Internship

Reading Time: 4 minutes

 

Quoting what IIT Delhi Global Internship Program FAQ;s Have to say:

https://sites.google.com/site/aicetinterns/

 

  I am a student of the <>th semester, can I apply ?

Every student is (wrongly) advised by seniors to go for a internship at the earliest opportunity. Senior students often tell junior students (wrongly) that grades don’t count, and that projects are all that matter. They are wrong. Grades count – we look at your grades very carefully when we select you for the Internship.

The best time to go for a Internship is in the summer following Semester 6 + Semester 7 (nearly 9 months), or the whole of Semester 7 + winter + Semester 8 (almost a year). Without doing your discipline courses in Semesters 6 and 7, you could be very badly prepared for any internship.

Please try to follow the advice below when you choose your Internship period:

 If you are a student of Semester …. : Advice 
 Semester 1,2,3
  1. Please do not come for this internship or ANY internship for that matter in Semester 1-3.
  2. Take your textbooks for the next semester and study the chapters.
  3. Try to solve the questions and read alternative textbooks in the area.
  4. Also, do NOT join C# / .ASP / .NET coaching classes – such courses only reduce your study time. An employer will probably hire a programmer for these skills and not a software engineer. 

    Confused ? The difference between a software engineer and a programmer is like the difference between a doctor and a compounder. Both can administer a injection, perhaps even equally well – but only the doctor would knowwhy the injection was necessary. Even if the compounder, due to long practice, gets to administer the injecton more deftly than the doctor, the doctor will still be the only of the two who knows why. The compounder would always know just how to administer the injection.

    If programming also interests you, buy a good book on the language you want to program in, download linux (www.ubuntu.com) and learn it for free at home.

 Semester 4
  1. Please avoid coming for a Internship in Semester 4 unless there is something special you think you need to do. Special things could be going to Institute X because there is a Scientist X there who specialises in Algorithm Y, taking a course in a area not taught in your Institute next semester.
 Semester 5, 6
  1. Prepare for your Internship by doing all of the following:
    1. Read the latest journals in areas of interest every Friday – either in the library or on the net (see www.webproforum.com)
    2. Read alternative text books
    3. Read IEEE / IEE Journals for recent papers – don’t bother if you don’t understand everything at first (30% understood is good enough). Keep reading.
    4. Form Special Interest Groups (SIGs), meet on a weekly basis and discuss topics
    5. Give (voluntarily) a Weekly Seminar on what you read – you could give this to your Special Interest Group
    6. Talk to your own Faculty / lab technicians for possible projects you could do – whether in lab-oriented or theoretical projects.
    7. Start identifying faculty in your institute or outside your Institute in the areas of interest. Write to them.
      Do NOT write emails indiscriminately to hundreds of people – it will backfire on you when you are found out.
    8. Attend conferences, talks and lectures in your city.
    9. Watch Discovery, CNN, National Geographic and Eklavya.
    10. Join a local library. Visit the local University library. Read fiction and non-fiction. Take Art classes. Take pottery classes. Learn to play a musical instrument.
    11. Watch lectures of the courses you are being taught on YouTube.
    12. Read the course material of the courses being taught to you on MIT’s Open courseware site or IIT’s NPTEL site.
    13. Apply for Internship in time
 Semester 7,8
  1. Try to do projects within your Institute. Accomodation is not a problem. People know you and your background and the chance of being handed a task you cannot execute is minimal.

    On the other hand, a Faculty Member in another Institute is very likely to assume that you have done something in your coursework which you have not done.  You avoid all the following when you do your project in your own Institute ! It is no joke – it cuts into work time and influences work moods significantly.Only when it is absolutely unavoidable, go outside your Institute to do a Internship. And if you do go to another Institute, give first priority to availability of accomodation on campus even if it is marginally more expensive. This saves time and you get to meet more people in your peer group, have longer working hours and tend to achieve much more in your Internship.

    1. Coming to a strange city or a strange country
    2. getting accomodation, or even having to adjust yourself into a relative’s home for six long months
    3. having constantly worried parents
    4. dealing with indifferent food
    5. going through long commutes
    6. suffering irregular mealtimes

 

Things I would like to add:

2 most inspiring and knowledgeable novel that will change your thinking:

Fountainhead By Ayn Rand

 Outliers – Malcolm Gladwell

For ones who are not not good at programming read “The C Programming Language (Ansi C Version) 2nd Edition” written by creator of C – Dennis Rotchie. It costs only Rs 146!!! Link

For 1st yearites the best option to get their 1st year concepts right by watching videos @ NPTEL’s & MIT 1st year course for EC & Comps students Link1 Link2

Videos of Basic 1st and 2nd sem subjects. Just watch them at 1.5x speed as you may feel them to be bit slow!!!

 Few good place to look for Internships online: www.internshala.com, www.twenty19.com

+ List of Online Portal to see video lectures, projects, departmental magazines, some god father tech sites is provided in “Extra Edgy Things For All Engineers” Blog

Basics of Solar Cell Technology

Reading Time: 8 minutes

Solar energy has enormous potential and it is highest among all the available sources of energy available whether it is renewable or non renewable sources. It is free, it is renewable and it is clean source of energy.

Now to begin, let’s start with one practical situation:

Assume that you have told to set up a solar power plant in India and you have given sufficient fund and land.  So what you will do??!!

