Phase continuous signal generation using direct digital synthesis

1. A direct digital synthesis system comprising:

a waveform generator comprising a waveform memory operable to store a plurality of waveform vectors and output a selected waveform vector;

a digital-to-analog converter operable to convert the selected waveform vector from a digital value to an analog signal responsive to a reference clock;

a controller operable to maintain phase continuity of the analog signal when an output of the analog signal is interrupted and restored; and

a signal error detector configured to determine a phase error of the analog signal with respect to a local oscillator driven by the reference clock.

2. The direct digital synthesis system of claim 1 , wherein the controller is operable to determine a closest frequency for encoding a waveform in the waveform vectors based on a storage capacity of the waveform memory, a desired frequency of the waveform, and a clock frequency of the reference clock, wherein the closest frequency is selected to maintain phase continuity between a last waveform vector and a first waveform vector in the waveform memory and scale the desired frequency of the waveform with respect to a number of the waveform vectors and the clock frequency of the reference clock through the local oscillator.

3. The direct digital synthesis system of claim 2 , wherein the signal error detector is operable to mix the analog signal with an output of the local oscillator operating at the closest frequency to determine the phase error of the analog signal and trigger an adjustment to the waveform generator based on comparing the phase error to an error threshold.

4. The direct digital synthesis system of claim 1 , further comprising:

at least one modulo counter operable to count and reset based on a periodicity of a desired waveform, wherein the selected waveform vector is selected from the waveform memory based on a value of the at least one modulo counter, wherein the controller maintains phase continuity of the analog signal by allowing the at least one modulo counter to continue counting while the output of the analog signal is interrupted, and the at least one modulo counter is used to determine an address in the waveform memory and identify the selected waveform vector from the waveform vectors based on the address.

5. The direct digital synthesis system of claim 1 , wherein the analog signal is controlled to perform device testing and/or operation of one or more semiconductor and cryogenic electronic device.

6. The direct digital synthesis system of claim 1 wherein the waveform vectors are populated with one or more complex waveforms that permit parameter extraction from one or more semiconductor and cryogenic devices.

7. The direct digital synthesis system of claim 1 , further comprising:

a second waveform generator comprising a second waveform memory operable to store a second plurality of waveform vectors and output a second selected waveform vector, wherein the second waveform generator is configurable to use a different number of number of vectors for the second plurality of waveform vectors than the waveform vectors of the waveform memory; and

a multi-waveform selector operable to select between providing the selected waveform vector and the second selected waveform vector to the digital-to-analog converter.

8. The direct digital synthesis system of claim 1 , wherein the waveform vectors comprise a combination of amplitude values of two or more waveforms overlaid and include more than one period of a highest frequency waveform of the two or more waveforms.

9. The direct digital synthesis system of claim 1 , further comprising:

a second waveform generator comprising a second waveform memory operable to store a second plurality of waveform vectors and output a second selected waveform vector;

a second digital-to-analog converter operable to convert the second selected waveform vector from a second digital value to a second analog signal; and

a power combiner operable to combine the analog signal and the second analog signal and produce a combined analog output to a device under test.

10. The direct digital synthesis system of claim 1 , wherein the analog signal is output to a device under test configured to operate according to at least one mode in response to a phase of the analog signal.

11. A method for direct digital synthesis, the method comprising:

outputting a selected waveform vector from a waveform generator comprising a waveform memory operable to store a plurality of waveform vectors;

converting the selected waveform vector from a digital value to an analog signal using a digital-to-analog converter responsive to a reference clock;

maintaining phase continuity of the analog signal when an output of the analog signal is interrupted and restored; and

determining a phase error of the analog signal with respect to a local oscillator driven by the reference clock.

12. The method of claim 11 , further comprising:

determining a closest frequency for encoding a waveform in the waveform vectors based on a storage capacity of the waveform memory, a desired frequency of the waveform, and a clock frequency of the reference clock, wherein the closest frequency is selected to maintain phase continuity between a last waveform vector and a first waveform vector in the waveform memory and scale the desired frequency of the waveform with respect to a number of the waveform vectors and the clock frequency of the reference clock through the local oscillator; and

encoding the waveform in the waveform vectors based on the closest frequency.

