Question & Answers - Microwave Engineering, ECE Electronics and Communication Engineering (ECE) Notes | EduRev

Electronics and Communication Engineering (ECE) : Question & Answers - Microwave Engineering, ECE Electronics and Communication Engineering (ECE) Notes | EduRev

 Page 1


 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
DEPARTMENT OF ECE 
 
EC1402 MICROWAVE ENGINEERING 
 (2 marks Questions and answers) 
 
 
FINAL YEAR 7
th
 SEMESTER  
 
Page 2


 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
DEPARTMENT OF ECE 
 
EC1402 MICROWAVE ENGINEERING 
 (2 marks Questions and answers) 
 
 
FINAL YEAR 7
th
 SEMESTER  
 
1. Define s-matrix 
In a microwave junction there is intersection of three or more components.There will be an 
output port ,in addition there may be reflection from the junction of other ports.Totally there may 
be many combinations,these are represented easily using a matrix called S matrix. 
 
2. What are the .Properties of s-matrix? 
1.It possess symmetric property sij =sji     2.It possess unitary property [s][s]*=[i] 
 
3.Why is s-matrix used in MW analysis? 
S matrix is used in MW analysis to overcome the problems which occurs when H,Y,& Z 
parameters are used in high frequencies. 
1.Equipment is not readily available to measure total voltage &total current at the ports of 
the network. 
2.Short and open circuits are difficult to achieve over a broad band of frequencies. 
3.Active devices,such as power transistor &tunnel diodes,frequently won’t have stability 
for a short or open circuit. 
 
4.Give ABCD matrix for a two port network 
V1=A B  V2 
I1    C D -I2 
 
5.What is ABCD matrix? 
ABCD matrix is a transmission matrix.these parameters express voltage and 
current at output in terms of those at input port. 
V1=AV2-BI2 
I1=CV2-DI2 
 
6.What are the advantages of ABCD matrix? 
1.They are used in power transmission lines. 
2.They are very helpful in the case of cascade networks. 
 
7.What is the Scattering matrix for N port device? 
[S]= S11 S12 S13…… S1n 
S21 S22 …………S2n 
S31 S32 ………….S3n 
. . 
. . 
Sm1 Sm2 ………...Smm 
 
8.Give the S matrix of uniform transmission line 
S= 0   e-
jbl 
    e
-jbl
  0 
 
9.Give the properties of impedence [x]&admittance[y] matrix? 
1.For a lossless junctionary y and z are symmetric . 
2.[y]=[z] -1 
3.Elements of matix [Z] &matrix [Y] are Frequency dependent. 
 
10.For a loss less junction all the elements in the impedence &admittance matrices are Pure 
imaginary 
 
 
Page 3


 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
DEPARTMENT OF ECE 
 
EC1402 MICROWAVE ENGINEERING 
 (2 marks Questions and answers) 
 
 
FINAL YEAR 7
th
 SEMESTER  
 
1. Define s-matrix 
In a microwave junction there is intersection of three or more components.There will be an 
output port ,in addition there may be reflection from the junction of other ports.Totally there may 
be many combinations,these are represented easily using a matrix called S matrix. 
 
2. What are the .Properties of s-matrix? 
1.It possess symmetric property sij =sji     2.It possess unitary property [s][s]*=[i] 
 
3.Why is s-matrix used in MW analysis? 
S matrix is used in MW analysis to overcome the problems which occurs when H,Y,& Z 
parameters are used in high frequencies. 
1.Equipment is not readily available to measure total voltage &total current at the ports of 
the network. 
2.Short and open circuits are difficult to achieve over a broad band of frequencies. 
3.Active devices,such as power transistor &tunnel diodes,frequently won’t have stability 
for a short or open circuit. 
 
4.Give ABCD matrix for a two port network 
V1=A B  V2 
I1    C D -I2 
 
5.What is ABCD matrix? 
ABCD matrix is a transmission matrix.these parameters express voltage and 
current at output in terms of those at input port. 
V1=AV2-BI2 
I1=CV2-DI2 
 
6.What are the advantages of ABCD matrix? 
1.They are used in power transmission lines. 
2.They are very helpful in the case of cascade networks. 
 
