Python Implementation and Mathematical Background of Fourier Transform

The python implementation, mathematical background, and noise removal using Fourier Transform are explored in this VIDEO..

https://youtu.be/-u8cUh8tlXY

Basics of Fourier Transform

Fourier Transform is a mathematical tool that is widely used in Signal processing applications.

Fourier Transform is explained in this VIDEO in just SIX minutes.

https://youtu.be/Og6JDPxQBFM

Instrumentation Amplifier

- Amplifier used in the field of Instrumentation (acquiring physical signals, convert it to electrical signals by Transducer and this electrical signal is too weak; so need amplification).

For  more, Click the below link

Instrumentation Amplifier

Working of a Lighter

It works on the principle of Piezo-electric effect.                               

When we start pushing the push button, it presses the hammer and spring assembly to move in the telescopic shaped plastic casing.                      

This force is enough for the crystal to generate a spark.                                                                            
Now, this spark falls on the gas and lights the air-gas mixture. 

TRF Vs Superheterodyne Receiver

RF to AF

RF to IF to AF

Ohm's Law

How Mosquito Racket works?

Parts: 

1. Power Supply

2. Oscillator

3. Transformer(Step-up)

4, Final mesh-nets

The circuit consists of a flyback topology transformer driven by a general NPN transistor 2SD965.

The feedback coil of transformer is of 10 turns, the primary is of 40 turns and the output or secondary coil is of 450 turns (40:450).

When this circuit is run by giving input of 3 Volts, the transformer generates about 2000-4000 volts at zero load, and the output is then coupled 3 times by using three IN4007 diodes and suitable capacitors, thus reaching our need of 5000-10,000 volts.

  The moment a mosquito or any bug comes in contact with the meshes, the stored high voltage in the capacitor discharges violently through the body of the entangled bug creating a big spark and electrocuting it instantly.

What are the Advantages of LabVIEW?

• Graphical User Interface
• Drag and Drop built in functions
• Modular and Hierarchical design
• Professional Development Tools
• Multi Platforms
• Flexibility
• Scalability
• Distributed Development
• Visualization capabilities
• Rapid development with Express Technology
• Simple application distribution
• Object oriented design
• Cost Reduction

Classification of Electric Motor

Difference between VHDL and Verilog

Mobile Hardware Components

Your Smart Phone was integrated into the followed MOBILE DEVICE COMPONENTS even though your Desktop PC Was not comes with. you must Separately want to plug the components as well as size of the components also big when compared to mobile devices These all are belongs to CMOS VLSI Chip Technology integrated into one device. The Processor and all components are designed as a chip and the Processor was programmed.

Today Quote : "Knowing is not enough, We must Apply Willing is not enough, we must do.."

Introduction to Android Applications (Messengers and VOIP)

Today the usage of smartphone is increased as well as usage of application also increased. All the applications are unique but has some little difference. so the user need the awareness for the usage of applications. here the table gives you the specifications of the applications. (Note : Subjects to be changed in Future)

Introduction to Mobile and Cellular Telephony

Introduction to Optical Communication System

Introduction to Television

Introduction to Satellite Communication System

Introduction to Communication Systems

A Journey through VLSI (Prezi)

Why Silicon is preferred over Germanium for Semiconductor Devices?

 As we all know, both Silicon and Germanium are semiconductor devices. But the present trend is to use Silicon instead of Germanium. What may be the reasons?

1. At room temperature, Silicon crystal has fewer free electrons than Germanium crystal. This implies that silicon will have much smaller Collector cut off current than Germanium.
2. The variation of Collector cut off current with temperature is less in Silicon compared to Germanium. 
3. The structure of Germanium crystals will be destroyed at higher temperature. However, Silicon crystals are not easily damaged by excess heat.
4. Peak Inverse Voltage ratings of Silicon diodes are greater than Germanium diodes.  
5. Si is less expensive due to the greater abundance of element. The major raw material for Si wafer fabrication is sand and there is lots of sand available in nature. 

But there is a disadvantage for Silicon over Germanium. 

The potential Barrier of Silicon is more compared to Germanium. 

