ANTENNAS AND WAVE PROPAGATION | AWP

 ANTENNAS AND WAVE PROPAGATION 

Table of Content(toc)

UNIT I - Antenna Basics 

Introduction:

• Radiation Mechanism
• Current Distribution on a Thin Wire Antenna

Fundamental Parameters of Antennas:

• Radiation Pattern
• Radiation Power Density
• Radiation Intensity
• Beam width
• Directivity
• Antenna Efficiency
• Gain, Beam Efficiency
• Bandwidth, Polarization
• Input Impedance
• Antenna Radiation Efficiency
• Antenna Vector Effective Length and Equivalent Areas,
• Maximum Directivity and Maximum Effective Area, 
• Antenna Temperature

UNIT II 

• Hertzian dipole
• Linear antennas 
• Basics of Arrays Fields

Power and Impedance 

• Infinitesimal Dipole (Hertzian Dipole)
• Half-Wavelength Dipole
• Monopole
• Folded dipole

Arrays: 

• Concept of point source
• two sources of any phase, any amplitude, uniform linear array, binomial array and 
• Dolph-Chebyshev arrays. 

UNIT III - Special Antennas

Aperture Antennas: 

• Horn Antenna & Slot Antenna
• Log Periodic Dipole Antenna (LPDA)
• Yagi-Uda antenna
• Helical Antenna
• Wearable Antenna. 

UNIT IV-Reflectors and Patch Antennas

• Flat-Sheet/corner reflectors
• Parabolic Reflectors
• Microstrip Patch Antenna
• parametric analysis of rectangular Patch Antenna design using CST/HFSS(Case Study)
• Introduction to MIMO Antennas.

Antenna Measurements: 

• Friis Transmission Equation
• Pattern Measurement, Outdoor/ Indoor.

UNIT V – Wave Propagation

Ground Wave Propagation-

• Plane earth reflection, 
• Space and Surface Waves
• elevated dipole antenna above plane earth
• Wave tilt of surface wave
• Spherical earth propagation. 

Tropospheric waves:

• Normal refraction
• abnormal refraction and reflection
• modified index curves and duct propagation,
• troposphere scatter. 

Sky Wave Propagation: 

• Structure and Layers of Ionosphere
• Electrical Properties of Ionosphere
• Refraction and Reflection by Ionosphere
• Critical Frequency, 
• MUF. LUF, 
• Skip Distance, 
• Maximum Single-hop Distance, 
• Virtual Height. 

