MTech(DCN) DEC-I Manual

ADVANCED COMMUNICATION LABORATORY

BLDEAs Association

V.P Dr. P.G.H. College of Engineering & Technology, Bijapur-586103.

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

Master of TechnologyIn

Digital Communication & Networking

DEC-LAB I

LABORATORY MANUAL

2014-15

SUBJECT: DEC LAB I (14ECS16)

SEMESTER: IstSem M.Tech (DCN)Expt. No.Name of the Experiment

1Study of digital modulation techniques using trainer kit(ASK,PSK,FSK)

2Measurement of guide wave length, frequency and VSWR using the Klystron Power Source.

3Determination of coupling coefficient and insertion loss of directional couplers.

4Matlab implementation to obtain the radiation pattern of an antenna.(Dipole Antenna )

5Radiation pattern of different antennas using matlab.

(Loop Antenna & linear array)

6Analysis of E & H plane horns using matlab.

7Determination of the modes transit time, electronic timing range and sensitivity of klystron source.

8Significance of pocklington's integral equation using matlab.

9Matlab Program to generate the pseudo random sequence.

10Determine the directivity and gains of Horn/ Yagi/ dipole/ Parabolic antennas using matlab.

STUDY OF DIGITAL MODULATION TECHNIQUES

Expt No: 1A

Date:AMPLITUDE SHIFT KEYING (ASK)

Aim: To study ASK modulation with the help of Trainer kitApparatus:

SI NoApparatusQuantity

1.ASK Trainer kit1

2.CRO1

3.Patch cords and probes--

Theory: The binary ASK signaling is one of the earliest forms of digital modulation used in the wireless telegraphy of the beginning of the century. While ASK is no longer widely used in the digital communication. It is smallest form of the digital modulation and serves as useful model for introducing certain concept. One binary ASK waveform can be described as

Z(t) = 1 ( t - ( k 1 ) Tb ) if bk = 0

2 ( t - ( k 1 ) Tb ) if bk = 1 ( k 1 ) Tb t kTbWhere 2(t) = A cos ct (0 t Tb) & S1(t) = 0 we will assume that the carrier frequency c = 2n/Tb where n is an integer.

In amplitude shift keying the carrier amplitude is varied with variables in the binary bit stream. An ASK wave can be generated by using product modulator whose input is the binary bit stream in unipolar format and a sinusoidal carrier of the amplitude A and frequency f. For detection of binary ASK signal we make use of coherent detection scheme.

In coherent detection scheme a multiplier is used to multiply the incoming signal with a locally generated carrier. The output of the multiplier is integrated by an integrator circuit for every successive bit interval. The integrated output is input to comparator or a three hold level is therefore very important in coherent detection of ASK.

Procedure:

Modulation:

1. Switch ON the experimental board.

2. Observe the bit clock frequency on oscilloscope. Adjust frequency to 10 KHz.

3. Set the SPDT switch pattern to desired code.

4. Parallel load by changing the switch to opposite side for a short duration and get back to shift position.

5. Observe the 8-bit word pattern at output of the 8 bit word generator.

6. Adjust the carrier frequency of 100KHz and 5V(p-p) & give this input to ASK modulation input using patch cords.

7. Connect the 8 bit word generator output to data input terminal of ASK modulator.

8. Observe the data input and ASK output simultaneously on CRO.9. Change the 8 bit word sequence with the help of SPDT switches and load it. Check the output of ASK modulator with respect to data signal.

Observations:

1. Amplitude of data I/P =

2. Frequency of the data I/P =

3. Amplitude of clock signal =

4. Frequency of clock signal =ASK MODULATION Modulator

PHASE SHIFT KEYING (PSK)

Expt No: 1B

Date:Aim: To study the operation of phase shift keying Modulation with the help of PSK kit.

