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== Advanced Cellular Phone Repair Course ==
Posted by Delano in Mobile videos Games PC on August 20, 2007 8:45:00 PM
CONTENTS :
1. Electronic Basics
2. Soldering Techniques
3. Ohm’s Law
4. Electrostatic Electricity
5. How a GSM Cellular Network Operates
6. Cell & Cell Sector Technology Explained
7. The Concept of Cellular technology and the GSM system
8. The GSM Concept
9. SIM Cards, identity numbers,IMSI, PIN, and PUK
10. How Cell Phones Work – the Cell Approach
11. From Cell to Cell
12. Cell Phones & CB Radios
13. Inside a Cell Phone -Components explained
14. Advanced Mobile Phone System – AMP
15. Digital System
16. Cellular Access Technologies
17. Cell Phone Towers and Base Stations
TECHNICAL SECTION
18. Component Identification – Base Band, RF Section, Control
19. Cellular Phone Repairs – Types of Damages incurred
20. Cellular Phone Repairs – Notes on Batteries
21. Trouble Shooting Steps – Introduction
22. Most Common Components Used in a Cellular Phone and problems that occur.
23. Dissasembly of Cellular Phones
24. Assembly of a Cellular Phone
25. Most Common Problems that occur
26. Cellular Phone Repairs – Replacing a LCD (Liquid Crystal Display)
27. Cellular Phone Repairs – Replacing Speakers
28. Cellular Phone Repairs – Replacing Microphones
29. Cellular Phone Repairs – Replacing Ringers
30. Cellular Phone Repairs – Replacing Charging
Block/Systems Connector
31. Cellular Phone Repairs – Replacing Antennas
32. Cellular Phone Repairs – Liquid & Moisture Damaged Phones
33. Cellular Phone Repairs – Refurbishing of Phones
34. Cellular Phone Repairs – Power on Procedure of a Cell Phone
35. Quick Trouble Shooting Guide & Required Action– Cell Phone Batteries
36. Quick Trouble Shooting Guide & required Action – Phone Has No Power – Switches Off
37. Quick Trouble Shooting Guide & Required Action – Phone Has No Power
38. Quick Trouble Shooting Guide & Required Action – Phone Not Charging
39. Quick Trouble Shootin
g Guide & Required Action – Phone Not Receiving Signal
40. Quick Trouble Shooting Guide & Required Action – SIM CARD related Problems
41. Quick Trouble Shooting Guide & Required Action –
Liquid Crystal Display (LCD) problems
42. Quick Trouble Shooting Guide & Required Action – Call Dropping
43. Setting Up your Workshop
44. Tools and Consumables.
ELECTRONIC BASICS
Persons new to electronics can have difficulties with the component values and
descriptions. Here are some guidelines for resolving these problems.
a) Basics
b) Resistors
c) Capacitors
d) Diodes
e)Transistors
f) IC's
Basics
The most often used terms in electronics are voltage and current
To give you a metaphor for this you can think of a river.
The voltage is the length of the river and the current can be seen the current of the river.
This current is due the difference in height between the start and end of the river.
One law you have to remember is law of Ohm. (See OHM’S LAW). It is a simple law.
Voltage = Current * Resistance
or U = I * R
Where voltage is in voltage [V], current in Ampere [A] and the resistance in
Ohm.
To make it easier for you to make conversions I will provide you [literally] a
rule of thumb.
Voltage [V]
-------------------------------
Current [i] * Resistance [Ohm]
Now just place your thumb over the unknown value and you will see what you have to do to find the value. For example. If you want the know the resistance then
you have to divide the voltage by the current.
Numbers can become quiet large in electronics. To prevent writing many zero's
they use often different names. The following names are used.
Value, milli-, micro-, nano- and pico-
Example: Farad [capacitor] Farad, milli Farad [mF], micro Farad [uF], nano Farad
[nF], pico Farad [pF]
Every step is 1000 smaller like 1 Kg is 1000 Grams.
Resistors
Symbol
---/\/\/\/\----
or
------
---| |-----
------
A resistor can be seen as a dam in a river. Water will have more difficulties to
pass this dam. In a resistor this will result in the generation of heat.
Resistors come in standard values to choose from. The value of a resistor can be
found with the help of a colour table. The resistor has a set of coloured rings
that will tell you its value.
