title: A digital beamformer for high-frequency annular arrays.
abstract: Digital transmit and receive beamformers for a 45-MHz, 7-element annular array are described. The transmit beamformer produces 0- to 80-Vpp monocycle pulses with a timing error of less than +/-125 ps. Up to four adjustable transmit focal zones can be selected. The dynamic receive beamformer uses a variable frequency sampling technique in which the frequency of analog-to-digital conversion on each channel is adjusted as the signals are received. The variable frequency clock signals required to trigger analog-to-digital conversion are obtained using a pair of high-frequency field-programmable gate arrays and a precision quartz oscillator. The gate arrays are also used to sum the digitized signals. A maximum receive beamformer timing error of less than +/-900 ps was obtained on each channel. The performance of the combined transmit and receive beamformer was tested by imaging wire phantoms. Images of CD-1 mice were also generated. The system produced images with a dynamic range of 60 dB.
authors.affiliation: Department of Physics, Queens University, Kingston, Ontario, Canada. 7jab4@qlink.queensu.ca
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Brown
authors.forename: Geoffrey R
authors.initials: GR
authors.lastname: Lockwood
mesh_terms: D000669:Amplifiers, Electronic; D000818:Animals; D004622:Embryo, Mammalian / Q000000981:diagnostic imaging*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007089:Image Enhancement / Q000295:instrumentation*; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation*; D051379:Mice; D019047:Phantoms, Imaging; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation*