M S Engineering College

Transcription

1 M S Engineering College (ISO , Affiliated to VTU, Belgaum) International Airport oad,navarathaagrahara, Sadahlli P.O, Bangalore- 560 ANALOG COMMUNICATION+LIC MANUAL (0ECL58) Department of Electronics and communication Engineering Prepared By Azra Jeelani MTech, (PhD),Associate Professor M S Engineering College, Bangalore Jagadish B S ME, Assistant Professor M S Engineering College, Bangalore Tejaswini MTech, (PhD), Associate Profeeor M S Engineering College, Bangalore Department of Electronics and Communication,MSEC Page

2 VTU PESCIBED SYLLABUS Sub Code:0ECL58 IA Marks :5 Hrs/ Week :03 ExamHours: 03 Total Hrs. :4 ExamMarks :50. Second order active low pass filter.. Second order active high pass filter. 3. Second order active band pass filter. 4. Second order active band reject filter. 5. Schmitt trigger design and test a given values of UTP and LTP 6. Design and test - DAC using OP-AMP. 7. Half Wave Precision ectifier 8. Full Wave Precision ectifier 9. Design and test the following circuits using IC 555 (a) Astable multivibrator for given frequency and duty cycle (b) Monostable multivibrator for given pulse width W. 0. Pulse Width Modulation. Pulse Position Modulation. Amplitude modulation using Transistor/FET (Generation and Detection) 3) Pulse Amplitude modulation and Detection 4) Frequency Modulation and Demodulation Department of Electronics and Communication,MSEC Page

3 CYCLE WISE EXPEIMENTS CYCLE -. Second order active low pass filter.. Second order active high pass filter. 3. Second order active band pass filter. 4. Second order active band reject filter. 5. Schmitt trigger design and test a given values of UTP and LTP CYCLE - 6. Design and test - DAC using OP-AMP. 7. Half Wave Precision ectifier 8. Full Wave Precision ectifier 9. Design and test the following circuits using IC 555 (a) Astable multivibrator for given frequency and duty cycle (b) Monostable multivibrator for given pulse width W. CYCLE Pulse Width Modulation. Pulse Position Modulation. Amplitude modulation using Transistor/FET (Generation and Detection) 3) Pulse Amplitude modulation and Detection 4) Frequency Modulation and Demodulation Department of Electronics and Communication,MSEC Page 3

4 SECOND ODE LOW PASS FILTE Aim : To design and set up a second order Butterworth low pass filter for the cutoff frequency f h = khz and to plot the respective frequency response Apparatus : µa74 opamp, resistor,capacitor,bread board,function generator, power supply, CO and connecting wires Theory: A filter is a circuit designed to pass a specified band of frequencies while attenuating all the signals outside the band. Filter network may be either Active or Passive.Active filters consist of Active devices like opamp, transistor etcpassive network consist of passive device like esistors, Capacitors, Inductors etc.there are 4 types of filters.low pass filter,high Pass filter, Band pass filter Band eject filter. Low pass filter : low pass filter is a circuit which passes only low frequency signals and attenuate the high frequency signal.an ideal low pass filter can be realized by multiplying a signal by rectangular function.lpf is used to drive subwufers and other type of loudspeaker to block high pitches that they cant efficiently broadcast.adio transmitter use lpf to block harmonic emissions which might cause interference with other communications.it can be used as an integrator.it also plays a significant role in the sculpting of sound for electronics music as created by synthesizers Circuit Diagram Department of Electronics and Communication,MSEC Page 4

5 Design Steps Voltage gain magnitude equation of second order low pass filter Af = Pass band gain f = Input frequency fh = cut off frequency Vo = Output voltage Vi = Input Voltage A + f f Let A f =.586 and = 7kΩ f = f = 0.586x 7 x 0 3 f = 5.8kΩ Higher cut off frequency fh = Let f h = khz C = C = C 3 =.0047µf C C 3 3 = = 3 f h = C f C h x x000x0.0047x0 6 =33.86kΩ Department of Electronics and Communication,MSEC Page 5

