Some studies on design and simulation of microstrip slot loaded miniaturized patch antenna based smart tracking system using beam steering technique

Abstract

In this Thesis work, a beam steering technique based smart tracking system is investigated to maximize the utilization of the radiated power from a base station towards a mobile user. The tracking operation is performed in the receiving chain that uses a received magnitude-based analysis to determine the user location accurately. The working principle of this technique is investigated numerically by moving a dipole (user) in front of a patch antenna array in the longitudinal and lateral directions, and the relation between the received magnitude levels with relative user location is established. The magnitude comparison is performed in the DC domain instead of RF to simplify this operation by avoiding the RF processing circuits. The RF outputs of each antenna are converted into DC using a rectenna circuit which consists of a single diode having a conversion efficiency of . Since the DC voltages can have an analog variation in their amplitude, an op-amp based comparator circuits is designed to convert these voltages into digital levels. They are further processed using a Boolean Logic Circuit to index the antenna element receiving the maximum RF from the user. As the antenna closest to the user has the minimum Euclidean distance between them, it will receive the maximum RF power from the moving user. Hence, the user location relative to the antenna array can be accurately determined with the above-mentioned antenna index. Once, the user location is determined, the antenna beam is steered at that direction. The steering is performed in the transmitting chain that uses the conventional phased array technique. It simplifies the steering circuit over other reported techniques in the literature, and can provide a good angular accuracy. The antenna index in the receiving chain is used to generate the required phase value to tilt the overall radiation towards user. A simple passive and lossless power divider and phase shifter circuit are designed and investigated with the proposed antenna array. Both the receiving and transmitting chains use a single antenna array for tracking and steering operations, respectively. The array is designed using an asymmetrically placed slot loaded miniaturized patch antenna to operate at . The beam steering operation is also carried out with the proposed antenna array in conjunction with the phase shifter circuit where the beam is steered over an angle of in the azimuthal direction. The transmit and receive chains are connected to the antenna using a circulator that works as a decoupling network and isolates the two sections by maintaining a unidirectional flow of EM power in the transceiver chain. A conventional ferrite loaded circulator as well as ferrite less circulator are designed and investigated here. The ferrite circulator has good impedance matching, with insertion loss of and more than - . isolation. Since, the presence of ferrite makes the circuit non-planar, a ferrite less approach is also investigated to design a planar circulator. Two Branch line couplers and one asymmetric Wilkinson power divider is used to design ferrite less circulator. Though the design is having a reduced isolation, it exhibits higher insertion loss, and provided here as a new design concept.