MEMS unrevealed by Anu (Great work) RF MEMS, examples, uses (nitinksaluja.blogspot.com)

What are MEMS?

ØMicroelectromechanical systems (MEMS) are very small devices or groups of devices that can integrate both mechanical and electrical

   components.

Ø MEMS can be constructed on one chip that contains one or more micro-components and the electrical circuitry for inputs and outputs of the components.

Ø The components include different types of sensors, transducers, actuators, electronics and structures (e.g. gears, sliding mirrors, diaphragms).

Ø Each type of components is designed to interface with an input such as light, gas molecules, and a specific type of radiation, pressure, temperature, or biomolecules.

Micro-Electro-Mechanical-Systems (MEMS) are batch-fabricated (micro-fabricated) systems that contains both electrical and mechanical components with characteristic sizes ranging

from Nano-meters to millimeters.

Other Names

 Micro-Electro-Mechanical Systems (MEMS):  Widely used in Americas

 MicroSystems Technology (MST)      :  Popular in Europe

 Micromachines        :  Used in Japan

 Microscience:  Some people prefer to call it this way as they begin to explore scientific aspects of MEMS.

 

wireless sensor network (from one of my frnd who is blessed with sharp mind sukomal thnx)

Wireless Sensor Network (WSN)

·        Sensor networks are the key to gathering the information needed by smart environments, whether in buildings, utilities, industrial, and transportation systems.

·        Recent terrorist and guerilla warfare countermeasures require distributed networks of sensors that can be deployed using, e.g. aircraft, and have self-organizing capabilities.  .

·        The emerging field of wireless sensor networks combines sensing, computation, and communication into a single tiny device.

·        WSN consists of spatially distributed sensors to monitor physical or environmental conditions, such as temperature, sound, vibration or motion to pass their data through the network to a main location.

·        Wireless sensor network can be looked as an event-based system with one “sink” subscribing to specific data streams by expressing interest and queries. The remaining sensors act as “sources” to report environmental events to the subscriber sink

·        The more modern networks are bi-directional, also enabling control of sensor activity.

·        The WSN is built of "nodes" – from a few to several hundreds or even thousands, where each node is connected to one (or sometimes several) sensors.

·        Each such sensor network node has typically several parts: a radio transceiver with an internal antenna or connection to an external antenna, a microcontroller, an electronic circuit for interfacing with the sensors and an energy source, usually a battery or an embedded form of energy harvesting.

·        A sensor node might vary in size and cost depending on the complexity of the individual sensor nodes.

·        Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational speed and communications bandwidth.

·        The topology of the WSNs can vary from a simple star network to an advanced multi-hop wireless mesh network.

·        The propagation technique between the hops of the network can be routing.

·        Basic features of sensor networks are:

Ø  Self-organizing capabilities

Ø  Short-range broadcast communication and multi-hop routing.

Ø  Dense deployment and cooperative effort of sensor nodes

Ø  Frequently changing topology due to fading and node failures

Ø  Limitations in energy, transmit power, memory, and computing power.

·        The development of wireless sensor networks was motivated by military applications such as battlefield surveillance; today such networks are used in many industrial and consumer applications, such as industrial process monitoring and control, machine health monitoring, and so on.

Classification of Wireless Sensor Network

A simple classification of Wireless sensor networks based on their mode of functioning

• Proactive Networks

The nodes in this sort of network periodically switch on their sensors and transmitters, sense the environment and transmit the data of interest. Hence, they collect the data for the relevant parameters at regular intervals. They are well suited for applications requiring periodic data monitoring. Some instances or protocols of this kind are the LEACH (Low Energy Adaptive Clustering Hierarchy) protocol, some improvements on LEACH such as and PEGASIS (Power-efficient gathering in sensor information systems)

• Reactive Networks

The nodes of the networks according to this scheme react immediately to sudden and drastic changes in the value of a sensed attribute. They are well suited for time critical applications.

• Hybrid Networks

The nodes in such a network not only react to time-critical situations, but also give an overall picture of the network at periodic intervals in a very energy efficient manner. Such a network enables the user to request past, present and future data from the network in the form of historical, one-time and persistent queries respectively. Such kind of network takes advantages of Proactive and Reactive networks.

Different type of antennas documented by Pooja (B.Tech student)

Antennas:- Types of antennas.

1.      Dipole antenna

2.      loop antennas

3.      yagi uda antennas

4.      reflectors antennas

5.      Microstrip antennas

6.      Fractal antennas

Dipole antenna:- 

A dipole antenna is a radio antenna that can be made of a simple wire, with a center-fed driven element. It consists of two metal conductors of rod or wire, oriented parallel and collinear with each other (in line with each other), with a small space between them. The radio frequency voltage is applied to the antenna at the center, between the two conductors. These antennas are the simplest practical antennas from a theoretical point of view. They are used alone as antennas, notably in traditional "rabbit ears" television antennas, and as the driven element in many other types of antennas, such as the Yagi. 

 the dipole antenna is the simplest antenna, despite of not being used Practically in applications, it is also known as reference antenna (becoz it is used to test antenna labs) a dipole antenna consists of 2 wires (lambda /4 for its length).

Loop antenna:-

as the diploe is the conventional electric field antenna, loopa are reference maganetic field antenna. Loop antennas can take different shapes like square, circle, triangle, ellipse or any other closed shape. In dipoles current moves till discontinuity occurs and then radiates (electric field).and in loop antenna when current circulates in the loop its obvious that a magnetic field is produced.

The single-turn loop antenna is a metallic conductor bent into the shape of a closed curve, such as a circle or a square, with a gap in the conductor to form the terminals. A multiturn  loop or coil is a series connection of overlaying turns. The loop is one of the primary antenna structures; its use as a receiving antenna dates back to the early experiments of

 Hertz on the propagation of electromagnetic waves.

Types of loop antenna:-

Electrically small loops

Electrically large loops

Shielded- loop antenna

Pulse-excited circular-loop antenna

Yagi Uda antenna:-

A Yagi-Uda array, commonly known simply as a Yagi antenna, is a directional antenna consisting of a driven element (typically a dipole or folded dipole) and additional parasitic elements(usually a so-called reflector and one or more directors). The name stems from it's inventors, as the Yagi-Uda array was invented in 1926 by Shintaro Uda of Tohoku Imperial University, Japan, with a lesser role played by his colleague Hidetsugu Yagi. However the "Yagi" name has become more familiar with the name of Uda often omitted. The reflector element is slightly longer (typically 5% longer) than the driven dipole, whereas the so-called directors are a little bit shorter. This design achieves a very substantial increase in the antenna's directionality and gain compared to a simple dipole.

Reflector antenna:-

Reflector:-while using aperture antennas we always need to increase the aperture area to increase its directivity, but as this is not practical , instead of using large apertures we place a reflecting surface face to face with the aperture , the reflecting surface collimates radiation to the small aperture and thus we satisfied high directivity with a small aperture, and overcome space limitations.

Microstrip antenna:-

Microstrip or patch antennas are becoming increasingly useful because they can be printed directly onto a circuit board. Microstrip antennas are becoming very widespread within the mobile phone market. Patch antennas are low cost, have a low profile and easily fabricated

happy holi

holi mubarak dosto next time tumhare sath hi holi khelenge! nakul, bhushui, siaini, and panniwala rockers