The spontaneous changes in the heartbeat provide valuable information regarding serious cardiac pathologies such as Sudden Cardiac Death. Subtle anomalies in the heart rate can be discovered via an analysis of the Heart Rate Variability (HRV) signal, a sequence of numbers representing the instantaneous heart rate over time. The HRV signal is commonly modeled by an integral pulse frequency modulation (IPFM) scheme. Based on the model, several techniques have been proposed in the literature to capture features of the HRV signal. They however, suffer from severe spurious peaks, especially when the HRV signals contain multiple spectral lines. In this paper, we propose a new method to minimize spurious spectral peaks via the technique of phase interpolation.