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Saturday 17 December 2011
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Advancement in Computer Technologies:
Since the introduction of the first computers the Computer technology has advanced at a very fast pace. Every single day a new innovation, a new concept is being introduced in the computer technology. The pace in the computer technology is so fast that if a person says about a task that it is impossible, a person in another part of the world is already working on it. These advancements have encouraged different companies to come up with their ideas and compete with the pioneers of the computer market.
Tablet PC’s: The latest and the best:
Tablet PC’s are the latest and the best form of computers. Users have found them and liked them a lot. A tablet PC provides in the true sense the portability and ease that the miniaturised computers have promised. Tablet PC’s, since their origin, have been made better and faster. A few companies have come up with some lightening fast and attractive tablet PC’s. These include Apples, Samsung, Amazon, LG and many others. All of them have tried to make the tablet PC’s faster and better. But if you are talking about the best in this field then there is no doubt only one and that is Samsung.
Samsung and Tablet PC’s:
Samsung has been the pioneers in producing Tablet PC’s. Samsung has always tried to give its customers the best. That is why latest processors and sleek stylish designs have been seen in Samsung’s Products. The latest in this field is the Samsung Exynos 5250 Chip. This 2 GHz Cortex A15 Exynos 5250 Chip is the latest and the fastest processor chip that has been yet made for the tabs. This dual core processor provides better speed and enhanced performance in the tablet PC. This design is better adaptive to 3D technology and provides a new maximum resolution of 2506x1600. Samsung says that this processor will be available in the market by the end of 2012.
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For Sony it was almost two years hard work to enter in to the Tablet market.
To launch a new product of already growing tablet market, where it has so many competitors like the obvious iPad, the Samsung galaxy tablets, Motorola and Acer.
The Sony Tablet S has therefore a different design and look. It has a very different look like it has been folded back from a single textured plastic. It is thicker from one end and very thin sleek surface at the other end.
The Tablet also weighs just 600g so it is very easy to carry compared to the iPad 2. The back is also textured so that it is very easy to carry.
There's a dual-core Tegra 2 processor clocked at 1GHz, 1GB of memory, capacitive touchscreen, and an SD expansion slot.
The Company has strived hard to make it as much versatile as it can from its competitors.
There are front and rear cameras, 1080p video capture and playback, PlayStation certification, which enables users to access a range of exclusive titles, and a host of Sony created apps, including a universal remote for controlling other Sony products.
It has a Beautiful screen quality, Excellent software keyboard, Excellent music application.
With access to the Android Market, you can browse through thousands of useful, time-saving and entertaining apps. There's also instant access to Google™ mobile services and applications including 3D maps and easy web search with Google Voice Search. Download what you want and make your tablet truly yours.
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Tuesday 13 December 2011
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Apple iCam is a concept that is
given by the Italian designer Antonio DeRosa. And it is likely to be a part of
new iPhone 5.
The camera will be having
interchangeable lenses, as well as it is going to be operated via your iPhone. So
that now we have a huge screen, high processing power, connectivity to various
applications and the internet.
The camera also has a rear panel
to which the iPhone can be easily connected. It features a 10.1-megapixel sensor and supports video
recording with high resolution Full HD at 60 fps.
The
iCams two front cameras bring 3D technology to palm of your hand. Which means
you can share, edit, record, take pictures all in 3D
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Dell 7-inch Streak tablet has been taken out of market, according to their website the company has stopped the production of this android tablet and it is no more available for sale on their website.
As the company has informed that it didn’t meet their market expectations of the previous year and it also failed to generate any significant interest.
The company now will launch their windows 8 tablet when the operating system will be launched next year.
According to the CEO of Dell the product has been stopped because it did not meet their market demand; however the Dell 10-inch tablet is still in production.
It appears that Dell has to look into their tablet production and have to take better contracts to make their tablets the talk of 2012.
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Monday 12 December 2011
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Ever LISTENED to a text message ???
No!!!
Well this project will make you do so.
Surprised ???
Don’t be because AUDIO STEGANOGRAPHY is the
method in which we can encode our secret messages on an audio signal
ensuring their safety. In this way we can decrypt a message on an audio signal
without its detection.
Lsb coding:-
The type of coding used in this project is the LSB
or the Least Significant Coding.
Least significant bit (LSB) coding is the simplest
way to embed information in a digital audio file. By substituting the least
significant bit of each sampling point with a binary message, LSB coding allows
for a large amount of data to be encoded.
Working:-
In this project we first read a wav file using the
MATLAB wavread command. Then we input a message from the user. This
message is then converted into its ASCII coded signal which then bit by bit
replaces the LSB of the wav file. In this way we convert our message into audio
form and transmit it.
At the receiver end when the signal is received or
the audio file is received, we just take out the last bit of the audio signal.
This now is our ASCII coded message we just convert it back into our message
signal.
