Communication Systems Lab Manual

DEPARTMENT OF ELECTRICAL

ENGINEERING

LAB MANUAL

COMMUNICATION SYSTEMS

SUBMITTED TO:

RESPECTED MR.NAVEED AKHTER

SUBMITTED BY:

ASAD NAEEM

2006-RCET-EE-22

RACHNA COLLEGE OF ENGINEERING AND

TECHNOLOGY GUJRANWALA

POWER ELECTRONICS LAB MANUAL

ASAD NAEEM

2006-RCET-EE-22

RACHNA COLLEGE OF ENGINEERING & TECHNOLOGY GUJRANWALA Page 2

EXPERIMENT#01

INTRODUCTION TO THE DEV-2786 COMMUNICATION

TRAINER

BASIC CONCEPTS ABOUT A SIGNAL:

Frequency Number of cycles per second

Carrier Signal Signal that is used as base for carrying signals over long distance usually high frequency signal

Modulating Signal Signal that is being modulated such as audio or low frequency signal relative to carrier

Modulated Signal Signal after modulating on the carrier

Noise Uncertainty or randomness in a signal

Clock TTL or square wave for digital control

Voltage A certain level of signal fixed and not varying e.g., 2.3Volts

Drift Slowly varying noise (undesired signal)

Offset/Bias DC level in a signal

Keying Shifting frequencies within discrete levels

Audio Signal Normally 300-3500Hz for communications application. Audible range is 20-20KHz, but the telephonic bandwidth is one given above.

Sampling Frequency Rate at which a signal is digitized by a analog to digital converter


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Power Signal for driving the devices and running the system electronic

INTRODUCTION TO DEV-2786 COMMUNICATION TRAINER

Mojor Parts of this Trainer are described below:

1) Parallel Port Interface a 25 pin male jack for connecting to the parallel port of a PC and an associated socket for interfacing its input and output to connections on the trainer.

2) RS-232C PC Serial Interface a 9-pin female jack for connecting to the serial port of a PC and an associated socket for interfacing its input and output to connections on the trainer.

3) Soft Key

4) Spk-IN Female socket of 10 connections for connecting an input to a speaker on the trainer.

5) Socket For Audio Amplifier Out

6) Buzzer and input socket


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7) Volume control

8) MIC

The MIC available is shown. Connect the output of the MIC to the input of amplifier. Connect the audio amplifier output to the speaker input. Now if you touch the MIC you will hear the output on the speaker.

9) Socket For Audio Amplifier In

10) MIC-OUT Female sockets of 10 connections for

connecting to the audio input of trainer

11) Supply Voltages

• +5 VDC Socket for +5V±1 0% DC fixed

• +12 VDC Socket for +12V±10% DC fixed

• GND socket for ground

• -5 VDC Socket for -5V±1 0% DC fixed

• -12 VDC Socket for -12V±10% DC fixed

• Probe LED’s and Female 10 pin socket

12) Amplifier IN: Input to waveform amplifier

13) Amplitude: Knob for varying the amplitude

of the function generator output waveform

14) Offset: Knob for adding DC offset to the

function generator waveform.

15) Amplifier Out: Output to waveform amplifier


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16) Signal Input: sockets for noise, signal and mixed waveforms. 17) Signal Level Knob

18) Signal & Noise Output Socket

19) Noise Level Control Knob

20) Noise Output

21) Frequency Measurement Selector switch:

A two-position selector switch selects between two

signals one of carrier signal and other Modulating

22) Modulating Signal output socket

23) External Capacitor: A socket is made available where you can add a capacitor of appropriate value to get a waveform

of desired frequency.

24) Carrier Frequency Range Knob

25) AM & FM Sockets

26) Fine Range: Knob for fine-tuning the selected frequency of the function generator output waveform.

27) Duty: A variable knob to vary duty cycle of the

output waveform of Function Generator.

28) Function: A 10-pin socket where either

sinusoidal or triangular waveform (as selected)

is available

29) Clock: A 10-pin socket where square wave

output of function generator is available

30) Frequency Range Selector Switch: A two-position selector switch selects between two ranges


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of waveform frequencies i.e. 1 KHz to 100 Hz.

