ES4F1 Mock QMP Test - Section B
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ES4F1 Mock QMP Test - Section B
Section B involves 4 numeric questions for 50% of the overall weight of the QMP exam. Two questions have 12 marks each, one question 10 marks and the other 16 marks. You are required to upload files of your working for all questions of Section B of the test. If workings are not submitted for a question in Section B, no marks will be awarded for that question.
Question 1 [ 10 marks]
(a) A satellite transmits an electromagnetic wave, at 12 GHz, via its transmitting antenna. The power radiated from the satellite antenna is (100 + a3) W. The distance between the satellite antenna and a receiving antenna on the earth’s surface is 3.7 107 m. The values of the directivity and radiation efficiency of the satellite antenna are 40 dB and 1, respectively. The satellite and receiving antennas are aligned for maximum power transfer. For both antennas, assume matched impedance conditions; thus Ae =λ2D/(4π), where Ae is the effective aperture, D is the directivity and λ is the wavelength. Ignoring ground effects and propagation loss (e.g. due to rain), determine the power received, Pr, if the receiving antenna is a (2 + a4/10) m diameter parabolic dish antenna with radiation efficiency ξp = 0.7 . State any assumptions you make.
Inset the value of Pr , correct to two decimal places, in the box below.
Note: a3 and a4 are the 3rd and 4th digits of your Warwick University ID number
Pr = ___0.13___ nW (5 marks)
(b) A designer of an 1.8 GHz wireless communication link would like to ensure, for health and safety reasons, that the power density does not exceed (1 + a3/10) mW/cm2 at a distance of 5 m from the antenna. If the gain of the antenna, in the direction of interest, is (12 + a4/10) dB, determine the maximum allowed transmitter power, Pt, supplied to the antenna.
Insert the value of Pt, correct to two decimal places, in the box below.
Note: a3 and a4 are the 3rd and 4th digits of your Warwick University ID number
Pt = ___198.22___ W (5 marks)
Question 2 [12 marks]
(a) The electric field of a plane wave propagating in a lossy medium is given by the expression:
E(z,t) = x(ˆ)4.44e一0. 126z cos[2πx(103 + a3 )t 一 0. 126z] V/m
Determine:
(i) The frequency of the wave, f.
(ii) The skin depth value, δ .
(iii) The distance z (z>0) at which the average power density has been reduced by (30 + a4/10) dB with respect to its value at z = 0.
Insert their values, correct to 1 decimal place, in the boxes below.
Note: a3 and a4 are the 3rd and 4th digits of your Warwick University ID number
f = __1000.0 Hz (1 mark)
δ = __7.9 m (1 marks)
z = __27.4 m (3 marks)
(b) A thin wire dipole antenna, made of metal, is operating at 100 MHz in free space. The length of the antenna is 1.5 m and the wire diameter is (1.2 + a3/10) mm. The conductivity of the metal is (4 + a4/10) x107 S/m. The permeability of the metal is μ0 = 4π x 10一7 H/m. The antenna wire is along the z-axis and the antenna is centred at the origin of the Cartesian co-ordinate system. Determine the value of the antenna’s loss resistance, Rloss, and insert this value, correct to 2 decimal places, in the box below.
Note: a3 and a4 are the 3rd and 4th digits of your Warwick University ID number
Rloss = ___1.25 Ω (3 marks)
(c) Assume that a plane wave propagating in medium 1 is normally incident at the interface between medium 1 and medium 2. The interface is assumed to be infinite and the two media are assumed to be semi-infinite. Determine the value of the plane wave reflectivity, R, if medium 1 is air (assumed to have the constitutive parameters of free space) and medium 2 has the constitutive parameters, εr2 = (81+a3), μr2 = 1 and
σ = (4 + a4/10) S/m.
Insert the value of R, correct to 2 decimal places, in the box below.
Note: a3 and a4 are the 3rd and 4th digits of your Warwick University ID number
R = __0.99 (4 marks)
Question 3 [12 marks]
In the figure below, the total path loss between points P1 and P2 must be at least (130+a3) dB at a frequency off = (0.9+a4/10) GHz. The medium surrounding the knife edge is air. Air is assumed to have the constitutive parameters of free space. Design the knife edge screen, by determining its minimum height h, to achieve this specification. Ignore ground reflections. Insert the minimum value of h, correct to 1 decimal place, in the box below.
Note: a4 and a5 are the 3rd and 4th digits of your Warwick University ID number
The minimum value of height his ___95.9 m
Question 4 [16 marks]
(a) Two boats are separated by a distance of (1+a3/100) km. They are equipped with radios operating at 1.9 GHz. The radios, including their antennas, are identical. When transmitting, the radio’s transmitter power supplied to the transmitting antenna is (32+a4/10) dBm. Assume the following:
(i) the sea surface is smooth and flat;
(ii) the sea water is lossless;
(iii) the constitutive parameters of air are those of free space;
(iv) the antennas of the radios are vertical, with respect to the sea surface, Hertzian dipoles;
(v) the height of the antennas is much less than the boat separation range; (vi) the antennas are matched.
The antennas of the radio frequency transceivers were tested in an electromagnetic anechoic chamber. When separated by 12 m and aligned for maximum power transfer, the received signal power from each antenna, when the supplied power by the transmitter was (32+a3/10) dBm, was -55 dBW. Design the communication link between the boats, by determining the minimum antenna height h above the sea surface (assume both antennas have the same height), such that the signal power received by each radio from the other is at least 0.1 nW. In your uploading, state all the assumptions you make. Insert the value of the minimum antenna height h, correct to 1 decimal place, in the box below.
Note: a4 and a5 are the 3rd and 4th digits of your Warwick University ID number
The minimum antenna height value is __2.2 m [8 marks]
(b) An antenna configuration consists of a short Hertzian dipole, of length L = λ/100, λ is the wavelength in free space) placed vertically at height h above an infinite perfectly magnetic conductor (PMC) plane. The surrounding medium is air which is assumed to have the constitutive parameters of free space. The frequency of operation of the antenna is (100+a3) MHz. The Hertzian dipole is assumed to carry a constant (phasor) current I0. Design the antenna configuration by determining the small (non-zero) value of h such that the antenna configuration exhibits a radiation null in the direction θn = (61+a4) 。from the vertical axis. Insert the value of h, correct to 2 decimal places, in the box below.
Note: a4 and a5 are the 3rd and 4th digits of your Warwick University ID number
The value of his __3.09___ m [8 marks]
2024-01-18
Radiowave Propagation and Wireless Communications Theory