  Modern imaging systems typically use single-carrier short pulses for
transducer excitation. Coded signals together with pulse compression are
successfully used in radar and communication to increase the amount of
transmitted energy. Previous research verified significant improvement in SNR
and imaging depth for ultrasound imaging with coded signals. Since pulse
compression needs to be applied at each transducer element, the implementation
of coded excitation (CE) in array imaging is computationally complex. Applying
pulse compression on the beamformer output reduces the computational load but
also degrades both the axial and lateral point spread function (PSF)
compromising image quality. In this work we present an approach for efficient
implementation of pulse compression by integrating it into frequency domain
beamforming. This method leads to significant reduction in the amount of
computations without affecting axial resolution. The lateral resolution is
dictated by the factor of savings in computational load. We verify the
performance of our method on a Verasonics imaging system and compare the
resulting images to time-domain processing. We show that up to 77 fold
reduction in computational complexity can be achieved in a typical imaging
setups. The efficient implementation makes CE a feasible approach in array
imaging paving the way to enhanced SNR as well as improved imaging depth and
frame-rate.
