Putting Information on Electromagnetic Waves

What alternative analog methods are used?

The “G” stands for generation. Early cell phones that could only make analog voice phone calls are called first generation devices, or 1G. Networks that use digital methods that allow many more simultaneous users are called second generation, or 2G systems. The increased capacity of 2G systems allows emails and short text messages to be exchanged between cell phones. In the year 2000 standards were released for 3G networks stating that these devices should be able to download television-like video and exchange video images. By 2009 “smart” phones were in common use. They include many of the features of computers, GPS location detection, video cameras, and telephones. The highspeed transfer of data to and from the phone offered by a 3G network is important for proper operation of the smart phones. Standards for 4G networks include transmission rates of 100 M bits/s, in comparison to 14 M bits/s for 3G networks. The technology, which requires new base stations, antennas, and phones, is still evolving.

As was described above, modulating a carrier wave produces additional frequencies above and below the frequency of the carrier. These frequencies are called sidebands. There is identical information in the two sidebands, so many radio services filter out one of the two sidebands, resulting in a single-sideband broadcast, or SSB. SSB can work with either AM or FM radios. It has half the bandwidth of a double-sideband broadcast, so more radios can use the same part of the spectrum.


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