Following are the points which you should think:

1) first you have to find a place in India where maximum solar power is hitting (Solar Ir-radiance ).solar-energy-distribution-india-map

 

2)      Lets say you have decided to put solar power plant in Gujarat. Now in Gujarat you have to see at what location exactly what amount of solar energy is hitting per square area.

Now we will  understand how it is calculated:

 

Any body which is above 0K  temperature will emit radiation according to planks law which is

given by:

download (1)

Above expression is for a body which is at particular  temperature and emitting radiation of a particular wavelength  but as we know body is  emitting radiations of all wavelengths from 0 to infinity. So we have to integrate that expression E(ƛ)d(ƛ) from o to infinity to find total emissive power emitted by the body.

Similarly consider sun as the source of solar radiations and earth is intercepting those radiations .the amount of solar radiation hitting on some area of earth will depend upon solid angle multiplied total emissive  power of sun.

rrr

 

So by doing integration of solar irradiance expression (emissive power) multiplied by solid angle of whole earth considering no atmosphere we will get a fix value known as solar flux and that is equal to 1367 W/m2.

Solar flux: The total energy flux (energy per time per area) incident on a unit area perpendicular to a beam outside the Earth’s atmosphere.

Air mass factor(AM): Air mass factor gives you idea about the relative position of sun w.r.t. to earth.

AM = 1/ CosƟ , where Ɵ equal to angle from vertcle line when sun is directly overhead to us.

download (3)

 

For e.g.  AM 1.5 = 1/CosƟ  => Ɵ=48.2*

AM0 means no atmosphere.

Now you have to calculate the solar flux which is hitting on your area in Gujarat. What you will do you will first of all find latitude of that area.

scs

After finding latitude we have to multiply that solar power density which is coming parallel to plane of equator with cosine of latitude because we want those photons which are hitting perpendicular to our solar cell.

 

3) So we have decided the location of power plant by calculating the exact solar flux hitting that area.

 

4) Now what next?? Before installing the solar panels we have to understand how solar cell works:

Working

  • The main part of solar cell is p-n junction. When p type and n type material are joined there is formation of space charge region/depletion region and It stays localized at the P-N junction and an electric field has been created.
  • If the solar cell is put in the sun, photons will strike the surface of the Silicon and pass their energy on to electrons. A typical photon can eject one electron from its nucleus creating a free electron and a vacancy. These free electrons will feel the effect of the electric field. They are pushed towards the junction on the N-side and away from the junction on the P-side. Likewise, the vacancy, which has a net positive charge, will be pulled towards the junction on P-side and pushed away from it on the N-side.
  • So there is current flowing from p type to n type material. This current is known as photo induced current and denoted by IL

 

1

  • This photo induced current generates voltage around load, but this voltage generation will also forward biased our p-n junction and there is another current  flows  through load known as forward biased current IF . so we will have net current I=I– IF   flows through our load.
  • Current vs voltage characteristics of our p-n junction is shown below:r3r
  • We can see from the graph that there is point where we are getting maximum power. so our aim is to find that point. This can be easily calculated by simple differentiation technique.
  • If still not clear , watch this video: https://www.youtube.com/watch?v=1gta2ICarDw

 

Efficiency

  • Efficiency is most important thing to any type energy system. We have reached maximum efficiency of  44% in case of solar cell.(search and find what are the efficiency of other sources of energy)
  • How to find efficiency of our solar cell???…

 

To find efficiency we have to first follow above procedure and calculate Jmax and Vmax

rgr

Above numerator term is Jmax* Vmax

Denominator is solar power denoted by Ps   at some AM value.

For e.g. Ps value at AM= 1.5 means

1367W/m2 *cos(41.8) =1000 W/m2

  5) After learning basics of solar cell, let’s build solar cell. Before we discuss the components of real solar cell,( just think what can be most imp building blocks of solar cell !!!  )

Following are the main components of solar cell:

  • P-n junction : Every p-n system is characterized by its unique band bap( ΔEg) or    forbidden energy gap.
  • Anti Reflecting Coating:  If ray of light incident on any surface ,some part is reflected and some part is transmitted.  we have to have maximize the transmittance .so we are applying the layer of such a material whose refractive index is the geometric mean of mediums which are above and below of anti reflective coating.

solar_cell

  • Glass: glass is used for two purposes first to concentrate the beam of light secondly to have self cleaning property so that any dust particle or any organic impurity can be washed off easily.

 

So to have self cleaning property of glass, two methods are used:

 

  1. We can coat a hydrophobic layer on glass which will make the contact angle for water – glass system to very large and consequently a spherical drop of water will from, which rolls down due to gravity taking away dust .
  2. We can coat a super hydrophilic coating on glass e.g. coating of TiO2. The glass cleans itself in two stages. The “photo catalytic” stage of the process breaks down the organic dirt on the glass using ultraviolet light and makes the glass super hydrophilic (normally glass is hydrophilic. During the following “super hydrophilic” stage, rain washes away the dirt, leaving almost no streaks, because water spreads evenly on super hydrophilic surfaces
  • Conducting wires: these are used to connect small -small solar cells into series and parallel.

