<P> Another variation, the Weaver modulator, uses only lowpass filters and quadrature mixers, and is a favored method in digital implementations . </P> <P> In Weaver's method, the band of interest is first translated to be centered at zero, conceptually by modulating a complex exponential exp ⁡ (j ω t) (\ displaystyle \ exp (j \ omega t)) with frequency in the middle of the voiceband, but implemented by a quadrature pair of sine and cosine modulators at that frequency (e.g. 2 kHz). This complex signal or pair of real signals is then lowpass filtered to remove the undesired sideband that is not centered at zero . Then, the single - sideband complex signal centered at zero is upconverted to a real signal, by another pair of quadrature mixers, to the desired center frequency . </P> <Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (March 2012) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (March 2012) (Learn how and when to remove this template message) </Td> </Tr>

Why is the use of ssb transmission limited