But if we consider the advantages listed above, we can conclude that Silicon is the best element for the Semiconductor Devices and Applications. 

However,  the  first transistor was made of germanium (Ge). :)

MAGNETIC RESONANCE IMAGING

Magnetic Resonance Imaging (MRI), nuclear magnetic resonance imaging (NMRI), or magnetic resonance tomography (MRT) is a medical imaging technique used in radiology to visualize internal structures of the body in detail. MRI makes use of the property of nuclear magnetic resonance (NMR) to image nuclei of atoms inside the body.

An MRI scanner is a device in which the patient lies within a large, powerful magnet where the magnetic field is used to align the magnetization of some atomic nuclei in the body, and radio frequency magnetic fields are applied to systematically alter the alignment of this magnetization. This causes the nuclei to produce a rotating magnetic field detectable by the scanner—and this information is recorded to construct an image of the scanned area of the body. Magnetic field gradients cause nuclei at different locations to precess at different speeds, which allows spatial information to be recovered using Fourier analysis of the measured signal. By using gradients in different directions, 2D images or 3D volumes can be obtained in any arbitrary orientation.

MRI provides good contrast between the different soft tissues of the body, which makes it especially useful in imaging the brain, muscles, the heart, and cancers compared with other medical imaging techniques such ascomputed tomography (CT) or X-rays. Unlike CT scans or traditional X-rays, MRI does not use ionizing radiation.

How MRI works

MRI machines make use of the fact that body tissue contains lots of water, and hence protons  which get aligned in a large magnetic field. Each water molecule has two hydrogen nuclei or protons. When a person is inside the powerful magnetic field of the scanner, the average magnetic moment of many protons becomes aligned with the direction of the field. A radio frequency current is briefly turned on, producing a varying electromagnetic field. This electromagnetic field has just the right frequency, known as the resonance frequency, to be absorbed and flip the spin of the protons in the magnetic field. After the electromagnetic field is turned off, the spins of the protons return to thermodynamic equilibrium and the bulk magnetization becomes re-aligned with the static magnetic field. During this relaxation, a radio frequency signal is generated, which can be measured with receiver coils.

Information about the origin of the signal in 3D space can be learned by applying additional magnetic fields during the scan. These additional magnetic fields can be used to only generate detectable signal from specific locations in the body (spatial excitation) and/or to make magnetization at different spatial locations precess at different frequencies, which enables k-space encoding of spatial information. The 3D images obtained in MRI can be rotated along arbitrary orientations and manipulated by the doctor to be better able to detect tiny changes of structures within the body. These fields, generated by passing electric currents through gradient coils, make the magnetic field strength vary depending on the position within the magnet. Because this makes the frequency of the released radio signal also dependent on its origin in a predictable manner, the distribution of protons in the body can be mathematically recovered from the signal, typically by the use of the inverse Fourier transform.

Protons in different tissues return to their equilibrium state at different relaxation rates. Different tissue variables, including spin density, T₁ and T₂ relaxation times, and flow and spectral shifts can be used to construct images. By changing the settings on the scanner, this effect is used to create contrast between different types of body tissue or between other properties, as in fMRI and diffusion MRI.

MRI is used to image every part of the body, and is particularly useful for tissues with many hydrogen nuclei and little density contrast, such as the brain, muscle, connective tissue and most tumors.

What is Darlington Pair?

This is two transistors connected together so that the amplified current from the first is amplified further by the second transistor. 

 
This gives the Darlington pair a very high current gain such as 10000. 

Darlington pairs are sold as complete packages containing the two transistors. 

They have three leads (B, C and E) which are equivalent to the leads of a standard individual transistor.

Static RAM Vs Dynamic RAM

CMOS Vs TTL

The difference between the two Logic Styles are:

• TTL circuits utilize BJTs while CMOS circuits utilize FETs.
• CMOS allows a much higher density of logic functions in a single chip compared to TTL.
• TTL circuits consumes more power compared to CMOS circuits at rest.
•  CMOS chips are a lot more susceptible to static discharge compared to TTL chips
• Propagation delay is more in CMOS compared to TTL
• Switching Speed is More for TTL compared to CMOS.
• CMOS devices are cheaper than TTL Devices. 
• The Power Supply requirement for TTL is  3 to 15V, small fluctuations are tolerated.
• The Power Supply requirement for CMOS is  5V ±0.25V, it must be very smooth, a regulated supply.
• TTL Can handle only less frequency compared to CMOS.