The program is also generating a graphical user interface, from which you can easily hide the message and can then extract it later. All the related codes as well as the audio files can be downloaded here.
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Sunday 11 December 2011
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VOIP stands for voice over internet protocol. VOIP is getting
popular nowadays in audio communication around the globe. It is providing the
people with less rates long distance calls. VOIP is basically digital form of
transmission compared to the older telephone system that uses analog
transmissions.
The analog systems consume more resources, like even if the signal
is not traversing on the channel the channel still remains dedicated to that
particular session.
Whereas VOIP, as compared to that, utilize the resources
efficiently. The information is sent in the form of packets that take any path
that is readily available; also the resources are allocated on demand. These packets
are than reassemble at the destination.
This compression of information and
utilization of different routes made it possible for the information to be sent
is less expensive form. With VOIP you have no set up fee, no per minute charges
or you don’t have to wait for specific days or places to call from. You can
call from anywhere in the world all you need is an internet connection. VOIP is
also particularly famous for the conference call service.
Different
types of VoIP calling are available
- The most common is calling from one computer to another. This service needs an internet connection, microphones and sound card installed in the computer. Also there would be software that provides you the option of VOIP based calls.
- IP phones are also available if a person is use to the traditional telephone sets. All the routing and forwarding options are available within that phone.
- Analog telephone adaptors (ATA) enable you to connect a standard telephone to your computer Internet connection in order to take advantage of VoIP options. ATA converts analog signals to digital so that it can be transmitted properly via the Internet.
- The newest option is the Wi-Fi phone, which uses short-distance Internet transmission of VoIP to replace cell phones calls. Wi-Fi broadcasts over the radio spectrum to cover short range areas for users in certain areas.
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The studies related to love and affection has always been
the main attraction for so long, but it is hardly ever given any thought that
what happens when relationships break up. What brain activities are involved in
such a scenario? Why it is always been so hard to break up? And does time really heals?
Well now we have some answers to these questions as reported
by a scientist name Helen Fisher at New Jersey. Helen has already studied a lot
about the love and knows everything regarding this most romantic and beautiful
relationships of on the mother earth. But now she thought about studying the
other side of picture.
She and her colleagues carried out the experiments on the
people who had recent broken relationships but were still in love. All the
patient’s brain activities were observed through MRI. It showed that they had
the activity in their brain reward system in the same way as the normal lovers
do. But the neural pathways were activated due to craving and
addiction.
Rejected lovers had an increased response in the controlling
emotion areas of brain. As they were considering the fact that what happened. How
should they react and what should they do next?
And as the time moves on they showed little and little
activity in the attachment linked region of brain. And as we say LOVE HURTS BUT
TIME HEALS.
Posted on
Friday 9 December 2011
The MATLAB code and related files can be downloaded here:-
Audio compression is data compression
designed to reduce the transmission bandwidth requirement of digital audio streams
and the storage size of audio files. Broadly compression techniques are
classified into two types:
- Lossless compression algorithms usually exploit statistical redundancy in such a way as to represent the sender's data more concisely without error. Lossless compression schemes are reversible so that the original data can be reconstructed
- Lossy schemes accept some loss of data in order to achieve higher compression.
In both lossy and lossless compression,
information redundancy is reduced, using methods such as coding, pattern
recognition and linear prediction to reduce the amount of information used to
represent the uncompressed data.
There are numerous methods of compressing
audio files. The Discrete Cosine Transform is a lossy technique that removes
certain frequencies from the audio data such that the size is reduced with
reasonable quality.
The Discrete Cosine Transform is a
first-level approximation to mpeg audio compression, which are more
sophisticated forms of the basic principle used in DCT.
This discrete cosine Transform Audio
Compression is performed in MATLAB.
It takes a wave file as input, compress it
to different levels and assess the output that is each compressed wave file.
The difference in their frequency spectra will be viewed to assess how
different levels of compression affect the audio signals.
PROGRAM WORKING:-
An audio waveform is a continuous sequence of data
in one long vector. In that sense, an audio data structure is different from an
image data structure. We will need to apportion the vector manually into
several pieces, and cannot rely on existing rows or columns.
- Read the audio file
- Determine a value for the number of samples that will undergo a DCT at once. In other words, the audio vector will be divided into pieces of this length.
- Again, we examine at different compression rates:
50%
75%
87.5%
- Resulting compressed-and-uncompressed audio waves
For simplicity, we iterate over the vector,
window-by-window, but we discard whatever remainder exists:
Now we plot
the time domain signals
However, closer inspection does reveal
qualitative differences in the densely packed regions (high frequencies).
A look at the spectrogram reveals a clear
idea of the loss of high frequencies.
