High resolution indoor source localization via DF/AOA techniques

The location of an indoor transmitter, such as a mobile phone in a building, can be determined by measuring power or the relative timing of the transmitted signal from simultaneous receivers located in the vicinity of the transmitter. A radio location finding system, consisting of at least two direction finders (DF), is placed outside the building for this purpose. The position of the emitter is the intersection point of bearings from each direction finder. A digital signal processing tool, cross correlation, is used to extract the angle of arrival information. The performance of the suggested direction finder has been measured for various environments, such as indoor and outdoor. We conclude that the system performs fairly well in the open air. However, especially at high frequencies, a resolution limit arises due to the finite sampling of the oscilloscope. This problem is solved by down converting the RF (radio frequency) signals into IF (intermediate frequency) by software.