SPICE (Simulation Program with Integrated Circuit Emphasis)

Circuit simulation is a technique to predict the behavior of a real circuit using a computer program. It replaces real components with predefined electrical models. It is not possible to conceder all the physical processes (in circuit level simulation) in the parts and all PCB parasitic so it will only reflect the specific model that is put into it. This is the reason behind that simulators can’t substitute bread boarding and prototyping. But they allow measurements of internal currents, voltages and power that in many cases are virtually not possible to do any other way.

SPICE (Simulation Program with Integrated Circuit Emphasis) is a general-purpose open source analog electronic circuit simulator. It is a powerful program that is used in integrated circuit and board-level design to check the integrity of circuit designs and to predict circuit behavior.

Integrated circuits, unlike board-level designs composed of discrete parts, are impossible to breadboard before manufacture. Further, the high costs of photo lithographic masks and other manufacturing prerequisites make it essential to design the circuit to be as close to perfect as possible before the integrated circuit is first built. Simulating the circuit with SPICE is the industry-standard way to verify circuit operation at the transistor level before committing to manufacturing an integrated circuit.

Board-level circuit designs can often be bread boarded for testing. Even with a breadboard, some circuit properties may not be accurate compared to the final printed wiring board, such as parasitic resistances and capacitance. These parasitic components can often be estimated more accurately using SPICE simulation. Also, designers may want more information about the circuit than is available from a single mock-up. For instance, circuit performance is affected by component manufacturing tolerances. In these cases it is common to use SPICE to perform Monte Carlo simulations of the effect of component variations on performance, a task which is impractical using calculations by hand for a circuit of any appreciable complexity.

Circuit simulation programs, of which SPICE and derivatives are the most prominent, take a text netlist describing the circuit elements (transistors, resistors, capacitors, etc.) and their connections, and translate this description into equations to be solved. The general equations produced are nonlinear differential algebraic equations which are solved using implicit integration methods, Newton’s method and sparse matrix techniques

SPICE was developed at the Electronics Research Laboratory of the University of California, Berkeley by Laurence Nagel with direction from his research advisor, Prof. Donald Pederson. SPICE1 was largely a derivative of the CANCER program, which Nagel had worked on under Prof. Ronald Rohrer. CANCER was an acronym for “Computer Analysis of Nonlinear Circuits, Excluding Radiation,” a hint to Berkeley’s liberalism of 1960s: at these times many circuit simulators were developed under the United States Department of Defence contracts that required the capability to evaluate the radiation hardness of a circuit. When Nagel’s original advisor, Prof. Rohrer, left Berkeley, Prof. Pederson became his advisor. Pederson insisted that CANCER, a proprietary program, be rewritten enough that restrictions could be removed and the program could be put in the public domain.

SPICE1 was first presented at a conference in 1973. SPICE1 was coded in FORTRAN and used nodal analysis to construct the circuit equations. Nodal analysis has limitations in representing inductors, floating voltage sources and the various forms of controlled sources. SPICE1 had relatively few circuit elements available and used a fixed-time step transient analysis. The real popularity of SPICE started with SPICE2 in 1975. SPICE2, also coded in FORTRAN, was a much-improved program with more circuit elements, variable time step transient analysis using either the trapezoidal (second order Adams-Moulton method) or the Gear integration method (also known as BDF), equation formulation via modified nodal analysis (avoiding the limitations of nodal analysis), and an innovative FORTRAN-based memory allocation system developed by another graduate student, Ellis Cohen. The last FORTRAN version of SPICE was 2G.6 in 1983. SPICE3 was developed by Thomas Quarles (with A. Richard Newton as advisor) in 1989. It is written in C, uses the same netlist syntax, and added X Window System plotting.

As an early open source program, SPICE was widely distributed and used. Its ubiquity became such that “to SPICE a circuit” remains synonymous with circuit simulation. SPICE source code was from the beginning distributed by UC Berkeley for a nominal charge (to cover the cost of magnetic tape). The license originally included distribution restrictions for countries not considered friendly to the USA, but the source code is currently covered by the BSD license.

