btec hnc - electrical and electronic principles - investigate two port networks

Investigate Two Port NetworksElectrical and Electronic Principles

By Brendan Burr

Brendan Burr BTEC Higher National Certificate in ElectronicsInvestigate Two Port Networks

Table of Contents

TABLE OF CONTENTS - 2 -

TASK 1 - 6 -

1.1 Find the characteristic impedance of the following pad sections :- - 6 -

(a) T Pad - 6 -Solution:- - 6 -

(b) PI Pad - 7 -Solution:- - 7 -

1.2 In the following symmetrical pad determine the following parameters :- - 8 -

(a) Short circuit resistance Rsc. - 8 -Solution:- - 8 -

(b) Open circuit resistance Rdc. - 8 -Solution:- - 8 -

(c) Characteristic Impedance . - 9 -Solution:- - 9 -

(d) Attenuation in dB. - 9 -Solution:- - 9 -

1.3 Find the power ratios in dB’s and Neper’s for the following power ratios :- - 10 -

(a) - 10 -

Solution:- - 10 -

(b) - 10 -

Solution:- - 10 -

2


1.4 Find the current ratios in dB’s and Neper’s for the following current ratios:- - 11 -

(a) - 11 -

Solution:- - 11 -

(b) - 11 -

Solution:- - 11 -

1.5 Find the voltage ratio’s in dB’s and Neper’s for the following voltage ratios:- - 12 -

(a) - 12 -

Solution:- - 12 -

(b) - 12 -

Solution:- - 12 -

1.6 The power output of an attenuator is 100 mW . If the attenuation is 20 dB’s determine the input power in Watts. - 13 -

Solution:- - 13 -Check:- - 13 -

1.7 The following T attenuator pad feeds a matched load. Determine the following parameters:- - 14 -

(a) The characteristic resistance - 14 -Solution:- - 14 -

(b) The insertion loss in dB’s. - 15 -Solution:- - 15 -

1.8 A symmetrical attenuator pad has a series arm resistance of 800 and shunt arms each of 250 . - 16 -

(a) Draw a well labelled circuit diagram of the attenuator connected to the load.- 16 -

Solution:- - 16 -

(b) Determine the characteristic impedance when feeding a matched load. - 16 -Solution:- - 16 -

(c) Determine the insertion loss in Nepers when feeding a matched load. - 17 -Solution:- - 17 -

3


1.9 Three identical symmetrical two port networks are connected in cascade. The total attenuation is 6.098 Neper’s and the total phase shift is 24˚. Determine the following parameters for each two port network:- - 18 -

(a) Attenuation coefficient in nepers - 18 -Solution:- - 18 -Check:- - 18 -

(b) Phase shift coefficient in radians - 19 -Solution:- - 19 -

(c) Propagation coefficient - 19 -Solution:- - 19 -

(d) Total attenuation in dB’s - 19 -Solution:- - 19 -

1.10 Using the results obtained in 1.9 above determine the following :- - 20 -

(a) The number of dB’s = 1 Neper. - 20 -Solution:- - 20 -

(b) The number of Nepers = 1 dB. - 20 -Solution:- - 20 -

TASK 2 - 21 -

2.1 Design a T pad attenuator to provide 18 dB voltage attenuation per section and is to match a 1.5k load. - 21 -

(a) Determine the values of R1 and R2. - 21 -Solution:- - 21 -

(b) Draw the circuit diagram. - 21 -Solution:- - 21 -

2.2 Design a pad attenuator to provide 15 dB attenuation per section and a characteristic impedance of 600. - 22 -

(a) Determine the values of R1 and R2. - 22 -Solution:- - 22 -

(b) Draw the circuit diagram. - 22 -Solution:- - 22 -

2.3. Test the two designs in 2.1 and 2.2 using the Croc Clips or Multisim S/W simulation. - 23 -

Solution:- - 23 -

4


2.4. Record the following voltage and current measurements using meters:- - 23 -

(a) - 23 -Solution:- - 23 -

(b) - 23 -Solution:- - 23 -

(c) - 23 -Solution:- - 23 -

(d) - 23 -Solution:- - 23 -

2.5. From these results determine the following measurements :- - 24 -

(a) Characteristic Resistance - 24 -Solution:- - 24 -

(b) Attenuation in dB’s - 24 -Solution:- - 24 -

2.6. Compare your results against the theoretical calculations and explain any differences. - 24 -

Solution:- - 24 -

EVALUATION - 25 -

CONCLUSION - 25 -

BIBLIOGRAPHY - 26 -

Books - 26 -

Catalogues - 26 -

Websites - 26 -

5


Task 1

1.1 Find the characteristic impedance of the following pad sections :-

(a) T Pad

Solution:-

6


(b) PI Pad

Solution:-

7


1.2 In the following symmetrical pad determine the following parameters :-

(a) Short circuit resistance Rsc.

