mobile and digital broadcasting course work

8/8/2019 Mobile and Digital Broadcasting Course Work

1/16

Msc in Digital Communications Networks

Module: Mobile Digital Broadcasting

CTP142N

RLC Circuit Analysis

&

VSSIM Circuit Simulations

Name: Mr. Pavana SMC Malladi

ID: 09034497

Deadline: 15th January 2010


2/16

RLC Circuit Analysis

Objective:To determine the Resonating frequency and Quality factor of series resonance circuit and to

compare theoretical and practical results

Equipment Required:

Computer system with SIMetrix software

Introduction:

Communication systems mainly consists of transmitter and a receiver tuned to same frequency.There should exist the frequency match between transmitter and receiver for conveying the data.Tuning circuit plays a key role in the communication system. Tuning circuit also called resistance-capacitance-inductance network or simply RLC circuit. Keynote is that electronic behavior of the

circuit is controlled by the resonating frequency of electronic signal across the circuit and the currentpassing within the circuit depends on the frequency. In this experiment we need to find the resonancefrequency and quality factor of the RLC circuit experimentally and compare the results withtheoretical values.

Circuit diagram:

Figure(1): series RLC Circuit

Experiment Description:

Open the SIMETRIX window open new schematic. Click on voltage source position it in the workspace and right click to deactivate it. Similarly continue the process for resistor, capacitor andinductor. Click on the component once to highlight the component and right click on it to change thevalue of the component. After making the necessary changes in the value of the components connectthe components with the pen probe and ground the circuit place the current probe at capacitor orinductor. Save the circuit with apt name. now go to the simulator option on the toolbar set the


3/16

analysis mode to AC. Make the necessary changes in the values of DC, Noise, TF based upon thecase. And choose Run option so that output gets displayed in the new window.

Simulation Results: variation in the curves with change in the resiatance

Figure(2): Flattening of curve by increasing the resistance value peak curve (100), flat curver=(270)

Figure(3): Improvement in the sharpness of the curve by setting the value of resistance to 18

Frequency / Hertz

1k 2k 4k 10k 20k 40k 100k 200k 400k 1M 2M 4M 10M

I(L1-N

)/mA

1

2

3

4

5

6

7

8

9

Frequency / Hertz

1k 2k 4k 10k 20k 40k 100k200k 400k 1M 2M 4M 10M

I(L1-N

)/mA

10

20

30

40

50


4/16

Output obtained:

Analysis:

Figure(4): Magnified View to know the accurate values

Formulaes:

Imax, Imax/2

Resonating Frequency= 1/2LC

Q=f0 /f

Practical Evaluation:

Imax = 55.199

(Imax /2) = 39.03

f= 34.71288K

f0 = 173.78008K

Quality Factor(Q)= f0 /f = 173.78008K / 34.71288K = 5.0062

Resonating Frequency= 173.78K

Q= 5.0062Resonating Frequency= 173.78Khz

Frequency / Hertz

100k 200k 500k

I(L1-N)/mA

3234

36

38

40

42

44

46

48

50

52

54

-1.24644m

40.28675m

39.04031m

34.71288k159.8770k 194.5898k

AREF


5/16

Theoretical Evaluation:

R=18 , L=82 ,C=10n

Supply Voltage= 10Volts

Resonating Frequency= 1/2LC= 1/ (2 x 3.14 x 82 x 10n)= 175.75 Khz

Therefore,

Resonating Frequency=175.75 Khz

Hence the results obtained by theoretical and practical evaluation are same. Hence the result


6/16

VisSim/Comm Circuit Simulations

Objective:

To determine type of modulation or type of Communication system can be associated with

the experiments individually. Determining the output variations with the change in circuitparameters.

Getting Started:

VisSim/Comm software is an application in which the model communication system block diagrams are

formed with the components available in the VisSim/Com tool kit. It is also termed as the block diagram

language for the simulation of the dynamic systems and embedded systems and this software is

developed initially by Visual Solutions of Westford, Massachussetts.

Why VisSim/Com?

In the modern world communication was undergoing drastic change day by day. What ever be the type

of communication. The principle of operation of the inbuilt communication system is almost the same to

know the proper working condition of the communication links we use VisSim/Comm software

simulation which provides a wide range of communication components to get connected within

workspace and to observe the changes in the outputs with the changes in the parameters mainly

(Frequency, Amplitude, Phase ,Gain etc)and this is the simplest way of estimating the communication

system.

Where is it applicable?

Main application of this software is in system design like

1) Control System Design

2) Multi Domain Design and Simulation in Digital Signal Processing

3) Model Based Embedded System development

Future Scope of VisSim/Comm software:

Model Based Embedded System development was gaining prominence day after day as if it shortens the

number of development cycles in the Embedded system hardware development.

