1.The imaginary part of the matching network is given by the relation:
a) ±(√(Z0– RL)/RL)Z0
b) ±(√(Z0– RL)/RL)
c) ±(√(Z0– RL)/ Z0
d) None of the mentioned
Explanation: By theoretical analysis, the expressions for real and imaginary parts of the impedance of the matching network are derived in terms of the load impedance and the characteristic impedance of the transmission line. This expression derived is ±(√(Z0– RL)/RL)Z0 .
2. Which of the following material is not used in the fabrication of resistors of thin films?
a) nichrome
b) tantalum nitride
c) doped semiconductor
d) pure silicon
Explanation: Certain physical properties are to be met in order to use a material to make thin film resistors. These properties are not found in pure silicon which is an intrinsic semiconductor.
3. Large values of inductance can be realized by:
a) loop of transmission line
b) spiral inductor
c) coils of wires
d) none of the mentioned
Explanation: Loop of transmission lines are used to make inductors to realize lower values of inductance. Coils of wires cannot be used to realize inductors at higher frequencies. Spiral conductors can be used to realize inductors of higher values at higher frequencies.
4. A short transmission line stub can be used to provide a shunt capacitance of:
a) 0-0.1µF
b) 0-0.1pF
c) 0-0.1nF
d) 1-10pF
Explanation: Since a transmission line consists of two wires, which can act plates of a capacitor, they can be used as a capacitor of very low values of the range 0-0.1pF.
5. Slotted line is a transmission line configuration that allows the sampling of:
a) electric field amplitude of a standing wave on a terminated line
b) magnetic field amplitude of a standing wave on a terminated line
c) voltage used for excitation
d) current that is generated by the source
Explanation: Slotted line allows the sampling of the electric field amplitude of a standing wave on a terminated line. With this device, SWR and the distance of the first voltage minimum from the load can be measured, from this data, load impedance can be found.
6. A slotted line can be used to measure _____ and the distance of _____________ from the load.
a) SWR, first voltage minimum
b) SWR, first voltage maximum
c) characteristic impedance, first voltage minimum
d) characteristic impedance, first voltage maximum
Explanation: With a slotted line, SWR and the distance of the first voltage minimum from the load can be measured, from this data, load impedance can be found.
7. A modern device that replaces a slotted line is:
a) Digital CRO
b) generators
c) network analyzers
d) computers
Explanation: Although slotted lines used to be the principal way of measuring unknown impedance at microwave frequencies, they have largely been superseded by the modern network analyzer in terms of accuracy, versatility and convenience.
8. If the standing wave ratio for a transmission line is 1.4, then the reflection coefficient for the line is:
a) 0.16667
b) 1.6667
c) 0.01667
d) 0.96
Explanation: ┌= (SWR-1)/ (SWR+1). Substituting for SWR in the above equation for reflection co-efficient, given SWR is 1.4, reflection co-efficient is 0.16667.
9. If the reflection coefficient of a transmission line is 0.4, then the standing wave ratio is:
a) 1.3333
b) 2.3333
c) 0.4
d) 0.6
Explanation: SWR= (1+┌)/ (1-┌). Where ┌ is the reflection co-efficient. Substituting for the reflection co-efficient in the equation, SWR is 2.3333.
10. Expression for ϴ means phase angle of the reflection co efficient r=|r|-e^jθ, the phase of the reflection co-efficient is:
a) θ=2π+2βLmin
b) θ=π+2βLmin
c) θ=π/2+2βLmin
d) θ=π+βLmin
Explanation: here, θ is the phase of the reflection co-efficient. Lmin is the distance from the load to the first minimum. Since voltage minima repeat every λ/2, any multiple of λ/2 can be added to Lmin .