First ring : First number
Second ring : Second number
Third ring : Number of zeros to add
Fourth ring : Tolerance [quality of the resistor. Mostly 5%]
1 Brown Examples:
2 Red 4700 Ohm 1 000 000 Ohm
3 Orange Yellow Purple Red Brown Black Green
4 Yellow
5 Green
6 Blue
7 Purple Brown Black Brown Red Red Red
8 Grey 100 Ohm 2200 Ohm
9 'White'
0 Black
Values are often written as 10K, 1M or 4K7. This means in this case 10.000,
1.000.000 and 4700 Ohm. The 'K' just stands for Kilo and tells you that there is
a factor 1000 there. The 'M' stands for mega and adds another factor 1000
Capacitors
\
Symbol
||
---||---
||
A capacitor can have more functions but one of them is to store some energy in
them. They act like a bucket. You can fill them with energy and drop the
contents back when you need it.
Values are often written as 10N or 2N2. This means in this case 10.000 and 2200
nano Farad. The 'N' just stands for nano. Small capacitors can have only numbers
on them like 104. The first two digits is a number and the third digit tells you
how many zeros you must add. In this case its four. The correct value of this
component is 100 000 pF. [note: 100 nF or 0.1uF is also correct]
Diode
Symbol
|\ |
___| \|___
| /|
|/ |
Diodes are the passive one-way locks in the river. Water can flow through them
only in one direction. And only when there is enough difference in height
[voltage].
Knowing this you may notice that a diode needs to have a direction to function.
To show this there is a small mark at the casing. Normally this is a ring. For
LED this isn't the case. You have to look inside and see the small plates. The
one with the largest plate is the side where the 'ring' would be.
Transistor
Symbol
| /c c = collector
___|/ b = basis
b |\ e = emitter
| \e
These are the active locks in the river. They have a lock gate that can control
the flow through them. They can also act like a switch. With a little current
they can be opened and let a strong current pass. In the symbol there is also a
arrow that will tell you the direction of flow. There are two basic transistor
types namely; PNP and NPN. They are named todifferentiate between different internal designs. A PNP has a symbol with the arrow pointing inwards and a NPN
transistor has a arrow pointing outwards.
IC (Intergrated Circuit)
Symbol
An IC doesn't have a universal symbol.
It all depends on its use. A few
examples are shown here.
|\ +---+
___| \___ -| & |
| / -| |-
|/ +---+
A little box that contains many small components as above. A complete circuit
can be inside the black plastic casing.
They have often 8, 14 or 16 pins.
They are used for many purposes. The casing has a small notch on top of it or carved out of it.
If you look at this mark and holding the mark on top then the first
lead on the right side will be pin number one.
All diagrams with detailed description included - Download
Mobile videos Games PC
topic 2. Soldering Techniques
How important is soldering?
Among the foremost of reasons an electronic project frequently fails to work
properly is due to "poor" soldering practices. This is usually caused by "dry
joints" when soldering. Here we discuss the correct procedures for soldering
electronic projects.
Dry joints when soldering
At first glance many solder joints appear to be quite "O.K." but on closer
examination many are in fact defective. The insidious problem with dry joints in
soldering is that the circuit frequently performs alright for a period of time,
even years before failure.
This problem even occurs with manufactured equipment. Ask any TV / Video repair/Cell Phone technician who has torn a lot of hair out over an elusive fault ultimately traced back to a dry joint.
Good soldering practices for your electronic project
The cause of dry joints in soldering is mostly the improper application of heat.
Both the component leg and the PCB need to be both heated simultaneously to the
correct temperature to allow the solder to flow freely between BOTH surfaces.
Obviously this requires practice and most newcomers inevitably get it wrong.
Improper heating while soldering and its consequences can be seen below.
Figure 1 - correct soldering procedures to avoid dry joints
Here in figure 1 entitled "correct soldering procedures to avoid dry joints" we
have three examples of soldering depicted.
The first example indicates the component lead was heated while the PCB wasn't heated.As a consequence the solder only flowed onto the component lead.
In the second example of soldering in figure 1 we find the PCB was correctly
heated while little or inadequate heat was applied to the component lead. This
is the most treachorous example because although I have made it very obvious in
the diagram, in practice it is not always particularly obvious.
Often this type of dry joint "just" allows the solder to "touch" the component lead while not actually being "soldered" to the lead. Of course it might work for a period of time depending upon environmental conditions of heat and cold.
