Antennas: Assignment 10:

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1. For optimum gain pyramidal horn antenna, the maximum aperture phase errors that can be tolerated in E and H-planes are respectively:

450,900${45}^0,{90}^0$

900,450${90}^0,{45}^0$

900,1350${90}^0,{135}^0$

1350,900${135}^0,{90}^0$

Ans: a

2. A coaxial feed pyramidal horn antenna uses a rectangular waveguide WR75. What will be the cut-off frequency (in GHz) for TE10$T{E}_{10}$  mode operation?

3.94

7.87

15.75

23.62

Ans: b

      

Common Data for Questions 3-5: A coaxial feed pyramidal horn antenna is designed to operate at 2.45 GHz with following dimensions: 

Waveguide:  WR340, Aperture = 20 cm x 15 cm, Horn length from neck to mouth = 10 cm.

3. The dimensions of the waveguide a and b in mm are:

86.36, 43.18

86.36, 172.72

8.64, 4.32

8.64, 17.27

Ans: a

4. The maximum aperture phase errors in E and H-plane are respectively:

110.40,155.40${110.4}^0,{155.4}^0$

55.20,77.70${55.2}^0,{77.7}^0$

35.50,57.60${35.5}^0,{57.6}^0$

27.60,38.80${27.6}^0,{38.8}^0$

Ans: b

5. If efficiency of the horn antenna is 50%, then approximate gain of the antenna in dBi is:

16

15

11

8

Ans: c

6. In an aperture matched horn antenna, exponential ridges are used to increase ____ and aperture matching at the end is done to increase ____. 

Bandwidth, Gain

Bandwidth, Bandwidth

Gain, Bandwidth

Gain, Gain

Ans: a

7. For a corrugated horn antenna number of teeth per wavelength and depth of the teeth (in terms of wavelength) may vary between ______ and ______ respectively:

1-4, 0.1-0.25

4-10, 0.25-0.5

10-20, 0.5-1

>20, >1

Ans: b

Common data for Questions 8-10: For a coaxial feed pyramidal horn antenna,

8. As the probe radius increases, bandwidth:

Increases

Decreases

Remains same

First decreases then increases

Ans: a

9. As the probe length increases, frequency:

Increases

Decreases

Remains same

First decreases then increases

Ans: b

10. The approximate distance between the shorting wall of the waveguide and the coaxial feed should be:

λg${\lambda }_g/2$

${\lambda }_0/2$

λ0${\lambda }_0/4$

         λg/4

Ans:d

λg/4