Reconfigurable antennas for digital data communication systems

From the Shannon-Hartley theorem, the channel capacity depends on the received S/N (signal to noise ratio) and the data streams in communication system. The S/N and data streams depend on the performance of antenna. In order to improve the channel capacity in digital data communication, reconfigurable antennas play an important role for the communication system. According to the electrical performances, the reconfigurable antennas are divided into pattern reconfigurable antenna, polarization reconfigurable antenna, and impedance (or frequency) reconfigurable antenna. All these reconfigurable antennas are adaptive to the environmental condition to reduce the effects of propagation fading. The pattern reconfigurable antenna is an adaptive pattern with the maximum S/N in receiver. The phased array antenna and the adaptive antenna are example of pattern reconfigurable antennas. The change of polarization during wave propagation is another propagation fading. The change of polarization will also reduce the S/N in receiver. The polarization fading can be improved by the polarization reconfigurable antenna. The polarization reconfigurable antennas includes linear (vertical, horizontal, or slant) polarization and circular (right hand or left hand) polarization which is used to solve this polarization fading problem. Another reconfigurable antenna is changing the impedance of the antenna at the desired frequency. This is impedance or frequency reconfigurable antenna. Various kinds of developed reconfigurable antennas for digital data communications and the measurement of EVM (error vector magnitude) by using these reconfigurable antennas will be discussed in this talk.