Solution:-

(b) Open circuit resistance Rdc.

Solution:-

8


(c) Characteristic Impedance .

Solution:-

(d) Attenuation in dB.

Solution:-

9


1.3 Find the power ratios in dB’s and Neper’s for the following power ratios :-

(a)

Solution:-

(LOSS)

(b)

Solution:-

(UNITY GAIN BUFFER)

10


1.4 Find the current ratios in dB’s and Neper’s for the following current ratios:-

(a)

Solution:-

(LOSS)

(b)

Solution:-

(GAIN)

11


1.5 Find the voltage ratio’s in dB’s and Neper’s for the following voltage ratios:-

(a)

Solution:-

(LOSS)

(b)

Solution:-

(GAIN)

12


1.6 The power output of an attenuator is 100 mW . If the attenuation is 20 dB’s determine the input power in Watts.

Solution:-

Check:-

13


1.7 The following T attenuator pad feeds a matched load. Determine the following parameters:-

(a) The characteristic resistance

Solution:-

14


(b) The insertion loss in dB’s.

Solution:-

15


1.8 A symmetrical attenuator pad has a series arm resistance of 800 and shunt arms each of 250 .

(a) Draw a well labelled circuit diagram of the attenuator connected to the load.

Solution:-

(b) Determine the characteristic impedance when feeding a matched load.

Solution:-

16


(c) Determine the insertion loss in Nepers when feeding a matched load.

Solution:-

Insertion Loss

If (Which it does)

(to the nearest whole number)

17


1.9 Three identical symmetrical two port networks are connected in cascade. The total attenuation is 6.098 Neper’s and the total phase shift is 24˚. Determine the following parameters for each two port network:-

(a) Attenuation coefficient in nepers

Solution:-

Total Attenuation = 6.098 Np’s

Nepers

Check:-

Attenuation Coefficient =

Nepers

18


(b) Phase shift coefficient in radians

Solution:-

Radians

(c) Propagation coefficient

Solution:-

Rectangular Form

OR

Polar Form

(d) Total attenuation in dB’s

Solution:-

(to the nearest whole number)

19


1.10 Using the results obtained in 1.9 above determine the following :-

(a) The number of dB’s = 1 Neper.

Solution:-

So:

(b) The number of Nepers = 1 dB.

Solution:-

So:

20


Task 2

2.1 Design a T pad attenuator to provide 18 dB voltage attenuation per section and is to match a 1.5k load.

(a) Determine the values of R1 and R2.

Solution:-

(b) Draw the circuit diagram.

Solution:-

21


2.2 Design a pad attenuator to provide 15 dB attenuation per section and a characteristic impedance of 600.

(a) Determine the values of R1 and R2.

Solution:-

(b) Draw the circuit diagram.

Solution:-

22


2.3. Test the two designs in 2.1 and 2.2 using the Croc Clips or Multisim S/W simulation.

Solution:-

Vin Iin Rin Vout Iout Rout -Av2.1

T Pad Table

AC 4.05 V 2.71 mA 1,495 Ω 498 mV 332 uA 1,500 Ω 18.20 dB’s8.09 V 5.43 mA 1,490 Ω 997 mV 664 uA 1,502 Ω 18.19 dB’s

DC 10 V 6.71 mA 1,490 Ω 1.23 V 821 uA 1,498 Ω 18.20 dB’s7 V 4.7 mA 1,489 Ω 862 mV 575 uA 1,499 Ω 18.19 dB’s

2.2Pi Pad Table

AC 5 V 8.33 mA 600 Ω 889 mV 1.48 mA 601 Ω 15.00 dB’s9.51 V 15.9 mA 598 Ω 1.69 V 2.82 mA 599 Ω 15.00 dB’s

DC 10 V 16.7 mA 599 Ω 1.78 V 2.96 mA 601 Ω 14.99 dB’s7 V 11.7 mA 598 Ω 1.24 V 2.07 mA 599 Ω 15.03 dB’s

2.4. Record the following voltage and current measurements using meters:-

(a)

Solution:-

See 2.3 Table (Under Heading Vin).