The qualitative difference is clearly
apparent when listening to the audio files
- Saving the files and viewing the difference in size
CODE
%read a file and
convert it to a vector
%chosing a block
size
%changing
compression percentages
%initializing
compressed matrice
%actual
compression
%plotting audio
signals
%expanded view of
audio signals
%spectrogram of
audio signals
%playing files
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A 3 bit microprocessor can be designed using a 89C51 micro controller. This code for the program is written in the C language. The
code is then loaded into the "Keil uVision 2" Software and a hex file is made
through the software. The Hex File is then burned on to the micro controller
using a micro controller burner. The circuit diagram is shown below and "Proteus"
was used to simulate the software. The Hex file can be directly loaded into the Micro controller using the Proteus Software.
Working of the Project:
Setting numbers as Input:
The project makes use of the basic
programming techniques using the C language. First of all basic programs are
made as functions like addition function, subtraction function, multiplication function
and so on. Then the number is input
through the Port 0 of the micro controller. The input is always a binary
number.
Selecting an Operation:
After the two inputs are set onto
the switches then the operation switch is turned on. Operations are defined on the Port 1 of the micro controller. As it
is a 3 bit microprocessor so the total number of operations would be 23=8.
So the whole Port 1 is for operations. The operations include the basic
mathematical and logical operations. Selection of two operations at the same
time will generate an error and the error bit (Port 2 Pin 7) will turn on
indicating the error.
Displaying an Output:
The output is displayed in
the output registers. As it is a 3 bit microprocessor so all the registers will
be of 3 bits, so when the output of addition is increases than 7 or can’t be
displayed in the three bits the overflow bit (Port 2 Pin 0) is turned on
indicating the overflow.
In case
of multiplication, if the input goes higher than 3 bits then the second
register is used to display the remaining bits of the solution. In this way the
basic architecture of the computer is followed in the microprocessor.
Flag Register:
Flag register is again of
three bits. It contains 3 flag indicators that are zero flag, overflow flag and
the sign flag. The zero flag turns on to indicate a result equal to zero. The
overflow flag turn to indicate the overflow of the 1st output
register. The sign flag indicates a negative result.
Error Bit:
Error
bit is used to indicate an error either in the input port or the operations
port. In case of two operations being turned on at the same time, the error bit
turns on. Similarly when there is division by zero, the error bit indicates the
error.
Note:
This project was implemented and is found fully working. The
hex file and the C file are attached for the help. Furthermore the Proteus design
is also attached along with the files.
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Thursday 8 December 2011
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Mixer is a non-linear circuit that combines two signals in such a way to produce the sum and difference of the two input frequencies at the output.
COMPONENTS:-
C1 = 0.1uF
C2 = 0.1uF
C3 = 0.1uF
R1 = R2 = 10kOhm
R3 = R4 = 100kOhm
R5 = 6.8kOhm
The design and simulation was carried out in ADS software. And the circuit is like this:-
The mixer is implemented by an NPN transistor 2N3904.
The circuit used was basically for audio mixing, it had an input from the triangular wave generator and the noise generator. And it is passsed through the audio mixer to form the wave.
The practical waveform was like dis:-
While the waveform from simulation in ADS was like this:-
Posted on
Tuesday 6 December 2011
At server level this chip can reduce the power level up to 45W. Even more! The Samsung 20nm DDR3 can reduce the temperatures of the server by almost 21° Celsius. And by this the server fan noise will also be reduced due to low heat generation.
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Samsung’s all new 20nm class DDR3 and SSD is not just great
news for the processors but also for the planet. As Samsung is going all green with this new
mass production.
This semiconductor chip is more speed and less energy
device, not only consumes 38% less energy but is 3.5x faster than other
memories in use. It has a really high potential of reducing the waste of
energy.
At server level this chip can reduce the power level up to 45W. Even more! The Samsung 20nm DDR3 can reduce the temperatures of the server by almost 21° Celsius. And by this the server fan noise will also be reduced due to low heat generation.
This performance was shown not just for the new processors
but also worked the same with the older ones.
The company expects it market level to rise and the chip
would be made the part of every technological environment.
The company is also planning to make 4GB memory chips very
soon and then moving on to the 8GB, 16GB and so on.
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Monday 5 December 2011
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The robot project works with two motors for driving the rear
wheels while the front wheels are free.
It uses 4 infra red sensors for detecting the line that it
has to follow. It can be either a black line on white background or a white
line on black background.
AT89C2051 microcontroller is used in the project for instructing the robot to move according to
the sensors input. The motor driving circuit is made with L293D, which is an
H-bridge IC. It can control the two motors simultaneously.
The code is written in C and is a fully functional code.
Care must be taken while choosing the motors. It should be a
high torque motor so that it can take the weight of your robot. Otherwise the
wheels would work fine while in the air but would not move once the robot is
set down.
The sensor circuits as well as the control circuit is given
below and the C code can be downloaded as a word file.
Control circuit:-
Sensors circuit:-
These sensor circuits need to be attatched at the points labeled as sensors in the main figure.
Position of Sensors:-
C code:-
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Sunday 4 December 2011
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Although the brain of a paper wasp is somewhat a millionth
in size to that of human brain still they have developed this strange ability
of distinguishing faces.