Apparatus:


1.PSK Trainer kit1

2.CRO1


Theory:

Digital PSK modulation scheme is a binary 1 is represented by a sinusoidal carrier of amplitude A & frequency fc with phase 1 which a binary 0 is represented by sinusoidal carrier amplitude A & frequency fc with phase 2. Generally 1=0 & 2=180 which implies that the difference in phase of the two carrier used to represent 0 & 1 is 180. Mathematically binary PSK wave can be represented as,S(t) = Ac cos(2fct) symbol 1

= Ac cos(2fct+) symbol 0

a) Generation of BPSK wave:

A binary PSK wave is generated using a product modulator whose input are the sinusoidal carrier Acos(2fct) & binary bit scheme in the polar form. The PSK wave is somewhat similar to a DSB-SC wave.

b) Detection of BPSK wave:

The scheme of the detection of BPSK signal consists of multiple in the first phase which is used to multiply the coming BPSK wave with a logically generated carrier. The output of the multiplier is integrated by integrator circuit for every bit interval. The integrated O/P is the I/P to the comparator or a threshold device whos O/P is either logic 1 or 0.Procedure:1. Switch ON the PSK kit.

2. Apply the carrier signal to the input of modulator.

3. Apply the modulating signal to modulation input and observe on channel 1 of CRO.4. Observe the output of PSK modulator on channel 2 of CRO.

5. Apply this PSK output to the demodulator input & also apply carrier input.

6. Observe the demodulator output & compare it with modulating data signal applied to the modulator input.

Observations:

1. Amplitude of the modulating signal=

2. Frequency of the modulating signal=

3. Amplitude of the carrier signal=

4. Frequency of the carrier signal=PSK MODULATION Modulator

FREQUENCY SHIFT KEYING (FSK)

Expt No: 1B

Date:

Aim: To study FSK modulation using FSK Trainer kit.

Apparatus:


1.FSK Trainer kit1

2.CRO1


Theory:

In an FSK system a sinusoidal wave of amplitude A & frequency fc is used to represent a binary 1 where as a sinusoidal of amplitude 0.Mathematically a binary wave can be represented by

(t) = Ac cos(2*22/-7*fc*t) symbol 1

= Ac cos(2*22/7*fc*t) symbol 0

Generation of BPSK wave: A sinusoidal carrier of amplitude A and frequency fc and a binary bit stream in polar form is applied to frequency modulator. As the bit stream i/p changes from one level to another, the transmitted frequency also changes proportionally thus yielding a BPSK signal.

Demodulation of BPSK wave: A coherent detection is used for demodulation of binary PSK wave. Two characters which are tuned for different frequency corresponding to binary 1 and 0 are used. The two correlations o/p is compared using a comparator or CRO.Procedure:Modulator:1. Switch ON the experimental board.

2. Observe the bit clock frequency on oscilloscope. Adjust frequency to 10KHz.

3. Set the DIP switches to the desired patterns.4. Parallel load by the switch to PL side for a short duration.

5. Observe the 8-bit word pattern at output of the shift register. This is the modulating signal.

6. Connect the Oscilloscope to the o/p of the VCO7. Connect modulating I/p to GND. Measure the o/p freq. It should be 307.2 KHz otherwise adjust the 1M trim pot at pin2 to get freq.

8. Connect modulating I/p of VCO to + 5V. Observe o/p freq of VCO on CRO. It should be 614.4 KHz otherwise adjust the 50K pot.

9. VCO is tuned properly to match demodulator.

10. Connect the shift register o/p and modulating signal to the modulator.

11. Charge the DIP pattern and observe the o/p for different bit patterns.

Observations:

1. Amplitude of the modulating signal =

2. Frequency of the modulating signal =

3. Amplitude of the carrier signal =

4. Frequency of the carrier signal =FREQUENCY SHIFT KEYING Modulator

MEASUREMENT OF GUIDE WAVELENGTH, FREQUENCY & VSWR USING KLYSTRON POWER SOURCEExpt No:

Date:Aim: To determine the Guide wavelength, Frequency & VSWR of a rectangular waveguide.

