hello and welcome to this presentation understanding single-sideband in this presentation will provide a general technical introduction to single sideband modulation how it's used and the primary variants found in radio frequency communication systems single sideband is a special type of amplitude modulation so we'll start with a quick review of AM AM signals are usually created using a mixer the inputs to which are a nun modulated RF carrier and a low frequency modulating signal the result is a modulated RF carrier whose time domain envelope is a copy of the modulating signal in the frequency domain the information in an AM signal is contained in so-called side bands that appear both above and below the carrier frequency if we use a simple thousand Hertz sine wave signal as a modulation source this modulating signal appears as two tones in spectrum a thousand Hertz above and a thousand Hertz below the carrier our total signal width is twice the modulating frequency human speech on the other hand contains very broad and non-uniform spectral content so if we use human speech as our modulation source our upper and lower side bands will also be broad and non-uniform and the total width of our AM modulated signal will be twice the width of the highest modulating frequency note that the information contained in the upper and lower side bands is identical single sideband is a type of amplitude modulation in which both a carrier and one of the side bands is suppressed recall that both side bands contain the same information so there's no loss of information if we suppress one of the side bands which side bands should we suppress there are actually two different types of single sideband upper sideband which is what we see here suppresses the lower sideband whereas lower sideband suppresses the upper sideband the main application for single sideband is the transmission of voice although data is also sometimes sent using single sideband sideband is also primarily used at HF where spectral efficiency is very important but can sometimes be found in the low VHF range as well single sideband offers several advantages compared to standard or double sideband a.m. as we've already seen sideband is more spectrally efficient that is it uses less bandwidth since we're eliminating approximately half of the signal using single sideband also allows us to put all of our power into one sideband and not waste power transmitting the carrier and the other redundant sideband there's also a reduction in the received noise due to a reduction in the bandwidth of the received signal with regards to which sideband should be used there's no real difference or advantage in using upper versus lower sideband this is usually decided by mutual agreement or by convention for example in amateur radio lower sideband is used for most transmissions below nine megahertz and upper sideband is used above nine megahertz on the transmit side a single sideband transmitter suppresses the carrier and one sideband on the receive side the carrier must be reinserted before the signal can be demodulated this is done using a so called carrier insertion oscillator or beat frequency oscillator in the ideal case the carrier would be reinserted at the precise frequency that was originally used any offset from the original frequency will change the pitch of the received audio if this offset becomes too large speech can become unintelligible there are numerous ways of implementing single sideband this presentation has been describing single sideband suppressed carrier which is by far the most common variant you may also find single sideband full carrier or reduced carrier in both of these cases the carrier is not completely suppressed which makes carrier reinsertion easier at the receive side the disadvantage to these schemes is that some of the transmit power goes into the carrier instead of into the sideband there are also two somewhat specialized variants the first is independent sideband in which there are two side bands but each carries different information one of the early proposals for AM stereo transmission used this variant in the vestigial sideband variant both side bands are present but one of the side bands is reduced or limited this variant was used for older analog television broadcasts let's summarize what we've learned single sideband is a type of amplitude modulation in which the carrier and one of the side bands is suppressed this is done for two main reasons first single sideband uses less spectrum than conventional amplitude modulation and second power that would have gone into the carrier and the redundant sideband can instead be placed into the transmitted sideband on the receive side the carrier must be reinserted to demodulate the signal differences between the frequency of the original carrier and the reinserted carrier can lead to pitch changes in the received audio or even unintelligible if the air is too great this presentation discussed single-sideband suppressed carrier which is the most common form of single sideband but other variants are possible some of these variants preserve either a full or a reduced carrier to facilitate carrier reinsertion special variants such as independent sideband and vestigial sideband were often used in various types of broadcast transmissions but are much less common today this concludes our presentation understanding single sideband thanks for watching