A study has been carried out in Michigan University, in which
the biologists reveal that the paper wasps have face-learning ability analogous
to the humans.
It’s the very first time that an insect has developed such
an intelligent activity. The paper wasps can recognize the individuals of other
species by the difference in the face markings. And are more aggressive to
those of unfamiliar species.
Some years earlier the biologists had published a paper
regarding the long term memory exhibited by these paper wasps. And interestingly
their behavior towards other individuals is based on previous interactions.
The biologist carried out the tests by teaching the wasps to
distinguish between two separate images. It was seen in the trials that the
wasps can pick out the differences between the original pictures more quickly
than those that has been edited. Similarly they can figure out the differences between
complicated shapes more readily than the geometric shapes.
The face recognizing ability may have been developed due to
the reason that these wasps live under colonies in which multiple queens raise
the offsprings together.
It appears that they treat the face learning as a different
thing from that of other images or objects. Several tests among other species
were also carried out but they showed no meaningful result.
The biologist was assisted by a research student and the
whole project was funded by the Michigan University and the student was given a
full scholarship for this purpose.
This evolutionary behavior shows that certain that
specialized cognition may result in to complex behavioral tasks over the time.
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Evolution of Air Planes:
Airlines and airplanes have a very brief yet very interesting history. Airplanes were first introduced commercially in 1914 and since then airplanes have gone through a very fast revolution. Due to this revolution we have seen some extra ordinary and state of the art airplanes. Airplanes have become the primary source of travel. Users find it easy and time saving to travel by air, so airlines have developed themselves such that they provide the users with best airline services and make the journey of users a memorable one.
Best Airline Services:
Some of the best airline services include Emirates, Thai Air, Qatar Airways and Singapore Airlines. The competition is very tough in the airline industry and so every airline is trying to produce something unique in their services so that users are attracted towards the airlines and choose the airline every time for their journey.
Environmental Friendly Airline Services: The Alaska Airlines:
In this regard Alaska Airline has introduced a very environmental friendly technique in their airplanes. According to this method the airplanes of Alaska airlines are now flown using bio-fuel. The blend used to fly the airplanes consisted of 80% Petroleum Fuel and 20% Bio Fuel. The Bio Fuel was made up from cooking oil. Yeah Alaska Airlines is running the airplanes using cooking oil.
Cooking oil for Airplanes:
This technique has made the airplanes to release less polluted gas from the exhausts and run as an environmental friendly airline. This technique will damage the environment less and will create an understanding in the other airlines to use such environment friendly techniques in their airlines as well. The bio fuel not only is user friendly but also energy efficient. The use of this technique in all the Alaska airline’s airplanes would decrease the energy consumption equivalent to 28,000 homes or 64,000 cars per annum.
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Microsoft is going to launch state of the art technology very
soon in Pakistan. More precisely on dec 11, 2011. As promised by their platform
manager while addressing a seminar. The surface technology will be a multi
touch product that will allow its users to communicate via the gestures. The communication
would involve motion of hands or the physical objects.
Microsoft has launched a portal for one million students and
41000 teaching staff from where they can download educational stuff, books etc
free of cost.
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Asthma is a disorder that is caused by the inflammation in
the airways of lungs. It occurs when the muscles surrounding the air passage
way are swollen and hence constricting the air passage way leading to difficult
breathing. The common causes are dust, pollen, chemicals, or other agents in
the air that are inhaled by the person.
Statistics shows that over 300 million people around the
world are suffering from asthma. Out of which 250,000 die annually due to this
cause.
Recently a new air cleaning machine has been developed
called Protexo. Protexo basically works in a way that it removes the toxic
agents surrounding the breathing area of a person. And generates a slightly cooler
air around them, it is operated during sleep.
This prevents the person from inhaling irritants and dust
particles present in air that triggers the asthma attacks during his sleep time.
People from different countries were observed for almost a
year using Protexo during the sleeping time. A major reduction in the nitric
oxide, which is an inflammatory agent, was seen among those patients. A better
lifestyle was observed.
Despite all this advances the condition among those that are
severely suffering is getting worse.
The machine is not yet available for private purchase. And costs
around 2000 pounds for six months use.
Posted on
Saturday 3 December 2011
Finger print recognition algorithm is used extensively in security related areas. For accessing any database, authenticating to any special services in your company or any other form of security service that use to ask about your ID cards or stuff like that previously.
Here we have provided the MATLAB code of the Finger Print Recognition Algorithm.
That takes the finger print as an image. The 'add to database' option lets you enrol your fingerprint into the database for future queries.
The 'match option then lets you match the finger print image with the database its going to have.
A user friendly GUI is also developed for this purpose with easily monitored buttons.
The attached file also have some fingerprint images for the testing purpose.