7.What is the Scattering matrix for N port device? 
[S]= S11 S12 S13…… S1n 
S21 S22 …………S2n 
S31 S32 ………….S3n 
. . 
. . 
Sm1 Sm2 ………...Smm 
 
8.Give the S matrix of uniform transmission line 
S= 0   e-
jbl 
    e
-jbl
  0 
 
9.Give the properties of impedence [x]&admittance[y] matrix? 
1.For a lossless junctionary y and z are symmetric . 
2.[y]=[z] -1 
3.Elements of matix [Z] &matrix [Y] are Frequency dependent. 
 
10.For a loss less junction all the elements in the impedence &admittance matrices are Pure 
imaginary 
 
 
11.What are the properties of scattering matrix for a lossless junctoion? 
1.The product of any column of the S-matrix with conjugate of this column equals unity. 
2.The product of any column of the scattering matrix with the complex conjugate of any other 
column is zero. 
 
12.What is transmission matrix? 
When a number of microwave devices are connected in cascade.Each junction is represented by a 
transmission matrix which gives the output quantities interms of input quantities. 
 
13.Define one port circuit.Give two examples. 
A one port circuit is a circuit for which power can enter or leave through a single wave 
Guide or transmission line. 
Examples: 
1.Short-circuited co-axial line 
14.Write the voltage matrix for an N-port microwave circuits. 
V1 Z11 Z12 ….. Z1N I1 
V2 Z12 Z22 …… Z2N I2 
. = . . …… …. . 
. 
VN ZN1 ZN2 . ZNN IN 
Where Zij=Elements of impedence matrix. 
[Z]=Impedence martrix 
 
15.For reciprocal media,the impedence and admittance matrices areSymmetrical 
 
16.For non-reciprocal media,the impedence and admittance matrices are 
Ans: Asymmetrical 
 
17.Give two examples for two port junctions. 
1.The junction of two rectangular guides of unequal height 
2.A symmetrical junction consisting of two similar rectangular guides joined by an Intermediate 
guide of greater width. 
 
18.State the unique property of Scattering matrix? 
Unitary Property: the row of a scattering matrix multiplied by the complex conjugate of the same 
row of the scattering matrix is one. 
 
19. Write the scattering matrix for a ideal waveguide section? 
[S]=[0 1 
        1 0] 
 
20. What are the various reasons pertaining to the wide use of microwaves 
Bandwidth,Improved directivity with an Aerial array ,Reliability, Power requirement. 
21. What are the two types of terminations. 
Matched load 
Variable short circuit 
 
22. What are ferrites and give its properties? 
Ferrites are ceramic like materials. These are maby by sintering a mixture of metallic oxides 
Properties 
Specific resistivitieis may be used as much as 1014 greater than that of metals 
Dielectric constants around 10to 15 or greater 
Page 4


 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
DEPARTMENT OF ECE 
 
EC1402 MICROWAVE ENGINEERING 
 (2 marks Questions and answers) 
 
 
FINAL YEAR 7
th
 SEMESTER  
 
1. Define s-matrix 
In a microwave junction there is intersection of three or more components.There will be an 
output port ,in addition there may be reflection from the junction of other ports.Totally there may 
be many combinations,these are represented easily using a matrix called S matrix. 
 
2. What are the .Properties of s-matrix? 
1.It possess symmetric property sij =sji     2.It possess unitary property [s][s]*=[i] 
 
3.Why is s-matrix used in MW analysis? 
S matrix is used in MW analysis to overcome the problems which occurs when H,Y,& Z 
parameters are used in high frequencies. 
1.Equipment is not readily available to measure total voltage &total current at the ports of 
the network. 
2.Short and open circuits are difficult to achieve over a broad band of frequencies. 
3.Active devices,such as power transistor &tunnel diodes,frequently won’t have stability 
for a short or open circuit. 
 