Watch the below link to know how solar cell is manufactured. This video is of company- ‘’Sun Tech Power”.

https://www.youtube.com/watch?v=IAufbqbUS6k

6) Now you have installed solar cells and production is started. Now you have to know what maintenance is required and what are the factors which affects the performance of my cell.

Following are the factors which affects the efficiency of solar cell:

  • Loss of photons which are below the band gap:

This loss is highest among all losses. We know that light which is hitting contains photons of various energies but out of 100% photons only 30% are capable of generating current because a p-n junction is fixed for photon which have energy equal to band width rest are of no use.

g

There are multiple p-n junction kept one below the another and of variable band gaps.

 

  • Loss of energy from relaxation of carriers to band edges:

To understand this lets go to atomic level of p type material. This material when irradiated with some light electron will make jump from valence band to conduction band. Now this electron from the conduction band of p type goes to conduction band of n type via space charge region and during this journey electron losses its potential energy and relax at the band edges which results in dissipation of heat   as shown in fig:

rf

 

  • Resistance losses (shunt and series resistances) which will decrease Voc and photo current:

This is the second largest loss after loss of photons. Generally two types of resistances are there series and shunt .These resistances arises because of:

Series: 1. Resistence of connecting wires.

2. Contact resistances.

Shunt (parallel) : These are mainly due to impurities phases lying from  p type to  n type material .

  •  Junction recombination: electrons which are generated by light, some of them will lost while going through depletion region.
  • Optical losses :
  • Dirt accumulation on the glass :
  • Effect of temperature:  There is optimum range of temperature in which solar cell works efficiently ,Increasing temperature will decrease the cell efficiency.
  • Carrier recombination at defects: This effect is due to grain boundaries resulting in decrement of light current.

7) At last these are materials used in solar cell technology with their efficiencies:

aaa

 

In India we have largest solar park of Asia at Charanka village, Patan district, Gujarat. There is video on it : https://www.youtube.com/watch?v=kIhHy8X0kCg

Refrences:

Stanford university free online course: “solar cell, fuel cell and batteries”

 

Cellular Communication

Reading Time: 6 minutes
OUTLINE:-
Electromagnetic Spectrum.
Why Micro-waves?
Why Cellular?-Frequency Reuse.
Basic Structure.
How do you call your friends?
Hand-off
Spectrum crunch
Cognitive radio
Cell breathing
Green communication.
Research in this domain.
Why micro-waves?

Microwaves are widely used

for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at the receiving antenna.
Less attenuation to water vapour,oxygen molecules,etc.

Range roughly from 800MHz-30GHz

FREQUENCY REUSE:- 
}Method used by service providers to improve the efficiency of a cellular network and to serve millions of subscribers using a limited radio spectrum.
}Based on the fact that after a distance a radio wave gets attenuated and the signal falls bellow a point where it can no longer be used or cause any interference.
}Transmitter transmitting in a specific frequency range will have only a limited coverage area
}Beyond coverage area frequency is reused by another transmitter.
}the entire network coverage area is divided into cells based on the principle of frequency reuse

Cells

• basic geographical unit of a cellular network
• Represented graphically as a hexagonal shape, but in reality it is irregular in shape
• Width of cells changes as demand changes.

Cluster

• is a group of adjacent cells, usually 7 cells; no frequency reuse is done within a cluster.
BTS (Base Transceiver Station)
• Main component of a cell
• Connects the subscribers to the cellular network
•Transmission/reception of information; it uses several antennas spread across the cell
 
BSC (Basic Station Controller)
• Interface between BTSs and it is linked to BTSs by cable or microwave links; it routes calls between BTSs; it is also connected to the MSC
MSC (Mobile Switching Center)
• Coordinator of a cellular network
• Connected to several BSCs,
• Routes calls between BSCs;
• Links the cellular network with other networks like PSTN through fiber optics, microwave or copper cable

 Home Location Register (HLR)

– maintained by the service provider

– permanent data about each subscriber (i.e. location, activity status, account status, call forwarding preference, caller identification preference)

  Visitor Location Register(VLR)

–stores temporary data about a subscriber; it is kept in the MSC of the of the area the subscriber is located in; when the subscriber moves to a new area the new MSC requests this VLR from the HLR of the old MSC

 Equipment Identity Register(EIR) –

-database located near the MSC and containing information identifying cell phones which are stolen or which are cloned.

Authentication unit:-

-This unit holds the security concerns that hover around the all channels, authenticating even the correct base station not the ones held for data recovery by some external agents.

Control channel

-dedicated channel for sending ack,tracking call,tracking messages,other control signals

-only control data ;no voice

Voice channel

-for only voice transmission

 

 

CALLING & RECEIVING :-

-the subscriber dials the receiver’s number and sends it to the BTS
-the BTS sends to its BSC the ID, location and number of the caller and also the number of the receiver
-the BSC forwards this information to its MSC
-the MSC routes the call to the receiver’s MSC which is then sent to the receiver’s BSC and then to its BTS
-the communication with the receiver’s cell phone is established
-when the receiver’ phone is in an idle state it listens for the control channel of its BTS
-if there is an incoming call the BSC and BTS sends a message to the cells in the area where the receiver’s phone is located
-the phone monitors its message and compares the number from the message with its own
-if the numbers matches the cell phone sends an acknowledgement to the BTS
after authentication, the communication is established between the caller and the receiver
-when the phone needs to make a call it sends an access request (containing phone identification, number) ; if another cell phone tries to send an access request at the same time the messages might get corrupted, in this case both cell phones wait a random time interval before trying to send again
-then the BTS authenticates the cell phone and sends an acknowledgement to the cell phone
-the BTS assigns a specific voice channel and time slot to the cell phone and transmits the cell phone request to the MSC via BSC
-the MSC queries HLR and VLR and based on the information obtained it routes the call to the receiver’s BSC and BTS
 the cell phone uses the voice channel and time slot assigned to it by the BTS to communicate with the receiver.

