1. Field of the Invention
The present invention relates to a waterproof part for a feedhorn, and more particularly, to a waterproof part having double waterproof units for a feedhorn to ensure return loss and useful bandwidth.
2. Description of the Prior Art
A feedhorn, which is also known as low-noise block converter, for a satellite antenna is disposed on a focus of a dish reflector of the satellite antenna. The feedhorn is used for receiving radio signals reflected via the dish reflector from a satellite or transmitting radio signals to the satellite. The satellite antenna is usually installed at an outdoor location such as a roof or an exterior wall of a building to ensure communication quality against signal blocking.
The feedhorn is normally equipped with a waterproof part made of insulation materials to prevent rain water from dripping into the feedhorn. During signal transmission, the satellite signals encounter insertion loss and part of the satellite signals are attenuated when the satellite signals pass through the waterproof part. Another part of the satellite signals transmit through the waterproof part to be reflected by the dish reflector to the air. However, due to dielectric constants and impedance differences between the waterproof part and the air, there is a reflected wave generated at an incident interface of the waterproof part, which is reflected backward to the feedhorn. In such a situation, a radiating efficiency of the feedhorn is decreased, and a useful bandwidth of the feedhorn may become narrower.
In addition, a return loss of the satellite signal or the feedhorn (i.e. a ratio of incident and reflected waves) is relative to the radiating efficiency and the useful bandwidth. Under some conditions, the waterproof part may improve the return loss but narrows the useful bandwidth, and thus the return loss and the useful bandwidth cannot be improved at the same time. Therefore, how to improve both of the return loss and the useful bandwidth of the satellite signals or the feedhorn has become a topic of the industry.