PSK/QPSK MODULATOR+HIGH PASS FILTERB.E. PROJECT REPORT

ADC(12811)

Prepared by

Salman Khaliq Bajwa (3746)

AdvisorAsstt. Professor, Muhammad Abbas

Lab EngineerMr. Zia ul Haq

College of Engineering

PAF-Karachi Institute of Economics & Technology

Karachi

DEDICATION

This report is dedicated to

My Parents, Teachers & Friends,

Whose love, affection and support helped me in bringing my work to this level of

accomplishments; I am also thankful to them for their unconditional support and encouragement

to pursue my interests, even when the interest went beyond the boundaries of field and scope.

Without their support and kindness this work would not have been possible.

ACKNOWLEDEMENT

Praise to Allah the most beneficent and the most merciful

We are grateful to our project advisor Mr. Abbas, for enlightening us with his precious

knowledge and vast experience to benefit us in the future. We also like to thank to our teachers

and lab assistants, lab engineer especially Mr. Zia ul Haq for their assistance and support.

We would also thank with all gratitude and depth of our hearts to our parents who helped us

not only financially but with integrity too and support us in all our hardships. Finally our sincere

thanks to our institute PAF-KIET, College of Engineering, for providing us the opportunity to

gave us the strength to undertake this research.

Special thanks to all our fellows and friends who lend us a hand throughout this project.

We pray this effort may prove to be the beginning of new era, a era in which Science and

Technology may make great progress in Pakistan and Pakistan may become a part of the

developed nations.

Thank you.

Objective:

The main objective of this project is to design and construct a PSK/QPSK modulator.

Description:

Before going to the PSK modulation, we first need to understand what is modulation and why do we need it?

Modulation:

It is the process of putting information on to a high frequency carrier for transmission.

Baseband signal Modulated Signal

Why Modulation?

In simple terms, modulation is required to transmit signals from variuos sources simultaneously over a

common channel by means of 'multiplexing'.For ex., the bandwidth of speech signals is 3.3KHz.,and

transmitting N no.of speech signals simultaneously each of BW 3.3KHz causes interference.Hence,to

overcome this problem, each speech signal is modulated onto one of N carriers of frequencies

60KHz,64KHz,68KHz etc...

There are 3 major reasons :

1) To use much more smaller antennas.

2) Channel allocation for todays thousands of todays users.

3) For better noise immunity.

What is Phase-shift keying (PSK) modulation?

Phase-shift keying (PSK) is a digital modulation scheme that conveys data by changing, or

modulating, the phase of a reference signal (the carrier wave).

Modulator

All convey data by changing some aspect of a base signal, the carrier wa (usually a sinusoid), in

response to a data signal. In the case of PSK, the phase is changed to represent the data signal.

There are two fundamental ways of utilizing the phase of a signal in this way:

By viewing the phase itself as conveying the information, in which case the demodulator

must have a reference signal to compare the received signal's phase against; or

By viewing the change in the phase as conveying information — differential schemes,

some of which do not need a reference carrier (to a certain extent).

A convenient way to represent PSK schemes is on a constellation diagram. This shows the

points in the complex plane where, in this context, the real and imaginary axes are termed the

in-phase and quadrature axes respectively due to their 90° separation. Such a representation

on perpendicular axes lends itself to straightforward implementation. The amplitude of each

point along the in-phase axis is used to modulate a cosine (or sine) wave and the amplitude

along the quadrature axis to modulate a sine (or cosine) wave.

In PSK, the constellation points chosen are usually positioned with uniform angular spacing

around a circle. This gives maximum phase-separation between adjacent points and thus the

best immunity to corruption. They are positioned on a circle so that they can all be transmitted

with the same energy. In this way, the moduli of the complex numbers they represent will be

the same and thus so will the amplitudes needed for the cosine and sine waves. Two common

examples are "binary phase-shift keying" (BPSK) which uses two phases, and "quadrature

phase-shift keying" (QPSK) which uses four phases, although any number of phases may be

used. Since the data to be conveyed are usually binary, the PSK scheme is usually designed with

the number of constellation points being a power of 2.

What is Quadrature phase-shift keying (QPSK)?

Sometimes this is known as quaternary PSK, quadriphase PSK, 4-PSK, or 4-QAM. (Although the

root concepts of QPSK and 4-QAM are different, the resulting modulated radio waves are

exactly the same.) QPSK uses four points on the constellation diagram, equispaced around a

circle. With four phases, QPSK can encode two bits per symbol, shown in the diagram with gray

coding to minimize the bit error rate (BER) — sometimes misperceived as twice the BER of

BPSK.

The mathematical analysis shows that QPSK can be used either to double the data rate

compared with a BPSK system while maintaining the same bandwidth of the signal, or to

maintain the data-rate of BPSK but halving the bandwidth needed. In this latter case, the BER of

QPSK is exactly the same as the BER of BPSK - and deciding differently is a common confusion

when considering or describing QPSK.

Given that radio communication channels are allocated by agencies such as the Federal

Communication Commission giving a prescribed (maximum) bandwidth, the advantage of QPSK

over BPSK becomes evident: QPSK transmits twice the data rate in a given bandwidth compared

to BPSK - at the same BER. The engineering penalty that is paid is that QPSK transmitters and

receivers are more complicated than the ones for BPSK. However, with modern electronics

technology, the penalty in cost is very moderate.

Process:

Circuit:

We had used KL-94006 modulator circuit in order to construct a PSK/QPSK modulator circuit.

The circuit diagram of the KL94006 modulator is given below;

Schematic:

Components:

ICL 8038 WAVEFORM GENERATOR

4052 DIFFERENTIAL 4-CHANNEL ANALOG MULTIPLEXERS/DEMULTIPLEXERS

4070 EXCLUSIVE OR

4094 8-STAGE SHIFT-AND-STORE BUS REGISTER

4520 DUAL BINARY COUNTER

LF356 SINGLE J-FET OPERATIONAL AMPLIFIERS

TL084 GENERAL PURPOSEJ-FET QUAD OPERATIONAL AMPLIFIERS

CD4096 Micropower Voltage Reference Diode

Resistors

Capacitors

Project 2: High Pass Filter

Objective:

The main objective of this project is to design and understand the basics and working of filters especially high pass filters.

Description:

High pass filters remove signals below the selected frequency, and pass the signals above the selected frequency unaffected (hence the term high pass). High pass filters have a slope measured in the amount of signal reduction (in dB) per frequency octave. Typically these values are in multiples of 6 dB/Oct. At the exact selected frequency of the high pass filter the signal reduction is usually -3 dB, however this can change based on filter design. A high pass filter is useful for removing low frequency rumble, unwanted vocal plosives, and dc offsets. This is Simple high pass Filter perform filter especial tall frequency can change only. By use IC 741, be the integrated circuit op-amp very the circuit helps to are high frequency Filter model to be simple. By from the circuit will let 750 HZ frequencies s go up change more well, 60HZ frequencies are or lower. By friends can change the value RC for filter the frequency that can want which can see the detail has followed circuit picture yes.

Circuit:

Schematic:

Design Procedure: Pick C1 = C2: __________ Calculate R1:1/((2)^1/2*C1*Frequency) Calculate R2:1/2R1 F=1Mhz

For any query, feel free to contact

Salman Khaliq Bajwa

salman_khaliq@hotmail.com

03009049060