In the final example of "correct soldering procedures to avoid dry joints" We
have depicted the solder bridging both the PCB and the component lead.
In this case the PCB and the component lead were both heated "simultaneously" AND the solder was applied to either the component lead or the PCB to "flow" freely from one to the other to provide a good "electrical" joint. Such a joint is always "bright and shiny", dull looking joints are often suspect.
You never apply the solder to the soldering iron "tip". Solder is always applied
to the "job", never the soldering iron. Allow the solder to "set" and cool
before proceeding to the next joint.
Other cases of soldering
We have discussed soldering components to a PCB yet this is not the only case of
soldering. Often we need to connect wires to switches and other components. A
common misconception is that soldering is designed to provide a good mechanical
joint. - It isn't!
Any connection should have it's own mechanical strength perhaps by twisting
wires together or twisting the wire around a binding post or through a hole
provided for the purpose.
The solder is only intended for a good "electrical" connection. Never provide a connection which can't stand mechanically on it's own merits.
What's soldering flux?
Modern quality electronics solders contain a "flux" resin within the solder.
This flux is designed to flow over the job and prevent contact with the
atmosphere.
Metals, particularly copper when heated tend to "oxidise" and prevent the alloying or good electrical bond between the copper and the solder.
Good solder containing the resin will have resin flowing over the leads and
prevent this oxidisation process and as the solder flows the resin is displaced
allowing the solder to form an "atomic" bonding with the items being soldered
together. A good resin helps to keep the surfaces clean.
Rules for good soldering
Of course some of these rules might seem very obvious but are worth repeating.
=> Use a reasonable quality iron of the correct wattage for the job.
=> Only use "electronic" resin cored solder of fine gauge.
=> Make sure all surfaces to be soldered are "bright, shiny" and thoroughly
clean.
=> If a mechanical joint, make sure it can "stand alone" before soldering.
=> Make sure the solder tip is clean, shiny and properly "wetted".
=>Remember the soldering iron tip is only to heat up the surfaces to be
soldered.
=> Apply the resin cored solder to the heated "job", not to the soldering iron
tip.
=>Remember to visually inspect ALL of your soldered joints, preferably with
magnifying glasses.
=> Consider using your multimeter to provide an "electrical continuity" check
between various parts of the circuit.
Why is ohms law so very important?
Ohms law, sometimes more correctly called Ohm's Law, named after Mr. Georg Ohm, mathematician and physicist b. 1789 d. 1854 - Bavaria, defines the relationship between power, voltage, current and resistance. These are the very basic electrical units we work with. The principles apply to a.c., d.c. or r.f. (radio
frequency).
Ohms Law is the a foundation stone of electronics and electricity.
These formulae are very easy to learn and are used extensively throughout our
tutorials.
Without a thorough understanding of "ohms law" you will not get very
far either in design or in troubleshooting even the simplest of electronic or
electrical circuits.
Mr. Ohm (that is his 'real'name) [Georg Ohm b 1789 d 1854 - Bavaria] established
in the late 1820's that if a voltage [later found to be either A.C., D.C. or
R.F.] was applied to a resistance then "current would flow and then power would
be consumed".
Some practical every day examples of this very basic rule are:
Radiators (electric fires), Electric Frypans, Toasters, Irons and electric light
bulbs.
Figure 1 - ohms law power consumption through a resistance.
The radiator consumes power producing heat for warmth, the frypan consumes power producing heat for general cooking, the toaster consumes power producing heat for toasting bread, the iron consumes power producing heat for ironing our
clothes, and the electric light bulb consumes power producing heat and more
important light for lighting up an area.
A further example is an electric hot water system. All are examples of ohms law at its most basic.
Hot and Cold Resistance encountered in Ohms Law.
One VERY important point to observe with ohms law in dealing with some of these
examples is that quite often there are two types of resistance values.
"Cold Resistance" as would be measured by an ohm-meter or digital multimeter and a "Hot Resistance". The latter phenomenon is an inherent characteristic of the type of material used as a resistor. It has a temperature co-efficient which often once heated alters the initial resistance value, usually dramatically upward.
A very good working example of this is an electric light bulb.
Measure the light bulb with a digital multimeter. It will show zero
resistance, in fact open circuit.
Again, using a light bulb marked "240V - 60W".