6 Tabular Column Frequency (Hz) Vo (volts) Vo Vi Vo Mag=0 log Vi khZ Ideal wave form: Procedure. Before wiring the circuit heck all the components using Multimeter and Ic Tester. Design the Filter and make the connections as in figure 3. Set the signal generator amplitude to v p-p and observe the Vin and Vo simultaneously on the CO 4. By varying the frequency of the input from few hertz to few kilo hertz Note down the output Voltage across pin no 6 wrt ground 5. The output voltage remains constant for low frequency range uptp cutoff frequency and afterwards Vo get attenuated 6. Tabulate the readings and Plot the Graph Department of Electronics and Communication,MSEC Page 6

7 SECOND ODE HIGH PASS FILTE Aim : To design and set up a second order Butterworth High pass filter for the cutoff frequency f L = khz and to plot the respective frequency response Apparatus : µa74 opamp, resistor,capacitor,bread board, function generator, power supply, CO and connecting wires Theory: A filter is a circuit designed to pass a specified band of frequencies while attenuating all the signals outside the band. Filter network may be either Active or Passive.High pass filter : High pass filter is a circuit which passes only High frequency signals and attenuates the low frequency signal below cutoff frequency.amount of attenuation varies from filter to filter. HPF is an opposite of low pass filter.a butter worth filter provides a flat response in passband.higher the order of the filterfaster the rate at which the gain changes.eg for first order hpf gain raise at the rate of +0db/decadebut for second order it is 40db/decade.High pass filter with very low cutoff frequency can be used to block DC signal which is undesired. Circuit Diagram Design Steps Vo Vi A f f L f 4 Vo = Output voltage Vi = Input Voltage Af = Pass band gain f = Input frequency fh = cut off frequency Department of Electronics and Communication,MSEC Page 7

8 A + f f Let A f =.586 and = 7kΩ f = f = 0.586x 7 x 0 3 f = 5.8kΩ Lower cut off frequency f L = Let f L = khz C = C = C 3 = 0.µf C C 3 3 = = 3 f L = C f C L x x000x0.x0 6 =.59kΩ Tabular Column Frequency (Hz) Vo (volts) Vo Vi Vo Mag=0 log Vi 00Hz 0KHz Department of Electronics and Communication,MSEC Page 8

9 Ideal wave form Procedure. Before wiring the circuit heck all the components using Multimeter and Ic Tester. Design the Filter and make the connections as in figure 3. Set the signal generator amplitude to v p-p and observe the Vin and Vo simultaneously on the CO 4. By varying the frequency of the input from few hertz to few kilo hertz Note down the output Voltage across pin no 6 wrt ground 5. The output voltage goes on increasing upto cutoff frequency and then remains constant for High frequency range 6. Tabulate the readings and Plot the Graph Department of Electronics and Communication,MSEC Page 9

10 SECOND ODE BAND PASS FILTE Aim : To design and set up a second order Band pass filter for the cutoff frequency f L = 4 khz and f h = 9khz and to plot the respective frequency response Apparatus : µa74 opamp, resistor,capacitor,spring board, power supply, CO and connecting wires Theory: A Band pass filter is basically a frequency selector it allows to pass a band of frequency once. Thus the band pass filter is between two cutoff frequencies f l and f h where f h > f L Any frequency outside the band is attenuated There are two band pass filter based on Q factor. Q<0 The Band pass filter is called wide band pass filter. Q>0 The Band pass filter is called Narrow band pass filter Wide Band Pass Filter: it is obtained by cascading a HPF and LPF.it has two stop band and one passband.the bandwidth of a filter is the difference between the upper and lower cutoff frequency. Circuit Diagram Design Steps For High pass filter Voltage gain magnitude equation of second order low pass filter Vo Vi A f f L f 4 fh = cut off frequency Vo = Output voltage Af = Pass band gain f = Input frequency Department of Electronics and Communication,MSEC Page 0

