Antennas: Assignment 3:

1. Directivity and input impedance of a monopole antenna on a large ground plane as compared to that of dipole antenna are: 

 Twice, Twice

 Twice, Half 

 Half, Half

 Half, Twice

Ans: b

2. A monopole antenna of radius 0.5 cm is designed at 900 MHz on a large ground plane. The wire length of the monopole antenna (in cm) is approximately:

 16.6

 15.0

 10.0

 7.5

Ans: d

3. A monopole antenna with large ground plane is printed on FR4 substrate having ϵrϵr = 4.4, h = 0.16 cm and tanδδ = 0.02. If the length and width of the printed monopole antenna are 33 cm and 1.2 cm respectively. The approximate resonance frequency in MHz is: 

 100

 200

 400

 900

Ans: b

4. Common Data for Questions 4-5: A bent monopole antenna is placed on a large ground plane. The wire length of 18 cm is bent perpendicularly at 6 cm to form a L-shaped antenna. Now, the vertical height of the monopole is 6 cm and the horizontal length is 12 cm. The diameter of the wire is 2 mm. 

The approximate resonance frequency is: 

 508 MHz 

 488 MHz 

 448 MHz 

 398 MHz

Ans: d

5. The approximate input resistance of the antenna is: 

 10 Ω   

 6 Ω 

 3 Ω 

 1 Ω 

Ans: a

6. Common Data for Questions 6-7: A N-turn circular loop antenna has loop diameter of 150 mm and the wire diameter is 2 mm.

The number of turns required to match this antenna with 50 Ω RF source at 50 MHz are:

 164

 82

 41

 20

Ans: b

7. If it is wound on a ferrite core, whose effective permeability is 10, then the number of turns required to match this antenna with 50 Ω RF source at 50 MHz are:

 16

 8

 4

 2

Ans: b

8. Common Data for Questions 8-9:  A printed resonant slot antenna is designed at 2.45 GHz on a one side metal FR4 substrate with e_r = 4.4, h = 0.16 cm and tand = 0.02. The width of the slot is 4 mm. 

The length of the slot in mm is: 

 57

 46

 28

 23

Ans: a

9. If width of the slot increases then:

 Resonance frequency decreases

 Bandwidth increases

 Both (a) and (b) 

 None of the above

Ans: c 

10. If Input impedance of a dipole antenna is 68 Ω, then what will be approximate input impedance of the complementary slot antenna?

 36 Ω

 75 Ω

 148 Ω

 522 Ω

Ans: d