It measured an initial "cold resistance" of 73.2 ohms. Then I measured our actual voltage at a power point as being 243.9V A.C. at that moment [note: voltages vary widely during a day due to locations and loads - remember that fact - also for pure resistances, the principles apply equally to A.C. or D.C.].
Using the formula which you will learn below, the resistance for power consumed
should be R = E2 / P OR R = 243.92 / 60W = 991 ohms .
That is 991 ohms calculated compared to an initial reading of 73.2 ohms with a
digital multimeter.
The reason?
The "hot" resistance is always at least ten times the "cold" resistance.
Another example is what is most often the biggest consumer of power in the
average home. The "electric kettle".
Take an “Electric Kettle " which is labelled "230 - 240V 2200W".
Yes! - 2,200 watts! That is why it boils water so quickly.
What are the ohms law formulas?
To make it much easier for you, I have put all the relevent formulas together for
you here complete with worked examples of ohms law.
You will notice the formulas share a common algebraic relationship with one another.
For the worked examples voltage is E and we have assigned a value of 12V,
Current is I and is 2 amperes while Resistance is R of 6 ohms.
(Note that the asterisk *means multiply by, while "/" means divide by. )
For voltage [E = I * R] E (volts) = I (current) * R (resistance) OR 12
volts = 2 amperes * 6 ohms
For current [I = E / R] I (current) = E (volts) / R (resistance) OR 2
amperes = 12 volts / 6 ohms
For resistance [R = E / I] R (resistance) = E (volts) / I (current) OR 6
ohms = 12 volts / 2 amperes.
Notice how simple it is?
Now let's calculate power using the same examples.
For power P = E2 / R OR Power = 24 watts = 122 volts / 6 ohms
Also P = I2 * R OR Power = 24 watts = 22 amperes * 6 ohms
Also P = E * I OR Power = 24 watts = 12 volts * 2 amperes .
That's all you need for ohms law - remember just two formulas:
For voltage E = I * R and; for power P = E2 / R
You can always determine the other formulas with elementary algebra.
Ohms law is the very foundation stone of electronics!
Knowing two quantities in ohms law will always reveal the third value.
I suggest you print these formulas out and paste them onto scrap cardboard to keep your ohms law as a handy reference until you are quite familiar with it.
what is Electrostatic Electricity?
Electrostatic Electricity is generally ignored or forgotten, yet the effects of static electricity can be DEVASTATING to CMOS semiconductors and other electronic components.
It is MOST IMPORTANT, that when working on a Cellular phone, the proper precautions be adopted at ALL TIMES. Ignoring these precautions will result in both costing you a lot of money and possibly destroying vital components on a Cellular Phone.
It is strongly recommended that an antistatic wrist strap and an antistatic mat be used when carrying out repairs. These are available from Celtrain on request.
Handling of CMOS and Electronic Components.
Field Effect Transistors (FET) and IC’s make use of Complementary Metal Oxide Semiconductor (CMOS) technology.
CMOS transistors and IC’s WILL BE DAMAGED by ELECTROSTATIC ELECTRICITY.
Electrostatic Electricity is bad in dry areas, and areas covered by NYLON floor covering.
When purchasing CMOS transistors, IC’s etc, they are normally supplied in a special conductive package which shorts out all pins, this may cause predamage. IC holders or sockets should be used to minimise handling.
ALWAYS LEAVE IC’s in it’s protective packing until you need to use them.
Sit down (Preferably in an area that does NOT have a nylon floor cover) and connect yourself to EARTH so as to discharge any Electrostatic charge on your body. Put on a wrist strap and connect this to ground.
Working on an ELECTROSTATIC MAT, remove the IC from it’s packing.
DO NOT TOUCH THE PINS!!!!!!!!!!!
Place the IC the correct way around into the IC holder being careful NOT to bend the pins.
Footnote: TAKE NOTE OF THE DANGERS AND DAMAGE THAT CAN BE CAUSED BY WORKING ON CELLULAR PHONES WHEN YOU ARE CHARGED UP WITH STATIC ELECTRICITY!
What kind of applications are good for circuit switched services, what are good for packet switched services?