11 Vi = Input Voltage A + f f Let A f =.586 and = 7kΩ f = =.586x 7 x 0 3 f = 5.8kΩ Lower cut off frequency f L = Let f L = 4khz C = C = C 3 = 0.µf C C 3 3 = = 3 f L = C f C L x4 x000x0.x0 6 = 400 Ω For lowpass filter Voltage gain magnitude equation of second order low pass filter Af = Pass band gain f = Input frequency fh = cut off frequency Vo = Output voltage Vi = Input Voltage A + f f Let A f =.586 and = 7kΩ f = = 0.586x 7 x 0 3 Department of Electronics and Communication,MSEC Page

12 f = 5.8kΩ Higher cut off frequency fh = ' ' 3 C ' C ' 3 Let f h = 9 khz C = C = C 3 = 0.0 µf = = 3 f h = C f C h x9 x000x0.0x0 6 =.8kΩ Tabular Column Frequency (Hz) Vo (volts) Vo Vi Vo Mag=0 log Vi 00Hz khz.. 0KHZ Department of Electronics and Communication,MSEC Page

13 Ideal waveform Procedure ) Before wiring the circuit heck all the components using Multimeter and Ic Tester ) Design the Filter and make the connections as in figure 3) Set the signal generator amplitude to v p-p and observe the Vin and Vo simultaneously on the CO 4) By varying the frequency of the input from few hertz to few kilo hertz Note down the output Voltage across pin no 6 wrt ground 5) The output voltage gets attenuated before 4khz(lower cutoff frequency) and after 9khz(Higher cutoff frequency) 6) Tabulate the readings and Plot the Graph Department of Electronics and Communication,MSEC Page 3

14 SECOND ODE BAND ELIMINATION FILTE Aim : To design and set up a second order Wide Band reject filter for the cutoff frequency f L = 9 khz and f h = 5khz and to plot the respective frequency response Apparatus : µa74 opamp, resistor,capacitor,bread board, power supply, function generator, CO,function generator and connecting wires Theory: A Band reject filter is basically a frequency selector it rejects a band of frequency. once. Thus the band reject filter rejects the frequency between two cutoff frequencies f l and f h. Any frequency outside the band is passed.it is a opposite of band pass filter. Band reject filter has two passband and one stopband.in this filter the ower cutoff frequency of HPF must be greater than the higher cutoff frequency of low pass filter.and passband gain for both hpf and lpf must be equal.it is used in signal processing unit. There are two types wide band reject filter and Notch filter. Circuit Diagram Department of Electronics and Communication,MSEC Page 4

15 Design Steps A + f f Let A f =.586 and = 0kΩ f = = 0.586x 0 x 0 3 = 5.86kΩ For HPF filter Lower cut off frequency f L = C C 3 3 Let f L = 9khz C = C = C 3 = 0.0µf = = 3 f L = C f C L x9 x000x0.x0 6 =.76kΩ For lowpass filter Higher cut off frequency fh = Let f h = 5khz C = C = C 3 = 0.0 µf = = 3 f h = C ' ' 3 C ' C ' 3 f C h x5 x000x0.0x0 6 = 3.3kΩ Department of Electronics and Communication,MSEC Page 5

16 Tabular Column Frequency (Hz) Vo (volts) Vo Vi Vo Mag=0 log Vi 00 0KHz Ideal wave form: Procedure ) Before wiring the circuit heck all the components using Multimeter and Ic Tester ) Design the Filter and make the connections as in figure 3) Set the signal generator amplitude to v p-p and observe the Vin and Vo simultaneously on the CO 4) By varying the frequency of the input from few hertz to few kilo hertz.note down the output Voltage across pin no 6 wrt ground 5)Tabulate the readings and Plot the Graph Department of Electronics and Communication,MSEC Page 6