Apparatus:

SI NOApparatusQuantity

1Gunn Power supply1

2Reflex klystron Mount1

3Isolator1

4Frequency meter1

5Slotted section1

6Tunable Detector probe1

7CRO1

8Matched load1

Theory:

A Rectangular waveguide is a hollow metallic tube used to guide an electromagnetic wave. Educational purpose Microwave benches are operating in X Band. But their general frequency range is between 3-100 GHz. Within this range they are superior to Co-axial transmission lines. The power handling capability is due to reflection from the walls. Also the power loss in waveguides is less than of transmission lines.

Modes of propagation:1. Transverse Electric mode(TE mode): In this mode there is no component of Electric field in the direction of propagation.2. Transverse Magnetic mode(TM mode): In this mode there is no component of Magnetic field in the direction of propagation. When a TEM wave is passed through the waveguide, electric field is short circuited through the walls, no potential exists. Hence, TEM wave cannot propagate.Guide wavelength: It is defined as the distance traveled by the EM wave in the z-direction when there is phase change of 2 radians. It also represents the axial length corresponding to one cycle i.e, distance between two consecutive minima of variation of electric field configuration.We have,g =Vp / f =2f / f

g =2 / 1-( / c)2

g =1 / 1-( / c)2 f

g = / 1-( / c)2The standing wave ratio is defined as,SWR=Vmax / Vmin

SWR results due to in phase & out of phase components. Thus we get maxima & minima and Guide wavelength g.

Procedure:

1) Keep the Beam voltage minimum & Repeller voltage greater than 250V.

2) Observe the Detected output (Square wave) on CRO.

3) Observe the DIP on CRO & Record the Frequency with the help of frequency meter.

4) Moving the probe carriage between maxima & Minima, record the distance between two consecutive minima on vernier scale.

5) Calculate g , Using g =2d in cms.

6) Repeat the procedure for three different frequencies.

7) Compare the observed and calculated.

Observations:

1. Horizontal Dimensions of the waveguide = a = 2.3 cms.

2. Cut-off wavelength = c = 2a = 4.6 cms.

3. Cut-off frequency = fc = c / cWhere c = Velocity of light in free space = 3 x 108 mts /sec.

fc = (3x108)/(4.6) = 6.52 GHz.

4. Repeller voltage =

5. Beam voltage =

6. Beam current =

TABLE 1SI No

Frequency in GHz (f)Wavelength in cms =c/fDistance between 2 consecutive minima in cmsMeasured Guide wavelength g in cms.Calculated Guide wavelength g in cms.

1

2

3

TABLE 2SI NoLoad typeVmaxVmax AVGVminVmin AVGVSWR=Vmax/Vmin

1MatchedLoad

2Open

Circuited

3Short

circuited

Calculation for guide wavelength:

LC = 1 Main Scale Division

Total No of Vernier Scale Division

= 0.1

10

= 0.01

Total Reading (TR) = MSR + (CVD x LC)

Where MSR = main scale reading & CVD = Coinciding vernier scale reading.

MEASUREMENT OF GUIDE WAVELENGTH , FREQUENCY, VSWR

NATURE OF GRAPH

DETERMINATION OF COUPLING COEFFICIENT AND INSERTION LOSS OF STRIPLINE DIRECTIONAL COUPLER

Expt no: Date:

Aim: To measure the coupling and isolation characteristics of a strip line directional coupler.

Equipments/Components:

1. Microwave signal source(2.2-3 GHz)

2. VSWR meter.

3. Coaxial detector.

4. Attenuator pads- 3dB,6dB,10dB

5. Matched Loads(50)-2

6. SMA/BNC connector fitted cables

7. Microstrip parallel coupled directional coupler.

Theory:

A directional coupler is a 4-port reciprocal passive network. The basic function of a coupler is to sample power flowing in one direction in a transmission line and reject power flowing in the opposite direction. It also performs the function of power division but with the output signals having 900 phase difference between them.

