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Oscillator metrology with software defined radio.

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Software defined radio (SDR) techniques utilizing digital signal processing (DSP) offer superior time and frequency metrology. These systems outperform traditional devices, achieving femtosecond-level precision in complex measurements.

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Area of Science:

  • Electrical Engineering
  • Metrology
  • Signal Processing

Background:

  • Analog electrical components introduce noise and coupling, limiting precision in time and frequency measurements.
  • Software Defined Radio (SDR) employs digital signal processing (DSP) to replace traditional analog circuitry.
  • Existing metrology devices are often specialized and can be outperformed by versatile digital techniques.

Purpose of the Study:

  • To demonstrate the capability of commercially available multi-channel SDRs for advanced time and frequency metrology.
  • To quantify the performance of SDRs in terms of time deviation noise floors and amplitude measurement instability.
  • To explore the application of SDRs for comparing oscillators across a wide range of frequencies, including optical clocks.

Main Methods:

  • Utilizing commercially available multi-channel Software Defined Radios (SDRs) for signal acquisition and processing.
  • Implementing digital signal processing (DSP) algorithms for time and frequency analysis.
  • Employing a femtosecond-laser frequency comb for ultra-wide frequency comparisons, including optical clock frequencies.

Main Results:

  • SDRs achieved time deviation noise floors of approximately 20 fs at 10 MHz and 1 fs at 6 GHz with short averaging times.
  • A relative amplitude measurement instability of 3 × 10(-7) was observed at 5 MHz.
  • Demonstrated femtosecond-level time comparisons between optical clocks with zero measurement dead-time using SDR and frequency comb technology.

Conclusions:

  • Commercially available SDRs provide a scalable and high-performance platform for time and frequency metrology.
  • SDR-based systems significantly outperform traditional, purpose-built metrology devices.
  • SDRs enable novel applications, such as precise time comparisons of optical clocks with unprecedented accuracy and flexibility.