31) External Capacitor: A socket is made available where you can add a capacitor of appropriate value to

get a waveform of any desired frequency.

32) Function selector Switch: a two position selector switch selects between sinusoidal and triangular waveform

33) LCD Display

Modules that are commonly used : In order to cover complete range of experiments that vary from institution to institution, RIMS DEV-2786 is supplemented by a number of add-on modules. The add-on module is conveniently placed on six mounting screws:

D DSB Module D Product Detector/Frequency Mixer Module D PAM/PCM Module D Channel Simulation Filters Module D AM/FM Detector/Demodulator Module D Delta Modulation/Demodulation Module D FSK Modem Module D Timers Module


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EXPERIMENT#02

TO ADD NOISE SIGNAL TO ANY ORIGINAL SIGNAL

USING THE DEV-2786 COMMUNICATION TRAINER

EQUIPMENT: • DEV-2786 Trainer

• Oscilloscope

• connecting wires

THEORY: Noise: Uncertainty or randomness in a signal that is represented by sufficient statistics such as mean, variance etc.

TYPES OF NOISE:

1. Gaussian Noise If we select Gaussian Noise, and increase the variance then we can see the signal output on Oscilloscope as shown in the figure.

2. Uniform Noise: If we select Uniform Noise and increase the variance i.e., maximize noise signals then you can see on the scope on noise output as shown.

PROCEDURE: • First of all select the signal from function generator

• Give the output of generated signal to the amplifier

input

• Observe the signal on oscilloscope taking from the


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Amplifier output

• Give the amplifier output to the input of noise generator

• Select the noise type using LCD display and specific push buttons

• Observe the noise signal on oscilloscope and

also give the noise signal to the MIC input and

give the output of that signal to the speaker input

this causes a non uniform sound or noise

• Take the signal+noise output from the noise generator

• Connect that output to the oscilloscope and the speaker

system. We observe that the original signal which was

seen before on oscilloscope is distorted due to the

addition of noise signal and speaker output was also

a distorted sound.

• Observe the output by changing the noise level.

That change in the noise level results in the change of shape

of output.

CONCLSION: Due to the addition of noise in original signal, our original signal’s shape

was changed. This is called distribution of signal. We observed that by increasing the

level distortion in the original signal was increased.


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EXPERIMENT#03 INTRODUCTION TO FILTERS

Filters:

Electronic filters are electronic circuits which perform signal processing functions, specifically intended to remove unwanted signal components.

• Types of Filters:

1. Low pass filter

2- High pass filter

3-Band pass filter

4-Band stop filter


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Low Pass Filter: A low-pass filter is a filter that passes low-frequency signals but attenuates (reduces the

amplitude of) signals with frequencies higher than the cutoff frequency. The actual

amount of attenuation for each frequency varies from filter to filter. It is sometimes called

a high-cut filter, or treble cut filter when used in audio applications.

. Signal Vout contains frequencies from the input signal, with high frequencies

attenuated, but with little attenuations below the cutoff frequency of the filter determined

by its RC time constant. For current signals, a similar circuit using a resistor and

capacitor in parallel works the same way. See current divider.

A stiff physical barrier tends to reflect higher sound frequencies, and so acts as a low-

pass filter for transmitting sound. When music is playing in another room, the low notes

are easily heard, while the high notes are attenuated.

• Electronic low-pass filters are used to drive subwoofers and other types of

loudspeakers, to block high pitches that they can't efficiently broadcast.

• Radio transmitters use low-pass filters to block harmonic emissions which might

cause interference with other communications.

• An integrator is another example of a low-pass filter.

• DSL splitters use low-pass and high-pass filters to separate DSL and POTS

signals sharing the same pair of wires.

• Low-pass filters also play a significant role in the sculpting of sound for

electronic music as created by analogue synthesizers. See subtractive synthesis.


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One simple electrical circuit that will serve as a low-pass filter consists of a resistor in

series with a load, and a capacitor in parallel with the load. The capacitor exhibits

reactance, and blocks low-frequency signals, causing them to go through the load instead.

At higher frequencies the reactance drops, and the capacitor effectively functions as a

short circuit. The combination of resistance and capacitance gives you the time constant

of the filter τ = RC (represented by the Greek letter tau). The break frequency, also called

the turnover frequency or cutoff frequency (in hertz), is determined by the time constant:

An active low-pass filter

.

