Increasing the frequency resolution of NCO-systems using a circuit based on a digital adder

A digital low cost solution for increasing the frequency resolution of Direct Digital Synthesizers (DDS) containing Numerically Controlled Oscillators (NCO's) is presented. The additional hardware can be used for all off-the-shelf NCO's offering a carry input of the internal phase-accumulator. Its simplicity makes it suitable for many applications, especially where cost-efficient solutions are required. An example of an actual implementation of a signal-generator using this technique is presented and described.