The fundamental requirement of all phased array instruments is the ability to configure a defined group of elements with the programmed pulser and reception delays commonly referred to as a focal law. The instrument forms images by sequencing focal laws with different pulser and receiver delays across the same aperture, or multiplexing the same law across stepped apertures.
During pulsing, a trigger is sent to a bank of pulsers with the delay sequence required to achieve the desired beam. At reception, the signals are digitized and delayed according to a focal law and summed to form a single RF response. This waveform is then amplified, filtered as required, digitized, processed and stored. As one sequence of focal laws is being completed, the image is simultaneously displayed along with an associated A-Scan and measurements. In linear scanning, groups of elements are stepped through a multiplexer to reduce cost and electronic complexity. A conceptual overview is shown below in a reduced configuration consisting of four pulser/receivers exciting an 8 element probe. Note that for sectorial scans the maximum number of elements that can be used is four.
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Specifications Conventional Instruments>>