Data services similar to those for GSM are also being developed for IS-136 TDMA and CDMA networks. But as a more mature digital technology, GSM has a strong head start. When GPRS is deployed, no other wireless data technology will be able to match its capabilities. But it is also important to remember that GSM already offers excellent data and fax capabilities that provide more than sufficient capability for many types of applications. As technologies like GPRS become available, the scope of data applications that are practical for wireless connectivity will only increase.
Chat
Textual and Visual Information
Mobile originating call: How mobile originating call is established from a mobile to fixed telephone network?
The BSS is located between two interfaces, Air and A. From the call establishment point of view, the MS must have a connection through these two interfaces before a call can be established. The MS starts the sequence by sending a message 'Channel Request'. This message contains a reason why the signalling connection through the BSS is needed. After this, the BSC allocates a signalling channel through so-called A-bis interface located between the BTS and the BSC. When the signalling channel is ready through the A-bis interface, the MS is told to move to the signalling channel in the Air interface. The MS informs it is on the signalling channel which then triggers the BSC to set up the A interface, i.e. the BSC requests the SCCP connection. When a signalling connection between the MS and the NSS has been opened as described, the MS starts the other signalling sequences in order to completed the original requested task
Still Images
Moving Images
Web Browsing
Document Sharing/Collaborative Working
Audio
Job Dispatch
Corporate Email
Internet Email
Vehicle Positioning
Remote LAN Access
File Transfer
Home Automation,
Incoming calls: If a user has subscribed voice, data, and fax services and the mobile is attached to GSM network, how the user can control which kind of calls (voice/data/fax) she wants to now receive?
The problem remains when the only information received by the GMSC is the called number (the MSISDN). Two solutions of general application have been put on the table. The first solution consists of letting the service be chosen by the called party. The message setting the call from the network to the mobile station does not specify the service, and the mobile station indicates it in return. This solution imposes the requirement that the service is set by the user in the mobile station before the actual start of the communication. A typical scenario to send a fax to a GSM subscriber is then first to phone him (speech communication), asking him to set the mobile station so that the next call will be treated as a fax call; then hang up and re-dial to establish the fax call.
This solution has minimal impact on network, but is not very convenient for the users. This is why an alternative solution was proposed, consisting in providing a GSM subscriber with as many MSISDNs as services for which he wishes to receive incoming calls ( for instance a speech number and a fax number). The service can then be chosen by the calling party, by using the right number. The relationship between numbers and services is held in the HLR.
Data call:
a) the mobile station
b) from the mobile station to the base station; the radio path
c) from the base station to the MSC
d) from the MSC to IWU (Inter Working Unit, special modem-like device)
e) from the IWU to AM (Analogue Modem)
The GSM-only components of these data/fax interfaces are not actually modems as we traditionally understand them: the "modem" component you need to send and receive data actually resides at the network headquarters (also known as the Mobile Switching Centre, or MSC), using a special modem-like device called an IWU, or Inter Working Unit.
Data is sent digitally from the PC via the special hardware adapter, through the phone and then through the air to the IWU. The GSM phone and the data/fax interfaces thus act as one extended digital "serial" or "air-interface" link between the PC and the IWU, which now acts as the Analogue Modem.
It is only when the digital data is received by the IWU that it is converted by the IWU to the analogue Frequency Shift Keys (FSK) tones characteristic of Analogue Modems, making it possible to connect via Telkom fixed-lines to an ordinary Analogue Modem. And if an ordinary fax machine or fax/modem sends data to your mobile phone, then the IWU converts the analogue tones received into the "digital data stream" suitable for transmission across the network to your GSM mobile.
If one mobile unit sends fax or data to another mobile, then there's no need for an analogue-to-digital conversion since the entire "air interface" is already digital, as is required by the GSM specification
Transparent vs. Non-transparent: What is the difference between transparent and non-transparent data?
Transparent Data Transmission: A method of transmission in which the transmission medium will not recognize control characters or initiate any control function. Transparent-based phones do not utilise any error correction. Thus the data sent and received MIGHT be corrupted unless a greater than two-bar cellphone signal is used (South African conditions). Non-transparent data uses a special ensure robust GSM-specific error correction technique called RLP for transmission. [6]
Non Transparent communication utilises a special GSM network-based error correction facility called "Radio Link Protocol" (RLP)that ensures more robust transmission. What this essentially means is that the GSM network's IWU will add special error correction codes to control the flow of data.
