Antennas and Microwave Engineering MCQs | Page - 2

 the three patterns required are, θ component of the electric field as the function of the angles as θ and φ, the φ component of the electric field as the function of the angles θ and φ, the phase of these fields as a functions of the angle φ and θ .

 the beam width of an antenna measure at half of the maximum power received by an antenna or the 3 db beam width of the antenna is termed as half null beam width.

 half power beam width of the antenna is obtained by equating the field pattern of the antenna to 0.707 (half power point) and finding θ. 2θ gives the value of beam width. twice the half power beam width gives the first null beam width. with the same steps applied, the half power beam width of the antenna is 450. first null beam width is 900.

 the beam area is the solid angle through which all of the power radiated by the antenna would stream if p (θ, φ) maintained its maximum value over beam area and zero elsewhere. this value is approximately equal to the angles subtended by the half power points of the main lobe in the two principal planes.

 a transmitting antenna is a device that converts a guided electromagnetic wave on a transmission line into a plane wave propagating in free space. it appears as an electrical circuit on one side, provides an interface with a propagating plane wave.

 dipoles, monopoles, oops, yagi-uda arrays are all examples for wire antennas. these antennas have low gains, and are mostly used at lower frequencies.

 array antennas consist of a regular arrangement of antenna elements with a feed network. pattern characteristics such as beam pointing angle and side lobe levels can be controlled by adjusting the amplitude and phase excitation of array elements.

 far field distance for a reflector antenna is given by 2d2/λ. d is the diameter and λ is the operating signal wavelength.

 radiation pattern of an antenna is a plot of the magnitude of the far field strength versus position around the antenna. this plot gives the detail regarding the region where most of the energy of antenna is radiated, side lobes and beam width of an antenna.

 omni directional antennas radiate em waves in all direction. if the radiation pattern for this type of antenna is plotted, the pattern is a constant signifying that the radiated power is constant measured at any point around the antenna.