Introduction

Antenna has a significant role in communication systems, RADAR, biomedical instruments and many other modern applications such as automated cars. Microstrip patch antenna first introduced in 1970s. This type of antenna due to ease of fabrication, low profile and miniaturized size and volume is in demanding state. Microstrip patch antenna can be built in any shape, for instance: rectangular, circular, triangular and square [1]. Phased array antenna is designed to steer beam in a particular direction and suppress ones from undesired directions. A phased array antenna is consist of three main blocks: radiating elements, feeding network and phased shifters. Feeding networks are classified in below categories: constrained feed, space feed and semi constrained feed. Constrained types are employed in parallel or series consist of power dividers. [2] Radiating elements can be fed by microstrip line feed, coaxial feed, aperture coupled feed, and proximity coupled feed. [3] Phase shifters are used to obtain desired shift by employing delay lines. Phase shifters usually have two main types: phase controller phase shifters and switched line phase shifters [4]. In this paper a rectangular 1x4 array patch antenna designed on ADS software at a center frequency of 2.4 GHz. The patch antennas were fed by microstrip line feeds while the feeding network was a parallel constrained network consist of a 1x4 Wilkinson power splitter. Phase shifters were designed based on switched line phase shifter to steer for 40o .