17 SCHMITT TIGGE DESIGN AND TESTING SCHMITT TIGGE CICUIT FO UTP AND LTP Aim : Design a Schmitt trigger for a given values of UTP and LTP. Apparatus : µa74 opamp, resistor,capacitor,bread board, power supply, CO,function generator and connecting wires Theory : The Schmitt trigger is a comparator application which switches the output negative when the input passes upward through positive reference voltage. It then uses a negative feedback to prevent switching back to other state until the input passes through lower threshold voltage. Thus stabilizing the switching against rapid triggering by noise as it passes the trigger point. Today comparators are connected to have positive feedback instead of negative feedback. For this circuit switching occurs near ground, with the amount of hystersis controlled by resistance and. Circuit Diagram Department of Electronics and Communication,MSEC Page 7

18 Department of Electronics and Communication,MSEC Page 8 ) ( EF V SAT V ) ( ref V SAT V Ideal waveform: Design Steps: UTP =.5v, LTP = v UTP = () LTP = () Assume = 5kΩ Adding equation () and () UTP + LTP = Ef V.5 + = Ef V 3.5= Ef V (3) Subtract equation () and () UTP - LTP = SAT V

19 .5 = VSAT Vsat = Vcc =v.5 = x 4 =.5 ( + ) Let = 5kΩ.5 = = kω.5 Consider eq (3) V EF = 3.5( ) 3.5(5k.5k) (5k).9v V EF =.9 v Procedure: ) Before wiring the circuit heck all the components using Multimeter and Ic Tester. ) Design the circuit and make the connections as in figure. 3) Provide a 0 volts p-p at 500hz sinusoidal input and observe the output of the circuit 4) Verify the hysteresis in XY mode of the CO 5) Compare the observed waveform with that given above and note down the parameters Department of Electronics and Communication,MSEC Page 9

20 Aim : Design And Test - Dac Using Opamp - DAC USING OPAMP Apparatus : µa74 opamp, resistor,capacitor,bread board, power supply, CO, function generator and connecting wires Theory : - ladder network provides a simple means to convert digital information to an analog output.although simple in design and function.it provide simple and inexpensive to perform digital to analog conversion. The most popular network are binary weighted ladder and / ladder.both the devices convert digital to analog information. Circuit Diagram Design Steps D 0,D,D,D 3 are the digital inputs. V (0) = 0 and V () = 5v The analog Vo for 4 bit DAC is given by V O 3 0 V D3 D D D0 4 let V = 5v V O D 3 4D D D 0 Let = kω = kω Choose =.kω Department of Electronics and Communication,MSEC Page 0

21 Tabular Column : Decimal Value Digital i/p Analog o/p Practical o/p D 0 D D D 3 Theoritical o/p Procedure : ) Before wiring the circuit heck all the components using Multimeter and Ic Tester. ) Design the circuit and make the connections as in figure and provide Vref as per the design 3)Provide a digital input through D 0 to D 6 4)Observe the analog output at Vout. 5) Draw the graph of Vo verses Decimal Value Department of Electronics and Communication,MSEC Page

22 PULSE AMPLITUDE MODULATION Aim : To conduct an experiment to generate PAM signal and Demodulation of PAM signal Apparatus : esistor,capacitor,diode (0A79),Transistor (SL00), bread board, power supply, CO, function generator and connecting wires. Theory: In the pulse Amplitude modulation the amplitude pulses ie carrier wave is varied in accordance with the instantaneous amplitude of the modulating signal.the width and position is kept constant.the Pam Transmitter design is very simple since the sampling the modulating signal at regular intervals produces pulse amplitude modulation Circuit Diagram Department of Electronics and Communication,MSEC Page

23 Design Steps : Vce(sat)=0.3V Vbe(sat)=0.7V I E =I C =3*0-3 β=00 V m (t)=4v V c (t)=5v - V m (t)+ V c (t)+ V E =0 V E =V m (t)-v cc (sat) =4-0.7=3.3V E =V E /I E =3.3/3*0-3 =.kω Applying KVL -V c (t) + I B B + V BE (sat) +V E =0 B = /I B =kω I B =I C /β =3*0-3 /00 =300µA Demodulation: fc >>freq fc>>500hz f 0 =/ C if c=0.µf =3.8kΩ Department of Electronics and Communication,MSEC Page 3

