Satellite System and Circular Polarization

Circular polarization is a type of electromagnetic wave polarization that is commonly used in satellite communication systems. In order to achieve circular polarization, a specific type of antenna is required. Out of the given options, the correct antenna for obtaining circular polarization in a satellite system is a helical antenna.

Explanation:

Circular polarization is the combination of two perpendicular waves, one with a clockwise rotation and the other with a counterclockwise rotation. It is an effective way to prevent signal degradation caused by polarization mismatch, especially in satellite communication systems where the orientation of the receiving antenna may vary.

Antenna Types:

1. Parabolic Antenna: A parabolic antenna is a common type of antenna used in satellite systems. However, parabolic antennas are primarily designed for linear polarization. They can be used with a feed horn to generate circular polarization, but this requires additional components and adjustments.

2. Horn Antenna: Horn antennas are widely used in microwave systems due to their broad bandwidth and high gain. However, horn antennas are also primarily designed for linear polarization. Similar to parabolic antennas, circular polarization can be achieved with additional components and adjustments.

3. Log Periodic Antenna: Log periodic antennas are designed to cover a wide range of frequencies with consistent performance. While they can be used for satellite communication, log periodic antennas are not specifically designed for circular polarization.

4. Helical Antenna: A helical antenna is a specially designed antenna that can generate circular polarization. It consists of a conducting wire wound in the shape of a helix. The helical structure and the spacing between the turns determine the polarization. Helical antennas are widely used in satellite communication systems due to their ability to efficiently transmit and receive circularly polarized waves.

Advantages of Helical Antennas:

- Wideband operation: Helical antennas can operate over a wide range of frequencies, making them suitable for satellite systems that require frequency agility.
- Circular polarization: Helical antennas can generate circularly polarized waves, which helps mitigate the effects of polarization mismatch and multipath interference.
- Compact size: Helical antennas can be designed to be compact, making them suitable for applications with size constraints.
- High gain: Helical antennas can achieve high gain, which is important for long-distance satellite communication.

Conclusion:

In a satellite system, circular polarization is typically achieved using a helical antenna. Helical antennas are specifically designed to generate circularly polarized waves and offer advantages such as wideband operation, compact size, and high gain.