A 2.4 GHz Phase Locked Loop for a Linear Phased Antenna Array

One way of performing indoor localization of objects is by means of Angle of Arrival (AoA). This technology is based on a phased antenna array which estimates the angle of arrival of an incident wave transmitted by a mobile node. This is achieved by measuring the relative phase shifts between the received signals. This paper presents the construction of a Phase Locked Loop (PLL) which synchronizes on the carrier transmitted by the mobile node in order to provide a carrier at exactly the same frequency and a reference phase to the receiving antenna elements. The PLL is designed to operate at 2.4 GHz which holds additional challenges. Since, at this frequency, the most commonly available phase detectors are of the frequency insensitive EXOR type, the PLL will, besides the standard PLL building blocks, such as phase detector, a loop filter and a voltage controlled oscillator, need a sweep circuit. On top of that, sufficient amplification and filtering of the received signal will be mandatory.