This ensures that the data transmitted first obtains a special acknowledgement signal from the receiver that informs the transmitter that the data has been received as transmitted and that the receiver is ready to receive the next set of data from the transmitter. If there is no such acknowledgement signal from the receiver, the networks will utilise their "data buffering" feature by using a special "forward correction" technique to ensure uninterrupted data transmission throughout. Not all cellphones support GSM's Non Transparent (RLP-based) data capabilities.
Transparent data transmission means that there is no GSM error correction supplied over the air interface.
Non-Transparent data only applies to data transfers and not faxing since the Group 3 standard for fax transmission is a transparent protocol.
(11) Understanding of TELEphony phenomena by using corded Intercom circuit diagram and a live model of the same.
(12) Theory of Operation of Basic Telephone and Cordless Phones
(13) Principles of FREQUENCY related phenomena leading to the Basics of mobile Phone Technology involved in the MOBILE PHONE
Advanced Module :
Advanced Module Begins exactly where the Basic Module has ended
(1) How Mobile Phones work
(2) Various Mobile technologies like GSM , CDMA etc.
(3) GSM Architecture
(4) Mobile Phone BLock Diagram and it's understanding
(5) SIM Architecture
(6) Batteries & Chargers
(7) Power Supply & Charging Circuit
(8) User Interface (UI)
(9) R.F Circuit Functions : IF Amplifier , DE-Modulator, Oscillator , Modulator , Power Amplifier , Antenna Switch and it's associated Circuits
(10) Audio Circuit
(11) Comparision with a Computer
(12) CPU , Flash ICs and RAM ICs - how they Handle and collaborate between Hardware and Software Functions
(13) Opening Procedure for Various Popular Models of mobile Phones with Pictorial Illustrations for later reference
(14) Understanding of Mobile Phone's Circuit Diagrams
(15) Tracing of Mobile Phone PCB Circuits with reference to it's Circuit Diagram or Schematic.
(16) Fault Finding and Common Faults Occuring
(17) Using Soldering Gun (Hot Air gun) for removing and soldering of Chips and BGA ICs
(18) Codes for Various Mobile Phone Functions
(19) Data Cable Connection for Communicating with the PC (personal Computer
(20) Solving Software Related Problems like Repairing Dead Phones , Unlocking etc. wity the use of Commonly used Softwares.
(21) Understanding of Multi Media Applications like Ringtones, Wallpapers, games, Softwares, Themes, MP3 Songs Playback, Video Clips Downloading etc.
Power Section:
A power section deals with power related tasks such as power distribution or charging the battery so this section can be divided into two sub sections like.
1. Power Distribution
A power distribution section is built around an "power IC" it takes 3.6V power from battery and regulates its power and then distributes to the other components used in mobile phone circuit. in some mobile phones tech "RF Power amplifier" uses more Power than provided bye mobile phone's battery .i.e. 4.7 V or 5.6 V in some phones. the power Ic with a power boaster coil is used to increase voltages. so we can say that power IC is used to provide power to other components how much they needed. either less than battery voltage or more than it.
* Charging Section
A charging section works for battery charging purposes.it is often consists a fuse, a coil, a protecting diode, a filter capacitor and charging IC and some other discreet. the charging section helps battery to be charged when it needs and when battery is charged, charging IC reads its state of charge and feels it full charged and then disconnects charging from it.
Radio Section:
A radio section has basically a set of four main functions.wich are.
*
* Receiver
Band Switching:
In the modern mobile phone communication techniques. the frequency of mobile phone communication is divided into three bands
*
* PCS (operates on 1900 MHz)
the third band is used only in USA whereas the first two bands are used in the rest of the world. band switching is done bye a "ceramic antenna switch" it reads from the radiation dispersed in the air and then switches to the appropriate band.
in the very first phase of mobile phones there were single band handsets which operated on single frequency band but now a days all the handsets are dual band or tri band in operation.
RF Power Amplifier
RF power amplifier is often called as ".PA" or"Transmitter" its functions is to amplify or boast the power which is being transmitted to air, so may it would be able to communicate with long distances. a typical .PA can amplify rf power up to 0.6W or 600mW. This amount of rf power is sufficient to communicate nearly 20 to 25 kilometers in open area, but all the PA's are controlled by there rf signal processor, so if we are near our cell base tower the PA of our phone will transmit low power but if we are far away it will produce its maximum power.
