A measure of the directivity of an antenna is the power per steradian in a direction...
A measure of the directivity of an antenna is the power per steradian in a direction in which this a maximum, divided by 1/(4pi) times the total power radiated. Calculate the directivity for an oscillating electric dipole and the directivity for an oscillating magnetic dipole.
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A measure of the directivity of an antenna is the power per
steradian in a direction...
Question 1 The power radiated by a lossless antenna is 10 watts.
Question 1 The power radiated by a lossless antenna is 10 watts. The directional characteristics of the antenna are represented by the radiation intensity of U = 2cos3θ watts/unit solid angle. Find the (a) Maximum power density at a distance of 1000 m (assume far-field distance) (b) Maximum directivity (c) Maximum gain Question 2 In target-search ground-mapping radars it is desirable to have echo power received from a target, of constant cross section, to be independent ofits range. For one such application, the desirable radiation intensity...
The approximate far zone normalized electric field radiated by a resonant linear dipole antenna used in wireless mobile...
The approximate far zone normalized electric field radiated by a resonant linear dipole antenna used in wireless mobile units, positioned symmetrically at the origin along the z- axis, is given by 0°0 180° 1.5 ejkr EaâgEa sin 0° e 360° where E is a constant and r is the spherical radial distance measured from the origin of the coordinate system. Determine the: (a) Exact maximum directivity (dimensionless and in dB) (b) Half-power beamwidth (in degrees) (c) Approximate maximum directivity (dimensionless...
9. (6 points) An antenna engineer is asked to design a X/2 dipole antenna to operate at 450 MHz. (a) Calculate the leng...
9. (6 points) An antenna engineer is asked to design a X/2 dipole antenna to operate at 450 MHz. (a) Calculate the length of the antenna if it is located in free space. (b) Calculate the magnetic field intensity, H, at a distance of 400km, polar position 0 = 30 degrees and current I = 2A (c) What value of the current I is needed for the total radiated power to equal 100 mW. (d) Determine the length of the...
1) A Hertzian dipole antenna is a short conducting wire carrying an approximately constant current over its length...
1) A Hertzian dipole antenna is a short conducting wire carrying an approximately constant current over its length If such a dipole is placed along the z-axis with its midpoint at the origin, and if the current flowing through it is i(t) ż lo cosot, assume I to be sufficiently small so that the observation point is approximately equidistant to all points on the dipole; that is, assume RR then the corresponding magnetic field is described by: olk2 sin e...
A Hertzian dipole is to be used by an radio amateur at 30 MHz. The FCC...
A Hertzian dipole is to be used by an radio amateur at 30 MHz. The FCC regulations indicate that the radiated field at a distance 2/27 (you can assume this distance is in the far field) and at a direction of maximum intensity must be less than 15 2 uV/m a) What is the average power flow density in a direction of maximum intensity if the electric field is equal to 15 2 uV/m? b) What is maximum time-average radiated...
The FCC typically regulates the maximum effective radiated power from an antenna (ERP or EIRP) be...
The FCC typically regulates the maximum effective radiated power from an antenna (ERP or EIRP) because of the potential for interference to other services. This restricts not just the maximum transmitter power, but also the maximum antenna gain. With microwave and millimeter wave systems, they also sometimes regulate the minimum antenna gain. Why might this be so? (Hint: what is the source of gain in an antenna which has no active elements?)
The FCC typically regulates the maximum effective radiated...
A 75 Ω lossless transmission line is terminated into a load 100 +j150 Ω. For this line, find: i. Reflection coefficient; ii. An antenna receiving a signal of 500 MHz has the following specificati...
A 75 Ω lossless transmission line is terminated into a load 100 +j150 Ω. For this line, find: i. Reflection coefficient; ii. An antenna receiving a signal of 500 MHz has the following specifications: input power Prad 3.25 kw; effective area of antenna Aeff 3.5 m2; total efficiency of antenna,-42%; radiation efficiency of antenna ecd-65%; tilt angle of the received signal ψ = 35°. Determine Voltage standing voltage ratio; b. i. Gain of the antenna (in dB) ii. Maximum radiation...
Calculate the maximum power density 1 km away from a half-wave dipole antenna that is radiating...
Calculate the maximum power density 1 km away from a half-wave dipole antenna that is radiating 100 milliwatts. Repeat the calculation for a dipole antenna that is much shorter than a wavelength. (The gain of a half-wave dipole antenna is 2.15 dBi.)
