This paper presents a flat four-beam compact phased array antenna. The low-cost and compact phased array antenna is designed using a circular array of four circular microstrip antennas made of low-cost material and four 1-bit phase shifters. The main beam of the antenna can be switched in four directions with the gain of about 4 dBi in each main-beam direction. More than 90° half-power beamwidth and over 10 dB F/B ratio are obtained. In addition, the diversity performance is considered and the diversity performance of this antenna can be provided with the envelope correlation about 0.6.
