Electronics Spectra - SMS Lucknow

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SMS Institute of Technology, L ucknow Department of Electronics & Co mmunication scriber get hundreds of channels with a digital subscriber line (DSL)? When a user changes the channel on his STB, the box does not tune a channel like a cable system. It switches channels by using the IP group membersh ip protocol v2 to join a new mult icast group. When the local office receives this request, it checks to make sure that the user is authorised to view the new channel, directs the routers in the local office to add the particular user to the channel's distribution index. In this way, only signa ls that are currently being watched ar e actually being sent from the loc al office to the digital subscriber line access multiplexer (DSLAM) and finally, to the user". Zigbee A Zigbee standard has evolved standardized sets of solution called layers. These layers facilitate the features that make Zigbee very attractive, low cost easy implementation, reliable data transfer, short range operation, very low power consumption and adequate security features. Zigbee is one of the newest technologies enabling wireless per sonal area network (WPAN). It is a wireless technology developed as an open global standard to address the un ique needs of low cost, low power w ireless M2M network. The Zigbee p rotocol has been ratified by mem ber companies of the Zigbee alliance. It is designed to provide an easy to use wireless data solution characterized by secured, reliable wireless network architecture. The name of the brand was originated with reference to the behaviour of honey bees after their retu rn to the beehive. Specified maximum range of operation for zigbee devices is 76 meters substantially further than that by used Bluetooth capable devices. A Zigbee protocol is de signed to communicate through hostile RF environments that are common i n commercial and industrial applications. Zigbee protocols features include; ‣ Support for multiple network topologies such as point to poin t, point to multipoint and mesh network. IPTV VS DTH, CABLE TV Although it is not appropriate to compare IPTV with other modes of broadcast, but there lies a difference that is " The entry cost of IPTV service is at par with cable TV but DTH and other cable TV require m uch more bandwidth (8 Mbps per hom e, per connection), whereas IPTV can be viewed at 2-3 Mbps." ADVANTAGES OF IPTV IPTV is a truly interactive service and can provide numerous services like e-commerce, e-governance, e-education, e-medicine, weather and entertainment. However, its penetration is heavily dependent on good qual ity, ‣ Low latency. ‣ Low duty cycle-provide long battery life. ‣ Direct spread spectrum. ‣ Collision avoidance. In Industry, Zigbee is being used for next generation automated manufacturing with small transmitt ers in every device on the floor, allowing for communication between devices to a central computer. high bandwidth and broadband c onnectivity. IPTV is still in it s nascent phase in India. Considering th e current scenario, IPTV can be said to have both pros and cons. One of the best advantages of IPTV is that it uses Internet protocol to provide two-way communication, making the television viewing experience truly interactive. Through this technology viewers not only receive data but can also send data back like e-mailing, instant messaging, ticket booking, etc. With the help of IPTV orders for buying different products can be placed. The number of application that can be put on IPTV are virtually infinite. Pooja Sharma EC - III year It provides the ability to run for years on inexpensive batteries for a host of monitoring and control applications. Automatic meter readi ng, lighting control, medical devices, fleet applications are just some of the many spaces where Zigbee technology is making significant advancements. 32 Electronics Spectra, 2010
SMS Institute of Technology, L ucknow MEMS INTRODUCTION A Micro-Electro-Mechanical System (MEMS) that contains both electrical and mechanical componen ts with its ranging size from nanometers to millimeters. MEMS is a device which is able to replace bulky networks, sensors, actuators on a common silicon substrate. These all are fabri cated using IC process sequences (e. g. CMOS, BICMOS process). This re - duces bulk, cost, weight and p ower consumption with increase in its performance, production volume. Furthermore, there are many applications to come including g enetic and disease testing, power dev ices, RF devices, weapon system and data storage. Micromirror- based switches have already proven their importance. MEMS promises to revolutionize almost all product category by fabricating together silicon-based microelectronics with micromachining technology, making possible the realization of complete system-on-chip. FABRICATION The fabrication technique used in MEMS consists of the conventio nal techniques developed for integrated circuit processing. The essential elements in conventional silicon processing are deposition, lithograph y, and etching. DEPOSITION The essential element in MEMS processing is the ability to deposit thin films of material. In this process, we assume that a thin layer to ha ve a thickness anywhere between a f ew nanometers to 100 micrometer. The thin film then can be etched with the help of developer. There may be various types of deposition used for this process which are as under: ‣ Chemical vapour deposition ‣ Epitaxy ‣ Oxidation ‣ Physical deposition: Sputtering Evaporation Spin-on method LITHOGRAPHY Lithography includes three sequential steps: ‣ Application of photoresist, which is a photosensitive emulsion layer; ‣ Optical exposure to print an i m- age of the mask onto the resist; ‣ Immersion in an aqueous developer solution to dissolve the exposed resist and render visible the latent image. The pattern layout is generate d using a computer aided design and transferred into a layer a specialized mask-making facility, often by electron beam or laser beam. A complete microfabrication involves several lithographic operations with differ ent masks. ETCHING ‣ Etch rate- The speed of the etching should be fast enough to be good for production but is als o controllable. ‣ Uniformity- The etching is not location dependent. ‣ Selectivity- Selection of developer through which etching is done is important. ‣ Directionality- They can be isotropic , or anisotropic. Isotropic etchants etch unifor mly in all direction, resulting in rounded cross sectional. CATEGORIES OF MEMS There are several different c ategories of MEMS which are as under: Department of Electronics & Co mmunication Bulk micromachining Tejashwani Dubey EC - II year Bulk micromachining is a technique which builds mechanical elements by starting with a silicon wafer, and then etching away the unwanted parts and left with useful mechanical devices. Today almost all pressure sensors are built with bulk micromachining. Bulk micromachined pressure sensors offer several advantages over tradit ional pressure sensors. They cost less, are highly reliable, manufacturable, and there is very good repeatabili ty between devices. The small size and high reliability of micromachined pressure sensors make them ideal for a various of medical fields. Surface Micromachining In bulk micromachining, the de - vices are build by etching into a warfer, Surface micromachining builds devices from the wafer layer by layer. A Surface Micromachining is a repet itive 33 Electronics Spectra, 2010
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