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MID 2 PAPER IMP QUESTIONS

1-12 set 1 

13-25 set 2

1	Design of a 54 to 216 MHz Log- periodic Dipole Antenna. Desired Gain: 6.5 dB(Assume Directivity = 7.5 dB for 1 dB loss, τ = 0.822 and σ = 0.149).
2	What is electromagnetic horn antenna? What are the various types of horn? What are their practical applications?
3	Explain in detail about the different modes of operation in Helical Antenna.
4	Mention the design considerations of Yagi Uda Antenna.
5	Design a Rectangular Micro Strip Antenna for Wi-Fi application (2.400 to 2.483 GHz) Choose Substrate: ε r = 2.32, h = 0.16 cm and tan δ = 0.001.
6	b)Mention the Techniques used in MIMO.
7	With a clear procedure narrate about any one method of  pattern Measurement. Derive the Friis transmission equation for analysis and design of communication system.
8	Elucidate Spillover with reference to Parabolic Reflectors? Explain the remedial measures to reduce Spillover.
9	A free-space LOS microwave link operating at 10 GHz consists of a transmit and a receive antenna each having a gain of 25 dB. The distance between the two antennas is 30 km and the power radiated by the transmit antenna is 10 W. Calculate the path loss of the link and the received power.
10	Describe the ionosphere layers D, E, F1 and F2.
11	A line-of-sight 10 GHz microwave link is to be established on the surface of the earth (mean radius 6370 km). The straight line distance between the two antennas is 60 km and the height of the transmit antenna is 60 m. Calculate the minimum height of the receive antenna assuming that the propagation is taking place in the absence of atmosphere.
12	Explain the terms with necessary mathematical terms and diagrams about(i) Skip Distance (ii) Critical Frequency.
13		Evaluate the resonant frequency with L=1.56cm and W=1.25cm            ɛ r =2.2 and h=0.795mm.
14		What is electromagnetic horn antenna? What are the various types of horn? What are their practical applications?
16		Elucidate the construction and basic principles of operation of a helical antenna under (i) normal mode of operation (ii) axial mode of operation.
17		Mention the design considerations of Yagi Uda Antenna.
18		Explain Gain and Aperture Efficiency of Parabolic Reflector Antenna.
19		Mention the features and challenges in a decent wearable textile Antenna.
20		Design a Rectangular Micro Strip Antenna for Wi-Fi application (2.400 to 2.483 GHz) Choose Substrate: ε r = 2.32, h = 0.16 cm and tan δ = 0.001.
21		b) With a clear procedure narrate about any one method of pattern Measurement.
22		A free-space LOS microwave link operating at 10 GHz consists of a transmit and a receive antenna each having a gain of 25 dB. The distance between the two antennas is 30 km and the power radiated by the transmit antenna is 10 W. Calculate the path loss of the link and the received power.
23		Discuss the salient features of Ground wave Propagation.
24		A line-of-sight 10 GHz microwave link is to be established on the surface of the earth (mean radius 6370 km). The straight line distance between the two antennas is 60 km and the height of the transmit antenna is 60 m. Calculate the minimum height of the receive antenna assuming that the propagation is taking place in the absence of atmosphere.
25		Explain the terms with necessary mathematical terms and diagrams about (i) Skip Distance (ii) Critical Frequency.

 

MID 1 QUESTIONS TO BE STUDIED: 

1. Explain the radiation mechanism of an antenna. 
2. Explain the following parameters: 1) Polarization, 2) Effective area and 3) Realized gain
3. A lossless half wave dipole with Zin = 75 Ω is connected to a transmission line of Z0 = 50Ω, having Radiation intensity U = B0 sin^3( θ), Find Maximum Directivity, Reflection Coefficient and realized gain
4. What is the difference between Radiation Intensity and Radiation Density
5. Derive the E and H fields of Hertzian Dipole antenna and half wave dipole
6. Derive the array factor of a two point source isotropic elements and explain the BSA and EFA conditions
7. Plot the radiation pattern of an array with δ = - βd, d = λ/2, while calculating Maxima and minima directions
8. Explain the following parameters: a) Directivity b) Radiation Efficiency c) Absolute Gain d) Realized gain, e) Antenna efficiency f) directivity g) HPBW h) FNBW
9. An antenna has D = 15 dB, Antenna efficiency = - 3.5dB, Find the Gain
10. Explain the concept of Binomial Array.
11. A 1m long car radio antenna operates in AM frequency of 4.5 MHz, Find the Current required to transmit 6W of power. 

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1. Explain the radiation mechanism of an antenna. 
2. A transmission line has Z0 = 50 Ω, Zin of antenna is 75 Ω, Find the reflection coefficient and VSWR.
3. Find Uavg, Umax, Maximum Directivity (Dmax ) for U = sin^2(2θ) 0< θ<π , 0 < ϕ < 2π
4. With illustration explain the Pattern multiplication principle of arrays
5. Plot the radiation pattern of an array with δ = 0, d = λ, while calculating Maxima and minima directions. 
6. Calculate HPBW in E plane for U = sin2θ sin ϕ, 0< θ<π, 0 < ϕ < π.
7. Explain the concept of Folded Dipole antenna
8. Explain the concept of Dolph - Tschebyseff Array
9. Find the total radiated power of Hertzian dipole whose dl = λ/50, I0 = 15A
10. Problems on Rrad and Prad of Hertzian dipole