1. Stub spacing that are near 0 and λ/2 lead to more frequency sensitive matching networks.
a) true
b) false
Explanation: Though theoretically the stub spacing must be small enough to reduce the forbidden area, for practical considerations, the stubs have to be placed sufficiently far enough for fabrication ease and reduce frequency sensitivity.
2. The standard stub spacing usually used is:
a) 0, λ/2
b) λ/4, λ/8
c) λ/8, 3λ/8
d) none of the mentioned
Explanation: While stub spacing of 0, λ/2 lead to frequency sensitive matching circuits, an optimum value of spacing is chosen taking into consideration, the various design constraints. This optimum spacing usually used is λ/8, 3λ/8.
3. If the length of the line between the first stub and the load can be adjusted, the admittance can be moved from the forbidden region.
a) true
b) false
Explanation: If the design requirements for impedance matching are more flexible, then the length of the line between the load and the first stub can be varied. This would result in moving the load admittance point out of forbidden region in the smith chart thus enabling impedance matching.
4. A quarter wave transformer is useful for matching any load impedance to a transmission line.
a) true
b) false
Explanation: Quarter wave transformers are a simple circuit that can be used to match real load impedance to a transmission line. Quarter wave transformers cannot be used to match complex load impedances to a transmission line.
5. Major advantage of a quarter wave transformer is:
a) It gives proper matching
b) It gives high gain
c) Broader bandwidth
d) None of the mentioned
Explanation: Quarter-wave transformers can be extended to multi section designs in a methodical manner to provide a broader bandwidth
6. If a narrow band impedance match is required, then more multi section transformers must be used.
a) True
b) False
Explanation: If a narrow band impedance match is required, then a single section of quarter wave transformer is used. When a wideband impedance match is required, then multi-section quarter wave transformers must be used for impedance matching
7. The major drawback of the quarter wave transformer that it cannot match complex load to a transmission line cannot be overcome.
a) True
b) False
Explanation: The major drawback of the quarter wave transformer that it cannot match complex load to a transmission line can be overcome by transforming complex load impedance to real load impedance
8. Complex load impedance can be converted to real load impedance by:
a) Scaling down the load impedance
b) By introducing an approximate length of transmission line between load and quarter wave transformer
c) Changing the operating wavelength
d) None of the mentioned
Explanation: By introduction of a transmission line of suitable length between the load and the quarter wave transformer, the reactive component of the load that is the complex value can be nullified thus leaving behind only real load impedance to be matched.
9. Converting complex load into real load for impedance matching has no effect on the bandwidth of the match.
a) True
b) False
Explanation: Adding a length of line to the transmission line between the load and quarter wave transformer alters the frequency dependence of the load thus altering the bandwidth of the match
10. If a single section quarter wave transformer is used for impedance matching at some frequency, then the length of the matching line is:
a) Is different at different frequencies
b) Is a constant
c) Is λ/2 for other frequencies
d) None of the mentioned
Explanation: The length of the matching section is λ/4 for the frequency at which it is matched. For other frequencies, the electrical length varies. For multi section transformers, a wide bandwidth can be achieved.