FINAL YEAR PROJECT REPORT

MOHAMMAD ALI JINNAH UNIVERSITY ISLAMABAD

Hardware Implementation of CDMA Based Transmitter and Receiver

GROUP MEMBERS:

Muhammad Ikram Sarwar EE053050

Asim iqbal BT043002

Saqib Rehman EE053066

PROJECT SUPERVISOR:

Dr.NOOR KHAN

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2009MOHAMMAD ALI JINNAH

UNIVERSITY

Acknowledgement

First of all we are thankful to Almighty Allah who gave us opportunity to study and courage to complete our project. We would like to thank our project supervisor Sir Dr Noor Khan for his constant guidance, enthusiasm and support throughout this project. We are also thankful to our parents who prayed for us, and without their support and prayers we would be unable to complete our project.

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DECLARATION

We declare that this is our own work and has not been submitted in any form for another degree or diploma at any university or other institution for tertiary education. We have given the reference for the data we took from other books and from the internet.

Muhammad Ikram Sarwar Asim Iqbal Saqib Rehman EE053050 BT043002 EE053066

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CERTIFICATE OF APPROVAL

This is to certify that the project presented entitled “Hardware Implementation Of CDMA based

transmitter and receiver” was conducted by Mr. Muhammad Ikram Sarwar, Mr. Asim Iqbal and

Mr. Saqib Rehman under the supervision of Dr. Noor Khan.

Dr. Noor Khan Dr.Fazul-ur-Rehman

Project Advisor, Head of Department,

Dept. of Electronic Engineering, Electronic Engineering,

Faculty of Engineering and Applied Sciences. Faculty of Engineering and Applied Sciences.

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ABSTRACT

Code division multiple access (CDMA) is the technique being most seriously

considered for third generation wireless system. Code Division Multiple

Access is a method for transmitting simultaneous digital signals over a

shared portion of the spectrum. The CDMA technology can be implemented

by spreading the spectrum which can be done in the following two ways

Direct Sequence Spread Spectrum - DSSS

CDMA

Frequency Hopping - FH CDMA

We are using DS CDMA in our project.

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TABLE OF CONTENT Chapter 1 08

1.1 Overview 08

1.2 Purpose of Project 08

1.3 Expected Outcomes 08

1.4 Applications 08

1.5 Organization of report 08

Chapter 2 10

2.1 Overview 10

2.2 System model 10

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2.2.1 Hardware used 11

2.2.2 PN code 13

2.2.3Serial port interface 13

2.2.4 Working of serial port 14

2.2.5 Modulation 16

2.2.5.1 FSK modulation 17

2.2.5.2 FSK demodulation 17

2.2.6 MAX 232 circuit 17

2.2.7Basic of antennas 18

2.2.7.1 Antennas 18

Chapter 3 19

3.1 Overview 19

3.2 Patch Antenna Design 19

3.3 Amplifier 20

Chapter 4 21

4.1 Overview 21

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4.2 Results and Recommendation 21

References 21

Appendix 22

CHAPTER 18

INTRODUCTION

1.1 Overview

In this project we have one transmitter and two receivers. The transmitter will send voice and text over the same frequency using DS CDMA technique while one receiver will receive text and other receiver will receive voice on the basis of PN code. The aim of this project is learning the concepts and techniques used in wireless communication.

1.2 Purpose of Project

The purpose of the project is to implement technique used in wireless communication which is CDMA.This technology can be implemented using DS CDMA or FH CDMA however we are using DS CDMA technique in our project.

1.3 Expected Outcomes

We will transmit voice and text from the one transmitter; we have two receivers and one receiver will receive text while the other will receive voice on the basis of PN code using DS CDMA technique.

1.4 Applications

DS CDMA has many applications for example it is used for security purpose because it is difficult to interrupt and jam. It has high bandwidth and multiple signals can be transmitted at the same frequency.

1.5 Organization of Report

In the upcoming chapter we have organized our report; in such a way that chapter 2 contains the description of the project.

In chapter 3 we have shown a brief and descriptive knowledge about designing and analysis of the hardware we used, i.e. why we chose the patch antenna and how its designing occurs, then its analysis. Further in later section of the chapter we have shown the different parts/hardware working and implementation on the Vero board.

In chapter 4 we have given the result and some recommendation about the project, so that one can easily understand the calculated and measured value.

