Quoted: how does the satellite radio work?
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Well, first, the XM or Sirius frequency division multiplexes (FDM's) the audio channels into one large or many smaller supergroups, the supergroups get sent into one or many Modulators. Immediately prior to modulation, the signal is sent through a trunk encryption devide. Then, the modulators heterodyne the audio frequencies onto an intermediate frequency (IF). That IF is then sent to an Up Converter.
That upconverter mixes that IF with a local oscillator frequency (LO) to produce the final transmit frequency in the S-Band of satellite frequencies (~2.3Ghz). That S-Band frequency is sent to a High Powered Amplifier (HPA) that is sent via waveguide to a large-aperature antenna. That signal is sent 22,369 miles above the Earth's surface to a pair of satellites (XM- Rock and Roll positioned above the west and east coast of the US respectively) or a mini constellation of satellites (Sirius- consists of 3 satellites in a slightly inclined orbit continually covering the continental US). Those satellites then translate and rebroadcast the encrypted data to the continental US receivers.
The signal is then broadcast down to the subscribers. The signals of that satellite get recieved by the antenna of the satellite receivers. That signal travels down the antenna cable to the down converter in the receiver. The downconverter then mixes that signal with an LO to recreate the IF. The IF is then sent to the Demodulator and the data is stripped off of the carrier.
If the chipset is authorized, after the demodulation the audio signal is decrypted. The decrypted signal is sent through a FDM demux that is then sent to the microprocessor in the receiver. The LCD then displays the decrypted channel options for your listening pleasure.
That in a nutshell is how Satellite Radio works.