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B. & B. INSTITUTE OF TECHNOLOGY, V.V.NAGAR
Department of Electronics and Communication Engineering
Term Work Submission for Subject
2361101
MOBILE COMMUNICATION
Name:
Enrolment No:
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B. & B. INSTITUTE OF TECHNOLOGY, V.V.NAGAR
Department of Electronics and Communication
Engineering
CERTIFICATEThis is to certify Mr. /Miss Of
class Diploma in E. & C. Engineering Enrolment No.
has satisfactorily completed his term work in subject 2361101- Mobile
Communication for the term ending in May 2013.
Date:
Submitted to: Signature
Mr. M. P. Shah
Mr. J. M. Patel
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INDEXNo Date Title Marks Signature
1 To study GSM system Architecture.
2 To study Mobile Station
3 To study User Interface Section of Mobile Handset.
4 To study the working of a SIM card in a GSM
handset.
5 To Study and analyze the vibrator in a GSM Handset.
6 To study and analyze the Buzzer in a GSM Handset.
7 To study and Analyze the LCD Module.
8To Study Of Direct Spread Spectrum Modulation
And
Demodulation Process
9To Study Of Code Division Multiple Access (DSSS)
Technique.
10To Study Of DSS S Mod ul at io n/Demodulation
Using Signal As an Input.
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Subject Code: 2361101 Subject Name: Mobile Communication
1 605 B. & B Institute Of Technology, V. V. Nagar 388120.
Practical: 1
Aim: To study GSM system Architecture.
Theory:
GSM frequencies:
The GSM system is a FDMA/TDMA system; each physical channel is characterized by
a carrier frequency & a time slot number. GSM system frequencies include two bands at 900
MHz commonly referred as GSM-900. For the primary band in GSM-900 system, 124 radio
carriers have been defined & assigned in two sub-bands of 25 MHz each in 890-915 MHz and
935-960 MHz ranges, with channel width of 200 KHz.
The GSM system comprises of MS, BTS, BSC, MSC and a set of registers to assist in mobility
management & security functions. All signaling between MSC & various registers as well as
between MSCs takes place using Signaling System 7(SS7) network.
Mobile Station (MS):
GSM mobile station is nothing but your handset or subscriber unit. At the time of
manufacturing a handset, an international mobile equipment identity (IMEI) is programmed
into the terminal. A subscriber identity Module (SIM) is required to activate & operate GSM
terminal. The SIM may be a removal unit that can be inserted by the user. Any GSM terminal
capable of receiving a detachable SIM card can become the users MS upon plugging into the
SIM card.
Base Station system (BSS):
The base station system comprises a base station controller (BSC) and one or more
subtending base transceiver stations (BTS). The BSS is responsible for all functions related to
the radio resource management.
Mobile switching center (MSC):
Its a local ISDN switch with additional capabilities to suppo rt mobility management
functions like location update, terminal registration and handoff.
MSC performs the following major functions:
Call set up, release Call routine Billing information Paging & altering Echo cancellation Registration etc.
GSM system Architecture:
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Subject Code: 2361101 Subject Name: Mobile Communication
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Home location registers (HLR):
It is a centralized database that has the permanent data fills about the mobile
subscribers in a large service area.
Visiting location register (VLR):
It represents a temporary data source and generally there is one VLR per MSC. This
register contains information about mobile subscribers who are currently in the service area &
which features are activated locally.
Authentication center (AC):
Generally associated with HLRM contains authentication parameters which are used in
initial location registration, location updates etc. it uses authentication & cipher key generation
algorithm A3 & A8 respectively.
Equipment identity registers (EIR):
It maintains information to authenticate terminal equipment so that fraud can be
identified & denied service.
Conclusion:
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Subject Code: 2361101 Subject Name: Mobile Communication
3 605 B. & B Institute Of Technology, V. V. Nagar 388120.
Practical: 2
Aim: To study Mobile Station
Theory:
For understanding the basic circuit of any mobile phone it can be divided in following
three sections:
A. Receiving sectionB. Transmitting sectionC. Base band control / UI section
RECEIVING SECTION
The receiver is direct conversion dual band linear receive. When any call is received in mobile
phone, the receiving signal comes at antenna first, which is of loop type then to pin no.4 ofantenna switch (Diplexer) through capacitorC593. This antenna switch makes function of
switching of receiving, transmitting, GSM and DCS frequency band. Switching signals is given
at its control pins from CPU for it, GSM-RX signal is made out from pin no. 14 of antenna
switch, which is given to p[in no. 7 of Z501 through capacitor C547 receiving signal passes
through band pass SAW filter (925-960 MHz) and is made out from pin 1.
Unwanted frequencies coming with GSM frequency bands are filtered by it and only required
band frequencies are passed further. Signal obtained from filter is given to LNA V501. Control
voltage is given to amplifier from HAGAR IC N500; amplification gain of LNA is controlled
by it. Because this control voltage controls gain of amplifier in automatic way hence
considered AGC. Output level of receiver remains stable by it.