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The results are also discussed in a theory form to have a clear understanding of the end result. Then at the end of the project appendix is given, in which datasheet of various Integrated Circuits and their functionality are described to have crystal clear understanding of the project. One can easily understand the working and implementation of the electronic parts.

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CHAPTER 2

SYSTEM MODEL

2.1 Overview

As already mentioned that we have one transmitter and two receivers from

the transmitter we will transmit voice and text signal. One receiver will

receive voice signal and other receiver will receive text. As there are number

of techniques used for the digital transmission namely PSK,FSK,QPSK,but

the most useful and easy to analyze in undergrad level is the FSK .In DS

CDMA PN code are used and we have generated the PN code using

microcontroller 89C51 in our project. A hyper-terminal is linked to the

transmitting elements in order to transmit and to receiver. Then we will show

how data was transmitted using FSK modulation scheme, and how the data

was demodulated on the receiver side. We are using patch antennas to

transmit signal.

2.2 System model

Our model of the project consists of one transmitter and two receivers.

Transmitter side consists of DB9. MAX 232, FSK Modulator ic XR2206, PN

code generator using microcontroller 89C51, Analog to digital converter The

block diagram of our project is shown below:-

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S

Figure-2.1

The brief description of above model is as follows:-

2.2.1 Hardware used

We have done our project on Vero board on which we have designed our

transmitter while our receiver is also on Vero board.

Further major elements which we used in our project are listed as below:-

Serial port cable DB-9.

PN code using micro controller

FSK Integrated circuit XR-2206.

Analog to digital converter

Exclusive or gate

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Max232 89C51 XOR

PN CODE

ADDER

MIC A2D CONVERTOR

XOR

PN CODE

XR2206

AMPLIFIER

DB9

VOICE

FSK demodulator Integrated circuit XR-2211.

MAX-232 Integrated circuit for serial port interface.

Patch antennas.

In the next section we have explained the each hardware in detail so

to have a clear understanding how the above mentioned hardware is

used and how it is configure so that we were able to transmit and

receive signal on the basis of PN code using DS CDMA.

Figure- 2.2

Figure- 2.3

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Demodulator

ADC XOR signal

Demodulator

ADC XOR signal

PN CODE

PN CODE

2.2.2 PN CODE

In DS CDMA technique different PN codes are used to transmit and receive

the signal. We Exclusive OR the signal with the PN code and the same PN

code is used on the receiver side to receive the signal. There are different

types of PN codes however we are using maximal sequence or m sequence

code. To generate the code we are using 89C51 microcontroller and we have

programmed it in assembly language [1].We have generated two code for

transmitter side and two code for receiver side. The transmitter and receiver

code should match for proper functioning.

2.2.3 Serial Port Interface

With the text signal serial ports is used to communicate between the

computer and the other hardware. The Integrated circuit IC which we are

using in this project is RS-232 with MAX-232 .RS-232 is a standard and

used for serial communications and used in many data acquisition systems.

And also it is the mostly commonly used serial communication and it is the

only way to support the communication to only one device connected to the

bus at a time and it only supports transmission distances up to 50 feet. It has

9 pin connectors that relay information, incoming or outgoing, one byte at a

time. Each byte is broken up into a series of eight bits, hence the term serial

port.

Serial ports are one of the oldest types of interface standards. Before internal

modems became common place, external modems were connected to

computers via serial ports, also known as communication or "COM" ports

[2]. Computer mouse and even keyboards also used serial ports.DB-9-pin

connector is mostly used. So there are DB-9 and DB-25 cables available.

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Serial ports differ from 25-pin parallel ports in that the parallel ports transmit

one byte at a time by using eight parallel wires that each carry one bit. With

data traveling in parallel, the transfer rate was greater. A parallel port could

support rates up to 100 kilobytes per second, while serial ports only

supported 115kbps.

At the consumer level, the USB interface has effectively replaced the serial

port. “Many manufacturers of personal computers and laptops consider serial

to be a legacy port and no longer include the serial interface. USB to serial

adapters are available to use with USB-only systems”[3]

2.2.4 Working of serial port

Devices which use serial cables for their communication are split into two

categories. These are Data Communications Equipment

Data Communications Equipment is a device such as your modem, TA

adapter, plotter etc while Data Terminal Equipment is Computer or

Terminal.

