The paper proposes a synchropahsor estimation (SE) algorithm that leverages the use of a delayed in-quadrature complex signal to mitigate the self-interference of the fundamental tone. The estimator, which uses a three-point IpDFT combined with a three-cycle Hanning window, incorporates a new detection mechanism to iteratively estimate and remove the effects caused by interfering tones within the out-of-band interference (OOBI) range. The main feature of the method is its ability to detect interfering tones with an amplitude lower than that adopted by the IEC/IEEE Std. 60255-118, this detection being notably challenging. Furthermore, it simultaneously satisfies all the accuracy requirements for the P and M phasor measurement unit (PMU) performance classes, while offering a reduction in the total computational cost compared to other state-of-the-art techniques.