Introduction
Communication satellites operate within two frequency bands for TV/Broadband service broadcast signals, C Band and Ku Band. The C Band overall frequency spectrum is 4.0 GHz - 8.0 GHz, while the Ku Band overall frequency spectrum is 10.7 GHz - 18.4 GHz.
Within these bands each satellite has a specific uplink and downlink frequency allocation.

For example:
■ Ku Band downlink frequency is 10.7 GHz-12.75 GHz and uplink frequency is 17.3 GHz-17.8 GHz.
■ C Band downlink frequency is 3.7 GHz-4.2 GHz and uplink frequency is 5.925 GHz-6.425 GHz

To use the frequencies that are available for satellite broadcast as efficiently as possible, and to accommodate an additional number of channels within a given frequency band, the transmission signal can be formatted to be either vertical and horizontal, or circular right-hand and circular left-hand simultaneously per frequency.