Antennas: Assignment 8

Common data for Questions 1 to 3: A circular MSA is designed at 1.8 GHz on a substrate having ε_r = 2.2 and h = 0.32 cm with dual feed as shown in Fig.1.

1. The approximate radius of the circular patch should be:

45.4 mm

41.6 mm

37.4 mm

31.5 mm

Ans: d

2. Approximate feed position should be x = y =

37.2 mm

21.6 mm

12.5 mm

5.5 mm

Ans: c

3. For left hand circular polarization, antenna feed amplitude and phase at x and y position should be:

1∠0o,1∠0o$1\mathrm{\angle }{0}^o,1\mathrm{\angle }{0}^o$

1∠0o,1∠90o$1\mathrm{\angle }{0}^o,1\mathrm{\angle }{90}^o$

1∠90o,1∠0o$1\mathrm{\angle }{90}^o,1\mathrm{\angle }{0}^o$

1∠0o,1∠180o$1\mathrm{\angle }{0}^o,1\mathrm{\angle }{180}^o$

Ans: b

Common data for Questions 4 to 6: A single feed nearly square MSA is designed at 2.5 GHz using a substrate having ε_r = 3.38 and h = 3.2 mm for right hand circular polarization (RHCP) as shown in Fig. 2. (Hint: To achieve RHCP for given feed point, L₁ < L₂ )

4. The dimension L1$L_1$  of MSA should be:

35.2 mm

29.6 mm

24.8 mm

20.6 mm

Ans: b

5. The dimension L2$L_2$  of MSA should be:

34.5 mm

31.4 mm

27.9 mm

24.2 mm

Ans: b

6. Gain of circularly polarized MSA will be:

3-5 dBi

5-7 dBi

7-9 dBi

9-11 dBi

Ans: b

7. Compared to conventional circularly polarized (CP) MSA array, sequentially rotated CP array provides:

(i) More gain (ii) High axial ratio bandwidth

(iii) Less axial ratio bandwidth (iv) Less gain

(i) and (ii)

(i) and(iv)

(ii) and (iii)

(ii) and(iv)

Ans: d

8. A series fed MSA array is designed at 5.8 GHz on substrate having e_r = 2.2 and h = 0.8 mm as shown in Fig. 3. To achieve broadside radiation pattern, approximate connecting feed line length should be:

25.8 mm

17.8 mm

12.9 mm

8.9 mm

Ans: b

9. A square MSA is designed at 1.8 GHz on RT Duroid 5870 substrate having e_r = 2.33, h = 1.6 mm, and tand = 0.0012. Side length of the square patch is 5.4 cm. An 11-elements central fed series array is designed with inter-element spacing of 0.65λ_o as shown in Fig. 4_. Total array antenna length will be:

74.4 cm

83.4 cm 

113.7 cm

124.6 cm

Ans: c

10. A square MSA has a gain of 6.2 dBi at 2.45 GHz. A 4 x 4 corporate fed array is designed using this square MSA. The approximate gain of this array will be:

8.0 dBi

12.0 dBi

18.0 dBi

22.0 dBi

Ans: c