SPICE inspired and served as a basis for many other circuit simulation programs, in academia, in industry, and in commercial products. The first commercial version of SPICE was ISPICE, an interactive version on a timeshare service, National CSS. The most prominent commercial versions of SPICE include HSPICE (originally commercialized by Shawn and Kim Hailey of Meta Software, but now owned by Synopsys) and PSPICE (now owned by Cadence Design Systems). The academic spinoffs of SPICE include XSPICE, developed at Georgia Tech, which added mixed analog/digital “code models” for behavioural simulation, and Cider (previously CODECS, from UC Berkeley/Oregon State Univ.) which added semiconductor device simulation. The integrated circuit industry adopted SPICE quickly, and until commercial versions became well developed many IC design houses had proprietary versions of SPICE. Today a few IC manufacturers, typically the larger companies, have groups continuing to develop SPICE-based circuit simulation programs. Among these are ADICE at Analog Devices, LTspice at Linear Technology, Mica at Freescale Semiconductor, and TISPICE at Texas Instruments. (Other companies maintain internal circuit simulators which are not directly based upon SPICE, among them PowerSpice at IBM, Titan at Qimonda, Lynx at Intel Corporation, and Pstar at NXP Semiconductor.)

SPICE became popular because it contained the analyses and models needed to design integrated circuits of the time, and was robust enough and fast enough to be practical to use. Precursors to SPICE often had a single purpose: The BIAS program, for example, did simulation of bipolar transistor circuit operating points; the SLIC program did only small-signal analyses. SPICE combined operating point solutions, transient analysis, and various small-signal analyses with the circuit elements and device models needed to successfully simulate many circuits.

Some of the popular circuit simulators are as follows:

1.            ASTAP

2.            Advanced Design System

3.            CircuitLogix

4.            CPU Sim

5.            GNU Circuit Analysis Package

6.            Gpsim

7.            ICAP/4

8.            List of free electronics circuit simulators

9.            Logisim

10.          Micro-Cap

11.          NI Multisim

12.          National Instruments Electronics Workbench Group

13.          Ngspice

14.          PSpice

15.          PowerEsim

16.          Quite Universal Circuit Simulator

17.          SPICE

18.          SapWin

19.          SmartSpice

20.          SNAP (software)

21.          Spectre Circuit Simulator

22.          SpectreRF

These simulators differs each other and are generally application specific. Most popular version of spice simulators for analog circuit simulations are PSpice offered by MicroSim but now incorporated in OrCAD of Cadence and National Instruments Multisim.

List of Approved Post Graduate Education and Research institutions for M Tech & M E

Here is a link having information of seats of M Tech and M E in various colleges in India , although the document is little bit older but will be very helpful for basic idea of available courses and information about seats. click the link bellow to download the document.

List of Approved Post Graduate Education and Research institutions Upto 30th September, 2004 (M.E/M.Tech)

"Semulation" an Introduction

Semulation is a computer science-related neologism that combines simulation and emulation. It is the process of controlling an emulation through a simulator.

Semulation in computer science

Digital hardware is described using hardware description languages (HDL) like VHDL, Verilog or System Verilog. These descriptions are simulated together with a problem-specific testbench. The initial functional verification of most IP designs is done via simulation at register transfer level (RTL) or gate level. In an event driven simulation method the code must be processed sequential by a CPU, because a normal computer is not able to process the implemented hardware parallel. This sequential approach leads to long simulation times especially in complex systems on chip (SoC) designs.

After simulation the RTL description must be synthesized to fit in the final hardware (eg.: FPGA, ASIC). This step brings a lot of uncertainties because the real hardware is normally not as ideal as the simulation model. The differences between real world and simulation are a major reason why emulation is used in hardware design.

Generally the simulation and emulation environment are two independent systems. Semulation is a symbiosis of both methods. In semulation one part of a hardware design is processed sequential in software (eg.: the testbench) while the other part is emulated.

An example design flow for semulation is depicted in the following block chart:

The database holds the design and testbench files and the information about the block whether it will be simulated or emulated. The left part shows the normal simulation path where the design files must be compiled for an HDL simulator. The right part of the state chart handles the flow for the emulation system. Design files for the FPGA must be synthesized to the appropriate target technology. A major point in semulation is the connection between the emulation system and the HDL simulator. The interface is necessary for the simulator to handle the connected hardware.

Advantages of Semulation

• Simulation acceleration: Simulating huge designs with an HDL simulator is a tedious task. When the designer transfers parts of the design to an emulation system and co-simulates them with the HDL simulation, the simulation run times can be decreased.
• Using real hardware early in the design flow.

Virtual Instrumentation

Virtual Instrumentation is the use of customizable software and modular measurement hardware to create user-defined measurement systems, called virtual instruments.

