An alternate form of patch antenna has independent feeds for each axis. The feeds are combined in a network that fully isolates the two feeds. Dual-feed antennas can provide nearly ideal characteristics but are inherently more expensive to build. Cisco Aironet Antennas and Accessories Reference Guide. Overview. Executive Overview. This antenna reference guide explains issues and concerns about antennas used with a Cisco. It details deployment and design, limitations and capabilities, and basic theories ofantennas. This document also contains information about the Cisco antennas and accessories, as well as installation scenarios, regulatory information, and technical specifications and diagrams of the available antennas. Piccola e non intrusiva antenna patch per i GSM/DECT, UMTS e 2.4GHz Wifi da montare sul finestrino o su vetro, plastica, legno etc., adatta anche per l'uso in autovettura. Ideale per il PC con l'antenna sotto la scrivaniae senza. Http:// presents an analysis of the patch antenna. In this video: (1) Why the patch antenna radiates, (2) How is it fed (3) what is its impedance, polarization and bandwidth, and (4) What are the fundamental parameters and how do they affect the performance. For more information, see the tutorial: http. International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 3, Issue 11, November 2013) 410 Microstrip Antenna Design Using Transmission Line Model Victor. Antenna Theory: Analysis and Design, John Wiley & Sons, Inc., 1982(1st ed., pp. 816), 1997(2nd ed., pp. 950), 2005(3rd ed., pp. 1,117), 2016(4th ed., pp. Advanced Engineering Electromagnetics, John Wiley & Sons, Inc., 1989(1st ed., pp. Overview Executive Overview This antenna reference guide explains issues and concerns about antennas used with a Cisco . It details deployment and design, limitations and capabilities, and basic. ANTENNA MAGUS: latest release update summary . Release Notes: Version 2016.0.1 Release date: 15 July 2016 Feature extensions and improvements: An error that may have. WIPL-D Lite is a limited, low cost version of WIPL-D Microwave Pro which performs analysis of simple electromagnetic projects. The mutual coupling between antenna elements affects the antenna parameters like terminal impedances, reflection coefficients and hence the antenna array performance in terms of radiation characteristics, output signal-to-interference noise ratio (SINR), and radar. Overview of Antennas. Each Cisco Aironet radio product is designed to perform in a variety of environments. Implementing the antenna system can greatly improve coverage and performance. To optimize the overall performance of a Cisco wireless LAN, it is important to understand how to maximize radio coverage with the appropriate antenna selection and placement. An antenna system comprises numerous components, including the antenna, mounting hardware, connectors, antenna cabling, and in somecases, a lightning arrestor. For a consultation, please contact a Cisco Aironet partnerat: http: //tools. WWChannels/LOCATR/jsp/partner. Federal Communications Commission (FCC) modified Part 1. The modification authorized wireless network products to operate in the industrial, scientific, and medical (ISM) bands using spread spectrum modulation. This type of modulation had formerly been classified and permitted only in military products. The ISM frequencies are in threedifferent bands, located at 9. MHz, 2. 4 GHz, and 5 GHz. This document covers both the 2. GHzbands. The ISM bands typically allow users to operate wireless products without requiring specific licenses, but this will vary in some countries. In the United States, there is no requirement for FCC licenses. The products themselves must meet certain requirements to be certified for sale, such as operation under 1- watt transmitter output power (in the United States) and maximum antenna gain or effective isotropic radiated power (EIRP) ratings. The Cisco Aironet product lines utilize both the 2. GHz bands. In the United States, three bands are defined as unlicensed and known as the. ISM bands. The ISM bands are as follows. This band is also known as the UNII band, and has threesubbands: UNII1 (5. GHz), UNII2 (5. 2. GHz), and UNII3 (5. GHz)Each set of bands has different characteristics. The lower frequencies exhibit better range, but with limited bandwidth and hence lower data rates. The higher frequencies have less range and are subject to greater attenuation from solid objects. Modulation Techniques. The IEEE 8. 02. 1. RF signal. These modulation techniques are used to enhance the probability of the receiver correctly receiving the data and thus reducing the need for retransmissions. The techniques vary in their complexities and robustness to RF signal propagation impairments. Direct- Sequence Spread Spectrum. The direct- sequence spread spectrum (DSSS) approach involves encoding redundant information into the RF signal. Every data bit is expanded to astring of chips called a chipping sequence or Barker sequence. The chipping rate, as mandated by the U. S. FCC, is 1. 0 chips atthe 1- and 2- Mbps rates and 8 chips at the 1. Mbps rate. So, at 1. Mbps, 8 bits are transmitted for every one bit of data. The chipping sequence is transmitted in parallel across the spread spectrum frequency channel. Frequency- Hopping Spread Spectrum. Frequency- hopping spread spectrum (FHSS) uses a radio that moves or hops from one frequency toanother at predetermined times and channels. The regulations require that the maximum time spent on any one channel is 4. For the 1- and 2- Mb FHSS systems, the hopping pattern must include 7. For wide- band frequency hopping (WBFH) systems, which permit up to 1. Mb data rates, the rules require the use of at least 1. With only 8. 