Satellite antennas radiate signal energy in distinct patterns that are reported as their radiation pattern envelope. These patterns consist of lobes which indicate the intensity of signal radiation radially on a horizontal plane emanating from the antenna. These patterns of signal strength are measured including both horizontal and vertical polarizations at three frequencies which represent the bottom, middle and top of the antenna’s band.
When the radiation signal strength is measured, a main lobe will indicate the main direction of the signal beam. This main lobe indicates the direction the signal will be effectively transmitted. The size of the lobes representing the strength of the signal will decrease as they get further from the main beam. Side lobes appear as small surges in signal radiation adjacent to the main beam. These side lobes can result in unwanted signal noise which can also reduce the antenna’s carrier signal.
The signal capacity of an antenna can be determined by dividing its carrier signal strength by its signal noise. Better antennas produce a better signal by creating minimal side lobes which reduces signal noise and increases the signal capacity. Antennas of lesser quality which have larger side lobes which diminish the antenna’s signal capacity. There are however ways improve an antenna’s signal capacity.
There are two main approaches to increasing an antenna’s signal capacity, increasing the carrier signal strength by increasing the transmission power, or by decreasing the signal noise. Increasing an antenna’s transmission power seems like an obvious solution, but it comes with added energy costs, and might not be applicable due to increased interference, regulatory restraints, and infrastructure limitations. Another way to increase the signal strength is to install a larger antenna, but installing a larger antenna is expensive, requires more maintenance, power, and a larger infrastructure. When increasing signal strength is too costly or not applicable decreasing the signal noise is an option. Simply realigning the antenna creating a different link path can drastically improve an antenna’s signal capacity, this is a low-cost way to decrease signal noise. The best solution would be to purchase an antenna that produces small side lobes. These are higher quality antennas that produce less signal noise resulting in a more optimized signal capacity.
Consulting an antenna’s radiation pattern envelope is important for selecting the right antenna for an application and important in designing and installing a communications system. Antenna manufactures publish radiation pattern envelope information for their products and make them available for review. When selecting, designing, installing, optimizing or troubleshooting an antenna or communications system always consider the antenna’s signal capacity by reviewing its radiation pattern envelope.