Adaptive transmit antenna

Adaptive techniques are commonly used to protect receiving antennas from interference. However, adaptive techniques have not been applied to transmitting antennas. An example of adaptively controlling a transmitting antenna is described. This adaptive transmit antenna concept was motivated by requirements for future personal communication systems. These antennas require broad antenna coverage to avoid antenna pointing requirements. This broad-coverage antenna requirement unavoidably results in multipath susceptibility that degrades communication performance. Rake receivers provide adaptive equalization and adaptive antenna element combining are well-known techniques to reduce multipath degradation for receiving systems. However, the performance of the transmit antenna remains degraded by multipath signals. Since the receive and transmit frequencies are separated, the adaptive receive combinations differ from those needed in the transmit case. This new adaptive transmit antenna provides a means to reduce multipath interference in the transmit case. Multipath distortions on transmission reduce the isolation between multiple users in CDMA systems, which is a well-known limit on overall system capacity.