(b)

Solution:-

See 2.3 Table (Under Heading Iin)

(c)

Solution:-

See 2.3 Table (Under Heading Vout)

(d)

Solution:-

See 2.3 Table (Under Heading Iout)

23


2.5. From these results determine the following measurements :-

(a) Characteristic Resistance

Solution:-

See 2.3 Table (Under Heading Rout)

(b) Attenuation in dB’s

Solution:-

See 2.3 Table (Under Heading –Av)

2.6. Compare your results against the theoretical calculations and explain any differences.

Solution:-

For Task 2.1, I was aiming to receive 18dB’s of Attenuation. From the measured results it was actually calculated at 18.20 and 18.19 dB’s. The difference was caused by the lack of decimal places that could be used for the resistor values in the T Pad circuit. I had calculated the resistor values to up to seven decimal places, but could only input one at most, I would expect this to be the cause of the final Attenuation amount to being different from that required.For Task 2.1, I did actually work out the Characteristic Resistance with the values of resistor that could be used, and it came to 1491.146874 Ohms, which is very close to the 1500 Ohms it was designed for.

For Task 2.2, I also worked out the Characteristic Resistance with the resistor values used in the simulation, and it came to 600.0053605 Ohms, which is extremely close to the 600 Ohms it was designed for. This closer Characteristic Resistance resulted in getting results which were much closer to the 15dB’s required, and in two instances out of four the simulation showed exactly 15dB’s of Attenuation.

I am putting the difference in Actual to Real Attenuation in the limitations of the software as further theoretical calculation shows that the full calculated resistor values would provide the required Characteristic Resistance.

24


EvaluationI found Task 1.1 relatively simple, as it was simply a case of inputting values of resistors into a predetermined equation. This was the same in both parts of the Task 1.1a and 1.1b.Task 1.2 went into more depth about the circuit and asked to determine multiple parameters. It took slightly longer to complete than Task 1.1, however it had similar principles as far as inputting values into an equation goes.Tasks 1.3, 1.4 and 1.5 involved working out two different values, one in Decibels and one in Nepers. The Power Ratios have a different formula to that of Voltage and Current. Power is precisely half the Log and Natural Log of that used when determining the Voltage and Current, this was something I had to look out for to prevent an error in my workings.For Task 1.6 I had to use Transposition of Formulae methods, to be able get the answer for the input Power. I managed to do this relatively easily as transposition is something we use every week at college.Task 1.7 was also a case of inputting known values into an equation and getting an output which then gets fed into another equation to get the answer. I fortunately didn’t struggle on this Task.In Task 1.8 it began to get more difficult. I had to determine the Open Circuit Resistance and the Closed Circuit Resistance and then take the Square Root of the Product of these two results. I found Task 1.9 a little bit difficult as I had to manipulate the example to be able to understand which equations I needed to use. Once I had done this though I could get an answer which I was able to check, using a different equation. Then using my value for N, which was 444, I could determine the number of Decibels to a Neper and visa-versa.Overall I found Task 1, relatively straight forward as the majority of the Task was deciding which equations were necessary to answer the question.For Task 2 I had to design and test an Attenuator circuit which provides an 18 dB and 15 dB Attenuation.I had to work out the resistance values for R1 and R2, and then create a circuit simulation in CrocTech which demonstrated the attenuations. For Task 2.1 I received an attenuation of 18.20 dB’s which wasn’t quite the 18 dB’s required. The most likely cause of this discrepancy was probably the lack of accuracy in the resistors which could only be entered to one decimal place at maximum. All of the other results look relatively accurate.

ConclusionTo conclude the assignment, I felt that it went well. The examples provided from class definitely helped in working out the assignment questions. They clearly showed which values from corresponding circuits were required to be entered in the equations.I felt my work has been to a high standard and I have managed to keep putting in a large amount of effort outside of work hours to ensure the assignments are complete in time. I will continue to try hard in this unit and others throughout the last month of the academic year, and hope it is to a high enough standard to receive the grades I am hoping for.

25


Bibliography

Through guidance from my lecturer, the following text books, catalogues and websites I was able to complete this assignment:

Books

BTEC National Engineering (Mike Tooley & Lloyd Dingle) ISBN: 978-0-7506-8521-4Success in Electronics (Tom Duncan & John Murray)ISBN: 0-7195-4015-1Higher Engineering Mathematics (John Bird) ISBN: 0-7506-8152-7

Catalogues

N/A

Websites

N/A

26

btec hnc - electrical and electronic principles - investigate two port networks

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