Following statements are given : (a) Beam width between first nulls for a broadside long array is given by \(\dfrac{2\lambda}{nd}\). (b) Beam width between first nulls for an end fire long array is given by \(2\sqrt{\dfrac{2\lambda}{nd}}\). (c) Beam width between first nulls for a broadside long array is given by \(\dfrac{\lambda}{nd}\). (d) Beam width between first nulls for an end fire long array is given by \(\dfrac{\lambda}{nd}\). Which of the above statements are correct ?
(a) & (b)
To determine which statements are correct, let's first understand the concepts of beam width in antenna theory.
Beam Width Between First Nulls:
- Broadside Array: For a broadside array antenna, the beam width between the first nulls is given by \(\dfrac{2\lambda}{nd}\), where \(\lambda\) is the wavelength, \(n\) is the number of elements, and \(d\) is the distance between the elements.
- End Fire Array: For an end fire array, the beam width between the first nulls is given by \(2\sqrt{\dfrac{2\lambda}{nd}}\).
Let's verify each statement based on these formulae:
- Statement (a): Beam width between first nulls for a broadside long array is given by \(\dfrac{2\lambda}{nd}\). This is correct based on the standard formula for a broadside array.
- Statement (b): Beam width between first nulls for an end fire long array is given by \(2\sqrt{\dfrac{2\lambda}{nd}}\). This is also correct as per the formula for an end fire array.
- Statement (c): Beam width between first nulls for a broadside long array is given by \(\dfrac{\lambda}{nd}\). This is incorrect as it does not match the known formula for a broadside array.
- Statement (d): Beam width between first nulls for an end fire long array is given by \(\dfrac{\lambda}{nd}\). This is incorrect as it does not align with the known formula for an end fire array.
Conclusion: The correct statements are (a) and (b). Therefore, the correct answer is (a) & (b).
Similar Questions
If the effective area of an antenna becomes \(\frac{2A}{3}\) from its initial value of 'A', while keeping its operating frequency same. Then, the antenna gain becomes \(\left(\frac{2x+4}{15}\right)\) times of its initial value. The value of x will be:
For a half wave dipole antenna
A. The average value of current is 0.64 (unit).
B. The ratio of electric field intensity just near to the antenna surface and the potential developed on the antenna surface after reception of signal, is equal to the effective height
C. Effective aperture will remain same if antenna gain will be improved by some technique.
D. The effective height will be 0.64 l, where l is the physical length of antenna.
E. If length of antenna becomes l = 0.1λ, then its current distribution become triangular.
Choose the correct answer from the options given below :
Match the following lists in terms of radiation resistances of various antennas :
List – I List – II a. Short vertical monopole i. \(31200\left(\dfrac{\text{Area of Loop}}{\lambda^{2}}\right)^{2}\) b. Small loop antenna ii. \(80\pi^{2}\left(\dfrac{L}{\lambda}\right)^{2}\) c. Dipole antenna iii. 73 ohms d. Radiation resistance of half wave dipole iv. \(400\left(\dfrac{\text{Physical height}}{\lambda}\right)^{2}\) Choose the correct answer from the codes given below:
Match List I with List II
LIST I (Type of Aperture Antenna) LIST II (Beam widtd half power points) A. Uniformly illuminated linear Array I. \(\frac{58}{D_\lambda}\) B. Uniformly illuminated circular aperture II. \(\frac{56}{a_{E\lambda}}\) C. Optimum E-plane rectangular horn III. \(\frac{67}{a_{E\lambda}}\) D. Optimum H-plane rectangular horn IV. \(\frac{51}{L_\lambda}\) Choose the correct answer from the options given below:
The most basic antenna element is :
The expression given below is :
\(P_{r}=P_{t}\dfrac{A_{et}\cdot A_{er}}{r^{2}\lambda^{2}}\ \left(\text{W}\right)\)
Important Questions from Antennas
Which of the following antennas is the standard reference antenna for the directiveness?
Consider the following statements:
(a) Fiber optic cable is much lighter than copper cable
(b) Fiber optic cable is not affected by power surges or electromagnetic interference
(c) Optical transmission is inherently bidirectional.
Which of the statements is (are) correct?Broadside arrays have
A. Number of dipoles of unequal size
B. Number of dipoles equally spaced
C. Collinear dipoles
D. Dipoles in phase
E. Dipoles are 90 out of phase
Choose the correct answer from the options given below:
To match the impedance of a 'ground penetrating radar antenna' to the ground, impedance of ground is given by the expression, (if ϵ r= 14, μ r= 1, σ = 10 −2 ℧/m, operating frequency = 200 MHz)
For an isotropic antenna P n(θ, φ) = 1, D = 1, for all θ and φ. The beam area for the isotropic antenna is given by:
