Toward a modular open scanner: design of the front-end unit

Open scanners are increasingly used in a wide range of applications requiring probes with different elements. Most open scanners are limited to 256 channels, in some cases expandable by using multiple synchronized scanners. Here we discuss an approach based on a small (64-channel) front-end module (FEM) that can be arbitrarily replicated (N-times) to build a large (N×64-channel) open scanner suitable to individually control all elements of 2-D probes. Details of the FEM design are provided, and issues related to the interconnection with the probe and backend are discussed.