High Pass Filter:

A high-pass filter is a filter that passes high frequencies well, but attenuates (reduces the

amplitude of) frequencies lower than the cutoff frequency. The actual amount of

attenuation for each frequency varies from filter to filter. It is sometimes called a low-cut

filter; the terms bass-cut filter or rumble filter are also used in audio applications. A high-

pass filter is the opposite of a low-pass filter, and a band-pass filter is a combination of a

high-pass and a low-pass.


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It is useful as a filter to block any unwanted low frequency components of a complex

signal while passing the higher frequencies. The meanings of "low" and "high"

frequencies are relative to the cutoff frequency chosen by the filter designer. Contents

A passive, analog, first-order high-pass filter, realized by an RC circuit

The simplest electronic high-pass filter consists of a capacitor in series with the signal

path in conjunction with a resistor in parallel with the signal path. The resistance times

the capacitance (R×C) is the time constant (τ); it is inversely proportional to the cutoff

frequency, at which the output power is half the input (−3 dB):

Applications:

• Such a filter could be used as part of an audio crossover to direct high frequencies

to a tweeter while blocking bass signals which could interfere with, or damage,

the speaker.

• High-pass and low-pass filters are also used in digital image processing to

perform transformations in the spatial frequency domain.[citation needed]

• High-pass filters are also used for AC coupling at the input and output of

amplifiers.[citation needed]


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EXPERIMENT#04

TO STUDY WORKING PRINCIPLES OF DEV-2762-21 DSB

MODULE

EQUIPMENT: • DEV-2786 Trainer with DSB Module

• Oscilloscope


THEORY: DSB-MODULE: DSB module is used for DSB modulation. It has an input for carrier (high

frequency) signal and an input for original (modulating) signal. It uses MC1496B IC and

gives modulated signal as output.

DSB-MODULATION: DSB modulation is one of the types of Amplitude modulation.

Amplitude modulation is characterized by the fact that amplitude “A” of a carrier

signal Acos (wct) is valid in proportion to the base band signal m(t),the modulating

signal. The frequency “wc” and Өc are constant, we can assume (Өc =0) without a loss of

generality. This type of modulation (DSB modulation) simply shifts the spectrum of m (t)

to the carrier frequency.

Modulated signal /Fourier Transform is as

m (t) cos(wct) <=> 1/2[M(w+wc) + M(w-wc)]

“M(W-Wc)” is “M(W)” shifted to the right by we and “M(w+wc)” is “M(w)” shifted to

the left by “wc”.Thus,the process of modulation shifts the spectrum of the modulating

sign to the left and the right by wc ,modulated signal spectrum centered at we is

composed of two parts :a portion that lies above wc known as the upper sideband

(USB),and a potion that lies below wc known as lower sideband (LSB).Hence, this

modulation is called DSB(double side)modulation.

USB LSB LSB USB

- wc 0 wc


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PROCEDURE: • First of all select the modulating signal(of low frequency) from function generator

• Observe the signal on oscilloscope as shown

• Select the carrier signal(of high frequency) from function generator


(CARRIER SIGNAL)

ORIGINAL SIGNAL MODULATING

SIGNAL INPUT

MC1496B MODULATED

SIGNAL

CARRIER

CARRIER SIGNAL SIGNAL

INPUT

(BLOCK DIAGRAM)

• connect both modulating and carrier signal to the DSB-MODULE inputs

• Take the modulated signal from the output of module

• change the modulation level and observe the variations on oscilloscope


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(AMPLITUDE MODULATION)

(100% MODULATION) (OVER MADULATION)

CONCLSION:

The carrier signal amplitude was varied according to modulation level, but

frequency of the signal remained constant.


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EXPERIMENT#05

TO STUDY WORKING PRINCIPLES OF PRODUCT

DETECTOR/FREQUENCY MIXER MODULE

EQUIPMENT: • DEV-2786 Trainer with Product Detector/Frequency Mixer Module

• Oscilloscope

• Connecting wires

THEORY: Product detector is a type of demodulator used for AM and SSB

signals. Rather than converting the envelop of the signal into decoded

waveform like an envelope detector, he product detector takes the product of

the modulated signal and a local oscillator, hence the name “product

detector” is a frequency mixer.