Downloads:
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Finger print recognition algorithm is used extensively in security related areas. For accessing any database, authenticating to any special services in your company or any other form of security service that use to ask about your ID cards or stuff like that previously.
Here we have provided the MATLAB code of the Finger Print Recognition Algorithm.
That takes the finger print as an image. The 'add to database' option lets you enrol your fingerprint into the database for future queries.
The 'match option then lets you match the finger print image with the database its going to have.
A user friendly GUI is also developed for this purpose with easily monitored buttons.
The attached file also have some fingerprint images for the testing purpose.
Downloads:
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The basic operation of the circuit is based on impedance matching and then amplifying the signal to give it to the output. Two normal speakers can be used both as the input and the output devices. The first stage which is at BC109C receives the signal in the common base configuration. It gives a good voltage gain and low input impedance which is used for impedance matching with the 8ohms speaker.
Self DC bias is used allowing variations in the transistor’s current gain.
The signal is then filtered for any DC part that may be present, through the capacitor. Thus a pure AC audio signal is sent to the 2nd part of the circuit which is the audio amplifier booster.
A constant Vcc is provided to this circuit, the two diodes check the backward flow of current. The signal is amplified on the 2nd stage through 2 transistors in cascade and later the signal is purified through a capacitor and sent to the output speaker. The basic function of the amplifier is to boost the voltage gain of the circuit and than provide it to the output speaker.
The circuit i used instead of LM386 is:-
OUTPUT ANALYSIS
The output analysis of the circuit tells that its providing 2 watts gain to the speaker so that the voice is audible. If the gain of the amplifier exceed s above the limit than the output signal is clipped off.
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The basic operation of the circuit is based on impedance matching and then amplifying the signal to give it to the output. Two normal speakers can be used both as the input and the output devices. The first stage which is at BC109C receives the signal in the common base configuration. It gives a good voltage gain and low input impedance which is used for impedance matching with the 8ohms speaker.
Self DC bias is used allowing variations in the transistor’s current gain.
The signal is then filtered for any DC part that may be present, through the capacitor. Thus a pure AC audio signal is sent to the 2nd part of the circuit which is the audio amplifier booster.
A constant Vcc is provided to this circuit, the two diodes check the backward flow of current. The signal is amplified on the 2nd stage through 2 transistors in cascade and later the signal is purified through a capacitor and sent to the output speaker. The basic function of the amplifier is to boost the voltage gain of the circuit and than provide it to the output speaker.
The circuit i used instead of LM386 is:-
OUTPUT ANALYSIS
The output analysis of the circuit tells that its providing 2 watts gain to the speaker so that the voice is audible. If the gain of the amplifier exceed s above the limit than the output signal is clipped off.
Posted on
Friday 2 December 2011
An optical cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and providing feedback of the laser light. They are also used in optical parametric oscillators and some interferometers. Light confined in the cavity reflect multiple times producing standing waves for certain resonance frequencies. The standing wave patterns produced are called modes; longitudinal modes differ only in frequency while transverse modes differ for different frequencies and have different intensity patterns across the cross section of the beam.[1]
Different resonator types are distinguished by the focal lengths of the two mirrors and the distance between them. (Flat mirrors are not often used because of the difficulty of aligning them to the needed precision.) The geometry (resonator type) must be chosen so that the beam remains stable (that the size of the beam does not continually grow with multiple reflections. Resonator types are also designed to meet other criteria such as minimum beam waist or having no focal point (and therefore intense light at that point) inside the cavity.[2]
IMPORTANCE OF A RESONATOR:
Certain devices when excited through a gunn oscillator doesnot produce satisfactory oscillations. There are certain jitters in whole range of frequencies. For this we use a resonator in which the beam of just a particular frequency is choosen to be reflected multiple times in order to produce oscillations. All the other frequencies are not reflected and hence no oscillations are generated at those frequencies. The advantage of the open cavity is that it is non reflecting hence the beam of frequencies which are not focussed at the mirrors move out of the cavity.
We have constructive interference at resonance and a destructive interference at all others. So a sharp peak is detected.[1]
Resonator modes:
Light confined in a resonator will reflect multiple times from the mirrors, and due to the effects of interference, only certain patterns and frequencies of radiation will be sustained by the resonator, with the others being suppressed by destructive interference. In general, radiation patterns which are reproduced on every round-trip of the light through the resonator are the most stable, and these are the eigenmodes, known as the modes, of the resonator.
Resonator modes can be divided into two types: longitudinal modes, which differ in frequency from each other; and transverse modes, which may differ in both frequency and the intensity pattern of the light. The basic, or fundamental transverse mode of a resonator is a Gaussian beam.
Resonator types:
For a resonator with two mirrors with radii of curvature R1 and R2, there are a number of common cavity configurations. If the two curvatures are equal to half the cavity length (R1 = R2 = L / 2), a concentric or spherical resonator results. This type of cavity produces a diffraction-limited beam waist in the centre of the cavity, with large beam diameters at the mirrors, filling the whole mirror aperture. Similar to this is the hemispherical cavity, with one plane mirror and one mirror of curvature equal to the cavity length.
