Antennas Practice Test 6

1. Which of the following is true for uniform linear array elements, to obtain the total field?

The single element field is multiplied by the directivity

The single element field is multiplied by the beamwidth

The single element field is multiplied by the array factor

The single element field is multiplied by the normalized array factor

2. The maximum of the first minor lobe of array factor occurs at 13.46 dB down the maximum major lobe.

True

False

3. Electronic scanning is more advantageous compared to mechanical scanning

False

True

4. Which of the following pattern represents the array factor of a two element array separated by a distance of λ/4 and phase difference is 0?

5. A 4-isotropic element broadside array separated by a λ/4 distance has nulls occurring at ____________

sin^-1 (±n)

cos^-1 (±n)

\(cos^{-1} (±\frac{n}{2})\)

\(sin^{-1} (±\frac{n}{2})\)

6. The array factor of 4- isotropic elements of broadside array is given by ____________

\(\frac{sin(2kdcosθ)}{kdcosθ} \)

\(\frac{cos(2kdcosθ)}{2kdcosθ} \)

\(\frac{sin(kdcosθ)}{2kdcosθ} \)

\(\frac{sin(2kdcosθ)}{2kdcosθ} \)

7. Which of the following is the necessary condition to avoid grating lobes in N-Isotropic element end-fire array?

d < λ

d=λ

d < λ/2

d > λ/2

8. The array factor of 4- isotropic elements of broadside array separated by a λ/4 is given by ____________

sin(sinθ)

sin(cosθ)

sinc(cosθ)

cos(sinθ)

9. The necessary condition for maximum of the second side lobe of n element array is __________

\( \frac{Nᴪ}{2}=±\frac{3π}{2}\)

\( \frac{Nᴪ}{2}=±\frac{π}{2}\)

\( \frac{Nᴪ}{2}=±\frac{4π}{2}\)

\( \frac{Nᴪ}{2}=±\frac{5π}{2}\)

10. The direction of the first minor lobe of 4 element isotropic broadside array separated by λ/2 is ___________

41.4°

90°

30°

60°