The electrical specifications of the serial port are contained in the

Electronics Industry Association RS-232C standard. It states many

parameters such as:–

The A space logic 0 is between the +3 and +25 volts and while the A

mark logic 1 will be between the -3 and -25 Volts and the while the

region of +3 and -3 is undefined and because it is not unknown. And the

open circuit voltage should never exceed 25 volts and it is the maximum

voltage and should not exceed then that and while the short circuit

current should not exceed 500 mA and while the driver should handle

this without any damage.

In the RS-232 standard and it specifies a maximum baud rate of 20 Kbps

which is rather slow by today's standards because now a days the baud

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rate is increased. A new standard, RS-232D has been recently released.

The shape of the DB-9 pin connector is shown below.

Figure 2.4 DB-9 serial port

Although all the pins have their own perspectives, but for the operation to know

that what pin actually do is given is full detail in the table 2.1 which is on the

next page.

D-Type-9 Pin No. Abbreviation Full Name

Pin 3 TXD Transmit Data

Pin 2 RXD Receive Data

Pin 7 RTS Request To Send

Pin 8 CTS Clear To Send

Pin 6 DSR Data Set Ready

Pin 5 GND Signal Ground

Pin 1 CD Carrier Detect

Pin 4 DTR Data Terminal Ready

Pin 9 RI Ring Indicator

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Table 2.1 FUNCTIONING OF DB-9 PINS

In DB-9 configuration, there are three pins of our interest are listed below:

Pin 2- RD: RECIEVER DATA.

Pin 3-TD: TRANSMIT DATA.

Pin 5- SG: SIGNAL OR SYSTEM GROUND.

Using the null modem cable the PC is interfaced with the transceiver circuit as the

pc has male connector so the female connector was used on the both ends of the

wire. Only three pins of the null modem cable were used one to transmit, other to

receive and one for the ground.

2.2.5 MODULATION

We are using FSK modulation to transmit the signal at the transmitter side and we

are using XR2206 modulator IC for this purpose. The modulation is we used is for

to encode the signal and to produce the next signal and the properties are matched to

the characteristic of the medium or the path and the path with which the signal is

transmitted is called modulation. [4].There are many different modulation

techniques which we are using and there are analog and as well as digital

modulation. In digital modulation an analog carries signal is modulated by a digital

bit stream and when it is modulated and digital bit stream technique is used for this

purpose. In digital modulation method we are doing digital to analog conversion

and in the demodulation we are doing analog to digital conversion..

In digital signals sometime distortion occurs due to high frequency component and

it is easily attenuated when the transmission distance is higher and when the

transmission distance is smaller and then attenuation doesn’t occurs usually. And if

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we want to improve the digital modulation and we are using Frequency Shift

Keying (FSK).

Mainly there are three common and widely used methods for digital transmission

which are given as below:

Amplitude modulation which leads to Amplitude Shift Keying

(ASK)

Phase modulation which leads to Phase Shift Keying (PSK)

Frequency modulation which leads to Frequency Shift Keying

(FSK)

Digital information can be transmitted by when we modulate the frequency of the

carrier and when the frequency of the carrier is modulated and then it will be

transmitted. In binary signal we are using two frequency which are f1 and f2 and we

are using to the transmit the information by using the two frequency[5]

While in the demodulation side 0 and 1 are generated for the two different

frequencies. The more detail of the FSK modulator and Demodulator is explained in

the next section.

2.2.5.1 FSK MODULATION

In FSK modulation, two frequencies are shifted and varied against the input signal

and the in this the signal changes because the carries come in the signal. One

frequency say for f1 corresponds to digital input high and say for other frequency f2

corresponds to digital input low. Also the FSK modulator is used to convert the

digital signal into the analog signal having two different frequencies corresponding

to the input signal levels.

In our project we have used the FSK modulation scheme for the digital transmission

of the data and which transmit the signal through antenna and we have to remember

one thing which is that antenna is an analog transmission. The digital data is to

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ensure that we able to know that transmission occurs and which was confirm by

hyper terminal point.

FSK modulator can be implemented by using LM566 but the limit of the frequency

is in hertz and for out project we are using XR2206 and while the limit of this IC is

in mega hertz and so that we are using high frequency modulation .To knows the

detail expression and diagram of the Integrated Circuit see appendix.

