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Pulse-frequency modulation

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Pulse-Frequency Modulation (PFM) is a modulation method for representing an analog signal using only two levels (1 and 0). It is analogous to pulse-width modulation (PWM), to which the reader may refer for more detailed information, as the magnitude of an analog signal is encoded in the duty cycle of a square wave. Unlike PWM, in which the width of square pulses is varied at constant frequency, PFM is accomplished using fixed-duration pulses and varying the repetition rate thereof. In other words, the frequency of the pulse train is varied in accordance with the instantaneous amplitude of the modulating signal at sampling intervals. The amplitude and width of the pulses is kept constant. The advantage of pulse frequency modulation is better immunity to noise interference than PAM. The disadvantage is more complex transmitter and receiver design.

Potential applications

It has been proposed that PFM could serve as a suitable retinal prosthesis device. PFM's ability to operate independently and asynchronously promotes the flow of nutrients through the chip which is essential for living cells. Cell stimulation would be accomplished through the output of pulse streams by PFM. A large dynamic range is also practical in the replacement of photoreceptors. [1] PFM could be used to transmit intelligence signals, such as audio signals, by demodulating the signal from the receiving end at the transmitting end.[2]

Pulse Frequency Modulation in Google Patents

See also

References

  1. ^ Ohta, J., Yoshida, N., Kagawa, K., & Nunoshita, N. (2002). Proposal of Application of Pulsed Vision Chip for Retinal Prosthesis. Japanese Journal of Applied Physics , 2322-2325.
  2. ^ US 2438950, Smith, Carl Harrison, Jr., "PULSE FREQUENCY MODULATION", issued 6 April 1948 

Lenk, John D. (1999). "Circuit Troubleshooting Handbook" p242. McGraw-Hill, New York

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