 

 

Calling & Receiving Continued:-

-When a request to deliver a call is made in the network, the MSC or the receiver’s home area queries the HLR; if the cell phone is located in its home area the call is transferred to the receiver; if the cell phone is located outside its home area, the HLR maintains a record of the VLR attached to the cell phone

– Based on this record, the MSC notes the location of the VLR and indicated the corresponding BSC about the incoming call

-The BSC routes the call to the particular BTS which uses the paging channel to alert the phone.

-The receiver cell phone monitors the paging channel periodically and once it receives the call alert from the BTS it responds to the BTS

-The BTS communicates a channel and a time slot for the cell phone to communicate

– Now the call is established

 

 

HAND-OFFS:-

-Why Hand-off?
-How to do Hand-off?
-What factors determine handoff?
-Types of hand-off
First generation Hand-off
MAHO-In 2g phones
First generation Hand-off:-
-In this signal strength measurements are made by base station & supervised by MSC.
-Each base station monitors the signal strengths of all the control channels to determine the relative location of each      mobile user with respect to the base station tower.
 The locator receiver is controlled by the MSC & is used to monitor the signal strength of users in need of hand-off.
  Based on the locator receiver signal strength info from each base station ,the MSC decides whether hand-off is      necessary or not.
MAHO-In 2g phones:-
Every mobile station measures the received power from surrounding base stations &  continually reports the results to these measurements to the serving base station.
A hand-off is initiated when power received from base station of a neighbouring cell begins to exceed the power received from current base station by a certain level or for a certain period of time.
Advantage………….
Cell breathing:-

is a mechanism which allows overloaded cells to offload subscriber traffic to neighbouring cells by changing the geographic size of their service area. Heavily loaded cells decrease in size while neighbouring cells increase their service area to compensate. Thus, some traffic is handed off from the overloaded cell to neighbouring cells, resulting in load balancing.

 

 

Why green Communication?

-Use of solar panels in place of diesel in base station.

-Dynamic Power Assignment based on load detection,

-A fixed control channel scans number of mobile users in an area of a cell & tells neighbouring bts whether or not to expand.

-if the minimum requirement fails then bts expand & area is served by that neighbouring bts. While the bts of that cell remains off.

 

RESEARCH IN THIS DOMAIN:-

Methods for Efficient Hand-off with same quality of service. (QOS)
Tackling Spectrum Crunch – Software defined Radio-cognitive radio.
Maintaining the QOS within a cell at specified power level.
Security in software defined radio.
Green wireless communication-focussing cell breathing techniques even in high traffic zones.
THINGS YOU NEED TO KNOW:-
Basic electronics.(1st year).-Websearch.
Signal & System.(2nd year).-Prof.S.C Dutta Roy IITD NPTEL
Analog Modulation.(2rd year)-Prof. Surendra Prasad IITD NPTEL
Digital Modulation.(3rd Year)-Taub –Communication Engineering.
Speech Coding(no year)-Rabiner;Rappaport;Youtube-E amberkairajah-video.
Wireless Communication(Final Year).-Rappaport;Prof.Ranjan K Bose-IITD NPTEL
Advanced 3G 4g NPTEL-IIT KANPUR
REFERENCES:-
Wireless Communication “Rappaport”-Pearson Publications.
NPTEL Videos-Prof.Ranjan K Bose-IIT Delhi.
IEEE Papers.
https://www.youtube.com/watch?v=KymIDyQiXZI-basic building block call transfer Mr. Vishwendra Choudhary.

 

Download materials:-

CELLULAR COMMUNICATION

Basic Communication:-

Types of Hand-offs:-

 

WIDEBAND MODULATION TECHNIQUE: OFDM

Reading Time: 3 minutes

OFDM is of great research interest in laboratories all over the world. It has already been accepted for the new wireless local area network. Also, it is expected to be used for wireless broadband multimedia communications as well. 

         Data rate is really what broadband is all about. The new standard specifies bit rates of up to 54 Mbps. Such high rate imposes large bandwidth, thus pushing carriers for values higher than UHF (Ultra High Frequency) band. For instance, IEEE802.11a has frequencies allocated in the 5- and 17- GHz bands.

         OFDM, orthogonal frequency division multiplex is a rather different format for modulation to that used for more traditional forms of transmission. It utilises many carriers together to provide many advantages over simpler modulation formats.

