Abstract: System are provided for blind echo cancellation in wireless signal processors, such as for wireless repeaters. A first embodiment of the echo cancellation system provides iterative echo cancellation for white signals, with channel identification. A second embodiment of the echo cancellation system provides iterative echo cancellation for band-limited signals, without channel identification, through the determination of a the second order statistics of a signal. The echo cancellation systems are fast, and can be implemented using modern DSP processors for CDMA and broadband wireless communication systems. Analyses and simulations show that the echo cancellation systems can achieve echo cancellation of 40 dB or more at a modest computational cost of several hundred MMACs.

Abstract: Signal delay and combining techniques are used with multipath signals to provide signal diversity gain within CDMA over-the-air repeater and low noise amplifier systems. An incoming signal from a remote user is typically processed through two processing paths, wherein one path adds a delay to the processed signal. The two signal paths are then combined and filtered through a sharp band pass filter, preferably a SAW filter. In an over the air repeater, the filtered signal is retransmitted towards a CDMA rake receiver at a base station, which can process the multipath signal to produce a clean signal representation. In a low noise amplifier, the filtered signal is transferred directly into a base station or repeater. The use of SAW filters protect the latter stages of the low noise amplifier, and also protect the base station from out-of-band signal interference.