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ECE Objective Questions { Transmission Lines and Waveguides }

36. Indicate the FALSE statement. Both transmission lines and waveguides
A. can pass several signals simultaneously
B. can use stubs, quarter-wave transformers and directional couplers
C. have equal power losses
D. can carry electromagnetic waves

37. Indicate the FALSE statement regarding ridged waveguides
A. main effect of adding ridge is to lower the value of cut-off wavelength
B. ridges allow a waveguide with smaller dimensions to be used at any given frequency
C. ridged waveguides have less attenuation per unit length than rectangular waveguides
D. ridges reduce the phase velocity

38. The voltage attenuation in dB provided by 20 cm length of a 1 cm x 0.5 cm waveguide in which 1 GHz signal is propagated in dominant mode is

39. After reflection from a plane conducting wall, electromagnetic waves acquire an apparent velocity which is greater than velocity of light in free space. It is called
A. normal velocity
B. group velocity
C. phase velocity
D. velocity of propagation

40. Indicate the FALSE statement When free-space wavelength X, of a signal equals the cut-off wavelength Al of a waveguide, then
A. phase velocity of signal becomes infinite
B. group velocity of signal becomes zero
C. wavelength in the waveguide becomes infinite
D. characteristic wave impedance Zo of the waveguide becomes zero for Tmo mode

41. Point out the FALSE statement. Dominant mode of propagation is preferred with rectangular waveguides because
A. it can be propagated in a guide that is too small to propagate any other mode
B. there is no energy loss through the spurious generation of other modes
C. it is the easiest to excite
D. resulting impedance can be matched to the loaddirectly

42.  Indicate the FALSE statement : As compared to rectangular waveguides, circular ones
A. need much bigger cross-sectional area for carrying thesame signal
B. have lower attenuation especially at frequencies in excess of 1 GHz
C. are more difficult to manufacture
D. are easier to join together in the usual plumbing fashion

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