WORKING PRINCIPLE
• It works on the principle of optics and probability(statistics).
• 2 walls are made reflecting to an extent that they behave as mirrors.
• Only 2 walls are contributing to receive the dominant mode at the coupling hole at resonance.
CALCULATIONS:
— a=22.86 mm b=10.16 mm
— Formulas used to calculate d:
k=2πf/c
d=(l π)/[k²-(π/a)]^0.5
— d=16.99021661 mm
RADIATION PATTERNS
REFLECTION COEFFICIENT:
• Hemispherical resonator
• Resonant frequency(theoretical)=11 GHz
• Resonant frequency(practical)=11.5 GHz
• Length of the resonator=d=16.99021661 mm
• Height of the resonator=2a=45.72 mm
• Mode used: TE₁₀₁
Q FACTOR:
OUTPUT POWER:
FEATURES:-
1. STABILITY:
Only certain ranges of values for R1, R2, and L produce stable resonators in which periodic refocussing of the intracavity beam is produced. If the cavity is unstable, the beam size will grow without limit, eventually growing larger than the size of the cavity mirrors and being lost. By using methods it is possible to calculate a stability criterion:
0 ≤ ≤ 1.
Values which satisfy the inequality correspond to stable resonators.
The stability can be shown graphically by defining a stability parameter, g for each mirror:
,
and plotting g1 against g2 as shown. Areas bounded by the line g1 g2 = 1 and the axes are stable. Cavities at points exactly on the line are marginally stable; small variations in cavity length can cause the resonator to become unstable, and so lasers using these cavities are in practice often operated just inside the stability line.
A simple geometric statement describes the regions of stability: A cavity is stable if the line segments between the mirrors and their centers of curvature overlap, but one does not lie entirely within the other.
IS OUR RESONATOR STABLE?
Putting our values into the inequality we get:
0.515
(since our R1=35mm>L=16.99021661mm and R2= ∞)
Thereby proving that our resonator is stable!
2. Q FACTOR:
The Q factor (quality factor) of a resonator is a measure of the strength of the damping of its oscillations, or for the relative linewidth.
• Definition via resonance bandwidth: the Q factor is the ratio of the resonance frequency ν0 and the full width at half-maximum (FWHM) bandwidth δν of the resonance:
Loaded and unloaded Q factors are important characteristics of a resonator used in high-power mm-wave sources[3]
The resonator is composed of parallel curved-plate waveguide sections [4], shorted at the end, with entrance and exit holes for transporting an electron beam through the resonator. In order to study the resonator’s characteristics, it is excited from an external source, such as a network analyzer. The polarizing grid coupler is illuminated by a free-space Gaussian beam, formed by means of a mode exciter and a mirror, as described in [5]
Q Factor of an Optical Resonator
The Q factor of a resonator depends on the optical frequency ν0, the fractional power loss l per round trip, and the round-trip time Trt:
(assuming that l << 1). For a resonator consisting of two mirrors with air (or vacuum) in between, the Q factor rises as the resonator length is increased, because this decreases the energy loss per optical cycle. However, extremely high Q values (see below) are often achieved not by using very long resonators, but rather by strongly reducing the losses per round trip.
High-Q Resonators
One possibility for achieving very high Q values is to use super mirrors with extremely low losses, suitable for ultra-high Q factors of the order of 1011. Also, there are toroidal silica microcavities with dimensions of the order of 100 μm and Q factors well above 108, and silica microspheres with whispering gallery resonator modes exhibiting Q factors around 1010.
High-Q optical resonators have various applications in fundamental research (e.g. in quantum optics) and also in telecommunications (e.g. as optical filters for separating WDM channels). Also, high-Q reference cavities are used in frequency metrology, e.g. for optical frequency standards. The Q factor then influences the precision with which the optical frequency of a laser can be stabilized to a cavity resonance. [6]
3. Phase Noise Reduction
— Q (unloaded) = 1097
— Bandwidth (practical) = 300Mhz
— Q (loaded) = 38.33
— 1/QL = 1/Qext + 1/Qo
— Qe = 39.71
— PNR=20 log (1+ Qo/Qext)
— PNR= 28.82 dB
— BW=300MHz
— Narrow bandwidth given that input is in GHz
— A load with high Q factor will improve it even further.
REFERENCES:
[1] www.wikipedia.com/opticalcavity
[2] A STUDY OF INTER-INJECTION-LOCKED PHASED ARRAYS Final Report by Karl D. Stephan October 10, 1989 Department of Electrical and Computer Engineering University of Massachusetts.
[3] Paschotta, Rüdiger. "Q Factor". Encyclopedia of Laser Physics and Technology. RP Photonics. http://www.rp-photonics.com/q_factor.html.
