The following coverage maps depict expected maximum information rates while operating a Kymeta u8 terminal mounted horizontally on a vehicle or vessel, on the Kymeta broadband network.

The following coverage maps depict the expected maximum information rates while operating a Kymeta u8 GO at broadside on the Kymeta Broadband network. (Scroll down for an explanation of broadside coverage, if you’re unsure).

To determine the gain of an ESA terminal, we must know its scan angle. The scan angle is one of two angles that define the direction of the satellite beam (known as the boresight vector) relative to the antenna in a spherical coordinate system (see below).

- Theta (θ) is the scan angle. This is the angle between the boresight vector and the broadside vector (the axis that is perpendicular to the plane of the antenna). If the plane of the antenna panel is horizontal, the broadside vector is vertical.
- Phi (φ) is the second angle coordinate that determines the direction of the boresight vector. It is measured in the plane of the antenna from a reference direction, which can be different for various antennas. For the Kymeta u8 antenna, the reference is a line connecting the center with the midpoint of the right side (the y-axis in the above diagram), and phi is measured.

To calculate ‘Signal to Noise Ratio’ (SNR), we need only consider theta, the scan angle.

In fixed applications, the broadside vector is normally pointed at the satellite, so the angle between the broadside and boresight vectors (theta) is zero. In mobility scenarios, however, the antenna is typically mounted horizontally, so that the broadside vector is always vertical, but since the boresight vector must always point at the satellite, theta is positive (unless the satellite is directly overhead).

Since less antenna area (aperture) is available to the beam in the case of a positive scan angle, the effective gain of the antenna is reduced. The reduction in gain with increasing theta is called the cosine (or scan) roll-off.

Copy courtesy of Kymeta’s ‘Link Budget Calculations‘ PDF.