Antenna-Exp.-1.1.docx

(1)

Experiment No. 1 Experiment No. 1

WAVE PROPAGATION IN A TRANSMISSION LINE DEMONSTRATING THE EFFECTS OF WAVE PROPAGATION IN A TRANSMISSION LINE DEMONSTRATING THE EFFECTS OF

LOSSES, ATTENUATION, AND STANDING WAVES LOSSES, ATTENUATION, AND STANDING WAVES Course:

Course: ECE503 ECE503 Experiment Experiment No.: No.: 11 Group

Group No.: No.: 6 6 Section: Section: EC51FC1EC51FC1 Group

Group Members: Members: ANTHONY ANTHONY SAGCAL SAGCAL Date Date Performed: Performed: 06/19/201706/19/2017 PAULA

PAULA ISABEL ISABEL SIGNO, SIGNO, BRYAN BRYAN TADURAN TADURAN Date Date Submitted: Submitted: 06/23/201706/23/2017 GRACE

GRACE AMIEL AMIEL TUPAS TUPAS Instructor: Instructor: ENGR. ENGR. FRANCIS FRANCIS B. B. MALITMALIT 1.Objectives(s):

1.Objectives(s): This activity aims to

This activity aims to introduce the basic concepts of transmission line and its introduce the basic concepts of transmission line and its abnormalities andabnormalities and effects. This experiment will provide the students to

effects. This experiment will provide the students to analyze how the electrical signal propagatesanalyze how the electrical signal propagates inside the transmission line and how it reacts to the irregularities on the line. This will

inside the transmission line and how it reacts to the irregularities on the line. This will also help thealso help the students to understand the concepts of

students to understand the concepts of characteristics impedanccharacteristics impedance e and reflections in and reflections in transmissiontransmission lines.

lines.

2.Intended Learning Outcomes(ILOs): 2.Intended Learning Outcomes(ILOs): The students shall be able to:

The students shall be able to:

2.1 Understand and explain the propagation of a signal in

2.1 Understand and explain the propagation of a signal in a match or a match or non-resonating line.non-resonating line. 2.2 Determine the effects of

2.2 Determine the effects of losses, attenuation, and dispersion, on the amplitude, frequency, andlosses, attenuation, and dispersion, on the amplitude, frequency, and phase of a signal

phase of a signal 2.3 Define the

2.3 Define the characteristic impedance and reflectionscharacteristic impedance and reflections 3.Discussion:

3.Discussion:

Propagation in a Transmission Line Propagation in a Transmission Line

There are many situations in which it is desired to connect a generator (source of

There are many situations in which it is desired to connect a generator (source of electricalelectrical power) to distant load

power) to distant load (power(power – – absorbing device). The generator usually is of absorbing device). The generator usually is of high power source,high power source, as in a power station, and the load is

as in a power station, and the load is of low power, as with in a of low power, as with in a microphonemicrophone; which maybe in of low; which maybe in of low frequency. Usually the power station, is a radio transmitter. In each case a pair of conductors is frequency. Usually the power station, is a radio transmitter. In each case a pair of conductors is required to convey the power from the generator to the load. Such a pair of

required to convey the power from the generator to the load. Such a pair of conductoconductors is called ars is called a “transmission line” or to simply

“transmission line” or to simply a ‘line’ when convenient.a ‘line’ when convenient. When a signal is applied at one end of tran

When a signal is applied at one end of transmission line at one end, the other end is notsmission line at one end, the other end is not immediately affected. Instead the signal travels along the line

immediately affected. Instead the signal travels along the line with finite velocity, and reaches thewith finite velocity, and reaches the load somewhat later. The potential difference between the conductors is associated with the load somewhat later. The potential difference between the conductors is associated with the magnetic field. Those fields interact with each other and with the line to form a

magnetic field. Those fields interact with each other and with the line to form a guidedguided electromagnetic wave travelling along the line. The maximum speed that a

electromagnetic wave travelling along the line. The maximum speed that a wave can have iswave can have is similar to the speed of light which is

similar to the speed of light which is 31031088_{m/s. In li}_{m/s. In lines having solid materials around the}_{nes having solid materials around the} conductors the speed or propagation could be much lesser. If

conductors the speed or propagation could be much lesser. If a sinusoidal signal is applied to ta sinusoidal signal is applied to thehe line, different phases of the sine-wave will be distributed in distance along the line owing to its line, different phases of the sine-wave will be distributed in distance along the line owing to its propagation characteris

propagation characteristics. A complete cycle of tics. A complete cycle of the wave occupies a distancethe wave occupies a distance λλ along the line along the line which is called the

which is called the wavelength. The wavelenwavelength. The wavelength is inversely proportional to gth is inversely proportional to the frequencythe frequencyffof theof the wave. They are related to the propagation velocity v using the formula v=

(2)

Trusted by over 1 million members

Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial

Cancel Anytime.

