[Technology Popularization] | Uncovering the mysterious pot covers on the roof that receive "alien" signals
The parabolic dish antenna is an antenna device that uses the parabolic reflection principle to transmit and receive electromagnetic waves. Its working principle is similar to that of a common satellite dish or a large radar antenna. It is usually composed of a metal parabolic reflector, a feed, and a bracket. The parabolic reflector is a parabolic-shaped curved surface and is the core of the dish antenna. When the electromagnetic wave encounters the parabolic reflector, it will be reflected and focused on the feed; the feed is a converter that converts the received electromagnetic waves into signals that we can process and send them to the receiver for further processing. The bracket is responsible for supporting the entire antenna to ensure that it can work stably in various harsh environments.
In addition to the parabolic reflector, feed and bracket, a complete dish antenna may also contain servo equipment - including a servo turntable and servo controller - to ensure that the antenna always maintains the correct pointing, thereby achieving efficient reception and transmission.
The feed source itself determines the operating frequency band and polarization mode of the dish antenna, while the size of the reflector has a more direct impact on the antenna's transmit and receive gain.
The pointing direction of the dish antenna is very important, and its pitch angle and azimuth angle need to be precisely adjusted, which requires the help of the servo equipment, the hero behind the scenes. Generally, the servo turntable is used to control the azimuth and pitch angles.
The servo controller can help the servo turntable determine the angle and can control the working mode of the antenna.
First, we need to understand the basic properties of the parabola. A parabola is a symmetrical surface, and the distance from any point to the focus is equal to the distance from the point to the axis of symmetry. This property means that when a beam of parallel light is irradiated onto the parabola, all the light will be reflected to the focus. When a dish antenna receives radio waves from a certain direction, these waves will be reflected by the parabola and focused to the focus of the antenna. Similarly, when the antenna needs to send radio waves, it will generate a strong electromagnetic field at the focus, which will be reflected and diffused by the parabola to form a narrow beam, thereby improving the directivity and gain of the antenna.
Another important feature of the dish antenna is its directivity. Due to the symmetry of the parabola, the dish antenna is only sensitive to radio waves in a specific direction, and has a strong suppression ability for signals in other directions. This makes the dish antenna very useful in situations where directional communication is required, such as satellite communication, radar detection, etc.
In addition, the performance of the dish antenna can be optimized by adjusting parameters such as its size, shape, and feeding method. For example, increasing the aperture of the antenna can improve its receiving ability, while optimizing the feeding network can improve its radiation performance.
In general, the dish antenna uses the reflection principle of the parabola to achieve the focusing and directional emission of radio waves, thereby improving the performance and application range of the antenna.
Satellite Communications
In satellite communications, dish antennas are widely used for signal transmission between ground stations and satellites. Its large aperture and high gain characteristics enable signals to be transmitted stably and efficiently, providing reliable protection for long-distance communications.
Radar detection——
Dish antennas also play an important role in radar detection. Radar systems use dish antennas to transmit and receive electromagnetic waves to detect and locate target objects. Radar is an indispensable tool in both military and meteorological observations.
Radio astronomy observations
Astronomers use dish antennas to capture weak radio signals from deep in the universe and study distant galaxies, pulsars, quasars and other celestial phenomena. These huge dish antennas, such as radio telescopes, have become important tools for humans to explore the mysteries of the universe.
Wireless Communications
In the field of wireless communications, dish antennas are also widely used in radio broadcasting, television, and mobile communications. They can transmit signals to a longer distance, improving the coverage and quality of communications.
Aviation and marine navigation——
Dish antennas also play an important role in aviation and marine navigation. By receiving navigation signals sent from the ground or satellites, dish antennas help aircraft and ships determine their own positions, ensuring safe and accurate navigation.
At this point we can summarize the advantages of dish antennas:
However, it also has some disadvantages that need to be considered during design and use:
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