 What is OFDM? – The concept

                       An OFDM signal consists of a number of closely spaced modulated carriers. When modulation of any form – voice, data, etc. is applied to a carrier, then sidebands spread out either side. It is necessary for a receiver to be able to receive the whole signal to be able to successfully demodulate the data. As a result when signals are transmitted close to one another they must be spaced so that the receiver can separate them using a filter and there must be a guard band between them. This is not the case with OFDM. Although the sidebands from each carrier overlap, they can still be received without the interference that might be expected because they are orthogonal to each another. This is achieved by having the carrier spacing equal to the reciprocal of the symbol period.

sanjay_OFDM_1
Traditional view of receiving signals carrying modulation

 

To see how OFDM works, it is necessary to look at the receiver. This acts as a bank of demodulators, translating each carrier down to DC. The resulting signal is integrated over the symbol period to regenerate the data from that carrier. The same demodulator also demodulates the other carriers. As the carrier spacing equal to the reciprocal of the symbol period means that they will have a whole number of cycles in the symbol period and their contribution will sum to zero – in other words there is no interference contribution.

sanjay_OFDM_2
OFDM Spectrum

Advantages

  • Can adapt easily to bad channels.
  • Robust against crosstalk between channels that are close together.
  • Robust against Inter-symbol interference (ISI) and fading caused by multipath propagation
  • High spectral efficiency
  • There are good implementations available
  • Few problems with errors that come from time synchronization.
  • Tuned sub-channel receiver filters are not required (unlike conventional FDM).

 

Disadvantages

  • Problems with Doppler shift.
  • Synchronizing frequencies can be problematic.
  • Sensitive to frequency synchronization problems.
  • High peak-to-average-power ratio (PAPR). This needs linear transmission circuits; they need a lot of power.
  • Loss of efficiency caused by Cyclic prefix/Guard interval.

Application

With OFDM, high data rate is achieved .So it is basically used in Digital audio and terrestrial TV broadcasting, Wireless LAN’s (802.11a,g and n), High-speed cellular data etc.

Sanjay Mangal

B.Tech III (ECE)

mangalsanjay25@gmail.com

SATELLITES : ENGINEERING EXCELLENCE

Reading Time: 6 minutes
GPS-IIRM
SATELLITE ORBITING EARTH
Ref : Google Images


                                                       

A satellite is one of the most complex machines ever built by mankind. It is a great challenge to make a satellite because of the harsh conditions of space, the shock waves, vibrations of launch, the varying temperatures (from -250 degrees to > 100 degrees warm), making adjustments in the orbit and dealing with space debris, solar flare and radiation, making it last for about 5-10 years. Sophisticated electronics are used which can withstand these harsh conditions, Apart from it there are no repair/ reservice  options either – one part damaged or malfunctioned , then goodbye satellite forever..!!

sat1
COMMUNICATION OF GROUND STATIONS THROUGH SATELLITE
Ref : Google Images

It has its own communication system module often termed as payload to receive the signal from earth (UPLINK) and filters the signal from noisy components, amplify it and send it back to earth where an antenna receives the signal (DOWNLINK). It does this work with the help of a transponder, which is an integrated radio signal receiver and antenna. The frequency is generated by a quartz resonator, which is the heart of satellite.

 

Classification of Satellites :

Satellites are orbiting the earth in three different orbits : Low Earth Orbit (LEO), Medium Earth Orbit (MEO) and Geosynchronus Earth Orbit(GEO).LEO satellites work at an altitude between 160 km and 1,600 km  above Earth. MEO satellites operate from 10,000 to 20,000 km .GEO satellites are positioned 35,786 km (22,236 miles) above Earth and they complete one orbit in 24 hours.

earth-orbits1
LEO, MEO AND GEO SATELLITE ORIENTATION AROUND EARTH
Ref : Google images

LEO Satellites

  • Advantages:
    • Reduces transmission delay
    • Eliminates need for bulky receiving equipment.
  • Disadvantages:Subdivisions: Little, Big, and Mega (Super) LEOs.
    • Smaller coverage area.
    • Shorter life span (5-8 yrs.) than GEOs (10 yrs).

 

Little LEO Satellite

  • 0.8 GHz range
    • Small, low-cost
    • Vehicle tracking, environmental monitoring and two-way data communication. Used for short, narrowband communications.

Super LEO Satellite

  • 2 GHz or above range
  • Can offer global services, which can be subject to regulatory requirements.
  • Used for technology devices such as high-speed, high-bandwidth data communications, and video conferencing. They carry voice and high-speed data services. The main uses are data communications and real-time voice delivery to hand-held devices.

 

 

MEO Satellite :

  • MEO satellites have a larger coverage area than LEO satellites
  • A MEO satellite’s longer duration of visibility and wider footprint means fewer satellites are needed in a MEO network than a LEO network
  • A MEO satellite’s distance gives it a longer time delay and weaker signal than a LEO satellite, though not as bad as a GEO satellite

Satellite use very high frequency range of signals for effective communications. The lower GHz frequency range bands are  L band,S band, C band extending upto Ku,Ka, X and Vbands which extend upto 50GHz range. The L,S,C bands have low power and Ku,Ka, X and V bands have high power.