(3)

Cancel Anytime.

Attenuation and Dispersion Attenuation and Dispersion The flow of current in t

The flow of current in the conductors’ resistance gives rise to energy losses. he conductors’ resistance gives rise to energy losses. FurtherFurther losses arise due to

losses arise due to imperfections in the isolation between conductors, such as surface leakingimperfections in the isolation between conductors, such as surface leaking across insulators, known as dielectric losses. In consequence if the power

across insulators, known as dielectric losses. In consequence if the power of a signal is of a signal is W(watts)W(watts) at the sending end of the line, it

at the sending end of the line, it may be reduced to 1/2W at some distance along the line; themay be reduced to 1/2W at some distance along the line; the same further on again it will be

same further on again it will be 1/4W. The signal is said to be attenuated. The diminution in power1/4W. The signal is said to be attenuated. The diminution in power is exponential: the decrease is by a

is exponential: the decrease is by a given factor per unit distance.given factor per unit distance. In mathematical treatment of a

In mathematical treatment of a transmission line, all the properties (velocity of transmission line, all the properties (velocity of propagation,propagation, attenuation, distortion of signals) are explain in terms of f

attenuation, distortion of signals) are explain in terms of four ‘line constants’. These are:our ‘line constants’. These are: L = the inductance of line per unit

L = the inductance of line per unit distance (H/m)distance (H/m) C = the capacitance of the line per unit

C = the capacitance of the line per unit distance (F/m)distance (F/m) R = the resistance of

R = the resistance of the line per unit distance (Ω/m)the line per unit distance (Ω/m) G = the conductance of the line per unit distance (S/m) G = the conductance of the line per unit distance (S/m)

The line constants in fact are only constant for a particular frequency, and may vary from The line constants in fact are only constant for a particular frequency, and may vary from one frequency to another. However, the variation is

one frequency to another. However, the variation is not usually so rapid as not usually so rapid as to spoil the to spoil the usefulnessusefulness of this theory.

of this theory. 4.Equipment: 4.Equipment:

1 -

1 - TransmissioTransmission Line Demonstrator (TLD511)n Line Demonstrator (TLD511)

11 – – Function Generator, Sine (eg Feedback VPG608) Function Generator, Sine (eg Feedback VPG608) 11 – – 600R Terminator 600R Terminator

22 – – Links Links

11 – – Extension Cord Extension Cord 5.Procedure:

5.Procedure:

PART A: PROPAGATION IN A TRANSMISSION LINE PART A: PROPAGATION IN A TRANSMISSION LINE

1.

1. Set the TLD511 controls as follows:Set the TLD511 controls as follows:

i.i. Hold/runHold/run set to ‘set to ‘run’run’ ii.

ii. Line lengthLine length set to ‘set to ‘8L’8L’ iii.

iii. Distributed attenuation set to ‘Distributed attenuation set to ‘min’min’ 2.

2. Set the function generator’s output voltage toSet the function generator’s output voltage to zerozero. The generator frequency should on a. The generator frequency should on a range allowing continuous variation between 2 and 0.5Hz. Set the f

range allowing continuous variation between 2 and 0.5Hz. Set the frequency torequency to 0.75Hz.0.75Hz. 3.

(4)

(5)

Cancel Anytime.

Figure 1.1 Figure 1.1

4.

4. Operate the switch forOperate the switch for ‘step input to A’‘step input to A’briefly until the light has appeared in the secondbriefly until the light has appeared in the second column. Observation:

column. Observation: All the lines lighted up from left to right until the secondAll the lines lighted up from left to right until the second

column but we need to hold the step input switch to A or else only a few columns of column but we need to hold the step input switch to A or else only a few columns of lines will light at a time.

lines will light at a time. 5.

5. Send a pulse from terminal ‘B’ to Send a pulse from terminal ‘B’ to ‘A’ by operating ‘‘A’ by operating ‘ step input to B’step input to B’. Observe that the pulse. Observe that the pulse disappear at the end. Why?

disappear at the end. Why? The same can be observed when we switched the stepThe same can be observed when we switched the step input to B but it is reversed.

input to B but it is reversed. 6.

