and radiators.
The DRA is a resonant antenna, fabricated from a low loss and high-permittivity dielectric ceramic material mounted on a ground plane and fed by a coaxial probe, a slot, a waveguide, or a micro strip line. The size of DRA is inversely proportional to dielectric constant of material and losses in the DRA are also inversely proportional to quality factor of material. As compared to the micro strip antenna, the DRA has a much wider impedance bandwidth ( 10 % for dielectric constant εr 10). This is because the micro strip antenna radiates only through the whol...
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...ation resistance of the antenna (Ω)
R_loss=loss resistance of the antenna (Ω)
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.
At higher frequencies, the dielectric constants are almost independent of frequency. This is because, at higher frequencies periodic reversal of the field takes place so rapidly that the charge carriers will hardly be able to orient
One of the first distinctions that should be drawn in this discussion is that between RF weapons and EMP weapons. An EMP (electromagnetic pulse) is usually employed by detonating a thermonuclear devices at high altitudes (500 miles or more) above the Earth. The resulting electromagnetic pulse cripples any electronic equipment within its path. Thus, one nuclear device can be used to cripple the modern infrastructure of an entire nation [1]. An RF device is effective over a much smaller range, but it can cause just as much damage [2].
Farina, A. Introduction to radar signal and data processing: the opportunity. SELEX SISTEMI INTEGRATI ROME (ITALY), 2006.
This chapter explains the passive solar design techniques both in general context as well as in context of havelis. It also explains the key factors of passive solar design used in havelis of Rajasthan.
Microwaves are used in our everyday lives but most most people don't realize that physics plays a large and important part in the simple household item. Whenever we heat our food we are oblivious to the forces that cause such a thing to occur and we don't fully understand what happens in front of our eyes and how our food really gets heated in such a simple and efficient way.
The first stage is the RF amplifier. The AM antenna runs into the RF amp where the desired frequency is selected. As stated by Grob (1997), the typical band for AM is 535 Hz to 1605 KHz. For the duration of the paper, we will assume that we are trying to receive a station that is located on 1290 KHz signal. The antenna used must be able to pick up all the stations on the AM dial. Knowing this, we need to select the one we want to hear. In this case, we want 1290 KHz or The Country KOWW. When the dial on the radio is turned to select 1290 KHz, it does two things. There are two variable capacitors
For an efficient Rectenna configuration MIM diode needs to have high responsivity, which is a measure of the rectified DC voltage or current as a function input radiant power [13]. Also low resistance, on the order of 100 Ω, to provide good impedance matching between the antenna and the diode. The third property of the diode that is linked to the responsivity and is important for solar rectennas is the asymmetry in the I(V) curve. Asymmetric characteristics are required for MIM diodes so that it can do a better impedence matching with
“One would think that so important a contribution to the world’s technology would be chronicled with great care at every step…This, unfortunately, is not the case, and for reasons quite understandable” (Page 14). Sometimes history can be hard to distinguish from truth and legend, the history of radar is no exception. Many contributions have been made to the development of radar over the years. For many years prior and during the Second World War, radar was considered a top-secret military tool. Once it was made public, people used the existing information about radar to come up with their own variations for different applications. As a result, the true origin of radar has become blurred within conflicting claims.
"Microwaves, also known as Super High Frequency (SHF) signals, have wavelengths approximately in the range of 30 cm (1 GHz) to 1 mm (300 GHz)."
“Too often we measure everything and understand nothing.” according to Jack Welch. So the government has decided to take a closer look at high powered Micro waves. In his paper I‘m going to speak to you about high power microwaves, it’s applications, a comparison of two different types, some of the history, and the findings in results of its research. “High power microwaves (HPM) is an imprecise term used by several communities [1]. In the DoD it pertains primarily to the generation of high peak power bursts of narrowband (coherent) electromagnetic radiation spanning” a specific frequency range, according to E. Schamiloglu of Department of Electrical & Computer Engineering, University of New Mexico. Directed energy once only apart of every day scifi television can now be apart of everyday life. Laser pointers used for night gazing, fax machines for work, and checkout product scanners are the norm, but a region of directed energy spectrum that has had much less concentration and interest is high power micro-wave technology radar and communication systems. More specifically “moderate average power, broad-bandwidth,” which is used for longer sustained power release and “active denial technology” which is used for nonlethal crowd control. We see as of late that the government has decided the role of high power microwave technology and its applications should be more for the defense es-abolishment, but there are so many more applications in todays world. In recent years and today the need in the modern battlefield is a “target rich environment” for high power micro-wave weapons. With the exception of the standard explosives knives and guns Nearly all equipment contains some kind of electronics. Recently in the gulf war The average sol...
A. D. Gianfranco. et. al. “Design of a 2.45 GHz rectenna for electromagnetic (EM) energy scavenging”, IEEE, 2010.
Mobile communications, wireless interconnects, wireless local area networks (WLANs), and cellular phone technologies compose one of the most rapidly growing industrial markets today. The advancement in the direction of wireless communication leads to a great demand of development of compact antenna to support multiple applications that can be easily integrated within the small space that is available inside the device. In the case of, portable antenna technology has grown along with mobile and cellular technologies. Proper antenna for a device is the most important factor. This will improve transmission and reception of signals, reduce power consumption, long lasting and improve marketability of the device.
Dielectrics and dielectric properties are defined generally and dielectric measurement methods and equipment are described for various
Electromagnetic energy has a very important role in everyday life. It can be seen from the field of technology, information, communication and in the field of health. Example in the field of communication can be seen with the use of mobile phones among the community. Thanks to microwaves, one can give orders