Why CMOS is Slower compared to TTL?

Since TTL has very little parasitic capacitance, the time delay is very small, & TTL is faster.

MOSFETs, based on voltage operations, have much greater capacitances, the charging & discharging of which consumes time (Ref: RC time constant), hence CMOS is slower.

An Introduction to Digital Logic Families

What is a Logic Family?

In Digital Designs, our primary aim is to create an Integrated Circuit (IC).

A Circuit configuration or arrangement of the circuit elements in a special manner will result in a particular Logic Family.

What are the advantages of creating different Logic Families?

Electrical Characteristics of the  IC will be identical. In other words, the different parameters like Noise Margin, Fan In, Fan Out etc will be identical.

Different ICs belonging to the same logic families will be compatible with each other.

Some Characteristics we consider for the selection of a particular Logic Family are:

• Supply voltage range 
• Speed of response 
• Power dissipation 
• Input and output logic levels 
• Current sourcing and sinking capability
• Fan-out 
• Noise margin

The basic Classification of the Logic Families are as follows:

• Bipolar Devices
• MOS Devices
• Hybrid Devices

 Bipolar Families:

1. Diode Logic (DL)
2. Resistor Transistor Logic (RTL)
3. Diode Transistor Logic (DTL)
4. Transistor- Transistor Logic (TTL)
5. Emitter Coupled Logic (ECL) or Current Mode Logic (CML)
6. Integrated Injection Logic (IIL)

MOS Families:

1. P-MOS Family
2. N-MOS Family
3. Complementary-MOS Family 
1.  Standard C-MOS
2. Clocked C-MOS 
3. Bi-CMOS
4. Pseudo N-MOS
5. C-MOS Domino Logic
6. Pass Transistor Logic

 Hybrid Family:

1. Bi-CMOS Family

Diode Logic 

In DL (diode logic), only Diode and Resistors are used for implementing a particular Logic.Remember that the Diode conducts only when it is Forward Biased.

Disadvantages of Diode Logic

• Diode Logic suffers from voltage degradation from one stage to the next.
• Diode Logic only permits OR and AND functions.

Resistor Transistor Logic
In RTL (resistor transistor logic), all the logic are implemented using resistors and transistors. One basic thing about the transistor (NPN), is that HIGH at input causes output to be LOW (i.e. like a inverter). In the case of PNP transistor, the LOW at input causes output to be HIGH.

RTL Circuit

Advantage:

• Less number of Transistors

Disadvantage:

• High Power Dissipation
• Low Fan In

Diode Transistor Logic
In DTL (Diode transistor logic), all the logic is implemented using diodes and transistors.

DTL Logic

Disadvantage:

• Propagation Delay is Larger

Transistor Tansistor Logic
In Transistor Transistor logic or just TTL, logic gates are built only around transistors.
TTL Logic has the following sub-families:

• Standard TTL.
• High Speed TTL
• Low Power TTL.
• Schhottky TTL.
• Low Power Schottky TTL
• Advanced Schottky TTL
• Advanced Low Power Schottky TTL
• Fast Schottky

Emitter Coupled Logic
The main specialty of ECL is that it is operating in Active Region than the Saturation Region. That is the reason for its high speed operation. As you can see in the figure, the Emitters of the Transistors Q1 and Q2 are coupled together.

Emitter Coupled Pair

Disadvantage:

• Large Silicon Area
• Large Power Consumption

Advanced Digital Audio Codecs

DTS standards
DTS (Digital Theater Sound) is a digital sound coding standard created by Universal. Compared with the Dolby Digital standard, DTS uses four times less compression and digitises sound at 20 bits instead of 16. Therefore, DTS's sound quality is theoretically higher, at the cost of a higher bit rate. To be able to play DTS-encoded media, you need a certified DTS decoder.