Signal obtained from amplifier gain is given to band pass SAW filter Z500, signal obtained
from pin no.4 of V501 is given to pin no. 1 of Z500. Many unwanted frequencies are amplified
with the amplification receiving signals. It is very essential to separate these frequencies,
otherwise further these frequencies can become reason of noise. Band pas filter Z500 makes
this function; signal is made out from its one output pin no.7 and given to balancing
transformer T501. the balancing transformers make balancing from single ended receiving
signal. Signal is made balance by transformer T501 and comes at pin no. C9 and B9 of IC
N500, which are input pins of GSN-RX of N500 RF IC (HAGAR IC).
Mixing and demodulation (conversion to LF) operation of receiving signal is made in HAGAR
IC N500. Oscillation signal produced by VCL G500 is mixed in these signals for this
operation. This VCO G500 produces separate local oscillation signals in GSM and DCS
frequency band. VCO produces 3700-3840 MHz for GSM and 3610-3760 MHz for DCS 1800.
This signal is given to pin no. J2 and J5 of IC N500 through signal transformer T502, this
signal is amplified in IC. It is divided by four, for GSM (local oscillation signal of 935 to 960
MHz) is obtained and by 2 for DCS 1800 PLL and dividers are in HAGAR IC. GSM receiving
signal is mixed in this signal, after that it is filtered and given to demodulator and made I/Q
signal. This receiving is made out from pin no. G5 and G6 of IF IC N500 which can be viewed
at TP. (3) and TP. (4), which is given to audio signal COBBA IC N100.
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Subject Code: 2361101 Subject Name: Mobile Communication
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Demodulation is completed digital to analog conversion and audio frequency
amplification etc functions are made in it. It also makes functions as interface for completing
control functions of AFC, PAC and AGC etc. CPU D300 has full control of al functions of this
IC. Audio frequency signal is obtained in this IC through a PCM signal. This is amplified by
audio frequency amplifier. This audio frequency signal is obtained from pin no. D1 and D2 of
COBBA IC N100, it is given to speaker and sound is obtained.
TRANSMITTER SECTIONAt the time of transmitting microphone converts voice signal in to electric signal. This
signal is given to pin no. A3 & B3 of audio frequency processing IC N100. Transistor V101
connected from pin no. D6 of this IC is a mic power supply controller transistor. This transistor
provides control voltage to microphone signal given by microphone is at first amplified in
COBBA IC N100. After that it is made PCM code and digital signal is obtained, this signal is
sent to central processing unit D300 for voice coding and channel coding at that place data
stream is made which is sent back to audio processing IC N10 for GMSK modulation. In this
way A/D conversion, coding, encryption, channel coding and modulation etc functions are
made in COBBA IC and CPU. I/Q signals are serially transmitted from COBBA IC and givento transmitting modulation process in HAGAR IC N500 which can measure at TP (5) and (6).
VCO signals are mixed with TX-IQ signal in HAGAR IC N500. These local oscillation
signals are produced by local oscillation modules G-500, VCO module G500 generates local
oscillation signals of two different values. Oscillation signals 3520 to 3660 MHz in condition
of GSM 900 frequency band, which is divided by four; 890 to 915 MHz is obtained and mixed
with transmitting I, Q signal. Signal output level at this stage is 5dBm working system of VCO
module G500 is controlled by PLL circuit made in HAGAR IC N500.
After the modulation, Tx signal is converted to single ended by balance circuit (mutual
coupler) and after filtering in 2500 (880915 MHz) the signal is amplified by pre-amplifiercircuit and buffered out the final amplification is realized with dual band power amplifier. It
has a gain control, which is controlled with a power control loop in HAGAR IC. Power
amplifier produces a signal over 2W in GSM band. Gain control range is over 35 dBm.
Now this signal is given to Dual band directional coupler connected between PA and
Antenna Switch, Directional Coupler take a sample from the forward going power with certain
ratio. This detected voltage is compared in error amplifier in HAGAR IC to a Tx voltage
generated by COBBA IC. Then the signal is given to Antenna switch and the signal is
transmitted through antenna, the signal is of +33dBm approx.
BASE BAND CONTROL / UI SECTION
This section contain base band, CPU, CCONT IC, charging IC, UI circuit such as
Buzzer, Vibrator, LED and memories flash / SRAM.
It makes functions for completing all functions of this mobile, checking them and
controlling system. All system control, communication control, field strength testing, battery
voltage and standby charge, key board scanning and display control, power supply control,
power ON / OFF control, sleeping state control etc.
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Subject Code: 2361101 Subject Name: Mobile Communication
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Conclusion:
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Subject Code: 2361101 Subject Name: Mobile Communication
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Practical: 3
Aim: To study User Interface Section of Mobile Handset.