In microstrip and stripline configurations, two basic forms of directional couplers are commonly used. They are called branch line coupler and parallel coupled directional coupler. These couplers form the basic blocks of many other microwave components, such as balanced mixers, variable attenuators and PIN diode shifters. In this experiment, the parallel coupled directional coupler is used.

Procedure :Matlab/C implementation of to obtain the radiation pattern of an antenna

Expt No:

Date:Aim: Write a C/Matlab program to obtain the radiation pattern of an antenna

Tools Required: Matlab 7.0

Windows xp

Theory :

Dipole antennaordoublet is the simplest and most widely used class ofantenna. It consists of two identical conductive elements such as metal wires or rods, which are usuallybilaterally symmetrical. The driving current from thetransmitter is applied, or for receiving antennas the output signal to thereceiveris taken, between the two halves of the antenna. Each side of thefeedlineto the transmitter or receiver is connected to one of the conductors.

Dipoles areresonant antennas, meaning that the elements serve as resonators, withstanding wavesof radio current flowing back and forth between their ends. So the length of the dipole elements is determined by thewavelengthof the radio waves used. Theradiation patternof a vertical dipole isomnidirectional ; it radiates equal power in allazimuthaldirections perpendicular to the axis of the antenna.Dipoles may be used as standalone antennas themselves, but they are also employed asfeed antennas(driven elements) in many more complex antenna types,such as theYagi antenna,parabolic antenna,reflective array,turnstile antenna,log periodic antenna, and phased array.Procedure :

1) Open the software matlab version 7.8

2) Write the program in the editor command

3) Run the script form the command window .

4) Enter the inputs and compare the result with analytic result.

5) Plot the figure for the obtained result.

Program for radiation pattern of dipole antenna:clc;

lamda=1;

l=input('enter your dipole length l in terms of lamda(for ex: 0.5 for 0.5lamda)= ');

ratio=l/lamda;

B=(2*pi/lamda);

theta= pi/100:pi/100:2*pi;

if ratio> pockling(1,0.4,1)

ans = 0.0022 - 0.0285icnd = 1

z = 0

I = 0.0003 + 0.0035i

ans = 0.0003 + 0.0035iProgram to Generate the Pseudo Random SequenceExpt No:

Date:Aim: Program to generate the pseudo random sequenceTools Required:Matlab 7.0

Windows xpTheory: Pseudo random signal processing has proven to be a critical enabler of modern communication, information, security and measurement systems. The signals pseudo random, noise-like properties make it vitally important as a tool for protecting against interference, alleviating multipath propagation and allowing the potential of sharing bandwidth with other users. One of the major applications of Pseudo random generation is to generate a key, which is then used to encrypt the data. There are various algorithms to generate pseudo random code. One such is the LFSR

Linear-feedback shift register(LFSR) is ashift registerwhose input bit is a linear functionof its previous state. The most commonly used linear function of single bits isexclusive-or(XOR). Thus, an LFSR is most often a shift register whose input bit is driven by the XOR of some bits of the overall shift register value.Right Shift

Figure: LFSR (Linear Feedback Shift Register)

Procedure:

1) Open the software Matlab version 7.8.2) Write the program in the editor command .3) Run the script form the command window.


5) Plot the figure for the obtained result.Program :clear

clc

shiftRegLength = 7;

shiftReg = round(rand(1,shiftRegLength));

for i = 1:2^shiftRegLength-1

outputSeq(i)= shiftReg(shiftRegLength);

c = xor(shiftReg(shiftRegLength),shiftReg(shiftRegLength-1));

shiftReg = [c shiftReg(1:shiftRegLength-1)];

end

plot(xcorr(outputSeq,outputSeq)) Simulation Results

Figure: Correlation Properties of the generated PSEUDO Random Signal

Program to determine the Directivity and Gain of Horn and Dipole antennasExpt No:

Date:Aim: To determine the Directivity and Gain of Horn and Dipole antennas.

