A low power detection method for small ultrasonic echo signals

Spinal cord stimulation is used for the management of chronic, intractable pain and vascular insufficiency. However, when stimulating at a constant voltage, the current density in the spinal cord changes due to the varying separation d between the spinal cord and the stimulating electrode, thus, preventing a stable clinical effect. Ln order to control the stimulation of spinal nerve fibers, a closed-loop system using ultrasonic delay time detection is being developed. This system is based on pulse-echo measurements using a piezoelectric transducer. The spinal cord stimulation system is an implanted system. Therefore, low power consumption (mu W) is an important requirement. A low power electronic circuit is developed to detect the small echo signals (mV) from the spinal cord. The detection method is based on amplitude demodulation of the echo signal. The method is simulated in MATLAB, and the simulation results are compared to the results of a simulated matched filter method. The amplitude demodulation method shows results similar to the matched filter method.