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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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Radar Basics – Antennae with Cosecant Squared Pattern

However, what does this term have to do with our antenna? Retrieved from ” https: Vertical projection of the radiation pattern of an antenna with cosecant squared characteristic. The angle 2 in the above equation and illustration. Views Read Edit View history. The shape of all these back side lobes is combined into a nearly parabolic slope.

It also illustrates that: Side-lobe Gain dB The side lobe gain of the antenna pattern. For ground-based radars, the same modification could be used to provide scanning at high angles above the station while still sending most of the energy towards low angles to detect aircraft at long range as they rose above the radar horizon.

Every feed horn already emits directionally. The angle m in the above equation and illustration. In the practice a cosecant squared pattern can be achieved by a deformation of a parabolic reflector.

Cosecant squared antenna – Wikipedia

A cosecant squared antennasometimes known as a constant height patternis a modified form of parabolic reflector used in some radar systems. Azimuth Beamwidth The full width of the beam in the x-y plane of the beam coordinate system. Antenna with Cosecant Squared Pattern Cosecant squared pattern.

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Efficiency The efficiency of the antenna a value between 0 and percent. According to definition mentioned above the height also shall be constant.

A possibility consists in lower bending of the top of the reflector. At an antenna array with Yagi- antennae the pattern is achieved by interference of the direct cosecaant with this at the earth’s surface reflected quotas.

Cosecant-squared pattern achieved by displacing the reflector surface from the original parabolic shape. However, when computing the antenna’s gain matrix or a link budget, etc.

Cosecant squared antenna

The name refers to the fact that the amount of energy returned from a target drops off with the square of the cosecant of the angle between the radar and the target. Stacked beam cosecant squared pattern. In reality, the diagram is superposed with a number of side lobes mainly on the back at higher elevation angles. It also illustrates that:. You can specify the following parameters: Design Frequency The frequency of the antenna. A possible method analogously for this one is, to bend the lower part of the reflector more intense.

Parameter Description Alpha 1 Angle The angle 1 in the above equation and illustration.

Alpha M Angle The angle m in the above equation and illustration. The ground directly below the aircraft is at a distance equal to the aircraft’s altitude, which produces the strongest signal. To counteract this, the scanning antenna was re-aimed so that it was pointed almost directly forward, thereby sending most of the radar energy at low angles relative to the aircraft, thereby increasing the energy available at long range.

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Main-lobe Gain dB The main lobe gain of the antenna pattern. 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 concept originated as part of the development of the H2S radarwhich scanned the area under an aircraft to provide a radar map of the ground below.

For an antenna linked to a receiver, transmitter, or radar, the Antenna Design Frequency value gets overridden by the Frequency value set on the Model Specs tab for the transmitter or receiver, and the on the Transmitter Specs tab for the Radar. This page was last edited on 30 Decemberat At use of several receiving channels a height allocation also can be carried out. To get the cosecant squared pattern, a part of the radiated energy must be turned up. The part of the rays which falls to the less bent area in the top is reflected up now.

The ideal pattern as shown in Figure 1 is a nearly rectangular shape with rounded corners. By the fact that the rays turned up don’t have a large power density, the maximum range in the antennz elevation is limited with that.

This gives in near range an additional gain required for constant echo strength after sensitivity time control.