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Do you know how a spinning dish antenna can achieve perfect circular polarization?
In the technical world of wireless communications, turntable antennas have received widespread attention for their innovative designs and diverse applications. What is unique about this antenna is its ability to provide excellent signal transmission capabilities in different operating modes, making it a classic that was born in 1935.
The turntable antenna is a type of antenna consisting of two identical dipole antennas overlapping each other at a 90-degree angle. Its design concept is to transmit high-quality signals in wireless communications.
The working modes of the turntable antenna can be divided into "normal mode" and "axial mode". In normal mode, the antenna produces linearly polarized radio waves, while in axial mode, it produces circularly polarized radiation. The flexibility of this design allows the turntable antenna to adapt to different communication needs, such as communication between the ground and satellites.
Operation mode of turntable antenna
Normal mode
In normal mode, the rotating disk antenna can radiate almost omnidirectional linearly polarized waves. Although the radiation pattern in this mode is nearly omnidirectional, it actually takes on the shape of a "four-leaf clover." In this mode, stacking multiple turntable antennas together can further enhance the radiation in the horizontal direction, thus enhancing the signal transmission efficiency. Some radio stations have applied this design to FM and TV broadcasts to improve signal stability and transmission range.
Axis mode
Compared with the normal mode, the turntable antenna in the axial mode emits circularly polarized radio waves. This allows the antenna to ensure stable signal transmission no matter which direction it receives the signal, thereby reducing the risk of signal loss. Therefore, in satellite and missile communications, axial mode turntable antennas have become a common choice.
The properties of circular polarization are crucial to satellite communications because they are relatively insensitive to the orientation of antenna elements, meaning that the received signal is likely to remain stable regardless of the attitude of the satellite antenna in the sky.
Antenna power supply method
In order for the turntable antenna to work properly, it needs to be powered with equal amplitude, but it must be ensured that the phase difference between the two dipole antennas is 90 degrees. This can be achieved through a variety of methods, such as using a bidirectional splitter to split the RF signal into two equal signals, which are then further phase delayed. This specific power supply method is called "phase difference power supply" technology, which allows the antenna to operate effectively.
Applications of turntable antenna
The design and characteristics of rotating disk antennas make them widely used in many fields. On the one hand, stacked array technology provides broadcast stations with high-gain and omnidirectional wireless transmission capabilities. On the other hand, the innovative shape of the "batwing" or super-swivel antenna further enhances the antenna's bandwidth and can meet the transmission needs of different frequencies, especially in the field of television broadcasting.
The future of interstellar communications
As space technology continues to advance, the application of turntable antennas in satellite communications is becoming more and more important. Its circular polarization characteristics can easily cope with unexpected variables in the space environment. Whether it is launching a space probe or maintaining contact with the ground control center, its stability cannot be underestimated.
With the development of science and technology, the demand for wireless communications will become stronger and stronger. How will the turntable antenna continue to exert its unique value in the future wave of science and technology?
