Indoor Units (IDU) are part of the ground station for satellite transmission, as well as for terrestrial signal reception and microwave directional radio. They are the components of a ground segment located inside a building.
During satellite transmission, the reception signal from the satellite is mixed down to an intermediate frequency of 950 MHz and 2.150 GHz in the LNB converter, which is located in the outdoor unit ( ODU). This intermediate frequency is transmitted via the antenna cable and is the input signal to the indoor unit (IDU). In a further mix, a VHF signal for the TV is obtained from the IDU input signal via a further intermediate frequency formation and, after demodulation, the useful signal, for example an FBAS signal. The VHF signal can be fed into the TV's antenna input, the FBAS signal into the SCART socket.
Indoor units can support Ethernet switching and routers for IP networks and MPLS networks in addition to the directional radio unit. They are connected to the outdoor units via waveguides or coaxial cables. They are equipped with various user interfaces for different Ethernet variants for SFP modules with single- mode fibers and multimode fibers, thus facilitating access to other transmission systems. .