Antenna Theory and Radiation

<p>Self impedance determines the maximum power that can be delivered from the transmitter to the antenna. (A)</p> Signup and view all the answers

<p>Mutual resistance (D)</p> Signup and view all the answers

<p>It states that the mutual impedance between two antennas is the same regardless of which antenna is the source and which is the receiver. (C)</p> Signup and view all the answers

<p>Directive gain is the ratio of the power density in the desired direction to the average power density over all directions. (C)</p> Signup and view all the answers

<p>Self resistance and self reactance are always equal. (B)</p> Signup and view all the answers

<p>Actual impedance is the sum of self impedance and mutual impedance. (C)</p> Signup and view all the answers

<p>Field pattern and Power pattern (B)</p> Signup and view all the answers

<p>The radiation pattern expressed in terms of field strength. (A)</p> Signup and view all the answers

<p>A region of high radiation intensity surrounded by regions of low radiation intensity. (C)</p> Signup and view all the answers

<p>Minor lobe (B)</p> Signup and view all the answers

<p>Main beam (A)</p> Signup and view all the answers

<p>Back lobe (C)</p> Signup and view all the answers

<p>Beam width and directivity are inversely proportional, meaning a larger beam width results in lower directivity. (B)</p> Signup and view all the answers

<p>The angle between the two points on the radiation pattern where the power is 1/2 the maximum power. (A)</p> Signup and view all the answers

<p>30 degrees (C)</p> Signup and view all the answers

<p>57.3 degrees (D)</p> Signup and view all the answers

<p>The shape of the radiation pattern, wavelength, and dimensions of the antenna all affect the beam width. (A)</p> Signup and view all the answers

<p>The antenna's impedance, which is crucial for efficient signal transmission and reception. (D)</p> Signup and view all the answers

<p>Bandwidth (C)</p> Signup and view all the answers

<p>3 dB Bandwidth (B)</p> Signup and view all the answers

<p>To focus the beam on a specific direction and minimize interference. (A)</p> Signup and view all the answers

<p>The polarization must be the same for successful transmission. (B)</p> Signup and view all the answers

<p>Converting the analog signal received to a digital signal for processing. (D)</p> Signup and view all the answers

<p>The distance between the first null in the main lobe and the first null in the side lobes. (C)</p> Signup and view all the answers

<p>The potential generated by an antenna that is delayed due to the finite speed of light. (C)</p> Signup and view all the answers

<p>Circular polarization. (B)</p> Signup and view all the answers

<p>The vector potential at a distant point is calculated by superimposing potentials due to various current elements along a conductor. (C)</p> Signup and view all the answers

<p>Providing amplification and phase adjustments to the signal. (B)</p> Signup and view all the answers

<p>The instantaneous Poynting vector is the cross product of the instantaneous electric and magnetic field intensities. (D)</p> Signup and view all the answers

<p>$S_{av} = \frac{1}{2}Re(\vec{E} \times \vec{H}^*)$ (D)</p> Signup and view all the answers

<p>The ratio of the maximum radiation intensity of the antenna to the average radiation intensity from the antenna itself. (B)</p> Signup and view all the answers

<p>G = K * D, where K is the efficiency factor. (A)</p> Signup and view all the answers

<p>The ratio of the power radiated by the antenna to the power input to the antenna. (D)</p> Signup and view all the answers

<p>The ratio of the maximum radiation intensity of the antenna to the maximum radiation intensity from a reference antenna produced in the same direction with the same input power. (A)</p> Signup and view all the answers

<p>An antenna is designed specifically to radiate or receive electromagnetic waves, while a general conductor may not be. (B)</p> Signup and view all the answers

<p>The antenna is made of imperfect conductors, leading to energy losses like heat. (A)</p> Signup and view all the answers

<p>λ / 2 (A)</p> Signup and view all the answers

<p>Maximum at the center and zero at the ends (A)</p> Signup and view all the answers

<p>A = (μ₀ / 4π) * ∫[I(t - R/c)] * (dl / R) (D)</p> Signup and view all the answers

<p>E = (jωμ₀ / 4π) * ∫[I(t - R/c)] * (dl × R) / R (B)</p> Signup and view all the answers

<p>Speed of light (c) (B)</p> Signup and view all the answers

<p>It accounts for the time delay due to the finite speed of light. (A)</p> Signup and view all the answers

<p>The radiation pattern is directly proportional to the current distribution. (B)</p> Signup and view all the answers

<p>The retarded scalar potential is related to the charge density, while the retarded vector potential is related to the current density. (B)</p> Signup and view all the answers

The total impedance of an antenna, comprising self and mutual impedance.

Graphical representation of an antenna's radiation properties in space.

Radiation expressed in terms of field strength from an antenna.

Radiation expressed in power per unit area; ratio to maximum values.

Regions of different radiation intensity in a radiation pattern.

Lobes in the direction of maximum radiation intensity, also called main lobes.

All lobes except the major lobes in the radiation pattern.

Side lobe is near main lobe; back lobe opposes direction of main lobe.

An antenna is a conductor system that radiates electromagnetic energy into space and matches transmitters or receivers to free space.

Power density describes the power associated with electromagnetic waves, represented by the Poynting vector.

The instantaneous Poynting vector is the product of instantaneous electric and magnetic field intensities, indicating power flow.

Average power density is obtained by integrating the instantaneous Poynting vector over one period and dividing by that period.

Directivity (D) is the ratio of maximum radiation intensity to average radiation intensity of an antenna.

Gain is the ratio of maximum radiation intensity in a specific direction to that from a reference antenna under the same input power.

The efficiency factor (K) relates directivity to gain, generally taken as 1 for ideal antennas.

Radiation density refers to the effective power density of electromagnetic fields, primarily real and associated with radiation.

A measure of how well an antenna focuses energy in a particular direction compared to an isotropic antenna.

The fictitious resistance that, when placed in series with an antenna, equals the power radiated by the antenna.

The impedance at a reference point on an antenna where RF power is connected, consisting of both reactive and resistive components.

The input impedance of an antenna when all other antennas are removed, consisting of self resistance and self reactance.

Power loss due to resistance in the antenna and its components, often manifesting as heat.

Power loss that occurs when energy radiates away from the antenna into space.

A principle stating that mutual impedances between two antennas are equal regardless of which antenna is used as the source.

The angle between points where power is half of its maximum.

The angle width defined by half maximum radiated power points.

Includes shape of radiation pattern, wavelength, and antenna size.

The range of frequencies an antenna effectively operates within.

Angle subtended by an arc equal to the radius in a circle.

Solid angle subtended by a spherical surface area equal to r².

An antenna that operates across a wide frequency range.

The effective current producing a field from an earlier time due to distance.

An antenna with a length of half a wavelength, used in arrays and symmetrical.

The distribution of current in an antenna; maximum at the center and zero at the ends.

A potential due to current elements taking retardation into account.

The shape of the electric field radiated by the dipole antenna.

The total power emitted by a half wave dipole antenna while radiating.

Ratio of radiation intensity in a direction to its average intensity.

The current at a specific moment in time, can be represented as I = Im sin(t).

Beamwidth between the first null in the major lobe and first null in side lobes.

Antenna arrays that can steer beams for optimal signal reception and interference nulling.

Estimation of the direction from which a signal arrives at the antenna.

Direction in which the electric vector of a radio wave is aligned.

An EM wave where the electric vector maintains a consistent orientation.

Occurs when two linearly polarized waves have equal amplitudes with a 90-degree phase difference.

Undesired radiation from an antenna, perpendicular to the desired radiation.

Fields obtained after considering the time delay from the current carrying conductor.