Frequency modulation via a biological signal using a controlled piezoelectric ceramic

When an AC voltage is applied to a controlled piezoelectric ceramic (CPC) changes in its dielectric constant are obtained, that is to say in its capacitance. These new devices are made of barium titanate (BaTiO₃) with a platinum implant. To excite the implant of the CPC with a voltage gives a variation in dielectric constant between the upper and lower walls of the ceramic. Taking advantage of this voltage dependant capacitance characteristic of the CPC a variable frequency oscillator can be constructed. The excitation signal applied to to demonstrate this effect was the heart beat as an electrocardiographic signal, which created a frequency modulated output signal. Demodulating the FM output returned the heartbeat. Clearly, the excitation source applied to the platinum implant is not restricted to the cardiac pulse, the technique can be used in different applications, opening a window of opportunity in the field of biomedical engineering and research.