4. Direct digital synthesis

The principle of the digital direct synthesizer (DDS) is shown in figure 15 .

The output of the R-bit phase accumulator addresses a ROM (read-only memory) containing an M-bit tabulated representation of the sine function. This ROM converts the phase information produced by the accumulator into a digital value representing the signal amplitude. An S-bit digital-to-analog converter (DAC) then translates this digital value to deliver the analog signal of frequency ν _S = (n/d)ν _E with d = 2 ^R . The signal obtained corresponds to the sampling of the ideal...