DTS falls into four different categories:

• DTS 6, the most commonly used 5.1 standard, which can encode six-channel sound with less compression than the Dolby Digital standard. The first five channels are used for the satellite speakers, while the last is reserved for the subwoofer. These devices are normally identified by the presence of this logo:

• DTS ES (Digital Theater Sound Extended Surround), 6.1 standard which uses an additional rear channel (rear central). DTS ES uses less compression than Dolby Digital EX.

The DTS ES standard has two variants:
o DTS ES Matrix, which has a seventh channel interpolated with the primary channels. This is called "virtualisation".
o DTS ES Discrete has an seventh independent channel.

• DTS 24/96 represents an audio format used for storing high-definition music with several channels. This format is primarily used in DVD Audio, or audio tracks which accompany video DVDs. The name comes from the fact that the tracks are recorded in 24 bits at 96 kHz. It may be in either stereo or 5.1.

• DTS Neo:6 is a format for upmixing (virtualising) from a stereo sound source.

Image Courtesy: http://electronics.howstuffworks.com http://www.logotypes101.com

Dolby Digital

Dolby Digital and DTS are six-channel digital surround sound systems and are currently the standard in major motion pictures, music, and digital television.

They both use the 5.1 speaker format The format consists of three speakers across the front and two speakers in the rear. The .1 is a sixth channel called an LFE that is sent to a subwoofer.

Dolby Digital uses the AC-3 file format, which any Dolby Digital Decoder can decoder to produce 5.1 audio. Dolby Digitalis the technical name for Dolby's multi-channel digital sound coding technique, more commonly referred to as Dolby 5.1.

A six-channel sound coding process (one channel each for front, left, center, right surround, left surround and a sub-woofer) originally created by Dolby for theaters, AC-3 was subsequently adapted for home use and is now steadily becoming the most common sound format for DVD.

The difference between Dolby Digital (AC-3) and DTS is:
Both systems are great but statistics for reference only..

• DTS seems to provide a deeper and tighter low frequency presence
• DTS allows the sound to breath - transparency
• AC-3 seems to leave the impression that something is missing from the mix.
• At lower bit-rates AC-3 starts to sound like MP3's encoded at 96kbps (artifacts)

An Introduction to Digital Audio

What is sound? 

Sound is vibrations in the air; that is, a series of rising and falling pressures in the air, deviating from the average, which is represented by atmospheric pressure. The simplest way to create a sound is to make an object vibrate.

In this manner, a violin makes a sound when the bow makes its strikes vibrate, and a piano sounds a note when a key is struck, because a hammer struck a string and made it vibrate.

Speakers are generally used to reproduce these sounds. They are a membrane connected to an electromagnet; as an electrical current travels in front of and behind the magnet very rapidly, it causes vibrations in the air in front of it, and that vibration is sound! This is how sound waves are produced; they can be represented in a diagram as changes in air pressure (or in the electricity level of the magnet) as a function of time.

A sonogram, on the other hand, depicts sound frequencies as a function of time. It should be noted that a sonogram shows fundamental frequency, on top of which higher frequencies, called harmonics, are superimposed. This is what allows us to distinguish between different sources of sound: low notes have low frequencies, while high notes have higher frequencies.
 

Sound as an input and output to the Computer

Sound sampling To play sound on a computer, it must be converted into a digital format, as this is the only kind of information computers can work with. 

 

 

 

A computer program intersperses small samples of the sound (which amount to differences in pressure) at specific intervals of time. This is called sampling or digitising sound. 

 

The period of time between two samples is called the sampling rate. As reproducing audio which sounds continuous to the ear requires samples at least once every few 100,000ths of a second, it is more practical to go by the number of samples per second, expressed in Hertz (Hz). 

 

Here are a few examples of common sampling rates, and what sound quality they correspond to:
Sampling rate -Sound quality 

44,100 Hz -CD quality 

22,000 Hz -Radio quality 

8,000 Hz -Telephone quality 

 

The sampling rate of an audio CD, for example, is not arbitrary. In fact, it follows from Shannon's theorem. 

