System and method for improving linearity of a DAC

1. A system for improving the linearity of a digital-to-analog converter (DAC), the system comprising:

a digital waveform generator that generates a digital sequence associated with a desired analog waveform;

a pseudo-random noise component that provides a pulse shaped band limited pseudo-random noise sequence that is in a frequency band outside a desired frequency of the analog waveform; and

a combiner configured to combine the digital sequence and the pulse shaped band limited pseudo-random noise sequence and provide the combined sequence to the DAC, the DAC including a differential output and further comprising a 180° hybrid configured to combine the differential outputs of the DAC into a single ended signal, the 180° hybrid partially removing the noise in the analog waveform associated with the pulse shaped band limited pseudo-random noise sequence.

2. The system of claim 1 , further comprising a filter configured to filter noise in the analog waveform associated with the pulse shaped band limited pseudo-random noise sequence and pass the desired frequency of the analog waveform.

3. The system of claim 1 , wherein the analog waveform is a sine wave.

4. The system of claim 3 , wherein the digital waveform generator comprises a phase accumulator and a sine look-up table.

5. The system of claim 1 , wherein the combiner is a summer that continuously adds the digital sequence with the pulse shaped band limited pseudo-random noise sequence.

6. The system of claim 1 , further comprising a filter configured to filter noise in the analog waveform associated with the pulse shaped band limited pseudo-random noise sequence and pass the desired frequency of the analog waveform.

7. The system of claim 1 , wherein the pseudo-random noise component comprises:

a pseudo-random number generator that generates a pseudo-random number sequence to provide a pseudo-random noise sequence; and

a finite impulse response filter configured to filter the pseudo-random noise sequence and pass a pulse shaped band limited pseudo-random noise sequence.

8. The system of claim 1 , wherein the pulse shaped band limited pseudo-random noise sequence is stored in a memory device and read from the memory device and combined with the digital sequence by the combiner.

9. The system of claim 1 wherein the pulse shaped band limited pseudo-random noise sequence is in a frequency band that is one of about DC and about one half (½) of a sampling frequency and the desired frequency of the analog waveform is at another portion of the useful spectrum.

10. A method for improving the linearity of reducing harmonic spurs from a Nyquist digital-to-analog converter (DAC), the method comprising:

generating a digital sequence associated with a desired analog waveform;

providing a pulse shaped band limited pseudo-random noise sequence in a frequency band outside a desired frequency of the analog waveform;

combining the digital sequence and the pulse shaped band limited pseudo-random noise sequence;

providing the combined sequence to the DAC, the DAC including a differential output;

operating the DAC at a Nyquist frequency associated with the desired analog waveform;

combining the differential outputs of the DAC into a single ended signal at a 180° hybrid; and

partially removing the noise in the analog waveform associated with the pulse shaped band limited pseudo-random noise sequence at the 180° hybrid.

11. The method of claim 10 , wherein providing a pulse shaped band limited pseudo-random noise sequence comprises:

generating a pseudo-random number sequence to provide a pseudo-random noise sequence; and

filtering the pseudo-random noise sequence to pass a pulse shaped band limited pseudo-random noise sequence.

12. The method of claim 10 , further comprising filtering noise in the analog waveform associated with the pulse shaped band limited pseudo-random noise sequence to pass the desired frequency of the analog waveform.

13. The method of claim 10 , wherein the pulse shaped band limited pseudo-random noise sequence is in a frequency band that is one of about DC and about one half (½) of a sampling frequency and the desired frequency of the analog waveform is at another portion of the useful spectrum.

14. The method of claim 10 , wherein the combining the digital sequence and the pulse shaped band limited pseudo-random noise sequence comprises continuously adding the digital sequence with the pulse shaped band limited pseudo-random noise sequence.