Apparatus: Mobile Phone Trainer (ST2132), DMM, connecting wires.
Theory:LED:
Light emitting diode, helps the user while performing function. The LED in mobile
phone is of SMD type instead of traditional LEDs due to much compactness required and
many mobile specifications. The LED circuit consists of CPU, UI IC and LED. The DC signal
is made out from pin C12 of CPU whenever handset is switched ON / OFF. Tx/Rx even a key
is pressed depending on the menu features. The signal obtained from the CPU is given to pin 7
& 15 of UI IC.
The UI IC gives output for keypad / Display LED separately but simultaneously. The
LEDs are connected in parallel. The anode of the LEDs is connected to VBAT. Varistors areconnected for protection. In addition resistors are connected for both (LED & keypad) LEDs
for intensity control. The time duration for the LED is software controlled often menu driven.
Circuit diagram:
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Observation:
Here, we will verify and analyze that intensity is Hardware Control.
Procedure for observation:
1.
Power ON the mobile Trainer.2. Vary the potentiometer to clock/anticlockwise.3. Observe the intensity changes in the Display Section LED.
ExperimentsTo study and analyze the DC level of LED.
Procedure (A):1. Power ON the Trainer2. Measure the Voltage at TP 41 & 42 with LED ON.
Note: we already know that for making LED glow at least we have to press any key.
Fault Insertion:Make the pin 3 of switched fault 5 to OFF POSITION.
DISPLAY LED NOT GLOWINGFault finding: constant voltage of 2V at TP 41.
Working principle:This is due to disconnection of path or faulty IC.
Procedure (B):1. Measure the Voltage at TP 42 with LED ON 1V (approx.).
Fault Insertion:Make the pin 4 of switched fault 5 to OFF POSITION.
PARTIAL LEDFault finding: constant voltage of 2V at TP 42.
Working principle:
This is due to breakage between the LEDs or LED faulty.
Conclusion:
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Subject Code: 2361101 Subject Name: Mobile Communication
8 605 B. & B Institute Of Technology, V. V. Nagar 388120.
Practical: 4
AIM: To study the working of a SIM card in a GSM handset.
Theory:
SIM is a short for Subscriber Identity Module. There are two different sizes used for GSMphones, one is the same size as a credit card and the other is about the size of a stamp. The two
SIM card sizes are standardized and are the same all over the GSM world. The advantage of
the small card is that it makes it possible for the manufacturer to build even smaller phones.
The SIM card is the part of the phone that contains the real phone. Its on the SIM card that all
personal facts are kept. The phone itself has no phone number. Its kept on the SIM card. In
other words you can borrow almost any other GSM phone and insert your own SIM card and
make calls as usual. There are many functions on the SIM cards like, for example; memory
space for names and phone numbers and SMSs (Short text messages). You can activate many
different services on the SIM cards.
The development of SIM cards is as fast as every thing else in the mobile phone business. TheSIM cards are becoming more and more sophisticated and more and more functions are being
added and improved. It contains some parameter of the user such as IMSI (International
Mobile Subscriber Identity). The SIM is also a database, its stores network state information
such as there current location, area identify (LAI). If the handset is turned off and back on
again it will take data of the SIM and search for the LAI it was in. This saves time by avoiding
having to search the whole list of frequencies that it normally would. The BSI line is connected
to SIM card and DETX line of CPU. When the power is switched on with SIM inserted the BSI
terminal is grounded by a resistor, all interface line raises to VSIM, DATA A, SIM RST,
SIMCLK. The battery identification line is used also for battery removal detection. The SIM
card is power down before the power is lost.
Description of SIM card circuit:
SIM card circuit is made mainly by CPU D300, Power IC N201, SIM card socket and V203.
As shown in fig. Among these, power IC N201 makes function as interface between CPU
D300 and SIM card socket. Power IC N201 gets all necessary SIM information from CPU
D300. SIM Clock is obtained from pin no. A12 of CPU, which is given to pin no D8 of power
IC N201.
SIM reset signal (SIM RST) is obtained from pin no. B11 of CPU which is given to pin E7 of
power IC N201. SIM I/O is made out from pin A11 of CPU and given to pin F6 of power IC
N201.SIM card detector signal is made out from pin K13 of CPU and given to pin B3 of powerIC N 201. SIM PWR signal obtained from pin D12 of CPU is made out and given to pin G6 of
IC N201. After processing in IC N201 SIM CLK TP (25), SIM RST, TP (23), V-SIM, TP (24),
SIM DATA is obtained at SIM socket from this IC. For detecting that SIM card is of 3V or 5V
this complete function is completed within one second of turning ON Power.
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Subject Code: 2361101 Subject Name: Mobile Communication
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Circuit diagram:--
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In this way, SIM card socket read the information of SIM card. After that this information is
given again to CPU through IC N201 for next processing and then after this is sent to base
station for registering. V203 is protector. Four diode are connected to it.
