The paper introduces a novel technique for the bearing estimation of radio sources that can be used for the precise localization and/or tracking of RF tags such as wireless sensor nodes. It is well known that the bearing to a radio source can be estimated by an array of antennas typically arranged in a circular manner. The method is often referred to as Quasi-Doppler measurement. The disadvantage of the existing method is that the receiver is relatively large because of the multiple antennas (typically 8 or 16) and it is computationally intensive to process the high frequency radio signals. Thus, it cannot be done on small, inexpensive radio tags. Instead, we propose to use the array on the transmitter side utilizing as few as three antennas. We use a radio interferometric technique to transform the useful phase information from the high frequency radio signal to a low frequency signal (< 1 kHz) that can be processed on low-cost hardware. Utilizing three anchors nodes with small antenna arrays, any number of low cost wireless nodes with single antennas can be accurately localized.