Traditional hardware instrumentation systems are made up of pre-defined hardware components, such as digital multimeters and oscilloscopes that are completely specific to their stimulus, analysis, or measurement function. Because of their hard-coded function, these systems are more limited in their versatility than virtual instrumentation systems. The primary difference between hardware instrumentation and virtual instrumentation is that software is used to replace a large amount of hardware. The software enables complex and expensive hardware to be replaced by already purchased computer hardware; e. g. analog to digital converter can act as a hardware complement of a virtual oscilloscope, a potentiostat enables frequency response acquisition and analysis in electrochemical impedance spectroscopy with virtual instrumentation.

The concept of a synthetic instrument is a subset of the virtual instrument concept. A synthetic instrument is a kind of virtual instrument that is purely software defined. A synthetic instrument performs a specific synthesis, analysis, or measurement function on completely generic, measurement agnostic hardware. Virtual instruments can still have measurement specific hardware, and tend to emphasize modular hardware approaches that facilitate this specificity. Hardware supporting synthetic instruments is by definition not specific to the measurement, nor is it necessarily (or usually) modular.

Leveraging commercially available technologies, such as the PC and the analog to digital converter, virtual instrumentation has grown significantly since its inception in the late 1970s. Additionally, software packages like National Instruments’ LabVIEW and other graphical programming languages helped grow adoption by making it easier for non-programmers to develop systems.

LabVIEW the new emerging tool

LabVIEW is a powerfull tool developed by NATIONAL INSTRUMENS having many new features….

Increase Throughput with Parallel Test test engineers use LabVIEW, multicore processors, and new bus technologies to create high-performance test systems capable of parallel processing, parallel measurements, and even parallel test on the production floor. Connect to Any Instrument, Any Sensor, Any Bus Built-in I/O and communication libraries in LabVIEW provide native connectivity to any instrument, sensor, bus, or software interface to simplify integration of these components into your test applications.

Boeing Uses LabVIEW to Develop a Low-Cost Test System LabVIEW software and NI hardware helped a single Boeing developer create a high-channel-count, synchronized test system in only six months to measure the effectiveness of new commercial jetliner designs in reducing noise during flight.

Acquire Measurements from Any Sensor, Any Bus LabVIEW may be used to create a fully functional measurement application with analysis and a custom user interface using a variety of PCI- and USB-based data acquisition hardware. Measure in Minutes with LabVIEW and the DAQ Assistant LabVIEW uses the interactive DAQ Assistant and high-level functions to combine the flexibility and scalability of traditional programming languages and the ease of use of configuration-based data acquisition tools.
Acquire, Analyze, and Present Data Quickly with Express VIs to develop a powerful DAQ application that includes advanced analysis and a custom user interface. See how tasks that would take several lines of code in traditional programming languages are interactively configured with Express VIs in LabVIEW.

Use LabVIEW to Program the Next-Generation PLC Industrial engineers pushing the boundaries of controller technology can use LabVIEW graphical programming and programmable automation controllers (PACs) to combine PC functionality with programmable logic controller (PLC) reliability. Add Advanced Analysis to Your PLC Add advanced analysis, signal processing, decision making, and debugging diagnostics to an existing PLC-based industrial application with LabVIEW and OPC connectivity.

Simplify Embedded Development with Graphical System Design Discover how LabVIEW graphical system design software provides domain experts with high-level tools, such as statecharts, to design and implement their systems on off-the-shelf hardware. Get to Market Faster with LabVIEW and COTS Hardware LabVIEW graphical programming and commercial off-the-shelf (COTS) hardware help design teams get products to market faster by accelerating every stage of development – from the earliest stages of design and simulation to prototyping the system with real-world signals and deploying to a chosen processor target.
Prototype and Deploy a Custom Controller with LabVIEWDrivven used LabVIEW and COTS prototyping hardware to quickly develop custom IP for an FPGA-based engine control unit (ECU) in a high-performance motorcycle engine.

Control Industrial Machinery Remotely with LabVIEW Nexans uses LabVIEW and NI reconfigurable embedded hardware to control the hydraulic systems on a remotely operated underwater excavator that prepares the ocean floor for a pipeline to extract natural gas.

Combine Graphical and Textual Programming to Reduce Design Time Reduce embedded design time by using a LabVIEW graphical system design approach to combine the traditionally separate tasks of theoretical design and prototyping. Choose between graphical and textual programming throughout the process. Choose the Software Preferred by Students for Signal Processing Professor Mark Yoder, Ph.D., recently transitioned the signal processing course at Rose-Hulman from The MathWorks, Inc. MATLAB® software to LabVIEW software. Dr. Yoder’s research later showed that students prefer LabVIEW as a learning tool by a 3 to 1 margin. MATLAB® is a registered trademark of The MathWorks, Inc.