24 Ideal Waveform Procedure : ) ig up the circuit as in figure. ) Apply the square wave carrier input of v p-p of frequency of 5khz. 3) Aplly the sinusoidal modulating signalof v p-p of frequency khz and vary the frequency from 500hz to khz emember that o/p will be proper only if the ratio of frequencies of modulating signal and carrier are in ratio of : 0 4) Observe the PAM output wrt modulating input. 5) Observe the demodulated o/p and verify with modulating signal. Department of Electronics and Communication,MSEC Page 4

25 PULSE WIDTH MODULATION Aim : To generate pulse width modulated signal for the given analog signal for a frequency < khz. Apparatus : µa74 opamp, resistor,spring board, power supply, CO, function generator and connecting wires Theory : Pulse width modulation is also known as pulse duration modulation. In this modulation a fixed amplitude and starting time of each pulse is maintained constant but the width of each pulse is varied.the pulses are of varying width because of varying power content.it convey information over the communication channel to control the amount of power sent to sent to a load Circuit Diagram : Design Steps : Frequency of c(t) =.5khz A f f let A f = f = Choose = 0kΩ f = 0kΩ Department of Electronics and Communication,MSEC Page 5

26 Ideal waveform Procdeure ) ig up the circuit as per the circuit diagram. ) Apply a triangular wave carrier and a sinusoidal modulating signal of 3v p-p of frequency 600 hz. 3) Vary the amplitude of the modulating signal and obtain PWM output wave form 4) For demodulation connect a second order LPF across PWM o/p Department of Electronics and Communication,MSEC Page 6

27 PULSE POSITION MODULATION Aim : To generate pulse position modulated signal. Apparatus :esistor, capacitor,diode (IN4007) generator and connecting wires. IC, spring board, power supply, CO, function Theory : In this type of modulation the amplitude and width of the pulse is kept constant while position of each pulse is varied by modulating signal.ppm can be obtained from pwm.ppm is a form of signal modulation in which message bits are encoded by transmitting a single pulse in one of the two possible time shift.this is repeated every T sec such that the transmitted bit rate is M/T bits per second. Circuit Diagram Department of Electronics and Communication,MSEC Page 7

28 Ideal waveform Procedure ) ig up the circuit as per the circuit diagram ) Obtain the PWM o/p and cascade it with PM circuit 3) Obtain the PPM o/p wrt modulating signal 4) For demodulator connect the second order LPF across the PPM o/p Department of Electronics and Communication,MSEC Page 8

29 FEQUENCY MODULATION Aim : To perform frequency Modulation using Apparatus : Diode (IN4007), esistor,ic 8038,capacitor, function generator,spring board,probes,co. Theory : In frequency modulation the frequency of the carrier is varied according to the message signal.in frequency modulation amplitude is of the carrier is kept constant while its frequency is varied.the amount of change in frequency produced by the modulating signal is known as frequency deviation.maximum frequency deviation occurs maximum amplitude of modulating signal and minimum frequency deviation occurs at minimum amplitude of modulating signal. Circuit Diagram Design fc = 9.khz Vi = from the data sheet if fo = C Vcc 3 Department of Electronics and Communication,MSEC Page 9

30 Assume a = b = =0 kω C=360pF=3300pF Ideal waveform Procedure ) ig up the circuit as per the circuit diagram ) Short pin 7 & 8 and connect the terminal to variable DC power supply 3) Vary the DC supply from to 0 volts in the frequency range of khz through c circuit and at each step note down the frequency of the output 4) Plot the graph of voltage versus o/p frequency Department of Electronics and Communication,MSEC Page 30

31 AMPLITUDE MODULATION Aim : Generation of amplitude modulated waveform. Apparatus : esistor, capacitor,fet (BC07), Diode spring board, power supply, CO, function generator and connecting wires. Theory Amplitude modulation is a technique used in communication.most commonly for transmitting information via radio carrier wave.in this modulation amplitude of the carrier is varied in accordance with the message signal.this is FET based AM generator.this circuit controls the size of the signal using a second signal as a control.to put this ability of the FET to work a second function generator, to drive the gate voltage so that so that this second signal modulates the amplitude of the i/p signal.let the frequency of the carrier is 5khz with amplitude of 5vand frequency of modulating signal is 500hz with amplitude of vfor stable display of output waveform trigger the scope on the modulation signal. Circuit Diagram Department of Electronics and Communication,MSEC Page 3