 

GEO Satellite :

  • Orbit is synchronous with the earth’s rotation.
  • From the ground the satellite appears fixed.
  • Altitude is about 23,000 miles.
  • Coverage to 40% of planet per satellite.
  • Geostationary satellites are commonly used for communications and weather-observation.
  • The typical service life expectancy of a geostationary satellite is 10-15 years.
  • Because geostationary satellites circle the earth at the equator, they are not able to provide coverage at the Northernmost and Southernmost latitudes.
  • Advantages:
    • Weather images can be displayed.
    • Television broadcasts are uninterrupted.
    • Used to track major developments such as hurricanes 24 hours a day.
  • Disadvantages:
    • It takes longer for the signal to get to earth and back to satellite (Delay of .22 s).
    • Increased difficulty of telephone conversations.
    • GEOs are not positioned in the farthest northern and southern orbits.
GSAT4 disassembled view
SATELLITE EXPLODE IMAGE : GSAT 4 DISASSEMBLED
Ref : Google Images

 

 

Satellite Components :

 

Bus Mainframe  :

It is the frame of the system. It contains antenna dishes, transponders, thrusters, fuel cylinders, engine, position control system,solar panels etc. It is made of aluminium and carbon fibre.

 

Command Control and Telemetry :

The station from earth monitors the health of satellite including its vital parameters continuously which ensure the satellite is operable for many years. They have a separate antenna and separate frequency to monitor and establish radio diagnostics and control (RDC).

 

Power System :

Photovoltaic cells are employed on solar panels which have a conversion rate of 20%.They power up the circuitry on board and recharge batteries. The panels are foldable and are constantly positioned for maximum collection of sunlight on panels. Apart from that on board Ni-Cd  batteries that have best power weight ratio and are used on eclipses, where shadow of the planet causes block in sunlight.

Orbital Position System:

The gravitational fields of earth and moon have effect on the orbit of the satellite. The fuel in satellite system, hydrazine is thrusted out to maintain on its elliptical path (Attitude Control System). The attitude and orbit control subsystem consists of sensors to measure vehicle orientation; control laws embedded in the flight software; and actuators (reaction wheels, thrusters) to apply the torques and forces needed to re-orient the vehicle to a desired attitude, keep the satellite in the correct orbital position and keep antennas positioning in the right directions.

Antenna and Receivers :

Every satellite has got a different range of antennas on it. Medium gain antenna , high gain antenna etc. are employed for various purposes. Different radiating power is needed for these antennas.LEO satellites need big antenna dish because of low power and low frequency and due to high frequency range of GEO satellites, need a small antenna system. They have carbon fibre skins bound on Kevlar honeycomb. They don’t have a smooth surface.

 

The Thermal Control Subsystem

The thermal control subsystem helps protect electronic equipment from extreme temperatures due to intense sunlight or the lack of sun exposure on different sides of the satellite’s body (e.g. Optical Solar Reflector).Vacuum deposited aluminium on kapton is used for thermal insulation too.

 

Transponder :

The second major module is the communication payload, which is made up of transponders. A transponder is capable of :

  • Receiving uplinked radio signals from earth satellite transmission stations (antennas).
  • Amplifying received radio signals
  • Sorting the input signals and directing the output signals through input/output signal multiplexers to the proper downlink antennas for retransmission to earth satellite receiving stations .

 

After serving its term the small thrusters fire off  the satellite using the last of on board fuel to its graveyard orbit away from earth in to the deep space.

 

satellite.2201
ENDING JOURNEY OF SATELLITE IN GRAVEYARD ORBIT
Ref : Google Images

 

 

 

SPEECH PROCESSING

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Speech processing is the study of speech signal and analysis of speech signal using ‘TIME DOMAIN’ and ‘FREQUENCY DOMAIN’ analysis parameter.

TIME DOMAIN ANALYSIS:-

Time domain often requires simple calculation and interpretation. Among the relevant features found readily in temporal analysis are waveform statics, power and fundamental frequency (Fo).

NEED FOR TIME DOMAIN ANALYSIS:-

Time domain analysis is found necessary when a signal has constant frequency over the time span of our analysis.

FREQUENCY DOMAIN ANALYSIS:-

Frequency domain analysis we find out the spectral properties of signal .Spectrum analysis provides us the mechanism of most useful parameter of speech signal like bandwidth, spectral energy, formant frequency (Formants are the distinguishing or meaningful frequency components of human speech and of singing) etc.

NEED FOR FREQUENCY DOMAIN ANALYSIS:-

Frequency domain is necessary when we want to filtering operation on speech signal .It is also crucial when fixed bend allocation to any system is needed.

AREA OF STUDY IN SPEECH PROCESSING:

1.) Voice recognition:-

It has two parts :-a) Speech recognition b)Speaker recognition

a.) Speech recognition:-

“Determine what is being said”. In computer science speech recognition is the translation of spoken word in text.

b.) Speaker recognition:-

“Determine who is speaking”. Speaker recognition is the identification of the person who is speaking by characteristics of their voice biometrics.

 

 

2.) Speech coding:-

Speech coding is an application of data compression of digital audio signal containing speech .Speech coding uses speech specific estimation using audio signal processing technique to model speech signal combined with data compression algorithm to represent resulting modeled parameters in a compact bit stream.

 

3.) Voice analysis:-

Voice analysis is the study of speech sound for purpose other than linguistic content such as in speech recognition, such study includes medical analysis of the voice.

4.) Speech synthesis:-

Speech synthesis is the artificial production of human voice. A computer system used for this is called speech synthesizer.

5.) Speech enhancement:-

Speech enhancement aims to improve speech quality using various algorithms. The objective of enhancement is improvement in speech and overall perceptual quality of degraded signal using audio signal processing.

