Radio frequency modulator

摘要

A transmitter architecture ( 200 ) provides for a stable and low noise modulator where the modulation bandwidth is uncorrelated to the TX loop bandwidth. The output signal ( 228 ) of the TX loop is demodulated by a demodulator ( 208 ) and the demodulated signal is compared by a comparator ( 206 ) with the modulating input signal ( 202 ). The output of the comparator is then used to adjust a digital pre-emphasis filter ( 204 ) which preconditions the modulating input signal ( 202 ) in the digital domain. The preconditioning approach of the present invention provides for low noise because the transmitter designer can chose a narrow band for the TX loop which will also filter out the noise coming from the additional synthesizer ( 226 ) used to down convert the input signal.