Target Area Extension in Synthetic Aperture Array Signal Processing for High-Frame-Rate Estimate of Two-Dimensional Motion Vector In vivo

摘要

A strategic synthetic aperture radar (SAR) along a flight path has been developed including a potential extensibility in a wide-range target area and an excellent spatial resolution by utilizing two-way range stacking, matched filtering, and chirp signal transmission. For the simultaneous ultrahigh-frame-rate ultrasonic imaging of microdynamics in a living tissue, a one-way synthetic aperture array processing of a real-time-received two-dimensional (2D) echo signal followed by a successive transmission is indispensable, in which the range stacking in SAR should be modified toward the pulsed ultrasonic irradiation generated by the array transducer. Therefore, the modification of the range stacking was proposed for pulsed radiation from a flexible point ultrasonic source. Firstly, a one-way receiving range stacking algorithm was described in a spatiotemporal frequency domain, and it was consequently extended to account for the forward-range- and cross-range-dependent time delay of the 2D echo signal in each range bin for the reconstruction of the target area. The overall system performance for the linear array transducer having 256 elements with a 3.0 MHz center frequency and a 0.25 mm pitch was verified for the reconstructed images in a numerical simulation and a hardware experiment.