This set of Basic Microwave Engineering Questions and Answers focuses on “Lumped Element Circuit Model of Transmission Line”.

1. The key difference between circuit theory and transmission line theory is:

a) circuit elements

b) voltage

c) current

d) electrical size

View Answer

Explanation: Circuit theory assumes physical dimensions of the network smaller than electrical wavelength, while transmission lines may be considerable fraction of wavelength.

2. Transmission line is a _________ parameter network.

a) lumped

b) distributed

c) active

d) none of the mentioned

View Answer

Explanation: Since no lumped elements like resistors, capacitors are used at microwave frequencies, only transmission lines are used. Hence they are called distributed parameter network.

3. For transverse electromagnetic wave propagation, we need a minimum of:

a) 1 conductor

b) 2 conductors

c) 3 conductors

d) bunch of conductors

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Explanation: With a single conductor, transverse electromagnetic wave propagation is not possible. Hence we need a minimum of 2 conductors.

4. To model a transmission line of infinitesimal length Δz, the lumped element that is not used is:

a) resistor

b) inductor

c) capacitor

d) transistor

View Answer

Explanation: In the lumped element circuit model of a transmission line, we use only resistor, capacitor and inductor. Hence no transistor is used.

5. _________ and __________ contribute to the impedance of a transmission line in the lumped element representation.

a) resistor, inductor

b) resistor, capacitor

c) capacitor, inductor

d) transistor, capacitor

View Answer

Explanation: Z=R+jωL. Hence, both resistor and inductor contribute to the impedance of the transmission line.

6. _________ and __________ contribute to the admittance of a transmission line in the lumped element representation.

a) conductance G, capacitor

b) conductance, inductor

c) resistor, capacitor

d) resistor, inductor

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Explanation:Y=G+jωC. Hence, both conductance and capacitance contribute to the admittance of the transmission line.

7. Characteristic impedance of a transmission line is:

a) impedance Z of a transmission line

b) impedance which is a constant at any point on the transmission line

c) reciprocal of admittance of a transmission line

d) none of the mentioned

View Answer

Explanation: Characteristic impedance is defined as that impedance of a line which is a constant when measured at any point on the line, Hence B.

8. Propagation constant γ is a :

a) real value

b) none of the mentioned

c) imaginary value

d) complex value

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Explanation: Since propagation constant is a complex value, containing attenuation constant α, phase constant β respectively as their real and imaginary parts.

9. Attenuation constant α signifies:

a) real part of propagation constant

b) loss that the transmission line causes

c) none of the mentioned

d) all of the mentioned

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Explanation: α is the real value of propagation constant, also signifies the loss that the transmission line causes and hence the total amount of energy transmitted. Hence all the mentioned.

10. Propagation constant γ is given by:

a) α+jβ

b) α-jβ

c) α/jβ

d) α.jβ

View Answer

Explanation: Propagation constant is a complex sum of α and β, α being the real value and β being the complex part.

11. Characteristic impedance Zₒ is given by:

a) √Z/Y

b) √ZY

c) √Z+√Y

d) √Z-√Y

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Explanation: Characteristic impedance Zₒ is the square root of ratio of impedance and admittance of the transmission line.

12. Propagation constant γ in terms of admittance and impedance of the transmission line is:

a) √Z/Y

b) √ZY

c) ZY

d) ZY*

View Answer

Explanation: Propagation constant is the root of product of impedance and admittance of the transmission line.

**Sanfoundry Global Education & Learning Series – Microwave Engineering.**

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