Transmitting
A mobile phone's rf section is basically built around an rf IC which is often called rf signal processor whereas in nokia it is called hagar IC in some hand sets and in some hand sets it is called Mjoelner. irrespectively of the brands and verity of names we call it rf signal processor. this IC works as transmitter and receiver as well. working as transmitter it takes instructions from phone's computer and also takes audio data from audio section and creates radio waves then mixes audio data to its radio waves according to the instructions given by computer section. this mixer of audio and radio is sent to PA to amplify its strength
Reciever
A reciver section for rf waves is built in rf IC, as it is said that this IC works for dual purposes first transmitting and section recieving. in the recieving section of mobile phones a radio signal is gather from ceramic antenna switch and then it is filtered and sent to rf IC to further process. in rf IC signal is detected and then rectified for audio and data which is sent to audio IC or computer section.
Computer Section:
A computer section in mobile phone consists of two main functions
CPU(central processing unit)
Memory (RAM, FLASH, COMBO CHIP)
CPU:
A CPU is used in mobile phones as a central processing arithematic or controler. the cpu controls various functions in mobile phones like signal, display, sound converting(DSP), charging, power on, rf channel controler, rf tx power conroller, LEDs, vibrator, data processing, data storing etc. so we can say that if a cpu is damaged in any mobile phone it cannot be repaired unless the CPU is not replaced but this type of fault is not even seen to me ever either memory chips can be damaged. in brand Nokia CPU is named with two different words (MAD or UPP)
Memory:
there are two main types of memories used in mobile phones
* RAM (Random Access Memory)
The RAM is used in mobile phones to store user data in mobile phones. So these a days we can store pictures, messages, ringtones, applications, themes and other these type of things in mobile phones so CPU stores these types of data in the RAM of our mobile phones.
* Flash (eeprom, ROM etc)
The flash chip is used in mobile phones to hold mobile phone's operating system in it. so if the flash chip is damaged in mobile phones the phone cannot power on properly because all the instructions to start a mobile phones and its various tasks like call making , display etc are stored in the flash chip of mobile phones.
* Combo Chip
In smoe mobile phones there is a combined type of memory used which is called combo memory chips these types of memories work for both like RAM and Flash.
WHAT ARE DIODES AND HOW LEDs WORK ?
Diodes are components that allow current to flow in only one direction. They have a positive side (leg) and a negative side. When the voltage on the positive leg is higher than on the negative leg then current flows through the diode (the resistance is very low). When the voltage is lower on the positive leg than on the negative leg then the current does not flow (the resistance is very high). The negative leg of a diode is the one with the line closest to it. It is called the cathode. The postive end is called the anode.
Usually when current is flowing through a diode, the voltage on the positive leg is 0.65 volts higher than on the negative leg.
A diode allows electricity to flow in one direction only and blocks the flow in the opposite direction. They may be regarded as one-way valves and they are used in various circuits, usually as a form of protection. There are different types of diode but their basic functions are the same. These are noted below along with examples of diodes in use.
How Light Emitting Diodes Work
Light emittingdiodes,commonlycalled LEDs, are real unsung heroes in the electronics world. They do dozens of different jobs and are found in all kinds of devices. Among other things, they form the numbers on digital clocks, transmit information from remote controls, light up watches and tell you when your appliances are turned on. Collected together, they can form images on a jumbo television screen or illuminate a traffic light.
Basically, LEDs are just tiny light bulbs that fit easily into an electrical circuit. But unlike ordinary incandescent bulbs, they don't have a filament that will burn out, and they don't get especially hot. They are illuminated solely by the movement of electrons in a semiconductor material, and they last just as long as a standard transistor.
In this article, we'll examine the simple principles behind these ubiquitous blinkers, illuminating some cool principles of electricity and light in the process.
u can check detailed diagram & info of DIODS & LED ..
What is capacitance?
Now a capacitor (formerly condenser) is an Electronic Component which has the ability to hold a charge of electrons. Sounds like similar to a Battery ? , you are not very wrong !
The Capacitor is somewhat like a Battery , but has some very different properties also .
The number of electrons it can hold under a given electrical pressure (voltage) is called its capacitance or capacity. Two metallic plates separated by a non-conducting substance between them make a simple capacitor. Here is the symbol of a capacitor in a pretty basic circuit charged by a battery.