2.2.5.2 FSK DEMODULATION

As in the previous section it is mentioned that the digital signal is converted into

FSK signal by FSK modulator for long distance communication. At the receiver

side an FSK DEMODULATOR is required to recover the original signal from the

received FSK signal and it removes the carries from the modulated signal and then

we get the original signal.

For the FSK Demodulator we can also choose the circuitry of LM-565 but same the

problem with the frequency so we used an easily available and affordable Integrated

Circuit named as XR-2211.The detail expression and diagram for the circuit which

we use in our project can be seen in appendix.

2.2.6 MAX-232 Integrated circuit for serial port interface

Computers can communicate with other devices through its serial and parallel port.

And so knowledge about them and voltage conversion should be required. It is

basically use for level conversion. The Integrated circuit actually converts signals

from serial port (RS-232) into levels which are compatible to digital logic circuits.

The Max-232 typically converts the RX,TX,CTS,and RTS signals.[6].The basic

configuration of the Max-232 is shown in the following diagram.

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Figure-2.5

2.2.7 Basic of antennas

An antenna is a device that transmits and/or receives electromagnetic waves.

Electromagnetic waves are often referred to as radio waves.

2.2.7.1 Antennas

Antennas are widely used in the communication field. As the world of antenna

progress different types of antenna come into being with some different and

complex properties or characteristics. Antennas are the most important part of the

communication field if one talking about communication especially wireless

communication without antenna has jobless meaning.

There are number of antennas and decide what type of antenna is to be used is

selected by its characteristic. In our project our main concern is to transmit the

signal in the line of sight so we require directive antenna so that’s why we are using

directional antennas which is patch antenna

Since all the types mentioned above are different from each other regarding their

characteristic perspective i.e. some of them are omni directional and some are

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directional. While the patch antenna is highly directive antenna from above

mentioned types. Further a patch antenna can be divided into different types

regarding its shape i.e. rectangular patch, square patch, circular patch, triangular

patch.

In our project me make use of patch antenna because they are highly directive

antenna and the type which we used is a square patch and we will explain it in the

next chapter.

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CHAPTER 3

ANALYSIS AND DESIGN

3.1 OVERVIEW

Some of the hardware used in our project required designing and specification as there are different electronic components can be used differently as per required use. So in this chapter we have explained in brief the analysis and design of the different types of the model which we have used in our project. The hardware as we mentioned in chapter 2 will now be explained in detail. For example the designing of the antenna (patch antenna), the power amplifiers and its configuration, the designing of monopole antenna is now explained in the following chapter’s section. So that we have a clear understanding about the antennas and different electronic components.

3.2 PATCH ANTENNAS DESIGN

As discussed in chapter 2 that antennas are the most important part of the communication field. There are different types of antennas having different characteristic and one using the antenna type is a difficult part to select what type should be used. As all the types exhibits some major and common characteristic like directivity, radiation pattern etc but the directivity and radiation pattern are different for different antennas.

In our project we have used the Patch Antenna to transmit and receive DS CDMA signal. The Patch antennas are the highly directive antennas and required a great attention while designing them. Different parameters such as width, length, height of substrate (as patch antenna requires a substrate), value of dielectric constant.

There are many shapes of the patch antenna such as square, rectangular, elliptical, triangular etc.In our project we are using the “Square shape patch”, whose complete designing is shown below, the formulation which we used for the designing are as below:-[7]

The length L of the patch usually taken as

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.3333λo < L < 0.5λo …………………………(3.1)

Where

λo = walength of free space

We have calculated the patch length at the given frequency i.e. 1200MHz .

The value of dielectric constant is taken after several experiments εr = 4.35.

λ = C/F

λ = 3*10^8/1200*10^6

λ=0.25

L= λ/4

L=0.25/4

L=0.0625

As we are using square patch antenna so the length and width are same.

3.3 Amplifier

To boost the signal we are using NPN transister.The Bipolar Junction Transistor (BJT) is an extremely common electronic device to all forms of electronic circuits. It can be used for a number of useful applications such as an amplifier, a switch, a buffer, an oscillator, a nonlinear circuit – so forth.

