The simplest form of amplitude modulation is called double sideband-amplitude modulation (DS-AM). The DS-AM transmitted signal is of the form
where 
is the so called carrier frequency and 
is a temporal representation of the message to be communicated. In particular,
for
,
Thus the complete spectrum of the of the message is mapped into two, redundant sidebands symmetrically disposed with respect to the carrier frequency.
The decoding of DSB-AM signals involves the least complexity, but the redundancy of the information carried by the two sidebands implies an inherent inefficiency in terms of both radiated power and frequency space utilization. In most practical AM systems the carrier and/or some part of one sideband is suppressed. Obviously, the Fourier amplitude at the carrier frequency carries no information so that the double sideband, suppressed carrier, amplitude modulation (DSB-SC-AM) format has enhanced power efficiency. In single sideband amplitude modulation (SSB-AM) format, both the carrier and one complete sideband are suppressed. Thus, SSB-AM is the most efficient in terms of radiated power and frequency space utilization, but involves the greatest complexity in receiver design. A compromise is found in vestigial sideband amplitude modulation (VSB-AM) where a major portion of one sideband is suppressed. VSB-AM is used in NTSC broadcast TV standard where 70% of the lower sideband is surpressed. Schematic spectral representations of typical SSB-AM and VSB-AM signals is sketch below.
