Electromagnetics

Q:   The points P, Q, and R shown on the Smith chart (normalized impedance chart) in the following figure represent:

• A:  P: Open Circuit, Q: Short Circuit, R: Matched Load
• B:  P: Open Circuit, Q: Matched Load, R: Short Circuit
• C:  P: Short Circuit, Q: Matched Load, R: Open Circuit
• D:  P: Short Circuit, Q: Open Circuit, R: Matched Load

Q:   A lossy transmission line has resistance per unit length R=0.05Ω/m . The line is distortionless and has characteristic impedance of 50Ω . The attenuation constant (in Np/m, correct to three decimal places) of the line is _______.

Q:   The cutoff frequency of TE01 mode of an air filled rectangular waveguide having inner dimensions a cm × b cm (a>b) is twice that of the dominant TE10 mode. When the waveguide is operated at a frequency which is 25% higher than the cutoff frequency of the dominant mode, the guide wavelength is found to be 4 cm. The value of b (in cm, correct to two decimal places) is _______.

Q:   Consider a wireless communication link between a transmitter and a receiver located in free space, with finite and strictly positive capacity. If the effective areas of the transmitter and the receiver antennas, and the distance between them are all doubled, and everything else remains unchanged, the maximum capacity of the wireless link

• A:  increasing by a factor of 2
• B:  decreasing by a factor of 2
• C:  remains unchanged
• D:  decreasing by a factor of √2

Q:   A two-wire transmission line terminates in a television set. The VSWR measured on the line is 5.8. The percentage of power that is reflected from the television set is___________

Q:   Concentric spherical shells of radii 2 m, 4 m, and 8 m carry uniform surface charge densities of 20 nC/m2, −4 nC/m2 and ρs, respectively. The value of ρ_s(nC/m2) required to ensure that the electric flux density D(bar) =0(bar) radius 10 m is _________

Q:   Two lossless X-band horn antennas are separated by a distance of 200λ. The amplitude reflection coefficients at the terminals of the transmitting and receiving antennas are 0.15 and 0.18, respectively. The maximum directivities of the transmitting and receiving antennas (over the isotropic antenna) are 18 dB and 22 dB, respectively. Assuming that the input power in the lossless transmission line connected to the antenna is 2 W, and that the antennas are perfectly aligned and polarization matched, the power ( in mW) delivered to the load at the receiver is ________

Q:   An air-filled rectangular waveguide of internal dimension a cm X b cm (a > b) has a cutoff frequency of 6 GHz for the dominant TE10 mode. For the same waveguide, if the cutoff frequency of the TM11 mode is 15 GHz, the cutoff frequency of the TE01 mode in GHz is __________.

Q:   The directivity of an antenna array can be increased by adding more antenna, as a larger number of elements

• A:  improves the radiation efficiency
• B:  increase the effective area of the antenna
• C:  results in a better impedance matching
• D:  allows more power to be transmitted by the antenna

Q:   A coaxial capacitor of inner radius 1 mm and outer radius 5 mm has a capacitance per unit length of 172 pF/m. If the ratio of outer radius to inner radius is doubled, the capacitance per unit length (in pF/m) is ________.