SIM CONNECTOR ELECTRICAL SPECIFICATION
PIN NAME PARAMETER MIN TYP MAX UNIT NOTES
1 SIMCLK Frequency
T rise/T Fall
3.25 25 MHz
ns
SIM clock Tp.25
2. SIMRST 5V Simcard 4 1 VSIM V SIM reset Tp. 24
3V SIMcard 2.8 1 VSIM
3. VSIM 5V SIMcard
3V SIMcard
4.8
2.8
5
3
5.2
3.2
V Supply voltage
Tp.23
4. GND GND 0 0 V GROUND
Tp.26
5. VCSim 5V SIMcard3V SIMcard
4.82.8
53
5.23.2
V Supply voltageTp.27
6. DATA 5V Vin/Vout
3V Vin/Vout
4
0
2.8
0
1
0
1
0
VSIM
0.5
VSIM
0.5
V Sim Data
Trise/Tfall max
1 s Tp.28
Note: Before performing the observation, fully charged the battery and keep the charging ON.
Observations:
1. Object:To study the SIM card detection.
Procedure:
Step 1: Switch ON the trainer without SIM card.
Step 2: Keep a watch on the LEDs CLK, VSIM, and Connected at the SIM card
terminal and connect the probe of the CRO to TP (25).
Step 3:The two LEDs will glow voltage will rise measured at TP (23) , TP (24), TP
(25). Sudden SIM card CLK rise and fall is observed.
Since SIM card is not present, it falls it happens in less than one second.
2.
Object:SIM detected:
Procedure:
Step 1: Insert the SIM card.
Step 2: Switch on the trainer.
Step 3: Observe the LEDs all two LEDs will glow RST, VSIM stays ON. Since SIM
card need power continuously and CLK goes within 6-8 sec. , after switching on the
trainer thats after registering to the network. A Rise can be observed when there is a
Tx/Rx of call or some function is accessed the clock of 3.2 MHz Approx.
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Observation Table:
Pin Name Measured Parameter TP No.
Experiments:
Insert the SIM card and switch on the Trainer.
1. Object:To study and measure the CLK of the SIM card.
Procedure:
1. Switch on the trainer with SIM.2. Connect the probe of the CRO to TP ( ).3. Observe the 3 MHz CLK.
Fault Insertion:
Make the Pin 4 of switched fault (1) to OFF.
INSERTSIM CARD appears on the screen.
Note: After fault insertion wait for 4 to 5 sec.
Again observe the CLK, it will not be there.
Working Principle:Since CLK is must for the card and the disconnection will break the path. So the result
is failure to detect the SIM.
Note: All the six terminals of the SIM card holds importance if any of the contact is
absent then card will not be accepted and shows INSERTSIM CARD. Usually this
occur when the SIM socket is bent / soiled or in loose contact with PCB or breakage of
path from the CCONT IC and also CPU else dry soldering of the IC.
2. Object:To study the SIM card detection:
Procedure:Switch on the trainer with SIM.
Fault Insertion:Make the pin to of switched fault 1 to off.
INSERTSIM CARD appears on the screen.
Working Principle:We already know that the SIM card is detected through loop formatted by the Status
pin of the battery, the disconnection of which fails the detection of SIM card.
Note: After fault insertion wait for 4-5 sec or press clear button C on the keypad.
Conclusion:
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Subject Code: 2361101 Subject Name: Mobile Communication
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Practical: 5
Aim: To Study and analyze the vibrator in a GSM Handset.
Theory:
The vibrator driving circuit is similar to that of ringer circuit. It is used for giving silent
information to user for incoming calls. This is also called Vibra Alert Device. When an
incoming call comes then this device gives its information to user by vibrating.
Circuit Description:
This Vibrator Driving circuit is mainly made by CPU IC N400 and Vibrator M400. Vibrator
Control Signal (VIBRA) is obtained from Pin G12 of CPU while there is an incoming
call/software activated and is given to pin no. 19 of N400 IC. This signal is amplified in IC
N400 and after amplification signal is made out from its pin no. 16 and given to vibrator M400
through R401. V BATT supply is given at other tapping of this vibrator. Operation of tuning
ON Vibrator is controlledby software. A vibra alerting device is similar to DC motor. In the
mobile phone it is used to generate a vibration signal for an incoming call. In the mobile phone,
the vibrator is lifted up from the PCB similar to the Buzzer. Vibrator pads are located on the
PCB.
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Subject Code: 2361101 Subject Name: Mobile Communication
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Interface CPU UI Switch
Signal Parameter Min. Typ Max Unit
VIBRA_PWM Vibra
Control Signal From
CPU
PWM low level, Logic
Low
0 0.2 0.5 V
PWM high level, Logic
high
2 2.5 2.9 V
Current CPU Output 2 mA
Vibra PWM Frequency 22k Hz
PWM Duty Cycle
(256 linear steps)
16 35 %
VIBRA_CNT Vibra
Control Signal in
UI - Switch
PWM low level, Logic
Low
0 0.5 V
PWM high level, Logic
high
2 2.8 2.85 V
Internal Pulldown
Resistor
60 100 180 kohms
Experiment
Note:a. Active the vibrator from the menu.
b. Vibrator doesnt circuit operate in charging ON mode.Object:
To study and measure the PWM signal of the Vibrator.