[4] M.E. Hill, W.R. Fowlex, X.E. Lin, and D.H. Whittum, Beam-cavity interaction circuit at W-band, IEEE Trans MTT 49 (2001), 998–1000.
[5] M.A. Shapiro and S.N. Vlasov, Study of a combined millimeter-wave resonator, IEEE Trans MTT 45 (1997), 1000–1002.
[6] "Quasioptical microwave and millimeter-wave power combining," by K.D. Stephan
and S.L. Young, SPIE (vol. 947) Conf. on Interconnection of High Speed and High Frequency Devices and Systems, Newport Beach, CA, March "1988.
An optical cavity or optical resonator is an arrangement of mirrors that forms a standing wave cavity resonator for light waves. Optical cavities are a major component of lasers, surrounding the gain medium and providing feedback of the laser light. They are also used in optical parametric oscillators and some interferometers. Light confined in the cavity reflect multiple times producing standing waves for certain resonance frequencies. The standing wave patterns produced are called modes; longitudinal modes differ only in frequency while transverse modes differ for different frequencies and have different intensity patterns across the cross section of the beam.[1]
Different resonator types are distinguished by the focal lengths of the two mirrors and the distance between them. (Flat mirrors are not often used because of the difficulty of aligning them to the needed precision.) The geometry (resonator type) must be chosen so that the beam remains stable (that the size of the beam does not continually grow with multiple reflections. Resonator types are also designed to meet other criteria such as minimum beam waist or having no focal point (and therefore intense light at that point) inside the cavity.[2]
IMPORTANCE OF A RESONATOR:
Certain devices when excited through a gunn oscillator doesnot produce satisfactory oscillations. There are certain jitters in whole range of frequencies. For this we use a resonator in which the beam of just a particular frequency is choosen to be reflected multiple times in order to produce oscillations. All the other frequencies are not reflected and hence no oscillations are generated at those frequencies. The advantage of the open cavity is that it is non reflecting hence the beam of frequencies which are not focussed at the mirrors move out of the cavity.
We have constructive interference at resonance and a destructive interference at all others. So a sharp peak is detected.[1]
Resonator modes:
Light confined in a resonator will reflect multiple times from the mirrors, and due to the effects of interference, only certain patterns and frequencies of radiation will be sustained by the resonator, with the others being suppressed by destructive interference. In general, radiation patterns which are reproduced on every round-trip of the light through the resonator are the most stable, and these are the eigenmodes, known as the modes, of the resonator.
Resonator modes can be divided into two types: longitudinal modes, which differ in frequency from each other; and transverse modes, which may differ in both frequency and the intensity pattern of the light. The basic, or fundamental transverse mode of a resonator is a Gaussian beam.
Resonator types:
For a resonator with two mirrors with radii of curvature R1 and R2, there are a number of common cavity configurations. If the two curvatures are equal to half the cavity length (R1 = R2 = L / 2), a concentric or spherical resonator results. This type of cavity produces a diffraction-limited beam waist in the centre of the cavity, with large beam diameters at the mirrors, filling the whole mirror aperture. Similar to this is the hemispherical cavity, with one plane mirror and one mirror of curvature equal to the cavity length.
WORKING PRINCIPLE
• It works on the principle of optics and probability(statistics).
• 2 walls are made reflecting to an extent that they behave as mirrors.
• Only 2 walls are contributing to receive the dominant mode at the coupling hole at resonance.
CALCULATIONS:
— a=22.86 mm b=10.16 mm
— Formulas used to calculate d:
k=2πf/c
d=(l π)/[k²-(π/a)]^0.5
— d=16.99021661 mm
RADIATION PATTERNS
REFLECTION COEFFICIENT:
• Hemispherical resonator
• Resonant frequency(theoretical)=11 GHz
• Resonant frequency(practical)=11.5 GHz
• Length of the resonator=d=16.99021661 mm
• Height of the resonator=2a=45.72 mm
• Mode used: TE₁₀₁
Q FACTOR:
OUTPUT POWER:
FEATURES:-
1. STABILITY:
Only certain ranges of values for R1, R2, and L produce stable resonators in which periodic refocussing of the intracavity beam is produced. If the cavity is unstable, the beam size will grow without limit, eventually growing larger than the size of the cavity mirrors and being lost. By using methods it is possible to calculate a stability criterion:
0 ≤ ≤ 1.
Values which satisfy the inequality correspond to stable resonators.
The stability can be shown graphically by defining a stability parameter, g for each mirror:
,
and plotting g1 against g2 as shown. Areas bounded by the line g1 g2 = 1 and the axes are stable. Cavities at points exactly on the line are marginally stable; small variations in cavity length can cause the resonator to become unstable, and so lasers using these cavities are in practice often operated just inside the stability line.
A simple geometric statement describes the regions of stability: A cavity is stable if the line segments between the mirrors and their centers of curvature overlap, but one does not lie entirely within the other.
