Antennas: Assignment 7:

                                        

1. For a given frequency, the size of the microstrip antenna cannot be reduced by:

Using shorting post at the centre

Using high dielectric constant substrate

Cutting Slots

Using shorting post and cutting slots

Ans: d

Common data for Questions 2 and 3: A shorted square MSA is designed to operate at 1.5 GHz using a large substrate with ε_r = 2.55 and h = 0.16 cm as shown in Fig.1. 

2. Approximate length L of the patch should be:

6.2 cm

4.5 cm

3.1 cm

1.5 cm

Ans: d

3. Approximate gain of this antenna configuration will be:

8-10 dBi

6-8 dBi

4-6 dBi

2-4 dBi

Ans: c

4. Compare to conventional RMSA, a fully shorted λ/4 compact RMSA has:

(i)   Less aperture area (ii) Less bandwidth

(iii) Less gain (iv) Low cross polar level

(i) and (ii)

(i) and (iii)

(i), (ii) and (iii)

All of the above

Ans: c

5. For the same radius, which one of the following configurations will provide lowest resonance frequency?

Circular MSA 

Semi-circular MSA

Shorted semi-circular MSA

Shorted 90^o sectoral MSA

Ans: d

6. A circular MSA with radius of 7.9 mm using single shorting post is shown in Fig. 2. The substrate parameters are: ε_r = 2.2 and h = 1.6 mm. Approximate resonance frequency of the shorted circular MSA will be:

2450 MHz

2145 MHz

1570 MHz

780 MHz

Ans: b

7. An RMSA with length L = 2 cm and width W = 3 cm is taken for a substrate having ε_r = 3.38, h = 0.16 cm and tan δ = 0.0012. A stub of width w = 0.2 cm and length l = 0.5 cm is added on one side of the radiating edge as shown in Fig. 3. Approximate fundamental resonance frequency for this antenna will be:

7.07 GHz

5.45 GHz 

4.15 GHz

3.75 GHz

Ans: d

Common Data for Questions 8 to 10: A dual band dual polarized rectangular MSA is designed on a substrate using orthogonal feeds as shown in Fig. 4. Substrate specifications are: ε_r = 2.33, h = 1.6 mm and tan δ = 0.0012. Length and width of rectangular MSA are 11 cm and 16 cm corresponding to frequencies f_L and f_W, respectively.

8. Approximate resonance frequency (f_L) corresponding to length is: 

620 MHz

895 MHz

1350 MHz

1790 MHz

Ans: b

9. Approximate resonance frequency (f_W) corresponding to width is:

620 MHz

895 MHz

1350 MHz

1790 MHz

Ans: a

10. For higher resonance frequency, antenna will provide:

Vertical polarization and less gain

Horizontal polarization and less gain

Vertical polarization and high gain

Horizontal polarization and high gain

Ans: d