 

Sampling frequency must be high enough to preserve the form of the signal. 

 

The Nyquist-Shannon theorem stipulates that the sampling rate must be equal to or greater than twice the maximum frequency contained in the signal. 

 

 

Our ears can hear sounds up to about 20,000 Hz. Therefore, for a satisfactory level of sound quality, the sampling rate must be at least on the order of 40,000 Hz. 

 

There are several standardized sampling rates in use:
• 32 kHz: for digital FM radio (band-limited to 15 kHz)
• 44.1 kHz: for professional audio and compact discs • 48 kHz: for professional digital multitrack recording, and consumer recording equipment (like DAT or MiniDisc)

A computer works with bits, so the number of possible values that the sample could have must be determined. This is done by setting the number of bits on which the sample values are encoded.

• With 8-bit coding, there are 28 (= 256) possible values.

• With 16-bit coding, there are 216 (= 65536) possible values. 

 

The second option clearly offers higher sound fidelity, but at the cost of using more computer memory. 

 

Finally, stereo sound requires two channels, with sound recorded individually on each one. One channel is fed into the left speaker, while the other is broadcast from the right speaker. 

 

In computer processing, a sound is therefore represented by several parameters:
• The sampling rate
• The number of bits in a sample
• The number of channels (one for mono, two for stereo, and four for quadrophonic sound
 

 

Memory required for storing a sound file 

 

It is easy to calculate what size an uncompressed audio sequence will be. By knowing how many bits are used to code the sample, you know its size (as the sample size is the number of bits) 

 

To find out the size of a channel, all you need to know is the sample rate, and thus the number of samples per second, and from that the amount of space taken up by one second of music.

 

Courtesy: http://en.kioskea.net  

Image Courtesy :http://freesoftwaremagazine.com

Short Notes on Bipolar transistors

NPN Transistor

Placing P-type semiconductor between two N-type semiconductor is NPN transistor

It operates by a small current flow from the emitter to base.current will not  flow from the emitter to the collector until a small voltage (at least 0.7 volts) is applied to the base.

Collector current is much larger than the base current.

SYMBOL

 PNP Transistor

 Placing N-type semiconductor between two P-type semiconductor is PNP transistor.

Its operation is same as NPN but reversed.The voltage relations also reversed.So to turn on the device both the collector and base must be negative.

PNP symbol

Amplification:

 Transistors are used as amplifiers to increase the input signals in TV ,stereo and others applications.It is often called as linear electronics since it contains direct relation with the input and output signal.

If the base is given with the power,it gets biased.It switch on the transistor.An increase or decrease in the input signals makes an increase and decrease in the output signal but with the signal inverse.Frequency remains the same.

Gain:

The measure of amplification is the gain.

For example, if the input signal has an amplitude of 0.2 volts, and the output signal has an amplitude of 10 volts, then:

Power gain =current gain x voltage gain.

Switching

Transistors can also be used for switching in case of digital circuits.Digital circuits needs switch on and off.

When the voltage is below 0.6v no current flows through the circuit.when transistor is not conducting ,it is said to be cut-off.

When the base voltage is about 0.85 volts, sufficient base current flows to turn the transistor fully on. The collector voltage drops to approximately half a volt because of the voltage drop across the collector resistor. A transistor which is conducting the maximum current is said to be in saturation.

Transistor Application

Linear:

Amplifiers

Digital:

Computers

Courtesy:http://silver-fox.ca

Hardwork Can Never Ever Fails..

Best Luck..

3D View of PN Junction

P Type and N Type Materials- Before forming the Junction

P and N type Materials Brought together

Recombination Started (Gold Balls- Recombination)

Depletion Region Formed

Courtesy: www.ineer.org
(From the article: 'Education in Three Dimensions: Using Virtual Reality in Education for Illustrating Spatial Relationships' by ALLPORT, Christopher, SINES, Paul, SCHREINER, Brandon & DAS, Biswajit)

What are MEMS?

