Non-linear amplifier effects in transmit beamforming arrays

The effects of memoryless (no feedback) amplifiers with amplitude non-linearities on the output of transmit beamforming arrays is studied. These studies are limited to "small signal" cases where the output signal is not undergoing significant compression by the amplifier; and where the amplifier non-linearities can be approximated well by a cubic polynomial. The performance of three "optimal" beamforming techniques are compared and contrasted when both linear and non-linear amplifiers are used in a two dimensional array. The two dimensional array considered is designed to simultaneously transmit two narrowband signals, at different frequencies, through a common aperture. Attention is focused on the non-linearity induced interaction of the stimulus signals, and the effect this has on the array's outputs as a function of the beamforming technique.