General

Earth station antenna is an important part in the Satellite communication earth stations. Following is as the example of Antesky 4.5m earth station antenna.The antenna mainly does the energy transformations between electric energy of alternating electro circuit and electromagnetic wave in the space. According to the required operational frequency, polarization and direction transmit and receive signals, and equivalently amplify the transmitting power and receiving power.

According to the antenna geometry, in the earth station there are axial symmetry and no axial symmetry antenna structures. At present in the actual application there is truss antenna structure, kingpost antenna, turntable antenna mount...etc. According to the function and application it can be classified as full motion antenna, limit motion antenna, vehicle mounted antenna, Marine antenna, portable antenna...etc. Blow takes the Cassegrain antenna as example, introducing the working principle and technical specification for the earth station antenna.

Working Principle

Cassegrain antenna is a dual reflector antenna with the symmetric form of rotary axes and it consists of main reflector, sub-reflector and feed. Main reflector is parabolic of revolution, sub-reflector is hyperboloid of revolution, and feed is horn radiator. One of the focus points in the hyperboloid of revolution locates on the focus point of the parabolic; another point locates on the phase center of the feed. The result that sphere electromagnetic wave from the feed is transmitted by the hyperboloid of revolution is the same as the sphere electromagnetic wave from the focus of parabolic irradiates the parabolic; and then reflect by the parabolic once again to form the electromagnetic wave beam equivalent to the parabolic and proceed along the axial direction of the main reflector. Thus transfer the sphere wave to the plane wave and form the narrow beam, and then radiate to the space. According to the antenna reciprocity principle, the process that the antenna receive the electromagnetic wave is converse to the one that the antenna transmit the electromagnetic wave. Generally the Cassegrain antenna efficiency is 50%-60%, Modified Cassegrain antenna improve the antenna efficiency further, now modified Cassegrain antenna is popular.

Earth station antenna capture the Satellite signal and tracking system track the signal together at the same time, after the receiving signal from the feed is low-noise amplified, and then it will be sent to earth station equipment for demodulation processing. Power splitter sends one way of signal to tracking receiver, tracking receiver receive beacon signal and output a DC voltage which is in proportion to the strength of the RF signal level. According to DC signal from beacon receiver the antenna control unit (ACU) control the azimuth and elevation motorized controller, until the DC signal becomes Maximum so that earth station can receive the Satellite signal steadily.

Specification

Take ANTESKY 4.5m earth station antenna as example, Antesky Science Technology Inc. is specially engaged in designing, manufacturing and installing satellite communication antennas and relevant servo equipments. Ante-sky can offer a complete line of earth station antenna products and systems, such as VSAT antennas, Tx/Rx antennas, TV receive only antennas, satellite news gathering Antennas, Flyaway, antenna control system and tracking system.

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<p><b> For further information, visit the Web site at: www.antesky.com   </b></p>

Please find below 4.5m antenna specification.

ELECTRICAL SPECIFICATION:

Operating Frequency, GHz

C-Band: Rx (3.625-4.2) Tx (5.85-6.425)

Ku-Band: Rx (10.95-12.75) Tx (13.75-14.5)

Antenna Gain (dBi):

C-Band: Rx 43.8 Tx 47.2

Ku-Band: Rx 53 Tx 54.5

VSWR: 1.25

-3dB Beam Width:

C-Band: Rx 1.14° Tx 0.72°        

Ku-Band: Rx 0.37° Tx 0.31°

Power Capability: 5kw/port for C-band Tx    1kw/port for Ku-band Tx

Feed Interface:

C-Band: Rx CPR-229F Tx CPR-137G

Ku-Band: Rx WR-75   Tx WR-75

Isolation, Tx to Rx, dB: 85

Cross Polarization Isolation:35

Polarization: Linear/Circular

Radiation Pattern: CCIR-580-4