Procedure:
1. Give a Call to mobile phone trainer and keep on ringing or press Menu and scroll withthe help of up/down buttons until you find Tone select, then Ring Tone select
and scroll a step up or down.
2. And wait until you observe the vibrator rotating.3. Connect probe of the CRO to TP(38). PWM signal is observed. Since make/break
phenomena rise/fall of the signal is obtained and vibrator will rotate.
Fault Insertion:
Make the pin (2) of switched faults 5 to OFF position.
NO VIBRATION (Even after menu activation)Fault Finding: Observe the signal TP (38) it will not be there and hence no vibration.
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Subject Code: 2361101 Subject Name: Mobile Communication
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Working principle:
Since PWM signal is must for the Vibrator. T is due to problem in the CPU, UI IC or
disconnection of path else faulty Vibrator.
Conclusion:
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Subject Code: 2361101 Subject Name: Mobile Communication
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Practical: 6
Aim: To study and analyze the Buzzer in a GSM Handset.
Theory:
Alerting tone or melodies are generated by a buzzer, (Marketing Target 105dB.) Ringing
driving circuit is mainly made by CPU, Driving C N400 and Buzzer. Whenever there is an
incoming call or message else ringing is software activated. Ringing Driving Control signal
thats a PWM signal is obtained from pin no. D9 of Central Processing Unit (CPU) and given
to pin no.3 of IC N400. After amplification in this IC this signal is made out from pin no.6 and
reaches at one tapping of buzzer. Second tapping of buzzer is connected with VBATT ring
sound is obtained from buzzer. In tables shows the relevant specifications
Interface CPU and UI Switch
Signal Parameter Min Typ Max Unit
BUZZ_PWM Buzzer
Control Signal From
The CPU
PWM low level, logic low 0 0.2 0.5 V
PWM high level, logic high 2 2.5 2.9 V
Current CPU Output 2 mA
Buzzer PWM Frequency 100 1000 Hz
PWM Duty Cycle
(256 Linear Steps)
0 100 %
BUZZ_CNT Buzzer
Control Signal in the UI-
Switch
PWM low level, logic low 0 0.5 V
PWM high level, logic high 2 2.8 2.85 VInternal Pulldown Resistor 60 100 180 Kohms
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Interface Ui IC and Buzer
Signal Parameter Min. Typ Max Unit
VBAT Supply Voltage 3 3.6 5.2 N
GND Ground 0 V
BUZZER Buzzer AverageCurrent
90 mA
Experiment:
Objective: To study and measure the PWM signal of the Buzzer.
Procedure:
1. Give a Call to trainer by making an incoming call and keep on ringing same as vibrator.2. Connect probe of the CRO to TP (39). PWM signal is observed. Since make/break
phenomena rise/fall of the signal is obtained and ring is heard.
Fault Insertion:
Make the pin (1) of switched faults 5 to OFF position
NO RING SOUNDFault Finding: Observe the signal, it will not be there.
Working principle:
Since PWM signal is must for the Buzzer. It is due to problem in the CPU, UI IC or
disconnection of path else faulty buzzer.
Conclusion:
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Practical: 7
Aim: To study and Analyze the LCD Module.
LCD module:
One liquid crystal display (LCD) module is used in display section of mobile phone. This LCD
module is made on basis of Chip-ON Glass (COG) technology. The display circuit includes
LCD modules GD 47 (84 x 48 pixels) and 2 capacitors. The connection method for the chip on
glass is ACF, Adhesive Conductive Film. The LCD module is connected to the PCB with
spring contacts. Capacitors are placed on PCB.
The display driver includes HW-reset, voltage triple or quadruple which depends on
temperature, temperature compensating circuit and low power control. Driver includes 84x48
bit RAM memory that is used when some elements are created on display. Elements are
created by software. Driver doesnt include CG-ROM. When any button s pressed in Mobile
Phone then at first its information comes in CPU. CPU contains data from memory accordingto that pressed button and gives to LCD module and that data displays at screen.
Pin Description of LCD module:
Pin no. 1 (RES): This is input pin. LCD reset signal (LCD RSTX) is given at this pin
from
pin no. A3 of CPU (D300).
Pin no. 2 (V Out): This is filter pin of LCD module. At this pin two capacitors areconnected
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in parallel. And voltage tripler output is available at this Pin. This
voltage
can be check at TP (33)
Pin no. 3 (GND): This pin is made ground.
