Binomial array as a multistate phase diversity antenna

If two in-phase plane waves arrive at an antenna from different directions, the resulting signal is not necessarily the coherent sum of the two incoming signals. This is due to the fact that the antenna radiation pattern is actually a complex quantity containing amplitude and phase properties. Thus, it can be stated that antenna phase characteristics may vary as a function of direction. In free space, the antenna phase pattern does not have any role in radio communications in contrast to mobile communications in an urban microcell where the radio channel is very complicated due to multipath propagation. Array antennas offer possibilities to control its phase properties in transmission and reception, which offer a simple technique to improve the combination of received multipath signal components. Binomial arrays are one possibility to implement similar directive beams which, however, have different phase patterns compared to each other. A set of these beams could be used in a discretely optimizing receiver system much in the same way as other diversity techniques are used. A four-element array and results from a microcell radio channel environment simulation are presented as a demonstration of this technique.