The time required for a capacitor to reach its charge is proportional to the capacitance value and the resistance value.
The time constant of a resistance - capacitance circuit is:
T = R X C
where T = time in seconds
where R = resistance in ohms
where C = capacitance in farads
The time in this formula is the time to acquire 63% of the voltage value of the source. It is also the discharge time if we were discharging the capacitance. Should the capacitance in the figure above be 4U7 (4.7 uF) and the resistance was 1M ohms (one meg-ohm or 1,000,000 ohms) then the time constant would be T = R X C = [1,000,000 X 0.000,0047] = 4.7 seconds. These properties are taken advantage of in crude non critical timing circuits.
Capacitors in series and parallel
Capacitors in parallel ADD together as C1 + C2 + C3 + ..... While capacitors in series REDUCE by:
1 / (1 / C1 + 1 / C2 + 1 / C3 + .....)
Consider three capacitors of 10, 22, and 47 uF respectively.
Added in parallel we get 10 + 22 + 47 = 79 uF. While in series we would get:
1 / (1 / 10 + 1 / 22 + 1 / 47) = 5.997 uF.
Note that the result is always LESS than the original lowest value.
Simplified calculations for Capacitors
We said above that parallel combinations simply add the values together. Series combinations are somewhat more difficult requiring 1 / (1 / C1 + 1 / C2 + 1 / C3 + ...).
This can be simplified somewhat to:
[(C1 X C2) / (C1 + C2)]
Try three or more in series. Do the first two then arrive at an intermediate value, then do the third with the intermediate value and so on.
A very important property of Capacitors
Capacitors will pass AC currents but not DC. Throughout electronic circuits this very important property is taken advantage of to pass ac or rf signals from one stage to another while blocking any DC component from the previous stage.
check images for detailed information
Know the Mobile Phone with Blocks
Have you experienced the fact that in a music listened from a very long distance, the sounds of drums are less audible than the sounds of other sharp instruments like guitar ?
YES
This is because the sound of a drum is a low frequency signal and low frequencies cannot travel long distances easily while the high frequencies like the sound of guitar or other string instruments can !
See how this is applied in the Radio, TV and Mobile Technology for yourself. After all the Mobile Phone is also a radio telephone ! The broad meaning of the word "Radio" is WIRELESS. The principle of a mobile phone can be compared with that of a Radio or a television system.
The Voice signal which is required to be sent to the other mobile phone is first converted from Analog to Digital type of Signal and is then mixed with a very high frequency signal in the mobile phone , this is called Modulation which means changing the signal by adding another frequency called carrier frequency to carry it. This is done to make it possible to be sent thro' Air to the nearest tower of the service operator. The basic principle being that the High Frequencies can travel longer distances easily. This was the transmitting part. (In Radio or Television systems, this is done at the Transmitting End which is the Radio or the TV Station.)
In the receiving part, the reverse (De-Modulation) is required to be done. The received signal from the service operator's tower is required to be Demodulated to remove the High Frequency Signal OR the carrier frequency signal from the received signal, so that only Digital Audio signal is left out. In Mobile Phones, this Digital Audio Signal is then converted to Analog Signal and after some amplification etc. is sent to the speaker to be heard by the user. (In Radio or Television systems, this is done at the Receiving End which is the Radio or the TV itself !)
Both this Transmitting (Tx) and Receiving (Rx) functions are required to be carried out in the Mobile Phone itself and is done by what can be called the RF section of the mobile phone.
some useful abbreviations
IMSI = International Mobile Subscriber Identity
MCC = Mobile country code
MNC = Mobile Network Code
MSIN = Mobile Subscriber Identification Number
PLMN = Public Land Mobile Network
MSC = Mobile Switching Centre
VLR = Visitor Location Register
HLR = Home Location Register
LAI = Location Area Identity
BSC = Base Station Controller
NSS = Network Subsystem
PAGCH = Paging Channel
AuC = AuthenticationCenter
SRES = signed response
BTS = Base Transceiver Station
MS = Mobile Station
TDMA = Time division multiple access
RLP = Radio Link Protocol
IWU = Inter Working Unit
FSK = Frequency Shift Keys
LAPD = link access procedure D-channel
SABM =Set Asynchronous Balanced Mode
UA = Use Air Interface
SCCP = Signalling Connection Control Part
GPS = Global Positioning System
COO = Cell Of Origin
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