Pin no. 4 (SCE): This is pin of LCD enable input. LCD enable signal (LCD ENX) is
given
at this pin from this pin D1 of CPU (D300)
Pin no. 5 (D/C): This pin s display control pin and is connected with the pin D3 (ROW 5
LCD CD) of CPU
Pin no. 6 [SD IN]: This is Screen Data input of LCD module that data is given at this pin
from pin B10 of CPU which has to display at screen.
Pin no. 7 [SCLK]: Clock Pulse (SCLK) from pin A10 of CPU (D300) is given at this pin.
Pin no. 8 [VDD]: This is positive supply pin of LCD module. VBB (2.8V) supply obtained
from pin no. C6 of power supply module N201 is given at this pin.
LCD Module Interface
Pin Line Signal Parameter Min Typical/
Nominal
Maximum
1-RES LCDRSTX Reset 0 0.3xVBB
0.7xVBB VBB
2-VOUT VOUT DC/DC VoltageConverter output
6 - 9
3-GND GND Ground 0
4-SCE LCDCSX Chip Select Input 0 0.3xVBB
0.7xVBB VBB
5-D/C LCDCDX
(ROW5)
Control/display data
Flag input
0 0.3xVBB
0.7xVBB VBB
6-SDIN SDA Serial data input 0 0.3xVBB
0.7xVBB VBB
7-SCLK SCLK Serial Clock input 0 4Mhz0 VBB
8-VDD VBB Supply Voltage 2.7 2.8 3.3V
240A
Note: Switch OFF the charging for better performance.
LCD Module Experiment:
Note: Before performing the observation, fully charged the battery and keep the charging ON.
1) Objective: To study and measure the reset pin in LCD Module
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We already know that Pin 1 is the reset Pin Voltage available at this pin is 2.8V can be
check at TP (32).
Procedure:
Power ON the trainer with or without SIM.
FAULT INSERTION
Make the pin 1 & 2 of switched fault (3) OFF.
Note: It make take within 1 min3 min for fault
NO DISPLAY
Measure the voltage at TP (32) and TP (33) it will be 0V.
Working principle:
This fault occurs usually due to lose contact between the PCB and the Display or spring
connector of the display. Else faulty display.
Note: LCD display is that section in mobile phone which becomes defective more then all.
When any fault is observed in display then at first loose contact should be check and spring
contact of the LCD for bent or soiled and then supply of display module should be checked.
After that it should be observed that its all indicated data are correct and all paths should be
checked or not so that it can be identified that fault is of man board or screen display.
2) Object:
To verify and study the importance of the voltage Tripler in the LCD Module.
We already know that Pin 2 is the Tripler output hence voltage at TP (33) is 6V 8V (approx).
FAULT INSERTION
Make the pin (2) of Switched fault (3) OFF.
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DARK BACKGROUND AND BLURRING IMAGE
By making the switched fault we have disconnected the pin from grounding. Measure the
voltage at TP (33) it will 6V8V only since it is generated in the display module internally
and hence voltage Tripler.
Working principle:
This usually happens when the Tripler output is not grounded due to break. The picture isvisible by pixels when voltage is given. The Tripler output which was disconnected from the
ground distributes the power in the LCD module and the result is dark screen.
3) Object:
To verify and measure the control pin of the LCD Module.
FAULT INSERTION
We already know that pin 5 is a Display control Pin voltage available at this pin is 2.8V can be
test at TP (34).
Make the pin (3) of switched fault (3) OFF.
MISPLACED DISPLAY
Measure the voltage at TP (34) it will be 0V.
Working principle:
Since Pin 5 is control pin disconnection of path from CPU, make it to loose control.
4) Object:
To study the clock pin of a LCD Module.
We already know that clock signal s measured at TP (36).
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FAULT INSERTION
Make the pin (4) of switched fault (3) OFF.
We already know that pin 7 is a clock pin
DISPLAY HANGED
Working principle:
Since clock is the heart beat without which the LCD fail to work. It s due to disconnection of
path or etc.
Conclusion:
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Practical: 8
AIM: To Study of Direct Spread Spectrum Modulation and Demodulation Process.
REQUIRMENT:
ST2115, CDMA Trainer Board.
CRO
Patch Cords.
THEORY:
Direct Sequence Spread Spectrum:
CDMA is a Direct Sequence Spread Spectrum system. The CDMA system works directly on
64 kbit/sec digital signals. These signals can be digitized voice, ISDN channels, modem data,
etc.
Figure 1 shows a simplified Direct Sequence Spread Spectrum system. For clarity, the figure
shows one channel operating in one direction only.
Signal transmission consists of the following steps:
1. A pseudo-random code is generated, different for each channel and each successive
connection.
2. The Information data modulates the pseudo-random code (the Information data is spread).
3. The resulting signal modulates a carrier.
4. The modulated carrier is amplified and broadcast.
Signal reception consists of the following steps:
1. The carrier is received and amplified.
2. The received signal is mixed with a local carrier to recover the spread digital signal.
3. A pseudo-random code is generated, matching the anticipated signal.
4. The receiver acquires the received code and phase locks its own code to it.
5. the received signal is correlated with the generated code, extracting the Information data.