6. Change line length to 2L and raise the output voltage of the generator to give full heightChange line length to 2L and raise the output voltage of the generator to give full height indication in each column. Describe the shape of

indication in each column. Describe the shape of the wave.the wave. It moves in a sinusoidal-likeIt moves in a sinusoidal-like pattern and we need to set the output voltage of the function generator to 5V peak pattern and we need to set the output voltage of the function generator to 5V peak to peak.

to peak. 7.

7. Operate hold. What part of the wave is shown?Operate hold. What part of the wave is shown? All the lines will hold up except for theAll the lines will hold up except for the first one.

first one. 8.

8. Release ‘hold’ and operate again at a different part of the input Release ‘hold’ and operate again at a different part of the input cycle: different parts of thecycle: different parts of the sine wave are displayed, but always the

sine wave are displayed, but always the same fraction of a same fraction of a wavelength.wavelength. 9.

9. Release ‘hold’ again and raise the frequency gradually to 2Hz. Point out the reduceRelease ‘hold’ again and raise the frequency gradually to 2Hz. Point out the reduce wavelength and operate ‘hold’

wavelength and operate ‘hold’ again. Observation:again. Observation: The wave moves faster. The wave moves faster. 10.

10. Determine v (for TLD511) using the formula 4L m/s where L is the Determine v (for TLD511) using the formula 4L m/s where L is the length in meters. Findlength in meters. Find the propagation time of the line length L.

the propagation time of the line length L. If we increase the frequency to 2Hz, the totalIf we increase the frequency to 2Hz, the total wavelength shall be reduced.

(6)

(7)

Cancel Anytime.

1.

1. Set the TLD511 controls as follows:Set the TLD511 controls as follows:

i.i. Hold/runHold/run set to ‘set to ‘run’run’ ii.

ii. Line lengthLine length set to ‘set to ‘2L2L’’ iii.

iii. Distributed attenuation set to ‘Distributed attenuation set to ‘min’min’ 2.

2. The generator frequency should on The generator frequency should on a range following a range following continuous variation betweencontinuous variation between 2 and2 and 0.5 Hz.

0.5 Hz. Choose a frequency about Choose a frequency about 1.75Hz.1.75Hz. 3.

3. Connect up the system as shown in Figure 1.2Connect up the system as shown in Figure 1.2

Figure 1.2 Figure 1.2 4.

4. Raise the generator’s output voltage to give a tRaise the generator’s output voltage to give a travelling sine wave display of full columnravelling sine wave display of full column amplitude. Point out that amplitude is the same at all points in

amplitude. Point out that amplitude is the same at all points in the linethe line 5.

5. Gradually raise the distributed attenuation to the ‘max’Gradually raise the distributed attenuation to the ‘max’ Observation:

Observation: We need a 9V peak to peak voltage to raise the amplitude of each linesWe need a 9V peak to peak voltage to raise the amplitude of each lines to max. The traveling pulse only reach the 9

to max. The traveling pulse only reach the 9thth_{column and the amplitude of each line}_{column and the amplitude of each line}

decreases. decreases. 6.

6. Reduce the frequency of the generator.Reduce the frequency of the generator. Observation:

Observation: The output wave becomes slower.The output wave becomes slower. 7.

7. Disconnect the line connecting to the generator. Set the length to ‘8L’ Set Disconnect the line connecting to the generator. Set the length to ‘8L’ Set the distributedthe distributed attenuation control about mid-way.

attenuation control about mid-way. 8.

8. Operate theOperate the ‘‘step input to Astep input to A’ switch until ’ switch until the second display column lights, to produce athe second display column lights, to produce a travelling pulse.

(8)

(9)

Cancel Anytime.

10.

10. Transfer the 600R terminator to the end ‘A’ end of Transfer the 600R terminator to the end ‘A’ end of the line. Operate the ‘step input to B’the line. Operate the ‘step input to B’ switch.

switch. ObservationObservation:: The amplitude moves at 2 line lights at a time in the reversedThe amplitude moves at 2 line lights at a time in the reversed direction and the amplitude varies.

direction and the amplitude varies.

PART C: TERMINATIONS, SIMPLE CASES PART C: TERMINATIONS, SIMPLE CASES

1.

1. Set the Set the TLD511 controls as follows:TLD511 controls as follows:

i.i. Hold/run Hold/run set set toto ‘run’‘run’ ii.

ii. Line Line length length set set toto ‘8L’‘8L’ iii.

iii. Distributed attenuation set to ‘Distributed attenuation set to ‘minmin’’ 2.

2. Set the function generator’s output voltage to zero and its frequency toSet the function generator’s output voltage to zero and its frequency to 1.5Hz.1.5Hz. 3.