Product detector can be designed to accept either IF or RF frequency

inputs. A product detector which accepts an IF signal would be used as a

demodulator block in a superhetrodyne receiver, and a detector designed for

RF can be combined with an RF amplifier and a low-pass filter into a direct-

conversion receiver.

Let the modulated signal is given by:

e (t) = m (t) cos2(wct)

= 1/2 [ m(t) + m(t)cos2wct ]

Now the Fourier transform of the signal e(t) is :

E(w) = 1/2 M(w) + 1/4 [M(w+2wc) + M(w-2wc)]

So, the signal e(t) contains two components:

m(t) and m(t)cos2wct

The first component 1/2 m(t) which is the original signal being a low

frequency signal is obtained by passing through a low pass filter.

PROCEDURE: • First of all select the modulating signal(of low frequency)

• from function generator


• Select the carrier signal(of high frequency) from function generator


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Original signal

Carrier signal modulated signal

Output signal

(BLOCK DIAGRAM)


(CARRIER SIGNAL)

• Connect these signals to the inputs of DSB-module to generate a

modulated signal


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• Observe the modulated signal on oscilloscope by taking the output of

DSB-module as shown

• Connect the modulated signal to the specified input of Frequency

mixer module

• Connect the same carrier signal which was used in modulation to the

other input of frequency mixer module

• Observe the output signal of frequency mixer module on oscilloscope,

which is the original signal.

(Output signal of frequency mixer module)

CONCLSION:

By using product detector & frequency mixer module we can get

back our modulating signal from the modulated signal. In fact this is the

simplest technique of demodulation.


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EXPERIMENT#06

TO DEMONSTRATE THE OPERATION OF THE 567-

PHASE LOCKED LOOP TONE DECODER

EQUIPMENT: • Function generator

• Oscilloscope


• IC 567

• Bread board

• Resistors (330Ώ,10k Ώ,18k Ώ)

• Capacitors (47,4.7 micro farad)

THEORY: Phase locked loop:

PLL is used to track the phase and frequency of the

carrier component of the incoming signal. It can be used for the

demodulation of AM signal with suppressed carrier. It can also be used for

demodulation of angle modulated signal.

PLL has here basic components:

• A voltage controlled oscillator

• A multiplier serving as phase detector

• A loop filter

Asin(wct+θi) e0(t)

Bcos(wct+θ0)


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PROCEDURE: Step 1:

Set the oscilloscope for the following settings:

• 1 volt/division

• 0.5 msec/div

• DC coupling

Step 2:

Connect the circuit as shown in the diagram. Apply the power supply from

unction generator at 200Hz and 2 volts peak to peak. The LED should not

light at this.

0.1µF

567-IC

0.1µF 47µF

Step 3:

Slowly increase the input frequency until he LED glows and record that

frequency as f1:

F1 = 588 Hz


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Step 4:

Slowly continue to increase the input frequency until the LED goes out and

record this frequency as f2:

F2 = 667 Hz

Sep 5:

Set the input frequency at about 800Hz and slowly decrease the frequency

until the LED glows and record that frequency as f3:

F3 = 645 Hz

Step 6:

Continue to decrease the frequency until the LED goes out and note that

frequency as f4:

F4 = 571 Hz

Step 7:

Now set the frequency at about 400Hz and measure the frequency at pin5 of

the IC which is the free VCO running frequency f0.

On increasing frequency lock will occur at f1 and will stay locked until the

input frequency reaches f2. For decreasing frequency, frequency will lock at

f3 up to f4.

The free running frequency is given by:

F0 = 1.10/RC

Where R=18k Ώ and C =0.1microFarad

Which is about 611Hz within 10%, this should agree with the value just

determined.

The %age bandwidth is found by:

% bandwidth = (f2-f1)/f0 ×100

F0 = 588 Hz

% bandwidth = (667-588)/588 ×100

= 13.43 %

Step 8:

By using the above values find the lock range (f2-f1) and capture range (f3-

f1) for this 567 tone decoder circuit.