32 Ideal waveform Department of Electronics and Communication,MSEC Page 3

33 Procedure ) ig up the circuit as per the circuit diagram ) Apply the sine wave carrier input of 0.5v p-p with a frequency of 5khz 3) Apply a sinusoidal modulating signal of v p-p og frequency 500hz 4) Observe the AM o/p wrt modulating i/p 5) Observe the demodulated o/p and verify with modulating.the frequency must be same.emember that o/p will be proper only if the ratio of frequency of modulating signal and carrier are in the ratio :0 Department of Electronics and Communication,MSEC Page 33

34 PECISION ECTIFIE Aim : To design and implement a full wave and half wave precision rectifier circuit using opamp Apparatus : esistor, opamp, Diode spring board, power supply, CO, function generator and connecting wires. Theory The precision rectifier is a configuration obtained with an operational amplifier in order to have a circuit behaving like an ideal diode or rectifier.it can be useful for high precision signal processing.precision rectifier is a rectifier which rectifies the A.C of small value.it consist of opamp two diodes and resistor.in fact diode act as a switch since the voltage drop across diode is divided by open loop gain of the opamp. Circuit Diagram Department of Electronics and Communication,MSEC Page 34

35 Design Gain = 0 Gain = f = = f = 0kΩ Ideal Waveform Department of Electronics and Communication,MSEC Page 35

36 Procedure : ) ig up the circuit as in figure ) Apply the sinusoidal modulating signal of 0.v p-p of frequency khz 3) Observed the precision rectified o/p wrt the input 4) Observe the transfer characterstics Department of Electronics and Communication,MSEC Page 36

37 ASTABLE AND MONOSTABLE MULTIVIBATO Aim : Design and test the Astable multivibrator for given frequency and duty cycle and Monostable multivibrator for given pulse width using IC555 Apparatus : IC 555Timer, esistor, Capacitor, breadboard, power supply, CO, function generator and connecting wires. Theory : An astable multivibrator is a timing circuit whose low and high states are both unstable. The output of Astable multivibrator toggles between low and high continuously generating a train of pulses. This is also known as pulse generator circuit.in this circuit capacitor C discharges through and eventually building up enough voltage to trigger an internal comparator to toggle the output flipflop.once toggled flipflop discharges C through into pin7, which is the discharge pin.when C s voltage becomes low enough,another internal comparator is triggered to toggle the output flipflop.this once again allows C to charge up through and and cycle starts all over again.a monostable multivibrator is a timing circuit that changes state once triggered, but returns to original state after a certain time delay. it has only one of its output state is stable.it is also known as one shot.in this circuit a negative pulse is applied at pin triggers an internal flipflop that turns off pin 7 s discharge transistor,allowing C to charge up through.at the same time the flip flop brings the output (pin 3) level to high. When capacitor C is charged upto about /3 Vcc The flipflop is triggered once again This makes the pin 3 output low and turning on pin 7 s discharge transistor.,which discharges C to ground. The circuit produces pulse of width t = C. The eset pin used to reset the timing cycle by pulling it momentarily low, should be tied to Vcc if it will not be used. Design : f = khz Duty cycle = 60% T 0. 5ms T l T h f T h D Vut = voltage at upper threshold frequency = Vcc/3 T l T h = 0.6 T = 0.3ms V lt = voltage at lower threshold frequency = Vcc/3 T l = T - T h = 0.ms T l = C Let C= 0.µf =.866kΩ =.7kΩ T h = ( + ) C =.443 kω =.5 kω Department of Electronics and Communication,MSEC Page 37

