ADC

1. PSK/QPSK MODULATOR+HIGH PASS FILTER
B.E. PROJECT REPORT
ADC(12811)
Prepared by
Salman Khaliq Bajwa (3746)
Ali Arsalan (4377)
Mohammad Ghazanfar (4965)
Advisor
Asstt. Professor, Muhammad Abbas
Lab Engineer
Mr. Zia ul Haq
College of Engineering
PAF-Karachi Institute of Economics & Technology
Karachi

2. 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.

3. 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.

4. 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 Modulator 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).

5. 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.

6. 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.

7. 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:

8. 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;

9. 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

10. 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:

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