The basic diagram of the BJT is shown below:

Collector

Base

Emitter

Figure 3.1

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BJT’s and all types of the transistors are made up of p and n types of semiconductors materials. The combination of p-type and n-type semiconductors give rise to two combinations i.e. n-p-n and p-n-p. As in our project we are using the n-p-n transistors whose complete specification is given in the appendix

CHAPTER 4

RESULTS

4.1 Overview

In this chapter we have concluded the results.

4.2 Results and Recommendations

After implementing the proposed model of the project certain results are

obtained. Data is transmitted successfully at the baud rate of 2400 using MAX232

integrated circuit. Frequency on which project is being operated is 1200 MHz.

Further patch antennas were designed on the basis of this frequency using Fr-4.

REFERENCES

[1] Satellite Communication Edition by Dennis Roddy Third

[2] http://www.answer.com/topic/serialport

[3] http://www.answer.com/topic/seiralportinterfacing

[4] http://www.answer.com/topic/modulation/fsk modulation

[5] http://www.answer.com/topic/modulation/fsk modulation

[6] http://en.wikipedia.org/wiki/MAX232,accessed

[7] Antenna Theory: Analysis and Design, Third Edition, by Constantine A.Balanis.

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Appendix

MAX-232

IC DESCRIPTION

The MAX232 is a dual driver/receiver that includes a capacitive voltage generator to supply TIA/EIA-232F voltage levels from a single 5-V supply. Each receiver converts TIA/EIA-232-F inputs to 5-V TTL/CMOS levels. These receivers have a typical threshold of 1.3 V, a typical hysteresis of 0.5 V, and can accept ±30-V inputs. Each driver converts TTL/CMOS input levels into TIA/EIA-232-F levels. The driver, receiver, and voltage-generator functions are available as cells in the Texas Instruments LinASIC library.

Meets or Exceeds TIA/EIA-232-F and ITU Recommendation V.28 Operates From a Single 5-V Power Supply With 1.0-_F Charge-Pump Capacitors Operates Up To 120 kbit/s Two Drivers and Two Receivers ±30-V Input Levels Low Supply Current . . . 8 mA Typical ESD Protection Exceeds JESD 22 -2000-V Human-Body Model (A114-A) Upgrade With Improved ESD (15-kV HBM) and 0.1-_F Charge-Pump

Capacitors is Available With the MAX202 Applications

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TIA/EIA-232-F, Battery-Powered Systems, Terminals, Modems, and Computers

Figure-3

LM386Low Voltage Audio Power AmplifierGeneral DescriptionThe LM386 is a power amplifier designed for use in low voltage consumer applications. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200.The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.Features

Battery operation Minimum external parts Wide supply voltage range: 4V–12V or 5V–18V Low quiescent current drain: 4mA Voltage gains from 20 to 200 Ground referenced input Self-centering output quiescent voltage Low distortion: 0.2% (AV = 20, VS = 6V, RL = 8, PO = 125mW, f = 1kHz) Available in 8 pin MSOP package

Applications AM-FM radio amplifiers

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Portable tape player amplifiers Intercoms TV sound systems Line drivers Ultrasonic drivers Small servo drivers Power converters

XR-2206SYSTEM DESCRIPTION

The XR-2206 is comprised of four functional blocks; a) and sine-shaper; a unity gain buffer amplifier; and a set of current switches. The VCO produces an output frequency proportional to an input current, which is set by a resistor from the timing terminals to ground. With two timing pins, two discrete output frequencies can be independently produced for FSK generation applications by using the FSK input control pin. This input controls the current switches which select one of the timing resistor currents, and routes it to the VCO.

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Figure.1

XR-2211

GENERAL DESCRIPTION

The XR-2211 is a monolithic phase-locked loop (PLL) system especially designed for data communications applications. It is particularly suited for FSK modem applications. It operates over a wide supply voltage range of 4.5 to 20V. It can accommodate analog signals between 10mV and 3V, and can interface with conventional DTL, TTL, and ECL logic families. The circuit consists of a basic PLL for tracking an input signal within the pass band, a quadrature phase detector which provides carrier detection, and an FSK voltage comparator which provides FSK demodulation. External components are used to independently set center

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frequency, bandwidth, and output delay. An internal voltage reference proportional to the power supply is provided at an output pin. The XR-2211 is available in 14 pin packages specified for military and industrial temperature ranges.

Figure-2

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