38 Circuit diagram Department of Electronics and Communication,MSEC Page 38

39 Ideal waveform Design : Let output pulse width = delay time Td = 0.5ms Output delay time Td =. C Let = 0 kω C =.045 µf choose c =.047 µf Here Vut = upper threshold voltage = /3Vcc Choose t Ct << Td select t Ct << Td/0 Let t = 0kΩ and Ct = 0.0 µf. Ground. Trigger input 3. Output 4. eset Input 5. Control voltage 6. Threshold 7. discharge 8. +Vcc ( 5v to 5v) Department of Electronics and Communication,MSEC Page 39

40 Procedure : Astable multivibrator. ig up the circuit as per the circuit diagram. switch on the Dc Power supply and observe the output waveform in CO and measure Td,Voh, Vut and verify the designed value Monostable multivibrator. ig up the circuit as per the circuit diagram. Switch on the Dc Power supply and observe the output waveform at pin 3 3. Measure the output pulse amplitude Voh,Vol 4.Observe the capacitor voltage at pin 6 and measure the maximum and minimum voltage level 5. Compare the capacitor voltage and output voltage and note the capacitor charging and discharging and Vc rises when output is high.capacitor C discharges through and Vc rises exponentially when output is low Department of Electronics and Communication,MSEC Page 40

41 CLASS C SINGLE TUNED AMPLIFIE Aim : study of working of amplitude modulation technique and to find the modulation index Apparatus : Transistor, audio frequency transformer,intermediate frequency transformer, esistor, Capacitor, breadboard, power supply, CO, function generator and connecting wires. Theory : Amplitude modulation is a technique which amplitude of the carrier is changed according to the modulating signal.the frequency of modulating signal should be less than carrier.the ratio of voltage of modulating signal to carrier voltage is called modulation index m and it is expressed as percentage.m ranges from 0 to and if m> it is overmodulation and m<0 it is undermodulation for perfect demodulation at the receiver end 0<m<.for amplitude modulation carrier is required to be generated at the transmitting end and at the receiving end it is not required. Circuit diagram Department of Electronics and Communication,MSEC Page 4

42 Ideal Waveform Department of Electronics and Communication,MSEC Page 4

43 Procedure. Connections are made as in figure. Modulating signal is switched off and tuned frequency of IFT is found by varying the carrier signal frequency 3. Carrier signal is set at IFT frequency with amplitude 5v and modulating signal is switched on.the Am signal is observed at the o/p of IFT 4. Modulation Index (m) is found Vmax Vmin m and m< V V max min 5. Plot the graph of Vm in volts v/s %m 6. AM signal was applied to the demodulation circuit and demodulated o/p waveform is observed. Department of Electronics and Communication,MSEC Page 43

44 Viva questions for analog communication lab. Define the word communication.. What are the basic components of electronic communication. 3. What is Transmitter. 4. What is receiver 5. What is communication channel? 6. State two types of communication? 7. What is baseband signal? 8. What is baseband transmission? 9. What is the need for modulation? 0.Define the carrier signal?.what is the classification of modulation?.what is frequency deviation? 3.Define noise? 4.Define the basic sources of noise? 5.What is shot noise?6.define signal to noise ratio? 7.What is noise factor? 8.State the equation for noise factor for cascade connection? 9.Define amplitude modulation? 0.Define modulation index?.state the bandwidth required for amplitude modulation?. What is frequency domain display? 3. What is time domain display? 4. What is maximum power of sideband of AM? 5. What is the maximum total power of AM wave? 6. Define a high level modulation? 7. Define a low level modulation? Department of Electronics and Communication,MSEC Page 44

45 8.Why amplitude modulation is used for broadcasting? 9.What is the position of the operating point of class-c? 30.What is the advantage of SSB over DSB-SC? 3.What is the function of Transistor mixer? 3.What is the principle of Envelope detector? 33.Where SSB transmission is used? 34.What is an op-amp and What are the applications of op-amp? 36.What isvirtual ground? 37.What are the ideal characteristics of op-amp? 38.What is slew rate, CM, PS? 39.What are the different types of adc and dac convertors? 40.What is Schmitt trigger? Department of Electronics and Communication,MSEC Page 45