PROCEDURE:
1) Switch data switches to 1 or 0 as per your choice of binary data pattern.2) Connect any two of the four taps viz. A, B, C or D to the input of EX-OR gate of PN
sequence generator. Connect 240 KHZ clock signal on board to the clock input of thePN sequence generator.
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3) Now switch ON the power supply and observe the output of binary data generator andPN sequence generator. since the data generator frequency used here is 30 KHZ and
that of PN sequence generator is 240 KHZ, and hence there are 8 PN sequence bits per
data bits for spreading the binary signal.
4) Change the positions of taps for feedback in the PN sequence generator block to obtaindeferent pattern of the PN sequence. Switch OFF and then ON the power supply toreload the changes, if changes do not appear in the output on changing the tap positions.
5) Connect output of binary data generator to one of the input of direct sequence spreadspectrum generator input.
6) Connect output of PN sequence generator to the other input of DSSS EX-OR gate.7) Now turn ON power supply and observe the output of DSSS generator block. This is
our DSSS signal.
8) Now Connect output of this DSSS block to the one of the input of EX-OR gate of datarecovery block. Connect the same output of PN sequence generator, which we have
taken for spreading to the other input of this recovery gate for same output pin where
from the PN sequence is taken for spreading the signal. This is because of the fact that
there is complete synchronization between the spreaded signal and PN sequence. Inother words there is not any significant delay involved in spreading process.
9) Observe the output of this data recovery block. This is recovered output without almostany error.
10)Now change the taps positions of shift registers (A, B, C or D) to get a new PNsequence and repeat the above process again. Thus you will observe that with each
different sequence we are quit able to recover the original data. Also with different PN
sequences, the modulated data looks different i.e. we can recover the data if and only if
we are using the same PN sequence for both modulation and demodulation. This
multiple access technique is known as code division multiple access(CDMA)technique.
CONCUSION:
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Practical: 9
AIM: To Study Of Code Division Multiple Access (DSSS) Technique.
REQUIRMENT:
ST2115, CDMA Trainer Board.
CRO
Patch Cords.
THEORY:
In a cellular wireless communication network, the coverage is divided into cells, each having a
base station (BS) to transmit and receive signals with mobile stations (MS's) within the cell.
The signals are then relayed via a mobile switching center to the backhaul switching network,
which handles call processing and billing etc. When a mobile station traverses a cell boundary,
it is required that the userbe connected to another base station for better link quality. The process of switching base
stations is called handoff [1][2] . For terrestrial wireless transmission in cellular andPCS
communication services, the mobile radio channel may suffer from impairments such as
multiple-access interference, multipath fading, shadowing, and distance path loss [1]. Multiple
access interference and multipath fading can be effectively mitigated by advanced signal
processing techniques such as multi-user detection [3], diversity combining [4], and error
control techniques [5]. The handoff process, on the other hand, mainly targets the shadowing
effect and distance attenuation by intelligent utilization of base station diversity. CDMA is a
widely adopted multiple access technique in the current and next-generation mobile cellular
networks. Its universal frequency reuse plan makes it possible for a
Mobile user to receive and send the same call simultaneously from and to more than one
different base station. Since its market introduction in early 90s, multiple accesses by CDMA
have been considered to offer the best combination of system quality and capacity. CDMA
implementation of handoff is called soft handoff, where the handoff transfer is achieved
gradually and allows the handoff mobile stations to connect to multiple base stations during
handoff. The cell receiving strongest signal strength handles signal detection. This feature,
accompanied with
proper power control, provides more reliable handoff and more than doubles capacity of a
heavily loaded system [1]. The fact that CDMA has become the de facto technology for the
third generation wireless systems motivates the development of better handoff schemes.
Different from the signal detection procedure in soft handoff, we propose a fusion handoffapproach in which the information from all the base stations in the active handoff cell set is
combined
to minimize the detection error using data fusion rules. Instead of communicating detection
decisions, each base station only calculates and transmits the sufficient statistic to a switching
center, which performs the signal detection using appropriate fusion rules. Performance gain is
achieved by optimal combining of the information diversity distributed among different base
stations, at the expense of increased Complexity and computational load at the switching
center. The complexity increase can be justified if there is a significant improvement in the
overall performance.
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PROCEDURE:
1) Switch data switches to 1 or 0 as per your choice of binary data pattern.2) Connect any two of the four taps viz. A,B,C or D to the input of EX-OR gate of PN
sequence generator. Connect 240 KHZ clock signal on board to the clock input of the
PN sequence generator.3) Now switch ON the power supply and observe the output of binary data generator andPN sequence generator. since the data generator frequency used here is 30 KHZ and
that of PN sequence generator is 240 KHZ, and hence there are 8 PN sequence bits per
data bits for spreading the binary signal.
