A High-Precision Counter Using the DSP Technique

Abstract : A high-precision counter using a digital signal processor (DSP) is designed for phase and frequency measurement. We use an analog-to-digital converter (ADC) to sample the device under test (DUT). Once the signal is digitized, the DSP will be used to run the phase correlation and obtain the necessary information. In our design, the counter is implemented on the Texas Instrument (TI) TMS329C6201 digital signal processor. The sample data from the ADC are input to the DSP. Additionally, the 5 MHz frequency from the Telecommunication Laboratories (TL) standard is used as the reference of the synthesized signal generator. Then the synthesized signal generator produces the specific frequency in the ADC to serve as the reference clock. The ADC will then sample the signal of the DUT. The frequency difference between the signal and the specific frequency of the synthesized signal generator is approximately 1 Hz and the floating part of the frequency produced by the DUT. In the DSP, the phase correlation is created for finding the floating part of the frequency. The 1-second sampling data are correlated with the next second s. The result of the correlation operation can produce the phase shift in a 1- second interval. Finally, we can determine the frequency difference between the DUT and the reference clock of the ADC. The resolution of the frequency accuracy can be 5 10-12.