From Satellite Communications, Fourth Edition

14.9 Satellite-Switched TDMA

More efficient utilization of satellites in the geostationary orbit can be achieved through the use of antenna spot beams. The use of spot beams is also referred to as space-division multiplexing. Further improvements can be realized by switching the antenna interconnections in synchronism with the TDMA frame rate, this being known as satellite-switched TDMA (SS/TDMA).

Figure 14.27a shows in simplified form the SS/TDMA concept (Scarcella and Abbott, 1983). Three antenna beams are used, each beam serving two earth stations. A 3 3 satellite switch matrix is shown. This is the key component that permits the antenna interconnections to be made on a switched basis. A switch mode is a connectivity arrangement. With three beams, six modes would be required for full interconnectivity, as shown in Fig. 14.27b, and in general with N beams, N! modes are required for full interconnectivity. Full interconnectivity means that the signals carried in each beam are transferred to each of the other beams at some time in the switching sequence. This includes the loopback connection, where signals are returned along the same beam, enabling intercommunications between stations within a beam. Of course, the uplink and downlink microwave frequencies are different.

Figure 14.27: ( a) Satellite switching of three spot beams; ( b) connectivities or modes.

Because of beam isolation, one frequency can be used for all uplinks, and a different frequency for all downlinks (e.g., 14 and 12 GHz in the Ku band).

Products & Services
Lasers are devices that produce intense beams of monochromatic, coherent radiation. The word "laser" is an acronym for Light Amplification by Stimulated Emission of Radiation.
Chilled Beams
Chilled Beams are a type of convection HVAC system that are used to heat or cool rooms. Pipes of hot or cold water are passed through the beam. As the beam heats or cools it radiates the warmth or coolness to the surrounding air.
Beam Steerers
Beam steerers are optical tools that allow the user to easily change a laser beam's optical axis height or direction.
Telephones and Cellular Phones
Telephones and cellular phones convert voice or other sound signals into a form that can be transmitted to another device that receives and reconverts the waves back into sound.
Plate Beamsplitters
Plate beamsplitters are semi-mirrors, which reflect part of the incident energy (absorb a relatively small part) and transmit the rest. Some are neutral and some are spectrally selective.

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