6.) Speaker diarization:-

Speaker diarisation (or diarization) is the process of partitioning an input audio stream into homogeneous segments according to the speaker identity. It can enhance the readability of an automatic speech transcription by structuring the audio stream into speaker turns and, when used together with speaker recognition systems, by providing the speaker’s true identity.

It is used to answer the question “who spoke when?” Speaker diarisation is a combination of speaker segmentation and speaker clustering. The first aims at finding speaker change points in an audio stream. The second aims at grouping together speech segments on the basis of speaker characteristics.

 

Li-Fi an alternative to Wi-Fi !

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Hey Guys!

I’m sure many of you know this…..but still just to give u a glimpse..

Have you ever wonder why should we deal with such low speed of internet ..well u just don’t have to worry about it in next few years! I see the future of technology alternative to WiFi. Oops!…and it is Light Fidelity.

Harald Haas – A professor of engineering at Edinburgh University is the pioneer behind a new type of light bulb that can communicate as well as illuminate – access the Internet using light instead of radio waves.

Haas Quote: “Everywhere in a day there is light. Look around. Everywhere. Look at your smart phone. It has a flashlight, an LED flashlight. These are potential sources for high-speed data transmission.”

The system, which he’s calling D-Light, uses a mathematical trick called OFDM (orthogonal frequency division multiplexing), which allows it to vary the intensity of the LED’s output at a very fast rate, invisible to the human eye (for the eye, the bulb would simply be on and providing light). The signal can be picked up by simple receivers. As of now, Haas is reporting data rates of up to 10 MBit/s per second (faster than a typical broadband connection), and 100 MBit/s by the end of this year and possibly up to 1 GB in the future.

He says: “It should be so cheap that it’s everywhere. Using the visible light spectrum, which comes for free, you can piggy-back existing wireless services on the back of lighting equipment.”

Herald Scotland “As well as revolutionizing internet reception, it would put an end to the potentially harmful electromagnetic pollution emitted by wireless internet routers and has raised the prospect of ubiquitous wireless access, transmitted through streetlights.”

Watch this link : https://www.youtube.com/watch?v=Qn_cFz5R6sk

Keep getting motivated and feel free to share your knowledge …stay connected!

Magical Screen- Augmented Reality

Reading Time: 2 minutes

Magical Screen- Augmented Reality

Imagine you’re a New York Yankee stuff walking down the famous Manhattan. You flash your smart phone’s camera towards the road and you come to know which metro substation is beneath and which is the next  metro train you can catch up to meet your loved ones.. Again you come across a hoarding which has Chines stuff written over it.. You again flash your camera over it and boom.. the English letters are revealed out the Chinese text..

It is night time and you’re looking at the bright moon and the pattern of stars makes you curious.. You flash your camera and find the virtual lines connecting the stars and telling you the constellations.

Folks wake up .. I ain’t telling you that your camera has a magic wand..!! It is Augmented Reality..

Yes .. Augmented Reality is nothing but adding a virtual screen on top of everything in order to make it more meaningful. It combines 2 words to deal with, “augmented” means enhanced and “reality”, which simply means enhanced reality. By using hardwares or tools such as your smartphones you can discover such beneficial details in the form of visual images that are not visible normally.

Augmented reality adopts new ways to add information discoveries to the reality in limitless possibilities from fun, games, sports and education to technology in engineering and medicine and more.It adds the graphics, sounds, feedback and smell to the natural world we see, thereby making it more alive. Thereby creating such a grand spectrum, let the field environment variables speak for your lively experience.

 

1334728405acrossair_nearest_sub_app_featured11                    mzl.nmsjqzoj.320x480-75

 

ACROSS AIR APP                                                                  CAR FINDER APP

google-sky-map

AUGMENTED SKY MAP

 

Thus there are apps to facilitate augmented reality. Across Air App  is a 3D navigator telling you restaurants, hotels,cinema,landmarks etc.near you and Augmented Car Finder App helps to find your car in a big parking place..

Go grab them to make your world more speaking to you!

These are available on your android platform .. And what more, these are for free.. !!

Extra Edgy Things For All Engineers

Reading Time: 3 minutes
World Class Education Websites :- 

1.) edX.org

2.) coursera.org

3.) NPTEL.ac.in (watch at 1.5 x speed )

 

Internship and Workshop : Companies

 

1.) I3 Indiya

2.) Wegilant( Speacilized in Cyber Security)

3.) Robosapiens

4.) Technophilia

5.) Thinkware (Good for Matlab)

6.) Thinklabs

7.) Waayoo

8.) Learnics.in

9.) Logicbrigade.com

10.) STP.mbsgroup.in-(Also Has Course on F1 Car Design and Development)

 

To-Do Projects :-

 

Electronics Engineering

1.) SMPS

2.) POV

3.) LED CUBE

4.) FM Receiver

5.) Line Follower

6.) Temperature Controlled Fan

7.) Phone Jammer

8.) 555 Timer Projects

9.) Raspberry Pi

 

Mechanical Engineering

1.) Robotic Arm

2.) RC Plane

3.) Hovercraft

4.) Wall Climbing Robot

5.) Rope Climbing Robot

6.) Pole Climbing Robot

7.)Tricopter/Quadcopter

8.) Hydraulic Lift Arm

 

