A method for subsample fetal heart rate estimation under noisy conditions.

In this paper, we consider a new approach for estimating the fundamental period in fetal ECG waveforms. The fundamental period contains information that is indicative of the physiological condition of the fetus such as hypoxia and acidemia. Our method is based on the minimization of a cost function that measures the differences between the discrete Fourier transform (DFT) of the fetal ECG waveform and the DFTs of its circularly shifted forms. By using the linear phase shift property of the DFT, we show that the minimization of this cost function is equivalent to finding the cosine waveform that matches best to the ECG power spectrum. The optimal cosine waveform is then used to estimate the fundamental period. We expand this method and discuss estimation of the fundamental period with subsample precision. Subsample estimates may be useful especially when a low sampling rate is used for a long period of monitoring. Comparison of performance of this method with Cepstrum and average mIn this paper, we consider a new approach for estimating the fundamental period in fetal ECG waveforms. The fundamental period contains information that is indicative of the physiological condition of the fetus such as hypoxia and acidemia. Our method is based on the minimization of a cost function that measures the differences between the discrete Fourier transform (DFT) of the fetal ECG waveform and the DFTs of its circularly shifted forms. By using the linear phase shift property of the DFT, we show that the minimization of this cost function is equivalent to finding the cosine waveform that matches best to the ECG power spectrum. The optimal cosine waveform is then used to estimate the fundamental period. We expand this method and discuss estimation of the fundamental period with subsample precision. Subsample estimates may be useful especially when a low sampling rate is used for a long period of monitoring. Comparison of performance of this method with Cepstrum and average magnitude difference function methods shows that our approach achieves very accurate period estimation results for both simulated and real fetal EGC waveforms that are taken at different stages of the gestation under noisy conditions.agnitude difference function methods shows that our approach achieves very accurate period estimation results for both simulated and real fetal EGC waveforms that are taken at different stages of the gestation under noisy conditions.

A least square DFT method for sub-sample fetal heart rate estimation under noisy conditions.

In this paper, we consider fundamental period estimation problem for fetal ECG waveforms. By means of a signal separation algorithm, a fetal ECG waveform can be obtained from abdominal ECG of a pregnant woman which contains both maternal and fetal ECG waveforms. We develop a new fundamental period estimator based on minimization of a cost function which measures the least square differences between the discrete Fourier transform (DFT) of the original fetal ECG waveform and the DFT of its circularly shifted form. This cost function attains to its minimum when the circular shift corresponds to integer multiples of the fundamental period. We minimize this cost function to obtain an integer fundamental period estimate. We also minimize this cost function with a gradient descent method to achieve sub-sample precision in fundamental period estimation. With two examples, we demonstrate applications of this method to fetal ECG waveforms and compare its performance to the well-known generalized correlation method.