B.TECH - Semester 6 antenna and wave propagation Question Paper 2021 (dec)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- Explain the directivity of an antenna.
- Derive an expression for effective aperture of a linear $\lambda / 2$ antenna.
- Calculate the distance at which an electromagnetic wave will have the same magnitude for induction and radiation fields if its frequency is 8 MHz .
- Explain Reciprocity theorem.
- Differentiate between BSA and EFA in terms of the array arrangement, radiation pattern and the way the elements are fed.
- Explain UHF mobile radio propagation.
- Derive an expression to find horn length.
- Differentiate between front feed and cassagraine feed system for a parabolic reflector.
- Derive an expression for critical frequency.
- Derive the relationship between skip distance, maximum usable frequency and critical frequency. Answer any two questions from each Module. Each question carries 10 marks.
- Find exact and approximate directivity of the pattern $E=\sin \theta \sin \phi . E$ has the value only for $\theta$ between 0 to $\pi$ and $\phi$ between 0 to $\pi$ and is zero elsewhere. Also find the decibel difference.
- An antenna has a loss resistance of $10 \Omega$, power gain of 20 , Directivity gain of 22. Find $\mathrm{R}_{\mathrm{r}}$.
- (a) Derive an expression for radiation resistance of a short dipole.
- (b) Derive a relation between maximum effective aperture and directivity.
- Draw the radiation pattern of two isotropic antennas of same amplitude and in phase quadrature. Assume the separation distance between sources as $\lambda / 2$ and $\delta=0$.
- Explain the working of Rhombic antenna. List its applications.
- (a) Find number of elements in a log periodic dipole array with 7 dBi gain and a 4 to 1 bandwidth. The scale constant $\mathrm{K}=1.2$ for apex angle of $15^{\circ}$.
- (b) Differentiate between the two radiation modes of a Helix.
- (a) Derive an expression for resultant field intensity in case of space wave propagation.
- (b) Explain Duct propagation with a neat diagram.
- Explain the mechanism of ionospheric propagation. Also derive an expression for refractive index of an ionospheric layer.
- Explain Tropospheric scattering phenomenon.