Increasing beamsteering directions using polyphase decomposition

In many implementations of digital delay and sum beamforming, a sample rate much higher than the Nyquist rate is used. This allows for many synchronous beamsteering directions. Severe demands are made upon the analogue to digital converters however. Several methods have been proposed for reducing the sample rate required. These methods incorporate the delays that are needed for beamforming in the time domain, or in the frequency domain. A more efficient method for implementing a time-domain delay and sum (interpolation) beamformer using polyphase decomposition is presented. This method results in significant computational savings when the desired angular resolution is high compared to the number of sensors used and the number of simultaneously formed beams