8. (6 points) A Hertzian dipole antenna in free space has /= 0.02. The following are in far-field: (a) What value of cu...
8. (6 points) A Hertzian dipole antenna in free space has /= 0.02. The following are in far-field: (a) What value of current I is necessary to radiate a total power of 60 mW? (b) What is the ratio of the magnetic field intensity, H, at the polar angles 0 = 10 degrees and 80 degrees (c) What fraction of the total radiated power is contained in the region 0 < 60 degrees (d) What is the radiation resistance, Rrad?...
2. A pulsed airborne radar operating at 12GHz has a peak power of 1 kW and uses an antenna with directivity of 2100. Total monostatic path loss is 1.8. The radar views a surface at normal range of 3...
2. A pulsed airborne radar operating at 12GHz has a peak power of 1 kW and uses an antenna with directivity of 2100. Total monostatic path loss is 1.8. The radar views a surface at normal range of 3 km and grazing angle of t/2. The available received clutter power (Sre) is 1.1x10-11 What is the effective surface scattering area of σ,-2.5x10-4 for the surface? (10pts) a) b) If the radar and target orientation are changed such that the grazing...
The approximate far zone normalized electric field radiated by a resonant linear dipole antenna used in wireless mobile units, positioned symmetrically at the origin along the z- axis, is given by 0°0 180° 1.5 ejkr EaâgEa sin 0° e 360° where E is a constant and r is the spherical radial distance measured from the origin of the coordinate system. Determine the: (a) Exact maximum directivity (dimensionless and in dB) (b) Half-power beamwidth (in degrees) (c) Approximate maximum directivity (dimensionless...
9. (6 points) An antenna engineer is asked to design a X/2 dipole antenna to operate at 450 MHz. (a) Calculate the length of the antenna if it is located in free space. (b) Calculate the magnetic field intensity, H, at a distance of 400km, polar position 0 = 30 degrees and current I = 2A (c) What value of the current I is needed for the total radiated power to equal 100 mW. (d) Determine the length of the...
1) A Hertzian dipole antenna is a short conducting wire carrying an approximately constant current over its length If such a dipole is placed along the z-axis with its midpoint at the origin, and if the current flowing through it is i(t) ż lo cosot, assume I to be sufficiently small so that the observation point is approximately equidistant to all points on the dipole; that is, assume RR then the corresponding magnetic field is described by: olk2 sin e...
A Hertzian dipole is to be used by an radio amateur at 30 MHz. The FCC regulations indicate that the radiated field at a distance 2/27 (you can assume this distance is in the far field) and at a direction of maximum intensity must be less than 15 2 uV/m a) What is the average power flow density in a direction of maximum intensity if the electric field is equal to 15 2 uV/m? b) What is maximum time-average radiated...
The FCC typically regulates the maximum effective radiated power from an antenna (ERP or EIRP) because of the potential for interference to other services. This restricts not just the maximum transmitter power, but also the maximum antenna gain. With microwave and millimeter wave systems, they also sometimes regulate the minimum antenna gain. Why might this be so? (Hint: what is the source of gain in an antenna which has no active elements?)
The FCC typically regulates the maximum effective radiated...
A 75 Ω lossless transmission line is terminated into a load 100 +j150 Ω. For this line, find: i. Reflection coefficient; ii. An antenna receiving a signal of 500 MHz has the following specifications: input power Prad 3.25 kw; effective area of antenna Aeff 3.5 m2; total efficiency of antenna,-42%; radiation efficiency of antenna ecd-65%; tilt angle of the received signal ψ = 35°. Determine Voltage standing voltage ratio; b. i. Gain of the antenna (in dB) ii. Maximum radiation...
8. (6 points) A Hertzian dipole antenna in free space has /= 0.02. The following are in far-field: (a) What value of current I is necessary to radiate a total power of 60 mW? (b) What is the ratio of the magnetic field intensity, H, at the polar angles 0 = 10 degrees and 80 degrees (c) What fraction of the total radiated power is contained in the region 0 < 60 degrees (d) What is the radiation resistance, Rrad?...
2. A pulsed airborne radar operating at 12GHz has a peak power of 1 kW and uses an antenna with directivity of 2100. Total monostatic path loss is 1.8. The radar views a surface at normal range of 3 km and grazing angle of t/2. The available received clutter power (Sre) is 1.1x10-11 What is the effective surface scattering area of σ,-2.5x10-4 for the surface? (10pts) a) b) If the radar and target orientation are changed such that the grazing...
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