Think if we can integrate a GPS System on every Parcel we are sending via Courier or Post. It will be very easy for us to track the current location of the Parcel and the Handling of the Parcel. But, the system should be small like a Chip, and it should be of least cost. Don't forget that the GPS System has a Processor and an Antenna to receive the signals from the Satellite. How can we integrate the entire system inside a Small Chip? Here comes the application of MEMS.

MEMS is an emerging technology in which Microscopic Machines are developed by the tools and techniques that were developed for the Integrated Circuit (IC)ndustry.

MEMS structure

Micro-Electro Mechanical systems (MEMS) is a technology that combines computers with tiny mechanical devices such as sensors, valves, gears, mirrors, and actuators embedded in semiconductor chips. 

These machines are built on standard silicon wafers.

MEMS are made up of components between 1 to 100 micrometres in size (i.e. 0.001 to 0.1 mm), and MEMS devices generally range in size from 20 micrometres (20 millionths of a metre) to a millimetre (i.e. 0.02 to 1.0 mm).

They usually consist of a Central Unit that processes data (the microprocessor) and several components that interact with the outside such as Microsensors.

Components of MEMS

What are the Advantages of MEMS?

By utilizing this technology, it is possible to integrate both Microelectronic circuits and Mechanical structures on the same chip, enabling monolithic integration while reducing the microsystem size and cost considerably.

What are the Applications of MEMS? 

SMART BIOMEM (LAB ON A CHIP)

This technology has an enormous number of application areas, including 

• Automotive Eg. Accelerometers for airbag systems, Roll-over detection systems, etc.
• Biomedical Eg.Neural prosthesis devices like hearing and visual aids, Smart drug delivery systems, On Chip body fluid analysis systems, Microsurgery tools, Pacemakers
• Telecommunication Eg. Micromirrors for fiber optic switching for fast internet,Smart Antennas
• Household appliances pressure sensors for water level detection, frost sensors for refrigerators
• Consumer Applications DLP projectors, i-phone,
• Defense applications Eg. Low cost night vision, Smart munitions

Image Courtesy

www.engineersgarage.com 
www.medgadget.com

How Electric fan work

An electric fan is an electric motor with some fan blades attached to its rotating shaft. As the motor spins, the fan blades rotate. Each blade is angled a bit, and as the inclined plane of the blade moves through the air, it forces the air ahead of it forward. Each blade does this on a continuous basis, and the result is a moving air stream. The fan is taking air from the area behind itself and blowing it out the front. The fan generates a movement of air, causing the warm, less dense air to rise, and the cool, dense air to descend, thus creating a feeling of coolness in the air.

HOW METAL DETECTOR WORKS

Transmitter

Inside the metal detector's loop there is a coil of wire called the transmit coil. Electronic current is driven through the coil to create an electromagnetic field. The direction of the current flow is reversed several thousand times every second; the transmit frequency "operating frequency" refers to the number of times per second that the current flow goes from clockwise to counterclockwise and back to clockwise again.
When the current flows in a given direction, a magnetic field is produced whose polarity  points into the ground; when the current flow is reversed, the field's polarity points out of the ground. Any metallic object which happens to be nearby will have a flow of current induced inside of it by the influence of the changing magnetic field, in much the same way that an electric generator produces electricity by moving a coil of wire inside a fixed magnetic field. This current flow inside a metal object in turn produces its own magnetic field, with a polarity that tends to be pointed opposite to the transmit field.

Receiver

A second coil of wire inside the loop, the receive coil, is arranged so that nearly all of the current that would ordinarily flow in it due to the influence of the transmitted field is cancelled out. Therefore, the field produced by the currents flowing in the nearby metal object will cause currents to flow in the receive coil which may be amplified and processed by the metal detector's electronics without being swamped by currents resulting from the much stronger transmitted field.
The resulting received signal will usually appear delayed when compared to the transmitted signal. This delay is due to the tendency of conductors to impede the flow of current (resistance) and to impede changes in the flow of current (inductance). We call this apparent delay "phase shift". The largest phase shift will occur for metal objects which are primarily inductive; large, thick objects made from excellent conductors like gold, silver, and copper. Smaller phase shifts are typical for objects which are primarily resistive; smaller, thinner objects, or those composed of less conductive materials.

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