Patent ID: 8184210

Claim:
A digital radio frequency (RF) modulator for modulating a base-band TV signal with a RF channel carrier frequency, said digital RF modulator comprising: an audio modulator configured to receive input audio signals and generate frequency modulated (FM) audio carrier; a video modulator configured to receive a composite video base-band signal (CVBS) and generate a filtered output video signal; and a RF converter connected to said audio modulator and said video modulator, said RF converter comprising: a complex adder configured to add the frequency modulated (FM) audio signals and the filtered output video signal to form a first sampling rate base-band TV signal having a first plurality of spectrum images; a complex frequency shifter configured to receive the first sampling rate base-band TV signal from an output of said complex adder and multiply the first sampling rate base-band TV signal with an exponential carrier having a frequency selected from a range of frequencies so as to frequency shift one of the plurality of spectrum images of the first sampling rate base-band TV signal uni-directionally by the selected frequency of the exponential carrier to a location at the RF channel carrier frequency; and a RF interpolator configured to receive the frequency shifted selected spectrum image of the first sampling rate base-band TV signal from said complex frequency shifter and increase said first sampling rate by a factor of N>1 to a second sampling rate.