A circularly polarized microstrip antenna array with Butler matrix

We have implemented a planar microstrip antenna array with a Butler matrix to form a switched beam smart antenna array that ensures real time mobile tracking in dynamic environments. If the transmitting and receiving antennas are both linearly polarized the misalignment between antennas expected to occurs frequently and affects strongly on the performance of the mobile tracking system; in order to improve the system performance, we have generated a circular polarized microstrip array that consists of four identical linearly polarized patches. A 2times2 circular polarized patch array and a 4times4 Butler matrix have been designed using ADS (Advanced Design System) and matlab software. The simulated results show that a combination of a circularly polarized patch array and a Butler matrix creates four narrower beams; each of these beams has a better gain, directivity, and radiated power than a single patch beam.