4.Give ABCD matrix for a two port network 
V1=A B  V2 
I1    C D -I2 
 
5.What is ABCD matrix? 
ABCD matrix is a transmission matrix.these parameters express voltage and 
current at output in terms of those at input port. 
V1=AV2-BI2 
I1=CV2-DI2 
 
6.What are the advantages of ABCD matrix? 
1.They are used in power transmission lines. 
2.They are very helpful in the case of cascade networks. 
 
7.What is the Scattering matrix for N port device? 
[S]= S11 S12 S13…… S1n 
S21 S22 …………S2n 
S31 S32 ………….S3n 
. . 
. . 
Sm1 Sm2 ………...Smm 
 
8.Give the S matrix of uniform transmission line 
S= 0   e-
jbl 
    e
-jbl
  0 
 
9.Give the properties of impedence [x]&admittance[y] matrix? 
1.For a lossless junctionary y and z are symmetric . 
2.[y]=[z] -1 
3.Elements of matix [Z] &matrix [Y] are Frequency dependent. 
 
10.For a loss less junction all the elements in the impedence &admittance matrices are Pure 
imaginary 
 
 
11.What are the properties of scattering matrix for a lossless junctoion? 
1.The product of any column of the S-matrix with conjugate of this column equals unity. 
2.The product of any column of the scattering matrix with the complex conjugate of any other 
column is zero. 
 
12.What is transmission matrix? 
When a number of microwave devices are connected in cascade.Each junction is represented by a 
transmission matrix which gives the output quantities interms of input quantities. 
 
13.Define one port circuit.Give two examples. 
A one port circuit is a circuit for which power can enter or leave through a single wave 
Guide or transmission line. 
Examples: 
1.Short-circuited co-axial line 
14.Write the voltage matrix for an N-port microwave circuits. 
V1 Z11 Z12 ….. Z1N I1 
V2 Z12 Z22 …… Z2N I2 
. = . . …… …. . 
. 
VN ZN1 ZN2 . ZNN IN 
Where Zij=Elements of impedence matrix. 
[Z]=Impedence martrix 
 
15.For reciprocal media,the impedence and admittance matrices areSymmetrical 
 
16.For non-reciprocal media,the impedence and admittance matrices are 
Ans: Asymmetrical 
 
17.Give two examples for two port junctions. 
1.The junction of two rectangular guides of unequal height 
2.A symmetrical junction consisting of two similar rectangular guides joined by an Intermediate 
guide of greater width. 
 
18.State the unique property of Scattering matrix? 
Unitary Property: the row of a scattering matrix multiplied by the complex conjugate of the same 
row of the scattering matrix is one. 
 
19. Write the scattering matrix for a ideal waveguide section? 
[S]=[0 1 
        1 0] 
 
20. What are the various reasons pertaining to the wide use of microwaves 
Bandwidth,Improved directivity with an Aerial array ,Reliability, Power requirement. 
21. What are the two types of terminations. 
Matched load 
Variable short circuit 
 
22. What are ferrites and give its properties? 
Ferrites are ceramic like materials. These are maby by sintering a mixture of metallic oxides 
Properties 
Specific resistivitieis may be used as much as 1014 greater than that of metals 
Dielectric constants around 10to 15 or greater 
Relative permeability is 1000 
 
23.Give some examples of ferrite devices? 
Isolator Circulator Phaseshifters, Modulators, Power limiters 
 
24. List two microwave devices using faraday rotation principles 
Isolator, Circulator 
 
25.What are powere dividers? 
Power dividers are used to divide the input power into a number of smaller amounts of power for 
exciting the radiating elements in an array antenna 
 
26.What is the S-matrix of 3 port circulators? 
Anticlockwise [S]= 0 1 0 
0 0 1 
1 0 0 
Clockwise [S]= 0 0 1 
1 0 0 
0 1 0 
 
27. Give the differences between Isolator and Circulator 
 
 
28.What is the S-matrix for 4 port circulators? 
Clockwise 
[S]= 0 0 0 1 
1 0 0 0 
0 1 0 0 
0 0 1 0 
Anticlockwise 
[S] = 0 1 0 0 
         0 0 1 0 
         0 0 0 1 
         0 0 1 0 
 
