Compact printed parasitic arrays for WLAN applications

Antenna arrays enable to achieve high gains and to select the main lobe direction; on the other hand, these arrays require a complicated feeding network. In this letter, we show that whenever a radiating structure with a planar geometry is preferable and only a moderate gain (<6 dB) is required, a microstrip array composed of an active monopole and two parasitic elements is a very simple, yet effective design. The phases of the currents flowing through the active and passive elements determine the main lobe direction and can be adjusted during the design procedure by inserting planar meanders. The active element can be fabricated on the front of a standard FR4 substrate, whereas the ground plane and the parasitic elements are located on the back of the same substrate. We present the design and the experimental characterization of both broadside and endfire arrays working in the wireless local area network (WLAN) band around 2.4 GHz. The design is extremely simple and neat since a balun section is not necessary, therefore the proposed antennas occupy a circuit board area smaller than 0.6 lambda X 0.5 lambda.