4) There are two outputs of PN sequence generator shown on the board. one of the outputis for spreading the binary data signal and the other one is for dispreading the coded
signal to recover back the original data.
5) Connect binary data and PN sequence output to the EX-OR gate of DSSS block.Connect the output of DSSS block to the input of unipolar to bipolar converter. Take
the output of this converter to the input of BPSK modulator. Connect sinusoidal carrier
from carrier generator to the input of BPSK modulator. This completes the modulatorconnections.
6) Now connect output of BPSK modulator to the input of BPSK demodulator block.Connect output of this block to the comparator input. Here we would receive original
chipped data.
7) Connect the recovered chipped data (output of comparator) to one the inputs of datarecovery block. Connect PN sequence for dispreading output of PN sequence
generator block to the other input of data recovery gate.
8) Now turn power supply ON. Observe data and PN sequence at their respective outputpins. Press load button if data is not appearing.
9) Observe the output of DSSS block. This is called chipped data.10)Observe the output of BPSK modulator. This is RF modulated chipped data.11)Observe the output of comparator and data recovery block. Adjust phase of recovered
carrier in BPSK modulator section and bias of comparator until you see a complete
replica of original binary data.
12)Change data pattern and repeat the whole procedure with this new data. Again adjustphase and bias of comparator so as to recover the data completely.
13)Change chip (PN sequence) pattern and the results.CONCUSION:
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Practical: 10
AIM: To Study Of DSSS Modulation/Demodulation Using Signal As An Input.
REQUIRMENT:
ST2115, CDMA Trainer Board.
CRO and cords
Patch Cords.
THEORY:
MODULATION
The resultant coded signal next modulates an RF carrier for transmission using Quadrature
Phase Shift Keying (QPSK). QPSK uses four different states to encode each symbol. The four
states are phase shifts of the carrier spaced 90_ apart. By convention, the phase shifts are 45,135, 225, and 315 degrees. Since there are four possible states used to encode binary
information, each state represents two bits. This two bit word is called a symbol. Figure 3
shows in general how QPSK works. First, well discuss Complex Modulation in general,
applying it to a single channel with no PN-coding (that is, well show how Complex
Modulation would work directly on the symbols). Then well discuss how we apply it to a
multi-channel, PN-coded, system.
Working with Complex Data
In order to make full use of the efficiency of Digital Signal Processing, the conversion of the
Information data into complex symbols occurs before the modulation. The system generates
complex PN codes made up of 2 independent components, PNi +jPNq. To spread the
Information data the system performs complex multiplication between the complex PN codes
and the complex data.
Summing Many Channels Together
Many channels are added together and transmitted simultaneously. This addition happens
digitally at the chip rate. Remember, there are millions of chips in each symbol. For clarity,
lets say each chip is represented by an 8 bit word (its slightly more complicated than that, but
those details are beyond the scope of this discussion).
At the Symbol Rate
Since the PN-code has the statistical properties of random noise, it averages to zero over long
periods of time (such as the symbol period). Therefore, fluctuations in I and Q, and hence the
phase modulation of the carrier, that occur at the chip frequency, average to zero. Over the
symbol period the modulation averages to one of the four states of QPSK, which determine
what the symbol is.
The symbol only sees the QPSK, and obeys all the statistical properties of QPSK transmission,
including Bit Error Rate.
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DEMODULATION
The receiver performs the following steps to extract the Information:
Demodulation
Code acquisition and lock Correlation of code with signal Decoding of Information data
Demodulation
The receiver generates two reference waves, a Cosine wave and a Sine wave. Separately
mixing each with the received carrier, the receiver extracts I(t) and Q(t). Analog to Digital
converters restore the 8-bit words representing the I and Q chips.
Code Acquisition and Lock
The receiver, as described earlier, generates its own complex PN code that matches the code
generated by the transmitter. However, the local code must be phase-locked to the encoded
data. The RCS and FSU each have different ways of acquiring and locking onto the others
transmitted code. Each method will be covered in more detail in later sections.
Correlation and Data Dispreading
Once the PN code is phase-locked to the pilot, the received signal is sent to a correlator that
multiplies it with the complex PN code, extracting the I and Q data meant for that receiver. The
receiver reconstructs the Information data from the I and Q data.
PROCEDURE:1) Make the connection as shown in above figure.2) Observe the output of audio signal block.3) Observe the output of DSSS block4) Observe the output of BPSK modulator.5) Observe the output of data recovery block. Adjust phase of recovered carrier and bias
of comparator until you see an extra replica of pulse width modulated data at the output
of this recovery block.
6) Observe the output of low pass filter section and compare it with the input audio signal.Change gain of the amplifier to remove any nonlinearity errors. if still output is not
proper then change amplitude of input audio signal and adjust the gain of the output
amplifier to remove distortions.
CONCLUSION:
Recommended