Office of Technology Transfer – University of Michigan

Frequency Shift Keying Demodulation Methods for Wireless Biomedical Implants

Technology #2525

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Khalil Najafi
Managed By
Joohee Kim
Licensing Specialist, Physical Sciences & Engineering 734-764-8202
Patent Protection
US Patent Pending


Wireless transfer of power and data is often achieved via inductive link between two magnetically-coupled coils. One application which requires transfer of large amounts of data to interface with many conduits include biomedical implants such as for cochlear implants and visual prostheses. For such applications, increased rate of data transfer and minimal power consumption are paramount to successful operation of the device. To date, amplitude shift keying data modulation is commonly used in biomedical implants due to its simple modulation and demodulation circuitry. However, this technology is limited for high-bandwidth data transfer, which is often circumvented at the expense of reduction in transferred power.


Researchers at the University of Michigan have developed frequency shift keying (FSK) demodulation methods for wireless data transfer from biomedical implants. The invention includes an improved demodulator, chip and method for digitally demodulating an FSK signal. For applications such as biomedical implants, where quality factor of the receiver coil is inherently low, FSK may be advantageous. Increase in data-rate to carrier-frequency ratio is achieved as transmitter frequency switches at a small fraction of a cycle, with consistent data transfer rate. In addition, FSK signal is much less susceptible to the coupled coil misalignment and motion artifacts, which are two major problems in biomedical implants that adversely affect the amplitude of the received signal.

Applications and Advantages


  • radiofrequency identification
  • remote sensing
  • MEMS
  • implantable biomedical devices
  • any other wireless application requiring >1 Mbps-nl-data transfer rate through an inductive link


  • less susceptible to coil misalignment and motion-nl-artifacts
  • robust system owing to fully digital data transfer-nl-protocol and demodulator