Σχεδίαση παρασιτικών στοιχειοκεραίων για χρήση σε συστήματα MIMO
The usage of multiple antennas, both at transmitters and receivers (MIMO), has been identified as an optimal solution to the system design of wireless networks, mostly due to their major benefits and advantages. However, the usage of MIMO techniques in wireless systems can increase the hardware complexity and the energy requirements. In order to achieve maximum system performance in parallel with simplified implementation, we designed MIMO systems using parasitic antenna array ESPAR (Electrically Steerable Parasitic Array Radiator). The ESPAR antenna is a single-feed-port array antenna composed of one active element and multiple parasitic elements terminated by either switched lumped circuits or variable reactors (weights). The ESPAR antenna elements are placed very close to each other because a strong coupling between antenna elements is required. The required radiation pattern can be achieved with appropriate adjustment of the parasitic elements’ weights. ESPAR antennas can be a solution for mobile terminals applications, which require small and low cost antennas. Several antenna types can be proposed using ESPAR antennas: - Parasitic antenna using four identical 3-element ESPAR, using dipoles λ/2. - 5-element ESPAR using monopole antennas - Parasitic antenna consisting of two identical 5-element ESPAR slighted rotated by angle φ. - Parasitic antennas using microstrip patch antennas. After designing and simulating the above antennas, it is concluded that the required radiation pattern can be succeeded with appropriate adjustment of the parasitic elements’ weights.