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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Cosecant Squared Pattern Antennas
However, what does this term have to do with our antenna? Efficiency The efficiency of the antenna a value between 0 and percent.
The same basic concept soon found many roles. Parameter Description Alpha 1 Angle The angle 1 in the above equation and illustration. The cosecant squared pattern isn’t restricted to parabolic reflectors. Retrieved from ” https: If 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. 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.
According to definition mentioned above the height also shall be constant. The angle m is the upward tilt angle of the beam relative to the horizontal, generally about half a beamwidth.
Cosecant squared antenna – Wikipedia
Vertical projection of the radiation pattern of an antenna with cosecant squared characteristic. Views Read Edit View history. You can specify the following parameters: The angle 2 in the above equation and illustration.
This page was last edited on 30 Decemberat A possibility consists in lower bending of the top of the reflector. The part of the rays which falls to the less bent area in the top is reflected up now.
Antnna with Cosecant Squared Pattern Cosecant squared pattern. Cosecant-squared pattern achieved by displacing the reflector surface from the original parabolic shape.
Open topic with navigation. The angle m in the above equation and illustration.
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. However, when computing the antenna’s gain matrix or a link budget, etc. To get the cosecant squared pattern, a part of the radiated energy must be turned up.
Alpha M Angle The angle m in the above equation and illustration. Azimuth Beamwidth The full width of the beam in the x-y plane of the suqared coordinate system. This gives in near range an additional gain required for constant echo strength after sensitivity time control. If one distributes the transmit power unevenly on the single radiating elements, then the antenna pattern approaches a cosecant squared pattern.
It is equal to the reciprocal value of the sine function.
Cosecant squared antenna
The lobe of the radiator is weaker to the margin to, therefore the margins of the reflector are hit weaker as the centre. Side-lobe Gain dB The side lobe gain of the antenna pattern. The following illustration depicts a typical use case of a cosecant squared antenna pattern applied to a ground-based air search radar. That means, we can shorten the height too without changing the dependence.
The ideal pattern as shown in Figure 1 is a nearly rectangular shape with rounded corners. CRC Presspp. 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. 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 cosecat. Absolute; not relative to the Main-lobe gain.
The result was an evener display pattern. Alpha 2 Angle The angle 2 in the above equation and illustration. By the fact that the rays turned up don’t have a large power density, the maximum range in the higher elevation is limited with that.
Antennae with constant height pattern or cosecant squared pattern are special designed for air-surveillance radar sets. The shape of all these back side lobes is combined into a nearly parabolic slope.
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.
The terrain at further distances returns much less signal due to the radar equation. In reality, cosedant diagram is superposed with a number of side lobes mainly on the back at higher elevation angles. It also illustrates that:. A radiator is in the focal point of a parabolic reflector and produces a relatively sharply bundled radiation lobe since the rays leave the reflector parallelly in the ideal case. The angle 1 in the above equation and illustration.
The opposite modification squsred also be used, bending the upper lip outward, with the same basic outcome.
The targets can be assigned to beams with defined elevation there. These permit an adapted distribution of the radiation in the beam and causing a more ideal space scanning.
This antenna pattern can get the required elevation coverage where the received power is independent of the radar range for a constant height target It is a means of achieving a more uniform signal strength at the input of the receiver as a target moves with a constant height within the squarex.