3. Connect the equipment as shown on Figure 2.1Connect the equipment as shown on Figure 2.1

4. Operate the switch forOperate the switch for ‘step input to A’‘step input to A’briefly until the light has appeared in the secondbriefly until the light has appeared in the second column. A pulse, two columns as

column. A pulse, two columns as wide as in Figure 2.2, will then twide as in Figure 2.2, will then travel to terminal ‘B’ eravel to terminal ‘B’ e ndnd of the line and disappear. Why?

of the line and disappear. Why? The pulse disappeared because of the 600RThe pulse disappeared because of the 600R terminator.

(10)

(11)

Cancel Anytime.

5.

5. This time remove the terminator from ‘B’ end of This time remove the terminator from ‘B’ end of the line and send a pulse from ‘A’.the line and send a pulse from ‘A’. Observe and record the results.

Observe and record the results. The light line still travel 2 columns at a time but at theThe light line still travel 2 columns at a time but at the end of the light line, the amplitude increased and the light lines traveled back.

end of the light line, the amplitude increased and the light lines traveled back.

6. Place a short-Place a short-link across the line at link across the line at ‘B’ (where the 600R terminator was) and again send a‘B’ (where the 600R terminator was) and again send a pulse from ‘A’. Observe and record the

pulse from ‘A’. Observe and record the results.results. The light lines with 2 columns ofThe light lines with 2 columns of amplitude travelled from left to right except for the last line, and then the traveled amplitude travelled from left to right except for the last line, and then the traveled back from right to left but in the negative peak amplitude.

back from right to left but in the negative peak amplitude.

7. Reconnect the set-Reconnect the set-up of Figure 2.1. Operate the ‘step input to up of Figure 2.1. Operate the ‘step input to ‘A’ switch to send a ‘A’ switch to send a pulsepulse from ‘A’, then immediately operate it in

from ‘A’, then immediately operate it in the reverse direction to sendthe reverse direction to send a pulse from ‘B’.a pulse from ‘B’. Record the results below.

Record the results below. The light lines from both directions each with 2 columns ofThe light lines from both directions each with 2 columns of amplitude traveled towards the middle and collided with each other.

(12)

(13)

Cancel Anytime.

8. Operate theOperate the ‘step input to A’‘step input to A’switch. Release only the switch after switch. Release only the switch after the signal has reachedthe signal has reached ‘B’. When the line is

‘B’. When the line is at rest remove the 600R terminator.at rest remove the 600R terminator. Observation:

Observation: All the light lines travelling with 2 columns of amplitude each lighted upAll the light lines travelling with 2 columns of amplitude each lighted up and removing the 600R terminator cause the amplitude to increase and the

and removing the 600R terminator cause the amplitude to increase and the eventually reverted back to its original amplitude.

eventually reverted back to its original amplitude. 9.

9. Operate theOperate the ‘step input to A’‘step input to A’switch. Release only the switch after switch. Release only the switch after the reflected signal hasthe reflected signal has returned to ‘A’.

returned to ‘A’. Observation:

Observation: blank!!!!!!!!!!!!!blank!!!!!!!!!!!!! 10.

10. Repeat procedure 8 and 9 of part C, using short-Repeat procedure 8 and 9 of part C, using short-circuit link at termination ‘B’.circuit link at termination ‘B’. Explain:

Explain: blank!!!!!!!!!!!!!!!!blank!!!!!!!!!!!!!!!! 11.

11. Set the line length to ‘2L’. Set the line length to ‘2L’. Replace the 600R terminator at ‘B’ ( Replace the 600R terminator at ‘B’ ( a value lower or higher thana value lower or higher than 600R)

600R) 12.

(14)

Cancel Anytime.

Cancel Anytime. 6. Observation: 6. Observation: 7. Interpretaion: 7. Interpretaion: 8. Conclusion: 8. Conclusion:

9. Questions and Problems: 9. Questions and Problems:

1.

1. Give examples of causes of attenuation.Give examples of causes of attenuation. 2.

2. Compare the reflected wave in an Compare the reflected wave in an open, short and properly matched line?open, short and properly matched line? 3.

3. Why do we need to terminate a line at Why do we need to terminate a line at its characteristic impedance? What are the effectsits characteristic impedance? What are the effects of not doing so?

of not doing so? 4.

4. Why is an Why is an ordinary extensioordinary extension cord usually is n cord usually is not considered a transmission line, while anot considered a transmission line, while a television antenna of the same length would

television antenna of the same length would be?be? 5.

(15)

Cancel Anytime.