Students Use LabVIEW to Create Segway-Inspired Machine A senior design team at Rensselaer Polytechnic Institute used LabVIEW to develop a two-wheeled robotic locomotion platform inspired by the Segway Human Transporter. With LabVIEW software and NI hardware, the students could use one platform throughout the project.

source: www.ni.com

WiFi

If you’ve been in an airport, coffee shop, library or hotel recently, chances are you’ve been right in the middle of a wireless network. Many people also use wireless networking, also called WiFi or 802.11 networking, to connect their computers at home, and some cities are trying to use the technology to provide free or low-cost Internet access to residents. In the near future, wireless networking may become so widespread that you can access the Internet just about anywhere at any time, without using wires.

One wireless router can allow multiple devices to connect to the Internet.

WiFi has a lot of advantages. Wireless networks are easy to set up and inexpensive. They’re also unobtrusive — unless you’re on the lookout for a place to use your laptop, you may not even notice when you’re in a hotspot. In this article, we’ll look at the technology that allows information to travel over the air. We’ll also review what it takes to create a wireless network in your home.

First, let’s go over a few WiFi basics.

What Is WiFi?

A wireless network uses radio waves, just like cell phones, televisions and radios do. In fact, communication across a wireless network is a lot like two-way radio communication. Here’s what happens:

1. A computer’s wireless adapter translates data into a radio signal and transmits it using an antenna.
2. A wireless router receives the signal and decodes it. The router sends the information to the Internet using a physical, wired Ethernet connection.

The process also works in reverse, with the router receiving information from the Internet, translating it into a radio signal and sending it to the computer’s wireless adapter.

The radios used for WiFi communication are very similar to the radios used for walkie-talkies, cell phones and other devices. They can transmit and receive radio waves, and they can convert 1s and 0s into radio waves and convert the radio waves back into 1s and 0s. But WiFi radios have a few notable differences from other radios:

• They transmit at frequencies of 2.4 GHz or 5 GHz. This frequency is considerably higher than the frequencies used for cell phones, walkie-talkies and televisions. The higher frequency allows the signal to carry more data.
• They use 802.11 networking standards, which come in several flavors:
  • 802.11a transmits at 5 GHz and can move up to 54 megabits of data per second. It also uses orthogonal frequency-division multiplexing (OFDM), a more efficient coding technique that splits that radio signal into several sub-signals before they reach a receiver. This greatly reduces interference.
  • 802.11b is the slowest and least expensive standard. For a while, its cost made it popular, but now it’s becoming less common as faster standards become less expensive. 802.11b transmits in the 2.4 GHz frequency band of the radio spectrum. It can handle up to 11 megabits of data per second, and it uses complementary code keying (CCK) modulation to improve speeds.
  • 802.11g transmits at 2.4 GHz like 802.11b, but it’s a lot faster — it can handle up to 54 megabits of data per second. 802.11g is faster because it uses the same OFDM coding as 802.11a.
  • 802.11n is the newest standard that is widely available. This standard significantly improves speed and range. For instance, although 802.11g theoretically moves 54 megabits of data per second, it only achieves real-world speeds of about 24 megabits of data per second because of network congestion. 802.11n, however, reportedly can achieve speeds as high as 140 megabits per second. The standard is currently in draft form — the Institute of Electrical and Electronics Engineers (IEEE) plans to formally ratify 802.11n by the end of 2009.
• Other 802.11 standards focus on specific applications of wireless networks, like wide area networks (WANs) inside vehicles or technology that lets you move from one wireless network to another seamlessly.
• WiFi radios can transmit on any of three frequency bands. Or, they can “frequency hop” rapidly between the different bands. Frequency hopping helps reduce interference and lets multiple devices use the same wireless connection simultaneously.

WiFi Hotspots

If you want to take advantage of public WiFi hotspots or start a wireless network in your home, the first thing you’ll need to do is make sure your computer has the right gear. Most new laptops and many new desktop computers come with built-in wireless transmitters. If your laptop doesn’t, you can buy a wireless adapter that plugs into the PC card slot or USB port. Desktop computers can use USB adapters, or you can buy an adapter that plugs into the PCI slot inside the computer’s case. Many of these adapters can use more than one 802.11 standard.

