microwave one mark short question

1. Define s-matrix

In a microwave junction there is intersection ofthree or more
components.There will be an output port ,in addition there may be reflectionfrom the
junction of other ports.Totally there may be many combinations,these are represented
easily using a matrix called S matrix.

2What are the .Properties ofs-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 representedby a transmission matrix which gives the output quantities interms of input quantities. 13.Define one port circuit.Give two examples. A one portcircuit 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 are
Symmetrical

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 oftwo 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 thescattering 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 00 1 10 0
Clockwise [S]= 0 0 1 100 010

27. Givethe differences between Isolator and Circulator