Antenna with cosecant squared pattern are special designed for air- surveillance radar sets. These permit an adapted distribution of the radiation in the beam. a fan beam. Figure Vertical projection of the radiation pattern of an antenna with cosecant squared characteristic, the blue graph shows the theoretically form, . This paper deals with the analysis and proper design of parabolic reflector antennas to obtain pencil beam, cosecant-squared and inverse cosecant- squared.

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By the fact that the rays turned up don’t have a large power density, the maximum range in the higher elevation anntenna limited with that. In the practice a cosecant squared pattern can be achieved by a deformation of a parabolic reflector. The ideal pattern as shown in Figure 1 is a nearly rectangular shape with rounded corners. Xntenna the echo has a uniform signal strength at the input of the receiver than the range is dependent on the square of the antenna gain in the fourth power linearly.

Cosecant Squared Pattern Antennas

Side-lobe Gain dB The side lobe gain of the antenna pattern. Open topic with navigation. The angle 1 in the above equation and illustration. Absolute; not relative to the Main-lobe gain. The same basic concept soon found many roles. If one distributes the transmit power unevenly on the single radiating elements, then the antenna pattern approaches a cosecant squared pattern.

The cosecant squared pattern isn’t restricted to parabolic reflectors. The part of the rays which falls coseecant the less bent area in the top is reflected up now.

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From Wikipedia, the free encyclopedia. However, when computing the antenha gain matrix or a link budget, etc. The terrain at further distances returns much less signal due to the radar equation. At use of several receiving channels a height allocation also can be carried out. Cosecant-squared pattern achieved by displacing the reflector surface from the original parabolic shape.

Cosecant squared antenna

The frequency of the antenna. At an antenna array with Yagi- antennae the pattern is achieved by interference of the direct wave with this at the earth’s surface reflected quotas. 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 xosecant relation to the radar.

This gives in near range an additional gain required for constant echo strength after sensitivity time control. Antennae with constant height pattern or cosecant squared pattern are special designed for air-surveillance radar sets. See Raemer, Harold R. Efficiency The efficiency of the antenna a value between 0 and percent. By using this site, you agree to the Terms of Use and Privacy Policy. To counteract this, the scanning antenna was re-aimed so that it was pointed almost directly forward, thereby sending most of the antenma energy at low angles relative to the aircraft, thereby increasing the energy available at long cosecwnt.

The slant range distance between the radar and the terrain is the cosecant of the angle between the fuselage and the target, and the energy falls off with the fourth root of that number.

Azimuth Beamwidth The full width of the beam in the x-y plane of the beam coordinate system. CRC Presspp.

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A cosecant squared antennasometimes known as sqhared constant height patternis a modified form of parabolic reflector used in some radar systems. This can be realized also with other kind of antennae. That means, we can shorten the height too without changing the dependence. However, what does this term have to do with our antenna?

The angle m in the above equation and illustration. The shape of all these back side lobes is combined into a nearly parabolic slope. Alpha M Angle The angle m in the above equation and illustration.

Vertical projection of the radiation pattern of an antenna with cosecant squared characteristic. The opposite modification could also be used, bending the upper lip outward, with the same basic outcome.

Views Read Edit View history. The ground directly below the aircraft is at a distance equal to the aircraft’s altitude, which produces the strongest signal. A possibility consists in lower bending of the top of the reflector.

Design Frequency The frequency of the antenna.

The lobe of the radiator is weaker to the margin to, therefore the margins of the reflector are hit weaker as the centre.

In reality, the diagram is superposed with a number of side lobes mainly on the back at higher elevation angles. It also illustrates that:. Alpha 2 Angle The angle 2 sqjared the above equation and illustration.