29.Give the S-matrix of E-plane Tee. 
[S] = 0.5  0.5      0.707 
         0.5  0.5     -0.707 
         0.5 -0.707  0 
 
30.Give the S-matrix of H-plane Tee 
[S] = 0.5     -0.5       0.707 
       -0.5       0.5       0.707 
        0.707   0.707   0 
Page 5


 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
DEPARTMENT OF ECE 
 
EC1402 MICROWAVE ENGINEERING 
 (2 marks Questions and answers) 
 
 
FINAL YEAR 7
th
 SEMESTER  
 
1. Define s-matrix 
In a microwave junction there is intersection of three or more components.There will be an 
output port ,in addition there may be reflection from the junction of other ports.Totally there may 
be many combinations,these are represented easily using a matrix called S matrix. 
 
2. What are the .Properties of s-matrix? 
1.It possess symmetric property sij =sji     2.It possess unitary property [s][s]*=[i] 
 
3.Why is s-matrix used in MW analysis? 
S matrix is used in MW analysis to overcome the problems which occurs when H,Y,& Z 
parameters are used in high frequencies. 
1.Equipment is not readily available to measure total voltage &total current at the ports of 
the network. 
2.Short and open circuits are difficult to achieve over a broad band of frequencies. 
3.Active devices,such as power transistor &tunnel diodes,frequently won’t have stability 
for a short or open circuit. 
 
4.Give ABCD matrix for a two port network 
V1=A B  V2 
I1    C D -I2 
 
5.What is ABCD matrix? 
ABCD matrix is a transmission matrix.these parameters express voltage and 
current at output in terms of those at input port. 
V1=AV2-BI2 
I1=CV2-DI2 
 
6.What are the advantages of ABCD matrix? 
1.They are used in power transmission lines. 
2.They are very helpful in the case of cascade networks. 
 
7.What is the Scattering matrix for N port device? 
[S]= S11 S12 S13…… S1n 
S21 S22 …………S2n 
S31 S32 ………….S3n 
. . 
. . 
Sm1 Sm2 ………...Smm 
 
8.Give the S matrix of uniform transmission line 
S= 0   e-
jbl 
    e
-jbl
  0 
 
9.Give the properties of impedence [x]&admittance[y] matrix? 
1.For a lossless junctionary y and z are symmetric . 
2.[y]=[z] -1 
3.Elements of matix [Z] &matrix [Y] are Frequency dependent. 
 
10.For a loss less junction all the elements in the impedence &admittance matrices are Pure 
imaginary 
 
 
11.What are the properties of scattering matrix for a lossless junctoion? 
1.The product of any column of the S-matrix with conjugate of this column equals unity. 
2.The product of any column of the scattering matrix with the complex conjugate of any other 
column is zero. 
 
12.What is transmission matrix? 
When a number of microwave devices are connected in cascade.Each junction is represented by a 
transmission matrix which gives the output quantities interms of input quantities. 
 
13.Define one port circuit.Give two examples. 
A one port circuit is a circuit for which power can enter or leave through a single wave 
Guide or transmission line. 
Examples: 
1.Short-circuited co-axial line 
14.Write the voltage matrix for an N-port microwave circuits. 
V1 Z11 Z12 ….. Z1N I1 
V2 Z12 Z22 …… Z2N I2 
. = . . …… …. . 
. 
VN ZN1 ZN2 . ZNN IN 
Where Zij=Elements of impedence matrix. 
[Z]=Impedence martrix 
 
15.For reciprocal media,the impedence and admittance matrices areSymmetrical 
 
16.For non-reciprocal media,the impedence and admittance matrices are 
Ans: Asymmetrical 
 
17.Give two examples for two port junctions. 
1.The junction of two rectangular guides of unequal height 
2.A symmetrical junction consisting of two similar rectangular guides joined by an Intermediate 
guide of greater width. 
 