Lock range = f2-f1

= 667-588 = 79 Hz

Capture range = f3-f1

= 645-588 = 57 Hz


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EXPERIMENT#07


CMOS PHASE LOCKED LOOP


• Oscilloscope


• IC 4046

• Bread board

• Resistors (27KΏ,4.7k Ώ,560Ώ, 100k Ώ)

• Capacitors (0.1,4.7 micro farad)

PROCEDURE: Step 1:


• 1 volt/division

• 0.5 msec/div

Step 2:

Connect the circuit as shown in the diagram. Apply the power supply from

unction generator at 1 KHz and 6 volts peak to peak. Connect the

oscilloscope to the common point of pin 3&4 of the 4046-IC. The output

frequency must be the same as input frequency.

Step 3:


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Set the oscilloscope time base to 2ms/div. now with a piece of wire connect

pin 9 to the ground. Record the output frequency of the phase locked loop

denoted by FL.

FL = 250Hz

This output frequency is the lower range of VCO, which is determined by

the 0.1µF capacitor connected between pin 6&7 and 100KΏ resistor

connected between pin 12 & ground.

Step 4:

Now set the oscilloscope time base to 0.2ms/div. Now with the same piece

of wire connect pin 9 to the +5V supply. Record the output frequency of the

phase locked loop denoted by FH that must be higher than the frequency

measured in step3.

FH = 5 KHz

This output frequency is the upper range of VCO, which is determined by

the 0.1µF capacitor connected between pin 6&7 and 560Ώ resistor

connected between pin 11 & ground.

Sep 5:


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Now remove the connection of pin 9 from +5V supply and output frequency

must be again 1 KHz same as that of function generator.

Step 6:

Now slowly continue to increase the input frequency, the output frequency

will also increase.

Step 7:

While watching the output frequency of phase locked loop, continue to

slowly increase the input frequency and stop to further increase the input

frequency when the output frequency become constant. Note the input

frequency:

Fin (H) = 2.18 KHz

Step 8:

Set the oscilloscope time base at 2ms/div. Now decrease the input frequency

until the output frequency again become constant. Note that input frequency:

Fin (L) = 135 Hz

This is the lower range of VCO. Consequently the phase locked loop circuit

follows the change in the input frequency for any frequency between upper

and lower range of VCO. Therefore the loop is locked. The range of

frequency for which it is locked is called “Lock-Range”.

Lock range = Fin (H) – Fin (L)

= 2.18 KHz – 135 Hz

= 2.045 KHz


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EXPERIMENT#08

TO DEMONSTRATE THE FUNCTION OF LOSS-OF-LOCK

INDICATOR WITH THE 4046-CMOS PHASE LOCKED

LOOP


• Oscilloscope


• IC 4001

• Bread board

• Resistors (100KΏ,330Ώ)

• Capacitor (0.1micro farad)

• LED

PROCEDURE: Step 1:

Wire the loss-of-lock circuit as shown in the diagram. Connect pin1 of 4001

CMOS NOR GATE to pin1 of the 4046-IC and pin2 of 4001 NOR GATE to

pin2 of the 4046 phase locked loop IC. Make sure that you have connected

the IN914 diode correctly across 100KΏ resistor. The anode goes to pin3

while cathode goes to junction of pin 5&6 of 4001-NOR GATE.

Step 2:


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Apply the power supply from unction generator at 500 Hz. The LED should

light at this frequency because it is in the lock-range of the loop. When the

loop is phase-locked, the output of the loss-of-lock circuit is at logic 1.

Step 3:

Increase the input frequency just past the upper range of the VCO. The LED

goes off because the phase locked loop is unlocked.

Step 4:

Now set the input frequency to 1 KHz. The LED should light because this

frequency lies in the lock range of the loop. You can use this circuit to

visually indicate whether the loop is locked or no.


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EXPERIMENT#09

TO STUDY WORKING PRINCIPLES OF AM-7910

MODEM MODULE

EQUIPMENT: • DEV-2786 Trainer with MODEM Module

• Oscilloscope


THEORY:

MODEM-MODULE:

� The Am7910 is a single-chip asynchronous Frequency Shift Keying (FSK) voice band modem.

� Digital signal processing techniques are employed in the Am7910 to perform all major functions such as modulation, demodulation and filtering.

