Antennas Assignment 1

 Antenna Fundamentals

    1)A cell tower antenna needs to cover an area with 120° angular coverage in horizontal plane. The radiation pattern of the antenna should be

 Isotropic

 Omnidirectional

 Directional

 Cannot be determined from the given data

      2)Antenna A and Antenna B have directivities of 2 dBi and 6 dBi in a given plane, respectively. Which of the two antennas would have larger   HPBW?

 A

 B

 Both A and B will have the same HPBW

 Cannot be determined from the given data

      3)The directivity of an antenna is 9.6 dBi. If the half power beam width (HPBW) is 70° in one plane, the HPBW in the orthogonal plane is, approximately:

 50°

 65°

 70°

 85°

4)An antenna has efficiency of 80%. If the directivity of the antenna is 7 dBi, then its gain will be, approximately:

 4 dBi

 5.6 dBi

 6 dBi

 7 dBi

    5)The E-field of the wave radiated by an antenna has two orthogonal components with amplitudes of 0.5 V/m and 0.3 V/m. If the phase difference between the two components is 90°, the polarization of the wave is:

 Linear

 Left hand circular

 Elliptical

 Right hand circular

 6)In a 50 Ω system, if input impedance of an antenna is 68 Ω, the corresponding value of VSWR is, approximately:

 1.15

 1.22

 1.36

 1.68

7) In a 50 Ω system, if input impedance of an antenna is (50 – j25) Ω at 2.45 GHz, the percentage power reflected from the antenna will be, approximately:

 94.12 %

 75.75 %

 24.25 %

 5.88 %

8)AGSM 900 cell tower antenna with 15 dBi gain is transmitting 20 W of power. The power density at a distance of 100 m in the direction of maximum radiation is 5 mW/ m2. What will be the value of power density at a distance of 200 m?

 0.25 mW/m2

 0.5 mW/m2

 1.25 mW/m2

 2.5 mW/m2

    9)Two identical transmitting and receiving antennas are located at a distance of 1 km. If power transmitted is 25 dBm at 10 GHz and received power is -65 dBm, the approximate gain of each antenna is:

 11.2 dBi

 13.2 dBi

 17.5 dBi

 21.3 dBi

10)The diameter of a parabolic dish antenna (with efficiency η = 60%) for 40 dBi gain at 10 GHz is:

 0.62 m

 0.85 m

 1 m

 1.23 m

Answers: 1)b,2)c,3)b,4)c,5)c6)b7)b8)c9)a10)c