2361101 MC Lab Manual

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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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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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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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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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Conclusion:

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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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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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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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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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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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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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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:


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:


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:

Documents

2361101 MC Lab Manual