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This paper presents a compact-size, low-cost smart antenna with electronically switchable radiation patterns, and reconfigurable polarizations. This antenna can be dynamically switched to realize three different polarizations including two orthogonal linear polarizations and one diagonally linear polarization. By closely placing several electronically reconfigurable parasitic elements around the driven antenna, the beam switching can be achieved in any of the three polarization states. In this design, a polarization reconfigurable square patch antenna with a simple feeding network is used as the driven element. The parasitic element is composed of a printed dipole with a PIN diode. Using different combinations of PIN diode ON/OFF states, the radiation pattern can be switched toward different directions to cover an angle range of 0 • to 360 • in the azimuth plane. The concept is confirmed by a series of measurements. This smart antenna has the advantages of compact size, low cost, low power consumption, reconfigurable polarizations, and beams.

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In this paper, we consider the application of directional antennas to the hub node of a wireless sensor network (WSN), whilst retaining an omni-directional antenna on each sensor node, thus enhancing link performance without increasing the cost, complexity or energy consumption of the sensor nodes. We propose a simple medium access control (MAC) protocol for the hub node, based on the ALOHA protocol but designed to support multiple antennas on the hub, whilst the sensors retain the original ALOHA protocol. The analysis and simulation results show a 217% increase in throughput. Further possibilities of this architecture include increased range and/or the reduced sensor power consumption.

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