K_u Band - Advantages

Advantages

Compared with C-band, K_u band is not similarly restricted in power to avoid interference with terrestrial microwave systems, and the power of its uplinks and downlinks can be increased. This higher power also translates into smaller receiving dishes and points out a generalization between a satellite's transmission and a dish's size. As the power increases, the dish's size can decrease. This is because the purpose of the dish element of the antenna is to collect the incident waves over an area and focus them all onto the antenna's actual receiving element, mounted in front of the dish (and pointed back towards its face); if the waves are more intense, fewer of them need to be collected to achieve the same intensity at the receiving element.

Also, as frequencies increase, parabolic reflectors become more efficient at focusing them. At 12GHz a 1-meter dish is capable of focusing on one satellite while sufficiently rejecting the signal from another satellite only 2 degrees away. This is important because satellites in FSS (Fixed Satellite Service) service (11.7-12.2GHz in the U.S.) are only 2 degrees apart. At 4GHz (C-band) a 3-meter dish is required to achieve this narrow of a focus beam. Note the inverse linear correlation between dish size and frequency. For Ku satellites in DBS (Direct Broadcast Satellite) service (12.2-12.7GHz in the U.S.) dishes much smaller than 1-meter can be used because those satellites are spaced 9 degrees apart. As power levels on both C and Ku band satellites have increased over the years, dish beam-width has become much more critical than gain.

The K_u band also offers a user more flexibility. A smaller dish size and a K_u band system's freedom from terrestrial operations simplifies finding a suitable dish site. For the end users K_u band is generally cheaper and enables smaller antennas (both because of the higher frequency and a more focused beam). K_u band is also less vulnerable to rain fade than the K_a band frequency spectrum.

The satellite operator's Earth Station antenna does require more accurate position control when operating at K_u band due to its much narrower focus beam compared to C band for a dish of a given size. Position feedback accuracies are higher and the antenna may require a closed loop control system to maintain position under wind loading of the dish surface.