-4-Circular Polarization Array Antenna

Mohamad Kamal A. Rahim, Mohd Nazri A. Karim, Thelaha Masri, Osman Ayop, Huda Majid, “Circular Polarization Array Antenna”, 2008 Asia Pacific Microwave Conference (APMC 2008), 16 - 20 Dec 2008. Macao, China.

Introduction:

Wireless Local Area Network (WLAN) application nowadays has become more popular. It allows users to access network services without using wired infrastructure. Point to point communication brings a crucial responsibility to antennas since they are expected to provide the wireless transmission between those devices. In high performance point to point application where size, weight, cost, performance, ease of installation are constraints, low profile antenna is very much required. This paper describes the design of microstrip patch array antennas operating at ISM band (2.4 GHz) using circular polarization for point to point communication system.

Antenna polarization is an important consideration when selecting and installing antennas. Most wireless communication systems use either linear (vertical, horizontal) or circular polarization. Knowing the difference between polarization can help maximize system performance for the user.

Polarization also called wave polarization is an expression of the orientation of the lines of electric flux in an electromagnetic field (EM field). Polarization can be constant that is, existing in a particular orientation at all times, or it can rotate with each wave cycle. Polarization is important in wireless communications systems. The physical orientation of a wireless antenna corresponds to the polarization of the radio waves received or transmitted by that antenna. Thus, a vertical antenna receives and emits vertically polarized waves, and a horizontal antenna receives or emits horizontally polarized waves. The best short-range communications is obtained when the transmitting and receiving (source and destination) antennas have the same polarization. The least efficient short-range communications usually takes place when the two antennas are at right angles (for example, one horizontal and one vertical). Over long distances, the atmosphere can cause the polarization of a radio wave to fluctuate, so the distinction between horizontal and vertical becomes less significant.

In a circularly-polarized antenna, the plane of polarization rotates in a corkscrew pattern making one complete revolution during each wavelength. A circularly polarized wave radiates energy in the horizontal, vertical planes as well as every plane in between. If the rotation is clockwise looking in the direction of propagation, the sense is called right- hand-circular (RHC). If the rotation is counterclockwise, the sense is called left-hand circular (LHC).