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A frequency shift maximum frequency follower Doppler demodulator with amplitude correction.

D H Follett1

  • 1Electronics and Bioengineering Development Unit, Department of Medical Physics, Bristol, England.

Clinical Physics and Physiological Measurement : an Official Journal of the Hospital Physicists' Association, Deutsche Gesellschaft Fur Medizinische Physik and the European Federation of Organisations for Medical Physics
|November 1, 1981
PubMed
Summary

This study introduces a novel, cost-effective Doppler demodulator that is easy to set up and provides amplitude independence. This new design offers potential for quantitative flow measurements, improving upon existing methods.

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Area of Science:

  • Biomedical Engineering
  • Signal Processing

Background:

  • Conventional maximum-frequency follower Doppler demodulators often rely on complex, difficult-to-stabilize voltage-controlled filters and multipliers.
  • These traditional systems present challenges in setup and achieving reliable, quantitative measurements.

Purpose of the Study:

  • To present an alternative Doppler demodulator design that is inexpensive, user-friendly, and offers amplitude independence.
  • To enable quantitative Doppler flow measurements through an improved demodulation technique.

Main Methods:

  • A switching modulator converts the Doppler spectrum into sidebands around a modulating frequency.
  • A voltage-controlled oscillator (VCO) generates the modulating frequency, with its output driven by a low-pass filter.
  • The system utilizes a feedback loop where the modulation frequency is adjusted to track the highest Doppler frequency.

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Main Results:

  • The proposed demodulator demonstrates cost-effectiveness and ease of setup.
  • Achieved amplitude independence over a 25 dB range, facilitating quantitative analysis.
  • The feedback loop design ensures stability and linearity primarily dependent on the VCO characteristics.

Conclusions:

  • The developed Doppler demodulator offers a practical and economical alternative to existing technologies.
  • Its amplitude independence and potential for quantitative results significantly enhance its utility in flow measurement applications.
  • This approach simplifies setup and improves the reliability of Doppler signal processing.