� The Am7910 contain son-chip analog-to-digital and digital-to-analog converter circuits to minimize the external components in a system.

� Clocking can be generated by attaching a crystal to drive the internal crystal oscillator or by applying an external clock signal.

� All the digital input and output signals (except the external clock signal) are TTL compatible.

� Supply requirements are ±5 volts. DATA TERMINAL READY (DTR) A LOW level on this input indicates the data terminal desires to send and or receive data via the modem. This signal is gated with all other TTL inputs and outputs so that a low level enables all these signals as well as the internal control logic to function. A HIGH level disables all TTL I/O pins and the internal logic.

REQUEST TO SEND (RTS)


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A LOW level on this input instructs the modem to enter transmit mode. This input must remain LOW for the duration of data transmission. The signal has no effect if DATA TERMINAL READY is HIGH (disabled). A HIGH level on this input turns off the transmitter. CLEAR TO SEND (CTS): This output goes LOW at the end of a delay initiated when REQUEST TO SEND goes LOW; Actual data to be transmitted should not be presented to the TRANSMITTED DATA input until a LOW is indicated on the CLEAR TO SEND output. Normally the user should force the TD input HIGH whenever CTS is off (HIGH).This signal never goes LOW as long as DTP is HIGH (disabled). CLEAR TO SEND goes HIGH at the end of a delay initiated when REQUEST TO SEND goes HIGH.


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PROCEDURE: � Connect the input signals to the inputs of modem Module

� Connect the two terminals of the TC to the RC � The carrier detect signal should now be ON. This

shows the presence of the valid carrier on the receiver input

� Now we can observe the input and output signal of module as under

(Input signal) (Modulated signal)

� When we add noise into the modulated signal, then

we can observe that the noise is added in the

transmitted signal which can be seen as shown in the

figure or we can hear noisy sound using speaker


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EXPERIMENT#10 THE PURPOSE OF THIS EXPERIMENT IS TO DEMONSTRATE

THE OPERATION OF 565 PHASE LOCKED LOOP AS A

FREQUENCY SHIFT KEYING DEMODULATOR. IN ADDITION

TWO 555 TIMERS ARE USED AS A SIMPLE FSK GENERATOR.


• Oscilloscope


• Power Supply

• Soldering Iron and Solder

• NE 555 IC's (#442-53) (02)

• 565IC (#442-654) (01)

• 741 op amp (#442-22) (01)

• 100KΩ (02)

• 10KΩ (05)

• 560KΩ (01)

• 560Ω (03)

• l5KΩ (01)

• 4.7KΩ (01)

• 10K potentiometer with solder leads (01)

• 0.022 µf capacitor (04)




• 0.001 µf (01)

• Speaker (01)

• NPN transistor (#417-801) (01)

(PIN-OUTS)


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PROCEDURE:

Step 1: Set your oscilloscope for the following setting Channel: IV/division

Time base 0.2 mS/division

Trigger Channel

AC coupling

Step 2: Wire circuit A (the fsk generator) on one section of the breadboard. Apply power to the

breadboard and connect channel of your oscilloscope to the fsk output. You should hear a

sort of "tweet-dell" sound that alternates between two different frequencies. You can also

see the frequency shifting on the oscilloscope screen.


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Disconnect the 100kO resistor from pin 3 of the No 1 555 timer (point" A") ground the

end of the resistor that was initially to pin 3. Measurement the output frequency of the

No.2 timer, which we will call the mark frequency and record your result

F (mark) = 10 KHz

Step 3: Next, connect the 10OKO resistor to the +5 volt supply voltage. You should now hear a

steady tone that is higher in frequency than before. Measure this output frequency, called

the space the space frequency, and record your result.

F (space) = 12.5 KHz

The frequency difference between the mark and space is called the frequency shift. As

pointed out previously in the discussion in the 565 phase-locked-loop data

communication system community use a 1070Hz (or 2025Hz) mark and a 1270Hz (or

2225Hz)space, resulting in a 200Hz shift. Amateur or "hum" radio teletypewriter use

frequencies of 2125Hz (170Hz shift) or 2125Hz and 2975Hz (850Hz shift)

Step 4: Reconnected the 100KQ resistor to pin 3 of the No 1 timer as shown in the schematic

diagram, next temporarily disconnected the power from the bread board.