Role of AD633:

AD633 is a functionally complete, four-quadrant, analog multiplier. It includes high impedance summing

input(Z), differential X and Y inputs and a high impedance. The low impedance output voltage is a

nominal 10V full scale provided by the buried Zener. The AD633 is the first product to offer these

features at low priced 8-lead DIP and SOIC packages.


7/16

The AD633 is laser calibrated to guaranteed total accuracy of 2% of full scale. Nonlinearity for the Y-

inputs is typically less than 0.1% and noise referred to the output is typically less than 100 V rms in a

10Hz to 10KHz bandwidth. A 1 MHz bandwidth, 20V/ s slew rate, and the ability to drive capacitive

loads make the AD633 useful in a wide variety of applications where simplicity and cost are key

concerns.

The AD633s versatility is not compromised by its simplicity. The z-input provides access to the output

buffer amplifier, enabling the user to sum the outputs of two or more multipliers, increase the multiplier

gain, convert the output voltage to a current, and configure a variety of applications.

The AD633 is available in an 8-lead plastic DIP, SOIC packages. It is specified to operate over the 00C to

+700C commercial temperature range (J Grade) or the -400C to +850C industrial temperature range (A

Grade). Coming to the differences of DIP and SOIC, DIP has 2 differential X and Y inputs on one side; high

impedance summing input Z, overall transfer function W taken on the other side. Where as it differs in

case of SOIC Package which can be observed in the figure given below.

Fig1: AD633 DIP Package Fig2: AD633 SOIC Package

Features of AD633:

1) AD633 is the cost efficient (low cost) 8 pin package

2) Its a complete system no need of extra components

3) It poses laser trimmed(sharp) Accuracy and Stability

4) High differential Impedances X and Y inputs

5) High Impedance Unity Gain Summing Input

6) Sharp(Laser Trimmed) 10V scaling reference

Applications of AD633:

1) Used for Multiplication, Division and Squaring of signals

2) Applicable in Phase detection, modulation and Demodulation of signals


8/16

3) Used in electronic component construction like VC(voltage controlled) Amplifiers, Filters and

Attenuators

AdvMod1a.vsm:

Figure(1a.1): output of the multiplier with DC Level +5

Figure(1a.2): output of the multiplier with DC Level -5

Observation:

From Figure 1a.1:

Initially set the DC Value to +5 keeping the parameters of the Carrier I/P constant. Then we can observe

that both the waves 1 and 2 are in phase as shown in figure 1a.1. now change the DC Level to -5 then we

can observe that the modulated signal getting out of phase with carrier signal. That is modulated signal

getting shifted left as shown in Figure 1a.2. And in both the cases we keep the gain within AD633

constant as 0.1.

Analysis:

Modulation:

No connection

1. modulated output

2. carrier signal

2

1


9/16

The characteristics of the high frequency carrier wave varies corresponding to the instantaneous values

of the modulating signal.

No parameters are getting varied in the above system except the shift of the modulated output.

Figure: Inner schematic of AD633

Description:

Coming to the inner schematic of AD633 the building blocks are a Multiplier, Additioncomponent(Summer), Gain factor. In the above schematic modulating input, carrier signal are fead to

multiplier which is in turn feed to gain factor of 0.1 let us term it as input 1. And coming to second input

no connection so the gain factor is unity(connection less) let us term it as input 2. Inputs 1 and 2 are

feed to summer where addition of two input signals is performed and we get the modulated output.

Multi lier

Gain

Addition

Gain1

Modulated

Out ut

No connectionCarrier Input

Modulating

input


10/16

AdvMod1b.vsm:

Figure 1b.1: Different AM Formats

Observation:

Graph1: (Double Side Band AM Wave)

Basically AM wave is also called (DSBLC: Double sideband large carrier wave), but here in the experiment

the output graph1 is termed as DSB. some times DSBSC(carrier gets suppressed) here the output

modulated wave is having modulation index of 1 because the modulated output reaches the minimum

value. Each part of the modulated output is termed as envelope which contains the original information

to be conveyed. In case of DSB signal carrier signal is used to convey redundant information but the

drawback is the communication system needs more power for transmission of signals. Suppression of

the carrier wave results in the reduction of power required for transmission. So, most of the time DSB SC

1

2

3

4

Graph1: AM Output

Graph2: AM + Carrier Output

Graph3: Multiplied Output

Graph4: Multiplier Output+ Phase

shift


11/16

signals are preferred. And Amplitude Modulation techniques are mostly used in Radio communications,

Telephony, Radar, Data communications etc

Graph2:(output(A)AM Wave+ Carrier signal)

The output obtained in the second graph is the combination of AM modulated wave and carrier. The

carrier signal is termed as the wave containing predominant high frequency harmonics. So, with the

combination of modulated signal reduces the amplitude of the modulated wave.