3 MHz of spectrum, WBFH limits the systems to 1. In every case, for the same transmitter power and antennas, a DSSS system will have greater range, scalability, and throughput than an FHSS system. Forthis reason, Cisco has chosen to support only direct- sequence systems in the spread spectrum products. Orthogonal Frequency Division Multiplexing. The orthogonal frequency division multiplexing (OFDM) used in 8. In the OFDM system, each tone is orthogonal to the adjacent tones and therefore does not require the frequency guard band needed for direct sequence. This guard band lowers the bandwidth efficiency and wastes up to 5. Because OFDM is composed of many narrow- band tones, narrow- band interference degrades only a small portion of the signal, with little or no effect on the remainder ofthe frequency components. Antenna Properties and Ratings. An antenna gives the wireless system three fundamental properties - gain, direction, and polarization. Gain is a measure of increase inpower. Direction is the shape of the transmission pattern. A good analogy for an antenna is the reflector in a flashlight. The reflector concentrates and intensifies the light beam in a particular direction similar to what a parabolic dish antenna would do to a RF source in a radiosystem. Antenna gain is measured in decibels, which is a ratio between two values. The gain of a specific antenna is compared to the gain of an isotropic antenna. An isotropic antenna is a theoretical antenna with a uniform three- dimensional radiation pattern (similar to a light bulb with no reflector). FCC uses d. Bi in its calculations. An isotropic antenna is said to have a power rating of 0 d. B, meaning that it has zero gain/loss when compared to itself. Unlike isotropic antennas, dipole antennas are real antennas. Dipole antennas have a different radiation pattern compared to isotropic antennas. The dipole radiation pattern is 3. Because the beam is “slightly” concentrated, dipole antennas have a gain over isotropic antennas of 2. B in the horizontal plane. Dipole antennas are said to have a gain of 2. Bi (in comparison to an isotropic antenna). Some antennas are rated in comparison to dipole antennas. This is denoted by the suffix d. Bd. Hence, dipole antennas have a gain of 0 d. Bd (=2. 1. 4 d. Bi). Note that the majority of documentation refers to dipole antennas as having a gain of 2. Bi. Theactual figure is 2. Bi, but is often rounded up. Types of Antennas. Cisco offers several different styles of antennas for use with access points and bridges inboth 2. GHz and. 5- GHz products. Every antenna offered for sale has been FCC- approved. Each type of antenna will offer different coverage capabilities. As the gain ofan antenna increases, there is some tradeoff to its coverage area. Usually high- gain antennas offer longer coverage distances, but only in a certain direction. The radiation patterns below will help to show the coverage areas of the styles of antennas that Cisco offers: omnidirectional, Yagi, and patch antennas. Omnidirectional Antennas. An omnidirectional antenna (Figure 1) is designed to provide a 3. This type of antenna is used when coverage inall directions from the antenna is required. The standard 2. 1. Bi “Rubber Duck” is one style of omnidirectional antenna. Figure 1. Omnidirectional Antenna. Directional Antennas. Directional antennas come in many different styles and shapes. An antenna does not offer any added power to the signal; it simply redirects the energy it receives from the transmitter. By redirecting this energy, it has the effect of providing more energy in one direction, and less energy in all other directions. As the gain of a directional antenna increases, the angle of radiation usually decreases, providing a greater coverage distance, but with a reduced coverage angle. Directional antennas include patch antennas (Figure 2), Yagi antennas (Figure 3), andparabolic dishes. Parabolic dishes have a very narrow RF energy path, and the installer must be accurate in aiming these types of antennas these at each other. Figure 2. Directional Patch Antenna. Figure 3. Yagi Antenna. Diversity Antenna Systems. Diversity antenna systems are used to overcome a phenomenon known as multipath distortion or multipath interference. A diversity antenna system uses two identical antennas, located a small distance apart, to provide coverage to the same physical area. Multipath Distortion. Multipath interference occurs when an RF signal has more than one path between a receiver and a transmitter. This occurs in sites that have a large amount of metallic or other RF reflective surfaces. Just as light and sound bounce off of objects, so does RF. This means there can be more than one path that RF takes when going from a transmit (TX) and receive (RX) antenna. These multiple signals combine in the RX antenna and receiver to cause distortion of the signal. Multipath interference can cause the RF energy of an antenna to be very high, but the data wouldbe unrecoverable. Changing the type of antenna and location of the antenna can eliminatemultipath distortion (Figure. Figure 4. Multipath Distortion. You can relate multipath distortion to a common occurrence in your car. As you pull up to a stop, you may notice static on the radio. But as you move forward a fewinches or feet, the station starts to come in more clearly. By rolling forward, you move the antenna slightly, out of the point where the multiple signals converge. How Diversity Antenna Systems Reduce Multipath Distortion. A diversity antenna system can be compared to a switch that selects one antenna or another, never both at the same time. The radio in receive modewill continually switch between antennas listening for a valid radio packet. After the beginning sync of a valid packet is heard, the radio will evaluate the sync signal of the packet on one antenna, and then switch to the other antenna and evaluate. Then the radio will select the best antenna and use only that antenna for the remaining portion of that packet. On transmit, the radio will select the same antenna it used the last time it communicated to thatgiven radio. If a packet fails, it will switch to the other antenna and retry the packet.
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