Once you’ve installed your wireless adapter and the drivers that allow it to operate, your computer should be able to automatically discover existing networks. This means that when you turn your computer on in a WiFi hotspot, the computer will inform you that the network exists and ask whether you want to connect to it. If you have an older computer, you may need to use a software program to detect and connect to a wireless network.

Being able to connect to the Internet in public hotspots is extremely convenient. Wireless home networks are convenient as well. They allow you to easily connect multiple computers and to move them from place to place without disconnecting and reconnecting wires. In the next section, we’ll look at how to create a wireless network in your home.

Building a Wireless Network

If you already have several computers networked in your home, you can create a wireless network with a wireless access point. If you have several computers that are not networked, or if you want to replace your Ethernet network, you’ll need a wireless router. This is a single unit that contains:

1. A port to connect to your cable or DSL modem
2. A router
3. An Ethernet hub
4. A firewall
5. A wireless access point

A wireless router allows you to use wireless signals or Ethernet cables to connect your computers to one another, to a printer and to the Internet. Most routers provide coverage for about 100 feet (30.5 meters) in all directions, although walls and doors can block the signal. If your home is very large, you can buy inexpensive range extenders or repeaters to increase your router’s range.

A wireless router uses an antenna to send signals to wireless devices and a wire to send signals to the Internet.

As with wireless adapters, many routers can use more than one 802.11 standard. 802.11b routers are slightly less expensive, but because the standard is older, they’re slower than 802.11a, 802.11g and 802.11n routers. Most people select the 802.11g option for its speed and reliability.

Once you plug in your router, it should start working at its default settings. Most routers let you use a Web interface to change your settings. You can select:

• The name of the network, known as its service set identifier (SSID) — The default setting is usually the manufacturer’s name.
• The channel that the router uses — Most routers use channel 6 by default. If you live in an apartment and your neighbors are also using channel 6, you may experience interference. Switching to a different channel should eliminate the problem.
• Your router’s security options — Many routers use a standard, publicly available sign-on, so it’s a good idea to set your own username and password.

Security is an important part of a home wireless network, as well as public WiFi hotspots. If you set your router to create an open hotspot, anyone who has a wireless card will be able to use your signal. Most people would rather keep strangers out of their network, though. Doing so requires you to take a few security precautions.

It’s also important to make sure your security precautions are current. The Wired Equivalency Privacy (WEP) security measure was once the standard for WAN security. The idea behind WEP was to create a wireless security platform that would make any wireless network as secure as a traditional wired network. But hackers discovered vulnerabilities in the WEP approach, and today it’s easy to find applications and programs that can compromise a WAN running WEP security.

To keep your network private, you can use one of the following methods:

• WiFi Protected Access (WPA) is a step up from WEP and is now part of the 802.11i wireless network security protocol. It uses temporal key integrity protocol (TKIP) encryption. As with WEP, WPA security involves signing on with a password. Most public hotspots are either open or use WPA or 128-bit WEP technology, though some still use the vulnerable WEP approach.
• Media Access Control (MAC) address filtering is a little different from WEP or WPA. It doesn’t use a password to authenticate users — it uses a computer’s physical hardware. Each computer has its own unique MAC address. MAC address filtering allows only machines with specific MAC addresses to access the network. You must specify which addresses are allowed when you set up your router. This method is very secure, but if you buy a new computer or if visitors to your home want to use your network, you’ll need to add the new machines’ MAC addresses to the list of approved addresses. The system isn’t foolproof. A clever hacker can spoof a MAC address — that is, copy a known MAC address to fool the network that the computer he or she is using belongs on the network.

  Sources

  • Borisov, Nikita, Ian Goldberg and David Wagner. “Security of the WEP algorithm.” University of California, Berkeley. (Aug. 7, 2008)
    http://www.isaac.cs.berkeley.edu/isaac/wep-faq.html
  • Geier, Jim. “802.11 WEP: Concepts and Vulnerability.” Wi-Fi Planet. June 20, 2002. (Aug. 6, 2008)
    http://www.wi-fiplanet.com/tutorials/article.php/1368661
  • IEEE. (Aug. 6, 2008)
    http://www.ieee.org
  • IEEE. “IEEE Standard for Information technology — Telecommunications and information exchange between systems — Local and metropolitan area networks — Specific requirements.” (Aug. 6, 2008) http://standards.ieee.org/getieee802/download/802.11-2007.pdf