Tools Required:Matlab 7.9 Windows xpTheory: Directivityis a fundamental antenna parameter. It is a measure of how 'directional' an antenna's radiation pattern is. An antenna that radiates equally in all directions would have effectively zero directionality, and the directivity of this type of antenna would be 1 (or 0 dB). When a directivity is specified for an antenna, what is meant is 'peak directivity'. Directivity is technically a function of angle, but the angular variation is described by its radiation pattern. An antenna's normalized radiation pattern can be written as a function inspherical coordinates:

A normalized radiation pattern is the same as a radiation pattern; it is just scaled in magnitude such that the peak (maximum value) of the magnitude of the radiation pattern is equal to 1. Mathematically, the formula for directivity (D) is written as:

This equation for directivity might look complicated, but the numerator is the maximum value of F, and the denominator just represents the "average power radiated over all directions". This equation then is just a measure of the peak value of radiated power divided by the average, which gives the directivity of the antenna.

The directivity of an antenna can vary over several order of magnitude. Hence, it is important to understand directivity in choosing the best antenna for your specific application. If you need to transmit or receive energy from a wide variety of directions (example: car radio, mobile phones, computer wifi), then you should design an antenna with a low directivity. Conversely, if you are doing remote sensing, or targetted power transfer (example: received signal from a mountain top), you want a high directivity antenna, to maximize power transfer and reduce signal from unwanted directions.

Antenna gain is usually defined as the ratio of the power produced by the antenna from a far-field source on the antenna's beam axis to the power produced by a hypothetical losslessisotropic antenna, which is equally sensitive to signals from all directions. This ratio is expressed indecibels, and these units are referred to as "decibels-isotropic" (dBi).

Procedure:1) Open the software Matlab version 7.9.2) Write the program in the editor command.3) Run the script form the command window.


5) Plot the figure for the obtained result.

Program :1) Dipole Antennasum=0.0;N=input('Enter the number of segments in the theta direction\n');Rr=input('enter the value of radiation resistance:\n');Roh=input('enter the value of ohmic resistance:\n');for i=1:Nthetai=(pi/N)*(i-0.5);sum=sum+(cos((pi/2)*cos(thetai)))^2/sin(thetai);endD=(2*N)/(pi*sum)RA=Rr+Roh;e=Rr/RA;G=e*D2) Horn Antenna

%Horn Antenna directivity and gain taking in consideration as TE01 mode and%Rectangular delta=input('Enter the path length difference in meters \n');a=input('Enter the aperture in meter\n');lambda=input('enter the wavelength in terms of meters');% We have to calculate the calculate the horn length L = a*a / 8 * deltaL = square(a) / ( 8 * delta );% Need to calculate the Flare angle in the E and H Plane Theta_E = 2 * (1/(tan(a/2*L))); % Taking 3 Lambda / 8 H Plane delta_H = (3 * lambda)/ 8 ;Theta_H = 2 * (1/(cos(a/2*delta_H))); % EPlane AperatureAE = 2*L*tan ( Theta_E / 2 );% HPlane AperatureAH = 2*L*tan ( Theta_H / 2 );% Effective Aperature Eaperture = AE/AH;% Directivity is calculated as D=(4*pi*AE)/((lambda)*(lambda))% Gain is calculated as G=(Eaperture)*DSimulation Results:

1)Dipole antenna

Enter the number of segments in the theta direction

10

enter the value of radiation resistance:

10

enter the value of ohmic resistance:

10

D = 1.6410

G = 0.8205

2)Horn AntennaEnter the path length difference in meters

1

Enter the aperture in meter

3

Enter the wavelength in terms of meters

1D = -5.0299

G = 3.2977

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MTech(DCN) DEC-I Manual