18.State the unique property of Scattering matrix? 
Unitary Property: the row of a scattering matrix multiplied by the complex conjugate of the same 
row of the scattering matrix is one. 
 
19. Write the scattering matrix for a ideal waveguide section? 
[S]=[0 1 
        1 0] 
 
20. What are the various reasons pertaining to the wide use of microwaves 
Bandwidth,Improved directivity with an Aerial array ,Reliability, Power requirement. 
21. What are the two types of terminations. 
Matched load 
Variable short circuit 
 
22. What are ferrites and give its properties? 
Ferrites are ceramic like materials. These are maby by sintering a mixture of metallic oxides 
Properties 
Specific resistivitieis may be used as much as 1014 greater than that of metals 
Dielectric constants around 10to 15 or greater 
Relative permeability is 1000 
 
23.Give some examples of ferrite devices? 
Isolator Circulator Phaseshifters, Modulators, Power limiters 
 
24. List two microwave devices using faraday rotation principles 
Isolator, Circulator 
 
25.What are powere dividers? 
Power dividers are used to divide the input power into a number of smaller amounts of power for 
exciting the radiating elements in an array antenna 
 
26.What is the S-matrix of 3 port circulators? 
Anticlockwise [S]= 0 1 0 
0 0 1 
1 0 0 
Clockwise [S]= 0 0 1 
1 0 0 
0 1 0 
 
27. Give the differences between Isolator and Circulator 
 
 
28.What is the S-matrix for 4 port circulators? 
Clockwise 
[S]= 0 0 0 1 
1 0 0 0 
0 1 0 0 
0 0 1 0 
Anticlockwise 
[S] = 0 1 0 0 
         0 0 1 0 
         0 0 0 1 
         0 0 1 0 
 
29.Give the S-matrix of E-plane Tee. 
[S] = 0.5  0.5      0.707 
         0.5  0.5     -0.707 
         0.5 -0.707  0 
 
30.Give the S-matrix of H-plane Tee 
[S] = 0.5     -0.5       0.707 
       -0.5       0.5       0.707 
        0.707   0.707   0 
 
 
31.Give the S-matrix of Magic Tee 
[S] = 0 0 0.707 0.707 
0 0 0.707 -0.707 
0.707 0.707 0 0 
0.707 -0.707 0 0 
 
32.Give the Smatrix of directional coupler 
[S] =    0  P  0  jq 
P  0  jq  0 
0  jq 0   P 
Jq 0  P  0 
 
33.Give an example for a two port MW device 
Isolator is an example for a 2 port MW device 
 
34.Give the applications of directional coupler 
1.Unidirectional power measurement 
2.SWR measurement 
3.Unidirectional wave launching 
4.Reflectometer 
5.Balanced duplexer 
 
35.What is Faraday’s rotation law? 
If a circulary polarised wave is made to pass through a ferrite rod which has been 
influenced by an axial magnetic field B ,then the axis of polarization gets tilted in clockwise 
direction and amount of tilt depends upon the strength of magnetic field and geometry of the 
ferrite. 
 
36.Define VSWR 
Voltage standing wave ratio is defined as the ratio of maximum voltage to the minimum 
vottage VSWR=Vmax/Vmin 
 
37.What is Gyrator? 
Gyrator is a two port device which provides a relative phase shift of 180 degree for 
transmission from port 1 to port 2 as compared to the phase for transmission from Port2 to port 1. 
 
38.What is the principle of Microwave phase shifter? 
When a wave propagates on a line,a phase difference prevails between any two arbitary 
points along its paths.The phase difference between two points, 
 
39.what are junctions?Give some examples 
A microwave circuit consists of several microwave devices connected in some way to 
achieve the desired transmission of MW signal.The interconnection of two or more microwave 
may be regarded as MW junction. 
Eg:Magic Tee,Hybrid Ring 
 
40.What is Tee junction?Give two examples 
In MW circuits a wave guide or coaxial junction with three independent ports is referred to 
as tee junction. 
Eg: E- Plane Tee,H-plane Tee 
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