Patent ID: 8439842

Claim:
A device for controlling the transmission power of an ultrasound signal produced by an ultrasound transducer used to monitor fetal heart rate (FHR), the device comprising: a signal to noise ratio (SNR) calculator that receives a returned signal from an ultrasound transducer, the returned signal having passed through the body of a patient and computes an SNR for the returned signal; a short term analysis (STA) template generator that receives the returned signal and creates an STA template from a short duration portion of the returned signal; a long term analysis (LTA) template generator that receives the returned signal and creates an LTA template for which a number of correlation peaks is maximized by iteratively correlating successive templates over a long duration portion of the returned signal; a template selector that selects between the LTA template and the STA template, and produces a control signal indicative of the selected template; an FHR detector that cross correlates the selected template with the returned signal to determine an instantaneous fetal heart rate; and a transmission power controller that receives the signal indicative of the selected template, selects a predefined optimal SNR range for the selected template, compares the computed SNR for the returned signal to the selected predefined optimal SNR range, and produces a control signal which is sent to the ultrasound transducer to modify the transmission power of the ultrasound transducer thereby modifying the SNR of the returned signal.