What is the main drawback with Cassegrain feed antenna?
A disadvantage of the Cassegrain is that the feed horn(s) must have a narrower beamwidth (higher gain) to focus its radiation on the smaller secondary reflector, instead of the wider primary reflector as in front-fed dishes.
What is the radiation pattern of parabolic antenna?
The radiation pattern of a parabolic antenna contains a major lobe, which is directed along the axis of propagation, and several small minor lobes. Very narrow beams are possible with this type of reflector.
What is F D ratio in antenna?
The ratio of focal length to aperture size (ie., f/D) known as “f over D ratio” is an important parameter of parabolic reflector. Its value varies from 0.25 to 0.50. The law of reflection states that the angle of incidence and the angle of reflection are equal.
What are the advantages of Cassegrain feed in parabolic antenna?
The Cassegrain feed system, although requiring a second reflecting surface has the advantage that the overall length of the dish antenna between the two reflectors is shorter than the length between the radiating element and the parabolic reflector.
What is meant by Cassegrain?
: a reflecting telescope that has a paraboloidal primary mirror and hyperboloidal secondary mirror, is equivalent in its optical effects to a telephoto lens, and usually has the light brought to a focus through a perforation in the center of the primary mirror.
Which of the following combination forms a Cassegrain antenna?
Which of the following combination forms a Cassegrain antenna? Explanation: A Cassegrain antenna is a dual reflector antenna and is axis symmetry. It consists of two reflectors and one primary feed. The main reflector is parabolic and sub-reflector is hyperbolic (convex).
What is the Cosecant squared pattern?
A cosecant squared antenna, sometimes known as a constant height pattern, is a modified form of parabolic reflector used in some radar systems. It is shaped to send more radio energy in certain directions in order to smooth out the reception pattern of objects as their range changes in relation to the radar.
Who invented Cassegrain?
Laurent CassegrainCassegrain reflector / Inventor
What type of image is formed by Cassegrain telescope?
“Classic” Cassegrain telescopes The “classic” Cassegrain has a parabolic primary mirror and a hyperbolic secondary mirror that reflects the light back down through a hole in the primary.
Which of the following regarding the Cassegrain feed system is false?
8. Which of the following regarding the Cassegrain feed system is false? Explanation: Spill over is the power loss when the reflector fails to redirect the energy.
What is feed offset in antenna?
An offset dish antenna or off-axis dish antenna is a type of parabolic antenna. It is so called because the antenna feed is offset to the side of the reflector, in contrast to the common “front-feed” parabolic antenna where the feed antenna is suspended in front of the dish, on its axis.
What is cosecant beam?
What is unique about a Cassegrain telescope?
The Cassegrain telescope has a curved focal surface which is located behind the primary mirror. Due to the onset of coma and astigmatism, the telescope has a modest useful field-of-view.
What is the magnification of Cassegrain telescope?
Common sense seems to indicate that, for the 12.5″ F/12.5 Cass, with an F/4.2 primary and a secondary magnification of 12.5/4.2 = 3, moving the secondary 0.01″ toward the primary should move the focal plane back 0.01″ * 3 = 0.03″.
Which of the following are the antenna pattern used in satellite communication?
The reflector antenna is most frequently used in communications satellites because of its simple structure, light weight, and high gain (Fig. 16). It has one or more reflective surfaces, which are paraboloid, hyperboloid, spheroid, etc.
What is feeding techniques in antenna?
There are four types of the feeding techniques and they are coaxial probe, microstrip line, aperture coupled and proximity coupled.