sideband, any frequency component of a modulated carrier wave other than the frequency of the carrier wave itself, i.e., any frequency added to the carrier as a result of modulation; sidebands carry the actual information while the carrier contributes none at all. Those frequency components that are higher than the carrier frequency are know as upper sidebands; those lower are called lower sidebands. The upper and lower sidebands contain equivalent information; thus only one needs to be transmitted. Such single-sideband signals are very efficient in their use of the frequency spectrum when compared to standard amplitude modulation (AM) signals. See radio.