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Sheet 3

The document contains a series of engineering problems related to antennas and wave propagation, focusing on calculations of radiation resistance, gain, radiation efficiency, electric and magnetic field strengths, power density, and maximum effective aperture. It includes specific scenarios involving dipoles of various lengths and frequencies, as well as parameters for wireless communication links. The problems require applying principles of electromagnetic theory and antenna design to derive solutions.

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7 views1 page

Sheet 3

The document contains a series of engineering problems related to antennas and wave propagation, focusing on calculations of radiation resistance, gain, radiation efficiency, electric and magnetic field strengths, power density, and maximum effective aperture. It includes specific scenarios involving dipoles of various lengths and frequencies, as well as parameters for wireless communication links. The problems require applying principles of electromagnetic theory and antenna design to derive solutions.

Uploaded by

ziadashraf258
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Higher Institute for Engineering & Technology Antennas and Wave Propagation

Communication and Electronics Department (ECE 4203)


Sheet 3

1. a) Find the radiation resistance of an infinitesimal current element with length of


1 cm and radiating at a frequency of 10MHZ.
b) if the radiation and loss resistances of infinitesimal dipole are .01ῼ and .1ῼ
respectively. find its gain.
2. Calculate the radiation efficiency of an infinitesimal short dipole with length of 0.01λ
if the loss resistance is 2 Ω. What is its maximum effective aperture if the frequency
of operation is 10 MHz?
3. A 6 cm long z-directed dipole carries a current of 1 A at 2.4 GHz. Calculate the
electric and magnetic field strengths at a distance of 50 cm along 𝜃 = 60 °.

4. Calculate the radiation resistance of a short dipole (with a triangular current


distribution) of length 0.3 m operating at 100MHz. If the total resistance of the
antenna is 2.2 Ω, calculate the maximum effective area and the radiation efficiency
of the dipole.

5. A short dipole of length 0.1λ is kept symmetrically about the origin, oriented along
the z- direction and radiating 1 kW power into free space. Calculate the power
density at r = 1 km along 𝜃 = 45 ° and 𝜑 = 90 °.

6. Calculate the radiation efficiency of a half wave dipole if the loss resistance is 1 Ω.
What is its maximum effective aperture if the frequency of operation is 145 𝑀𝐻𝑧.

7. Two half-wave dipoles operating at 2.4 𝐺𝐻𝑧 are used to establish a wireless
communication link. The antennas are matched to the transmitter and the receiver,
respectively. The maximum transmitted power is 100 𝑚𝑊 and for reliable
communication the received power has to be at least −80 𝑑𝐵𝑚. Calculate the
maximum possible distance over which reliable communication can be established
using this system. For a sphere of radius r, find the solid angle ΩA (in square radians
or steradians) of a spherical cap on the surface of the sphere over the north-pole
region defined by spherical angles of 0𝑜 ≤ θ ≤ 30𝑜, 0𝑜 ≤ φ ≤ 180𝑜.

1 With my best wishes


Assis. Prof./ Allam Ameen

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