Step 5: Now wire circuit B (the fsk demodulator) as shown in the schematic diagram. Set your

oscilloscope for the following setting.

• Channels 1 & 2:2 V /division

• Time base: 10mS/division

• Trigger: Channel-1

Move the channel-1 oscilloscope probe from the fsk out put to input "A"

Step 6: Apply power to the breadboard and connect the output of the fsk generator to the input of

the demodulator circuit. Adjust the 10KΩ potentiometer carefully until the waveforms

shown on channels 1 and 2 are the same. At this point, the fsk demodulator is phase-

locked-loop to both the mark and space input frequencies. The output of the demodulator

circuit is now a logic that corresponds to the mark and space audio tones.


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EXPERIMENT#11


CMOS PHASE LOCKED LOOP AND A 4017 DECADE

COUNTER AS AN ×10 FREQUENCY MULTIPLIER OR

PRESCALER.


• Oscilloscope


• 4046 (#442-647)

• 4017 (#443-929)

• 0.1 µf capacitor


• 4.7 KΩ resistor

• 27 KΩ resistor

• 100 KΩ resistor

PROCEDURE: Step 1:


• 1 volt/division

• 10 msec/div

• AC coupling

Step 2:


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Set the circuit shown in the schematic diagram and apply power to the bread

board. Adjust the function generator so that the input frequency (f1) is some where

between 80 and 90Hz. In addition, the peak-to-peak input voltage to 8 volts.

Step 3: Measure the input frequency and record your result:

Fin = 84 Hz

Step 4: Now connected the oscilloscope to pin 4 of the 4046 device. Set the time base to

0.2ms/division. Measure the output frequency and record your result:

F0 = 833 Hz

What relationship do you notice between the frequencies that you measured in this step

and the one in step 3?

The output frequency should be 10 times larger than the input. The input frequency that

you measured in step 3 normally has a resolution of ±0.1Hz. As an example, if you

measured an input frequency of 87Hz, this means that the input frequency could range

from 86 to 88 Hz. If the measured output frequency was 867 Hz, the input would be more

precisely 86.7Hz, not 87 Hz! Thus, if this circuit were used with a frequency counter, the

counters resolution would be increased 1 significant digit.


ASAD NAEEM

2006-RCET-EE-22


EXPERIMENT#12 TO DEMONSTRATE THE OPERATION OF 4046 CMOS

FREQUENCY SYNTHESIZER


• Oscilloscope


• 4046 (#442-647)

• 4017 (#443-929)



• 560 KΩ resistor

• 27 KΩ resistor

• 330 Ω resistor

• 68 pf capacitor

PROCEDURE: Step 1: Set your oscilloscope for the following setting

1. Channel-1: 1V/division

2. Time base : 20 µS/division

3. AC coupling

Step 2: Wire the circuit shown in the schematic diagram and apply power to the bread board. Be

sure to change capacitor "C” of the NE555 signal source to 68 pf. What frequency do you

measure at the output?

You should measure approximately 10 KHz which is the input frequency. This is because

the 4017 counter is set to divide by 1.


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2006-RCET-EE-22


Step 3: Set your oscilloscope time base to 10µs/division. Now connect pin 15 to pin 4 on the

4017. Do this by removing the wire from pin 2 and connecting it to pin 4. What is the

output frequency now?

It should be 20 KHz or twice the input frequency since the 4017 counter is now set to

divide by 2.

Step 4: Set your oscilloscope time base to 5µs/division. Now connect pin 15 to pin 7. What is the

output frequency now?

It should be 30 KHz or three times the input frequency. This is because the 4017 counter

is now set to divide by 3.

Step 5:

Now connect pin 1 to pin 10. What is the output frequency now?

It should be 40 KHz or four times the input frequency.

Step 6: Connect pin 15 to pin 1,5,6,9, and 11 one after and record the output frequencies obtained


ASAD NAEEM

2006-RCET-EE-22


at each position. You obtain multiples of the input frequency from x5 to x9. Thus, we

have a simple frequency synthesizer capable of output frequencies from 10 KHz to 90

KHz steps.

Documents

Communication Systems Lab Manual