13. The method of claim 12 , further comprising:

mixing the analog signal with an output of the local oscillator operating at the closest frequency, wherein the phase error of the analog signal is determined based on a result of the mixing; and

triggering an adjustment to the waveform generator based on comparing the phase error to an error threshold.

14. The method of claim 11 , further comprising:

controlling at least one modulo counter to count and reset based on a periodicity of a desired waveform, wherein the selected waveform vector is selected from the waveform memory based on a value of the at least one modulo counter;

allowing the at least one modulo counter to continue counting while the output of the analog signal is interrupted to maintain phase continuity of the analog signal;

determining an address in the waveform memory based on the at least one modulo counter; and

identifying the selected waveform vector from the waveform vectors based on the address.

15. The method of claim 11 , further comprising:

controlling the analog signal to perform device testing and/or operation of one or more semiconductor and cryogenic electronic device.

16. The method of claim 11 , further comprising:

populating the waveform vectors with one or more complex waveforms that permit parameter extraction from one or more semiconductor and cryogenic devices.

17. The method of claim 11 , further comprising:

outputting a second selected waveform vector from a second waveform generator comprising a second waveform memory operable to store a second plurality of waveform vectors, wherein the second waveform generator is configurable to use a different number of number of vectors for the second plurality of waveform vectors than the waveform vectors of the waveform memory; and

selecting between providing the selected waveform vector and the second selected waveform vector to the digital-to-analog converter.

18. The method of claim 11 , further comprising:

populating the waveform vectors with a combination of amplitude values of two or more waveforms overlaid and including more than one period of a highest frequency waveform of the two or more waveforms.

19. The method of claim 11 , further comprising:

outputting a second selected waveform vector from a second waveform generator comprising a second waveform memory operable to store a second plurality of waveform vectors;

converting the second selected waveform vector from a second digital value to a second analog signal using a second digital-to-analog converter; and

combining the analog signal and the second analog signal at a power combiner to produce a combined analog output to a device under test.

20. The method of claim 11 , further comprising:

outputting the analog signal to a device under test configured to operate according to at least one mode in response to a phase of the analog signal.

21. A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by processing circuitry to cause the processing circuitry to perform:

controlling a waveform generator to output a selected waveform vector, the waveform generator comprising a waveform memory operable to store a plurality of waveform vectors;

controlling a digital-to-analog converter to convert the selected waveform vector from a digital value to an analog signal responsive to a reference clock;

maintaining phase continuity of the analog signal when an output of the analog signal is interrupted and restored; and

determining a phase error of the analog signal with respect to a local oscillator driven by the reference clock.

22. The computer program product of claim 21 , wherein the program instructions executable by processing circuitry further cause the processing circuitry to perform:

determining a closest frequency for encoding a waveform in the waveform vectors based on a storage capacity of the waveform memory, a desired frequency of the waveform, and a clock frequency of the reference clock, wherein the closest frequency is selected to maintain phase continuity between a last waveform vector and a first waveform vector in the waveform memory and scale the desired frequency of the waveform with respect to a number of the waveform vectors and the clock frequency of the reference clock through the local oscillator; and

encoding the waveform in the waveform vectors based on the closest frequency.

23. The computer program product of claim 21 , wherein the program instructions executable by processing circuitry further cause the processing circuitry to perform:

controlling at least one modulo counter to count and reset based on a periodicity of a desired waveform, wherein the selected waveform vector is selected from the waveform memory based on a value of the at least one modulo counter.

24. The computer program product of claim 23 , wherein the program instructions executable by processing circuitry further cause the processing circuitry to perform:

controlling the at least one modulo counter to continue counting while the output of the analog signal is interrupted to maintain phase continuity of the analog signal;

determining an address in the waveform memory based on the at least one modulo counter; and

identifying the selected waveform vector from the waveform vectors based on the address.

25. The computer program product of claim 21 , wherein the program instructions executable by processing circuitry further cause the processing circuitry to perform:

selectively combining or switching between two or more waveforms to provide an analog output to a device under test; and

controlling the analog signal to perform device testing and/or operation of one or more semiconductor and cryogenic electronic device, wherein the waveform vectors are populated with one or more complex waveforms that permit parameter extraction from the one or more semiconductor and cryogenic devices.