IS OUR RESONATOR STABLE?
Putting our values into the inequality we get:
0.515
(since our R1=35mm>L=16.99021661mm and R2= ∞)
Thereby proving that our resonator is stable!
2. Q FACTOR:
The Q factor (quality factor) of a resonator is a measure of the strength of the damping of its oscillations, or for the relative linewidth.
• Definition via resonance bandwidth: the Q factor is the ratio of the resonance frequency ν0 and the full width at half-maximum (FWHM) bandwidth δν of the resonance:
Loaded and unloaded Q factors are important characteristics of a resonator used in high-power mm-wave sources[3]
The resonator is composed of parallel curved-plate waveguide sections [4], shorted at the end, with entrance and exit holes for transporting an electron beam through the resonator. In order to study the resonator’s characteristics, it is excited from an external source, such as a network analyzer. The polarizing grid coupler is illuminated by a free-space Gaussian beam, formed by means of a mode exciter and a mirror, as described in [5]
The Q factor of a resonator depends on the optical frequency ν0, the fractional power loss l per round trip, and the round-trip time Trt:
(assuming that l << 1). For a resonator consisting of two mirrors with air (or vacuum) in between, the Q factor rises as the resonator length is increased, because this decreases the energy loss per optical cycle. However, extremely high Q values (see below) are often achieved not by using very long resonators, but rather by strongly reducing the losses per round trip.
One possibility for achieving very high Q values is to use super mirrors with extremely low losses, suitable for ultra-high Q factors of the order of 1011. Also, there are toroidal silica microcavities with dimensions of the order of 100 μm and Q factors well above 108, and silica microspheres with whispering gallery resonator modes exhibiting Q factors around 1010.
High-Q optical resonators have various applications in fundamental research (e.g. in quantum optics) and also in telecommunications (e.g. as optical filters for separating WDM channels). Also, high-Q reference cavities are used in frequency metrology, e.g. for optical frequency standards. The Q factor then influences the precision with which the optical frequency of a laser can be stabilized to a cavity resonance. [6]
3. Phase Noise Reduction
— Q (unloaded) = 1097
— Bandwidth (practical) = 300Mhz
— Q (loaded) = 38.33
— 1/QL = 1/Qext + 1/Qo
— Qe = 39.71
— PNR=20 log (1+ Qo/Qext)
— PNR= 28.82 dB
— BW=300MHz
— Narrow bandwidth given that input is in GHz
— A load with high Q factor will improve it even further.
REFERENCES:
[1] www.wikipedia.com/opticalcavity
[2] A STUDY OF INTER-INJECTION-LOCKED PHASED ARRAYS Final Report by Karl D. Stephan October 10, 1989 Department of Electrical and Computer Engineering University of Massachusetts.
[3] Paschotta, Rüdiger. "Q Factor". Encyclopedia of Laser Physics and Technology. RP Photonics. http://www.rp-photonics.com/q_factor.html.
[4] M.E. Hill, W.R. Fowlex, X.E. Lin, and D.H. Whittum, Beam-cavity interaction circuit at W-band, IEEE Trans MTT 49 (2001), 998–1000.
[5] M.A. Shapiro and S.N. Vlasov, Study of a combined millimeter-wave resonator, IEEE Trans MTT 45 (1997), 1000–1002.
[6] "Quasioptical microwave and millimeter-wave power combining," by K.D. Stephan
and S.L. Young, SPIE (vol. 947) Conf. on Interconnection of High Speed and High Frequency Devices and Systems, Newport Beach, CA, March "1988.
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Computer Technology:
Computer Technology has advanced a lot in the past few
decades. We have seen some extremely eye catching and awesome computers being
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attractive body have made the use of computers easier and simple. To drive
these computers different companies have produced different operating systems.
Some in the line are Windows OS, Macintosh OS, Ubuntu, Linux, UNIX and many
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Operating Systems:
Operating Systems have been made better and better as the
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friendly OS in the line.
Improvement in the
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Microsoft has always been of the view point that the
consumers be provided with the best computer solutions. That is why the Microsoft
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secure and extremely user friendly. So to raise the bar even more a further
enhancement in the Windows 7 OS has been done and a new OS is going to be
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Windows 8: Safer,
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Windows 7 was a huge success for sure, and to make the
things better Microsoft has come up with the latest OS, named as Windows 8. Windows 8 is being
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version will be released in February in the next year. Users are anxiously
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Circuit Diagram:
Components:
Components:
·
2x LM 741 IC’s
·
20kΩ Resistor
·
5kΩ Resistor
·
10kΩ Resistor
·
1.1uF Capacitor
Working:
Assemble the components as shown in the circuit diagram
above. In the above diagram the capacitor C1 acts as a integrator and
integrates the square input into a triangular wave. In this way a triangular
wave is generated.
Results:
Result of the above circuit diagram is a perfect triangular
wave.