Graph3:Output B(Carrier IP x Modulated output A)

The output obtained in the third graph is the multiplication of the carrier input (high frequency

harmonics) and the modulated output A. Multiplication of both the signals during the first half cycle

increases (because multiplication of same polarity signals results increase in the amplitude)and the

amplitude of the positive half cycle while that of the negative half cycle comparatively low (almost

negligible because multiplication of opposite polarity signals results in the reduction in amplitude and

makes the signal negligible).

Graph4:(Output B + Phase change)

Output B is the signal which is the multiplication of (carrier IP and Modulated output A) now the Graph4

is the addition of output and carrier wave with a phase shift of 0 degrees which results in the output

similar to Graph3

Graph5: Output B + 90 Degrees phase change Graph6: Output B + 180 Degrees phase change

Graph7: Output B + 270 Degrees phase change Graph8: Output B + 360 Degrees phase change

Graph5: Output B + 90 Degrees phase change:

Again results in the AM envelopes which is the combination of two signals which are on the orthogonal

planes which results in double sidebands.


12/16


Now the output obtained here is same as the output with 0 degrees phase shift but as the 0 degrees

plane and 180 degrees plane lies on the same plane but of opposite polarity. Signal here gets reversed in

terms of polarity.


Again results in the AM envelopes which is the combination of two signals which are on the orthogonal

planes which results in double sidebands.


Now the output obtained hereis same as output obtained with 0

degrees phase shift as 0

degrees and 360 degrees

lies on same plane and same

direction.

Figure1b.2: outputs obtained by rotating the signal with 900

shift in each interval

00

3600

900

X negative Y

positive

Both X and Y

positive

1800

2700

Both X and Y

negative

X Positive Y

negative


13/16

AdvMod2:

Figure (AdvMod2): Summation and Multiplication of 2 sine waves

Observation:

Summation of two Sine Waves:

Two different sine waves Sum I/p1 and Sum I/p2 of frequencies 1kHz and 13kHz and with corresponding

amplitudes 1V and 3V respectively are feed to summing point and we get the output as output c.

Multiplication of two sine waves:

Now the output of the summer is feed to two inputs of AD633. So, two inputs to AD633 are same so

multiplying the same signals we get power signal which will be explained in the further discussion.

Multiplying two sine waves makes negative harmonics to get cancelled because multiplication of two

negative quantities gives the result positive same principle was applicable in this case.

Analysis:

Power(P) = V x I ------------------------(1)

Where V = Voltage; I = current

In turn V = I x R -------------- substitute in (1)

Sum i/ 1+ Sum i/ 2

Output c x output c


14/16

We get P = I2

x R = V2/R (since I = V/R)

From the above calculation we can observe power signal comprises of current signal multiplied by

current signal or voltage signal multiplied by voltage signal which is analogous to the experiment case

from this we can say that the signal obtained is power signal.

AdvMod3:

Figure AdvMod3: Determination of type of Sampling(over/ under sampling)

Description:

Modulation depth (or) Modulation Index is an important to determine the performance of the

communication system. Modulation depth indicates by how much the modulated variable varies around

its original level for AM it relates to the variations in the carrier amplitude which can be given by ratio of

max and min voltage values of AM envelope. Method to evaluate the modulation depth is by using the

envelope maximum and minimum amplitudes E max , E min values. this technique is applicable if the

carrier frequency is kept constant without any variations.

Formulae for Modulation index (m): (E max E min)( E max + E min)

m>1 (over modulation)

m = 1 (Full modulation)

m


15/16

Output at Modulating input: 10v carrier: 3v

E max = 10v, E min = 0v

(m)= (E max E min)( E max + E min)

Substituting values we get m= 1 (100%)

m = 1 (Full modulation)

Output at Modulating input: 50v carrier: 50vE max = 300v, E min = 150v


Substituting values we get m= 0.3333 (33.33%)

m < 1 (under modulation)

Output at Modulating input: 5v carrier: 12v

E max = 18v, E min = 6v


Substituting values we get m= 0.5 (50.00%)

m < 1 (under modulation)

Note: we are not concerned about over modulation

Figure AdvMod3: Different values of modulating, carrier voltages corresponding outputs and modulation

indexes

Overall Conclusion:

AdvMod1a:

We have studied the multiplier circuit by varying the DC level to +5v and -5v respectively observed the

output curves, shift in the curves with the variation In parameters keeping the carrier input constant.

AdvMod1b:

From this we have seen the output of multiplier (AD633) different combinations, their variation with the

change in phase by 90 degrees in each interval (which are 0, 90, 180,270,360 degrees respectively). And

we concluded that the wave forms obtained in this part as DSB signals.

AdvMod2:

We observed the addition and multiplication of two signals of different amplitudes and frequencies and

concluded the output signal as power signal.

AdvMod3:

From this experiment we observed modulated outputs of signals by varying the amplitudes of

modulating and carrier signals. Determined the Modulation Index and concluded whether the signal is

over modulated/ under modulated/ fully modulated by seeing the modulation index values.


16/16

mobile and digital broadcasting course work

Documents