Design and Validation of an Ultra-pure Sine Wave Generator Implemented on a PCB with Low-cost Components and Calibrated to Ultra-high Purity with the DAC-ADC Spectral Co-test Method Presented in this Project
Research Report Highlight
TxACE researchers at Iowa State report on measurements showing a method to generate ultra-pure sine waves from imprecise components. Results show the capability to test an ADC with -120 dB THD.
As data acquisition systems’ performance continues to increase, so does the need for a test and characterization solution to have an input test signal with purity that exceeds what is currently available in state of the art instruments. In this report, we present a new method for generating ultra-pure sine wave signals that can be used in such applications. The pure sine wave is generated by readily available DACs with distortions that could be thousands of times worse than the required system purity. A readily available ADC with similar purity as the DACs is used to measure the distortions in the sine wave generated by the DACs. An innovative algorithm is used to iteratively remove distortions present in the generated sine wave. Simulation results verified the proposed method by generating a -140dB ultra-pure sine wave using two DACs and an ADC with -85dB THD. A PCB board has been designed and measurement results demonstrated that the generated sine wave has sufficiently high purity and that it is capable of accurately testing an ADC with -120dB THD.