Chemical

1.) Batteries: Batteries of Your Own, like

  • Galvanic Cell
  • Zinc Air Battery
  • Al Air Battery
  • Al CU Battery

2.) Propulsion System: Car using

  • Vinegar+ Baking Soda
  • Decomposition of H2O2

3.) Search On MFC-Microbial Fuel Cell

4.) Research Alternate Source of Energy like Jatropha Seeds

 

 

 

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Electrical Engineering

1.) Power Generation from Moving Vehicles

2.) Power Theft Protection

3.) Booster Circuit

4.) Inverter Circuit

 

Civil Engineering

1.) Cardboard Model Building

2.) Designing On Softwares

3) Some Famous Civil Engineering Projects – Bridges, Tunnels and Dams

 

Computer Engineering

1.)Read: A Complete Reference to Java by Herbert Schildt

2.) Make Applets

3.) Android App Development

4.) Game Development

5.) AI-Artificial Intelligence: – Course on edX

6.) Read HTML: – HTML-5 for Web Development

7.) PHP

8.) Hacking

9.) Android- Learn to Root, Flash

10.) Google about Crack Paid Software using Decompiler and Disassembler!!!

11) Read  “C Programming Language” written by the creator of C – Dennis Ritchie

 

 

Extra-Edge Software

 

Civil

1.) Revit

2.) AutoCad

 

Computer Engineering

1.) Android App Development-IDE:-Eclipse

2.) Game Development Softwares

3.) Hacking-Backtrack OS

 

Chemical Engineering

1.) Aspen

2.) Super Pro Designer

3.) Open Foam

4.) Chemsketch

 

Mechanical Engineering

1.) Autodesk- AutoCad

2.)  Inventor

3.) Pro-e

4.) Google Sketch-Up

 

Electrical Engineering

1.) E-tap

2.) Matlab

3.) LabView

4.) PSCAD

5.) Simulink

6.) Lapack-Numerical Linear Algebra

 

Electronics

1.) MultiSim

2.) Proteus: Ckt and AVR MCU Simulation

3.) Eagle: PCB Designing

4.) Matlab: Mother of all things-

       Image Processing,Computer Vision,Control System Simulation, Digital Signal Processing

5.) NI’s LabView

 

Magazines

1.) ECE  – EFY

2.) Mech- Top Gear, Overdrive, AutoCar

3.) Chem- Chemical Engineering, World,Chemical Industry Digest

4.) Comps- Digit, Chip

5.) Electrical- Industrial Automation (IED Communications),IET(generation transmission and distribution)

 

Tech Fests

Even Semester

1.) IIT Bombay -Techfest Jan first week

2.) IIT Madras -Shaastra   Jan first week

3.) IIT Kharagpur -Kshitij Feb first week

4.) NIT Trichi-Pragyan-Feb End

5.) IIT Kanpur -TechKriti   March Mid

6.)BITS Pilani -Apogee   March Mid

7.) IIIT Hyderabad -Felicity

8.) IIT Roorkee -Cognizance

 

Odd Sem

1.) NIT Surathkal-Engineer – October End

2.) NIT Warangal-Technozion-   September End

 

God Father Sites

 

1.) http://www.howstuffworks.com/(Discovery’s Site-More of general Science)

2.) http://www.engineersgarage.com/

3.) http://www.extremeelectronics.com

4.) http://www.circuitstoday.com/

5.) www.societyofrobots.com (The best according to me)

6.) http://www.electronics-tutorials.ws/

7.) http://www.ece101.com/

8.) http://narobo.com/

9.) http://www.pyroelectro.com/

10.) http://students.iitk.ac.in/roboclub/tutorials.php

 

Electrical Engineering

1.) controleng.com

2.) control.com

3.) electric.net

4.) controlglobal.com

 

Mechanical Engineering

1.) pirate4x4.com

2.) carbibles.com

3.) SudhaCars.com

 

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Computer Engineering

1.) code.org

2.) codechef.com

3.) spoj.com

4.) Java Applets-http://walter-fendt.de/ph14e/

 

Others

1.) internshala.com

2.) knowafest.com

3.) twenty19.com

 

 

Sites to buy robotics stuff

In India:

1.) http://nex-robotics.com/

2.) http://www.robokits.co.in/

3.) http://www.vegarobokit.com/

4.) http://www.rcbazaar.com/default.aspx

5.) http://www.rcdhamaka.com/

 

World best online robotics store:

1.) Jameco

2.) Solarbotics

3.) Digi-key

4.) Radioshack.com

 

Movies

1.) Gravity

2.) October Sky

3.) Iron Man-1, 2, 3

4.) Wall-E

5.) Batman

6.) G I Joe-1, 2

7.) Transformers-1, 2, 3

8.) The Social Network

9.) Avatar

10.) Real Steel

11.) Pirates of Silicon Valley

12.) Blade Runner

13.) 2002: A Space Odyssey

TELEVISION SHOWS

 

Discovery, Discovery Science, Discovery Turbo

1.) How Tech Works

2.) Dark matters

3.) Extreme Engineering

4.) Deconstructed

 

History TV

1.) Modern Marvels

 

NatGeo TV

1.) Big, Bigger, Biggest

2.) MegaStructures

3.) MegaFactories

4.) I Didn’t Know That

5.) Ultimate Factories

6.) Mega Factories

 

 

CEV - Handout