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SELECTED ARTICLES

Digital Sync-Tip Clamping: A New Approach to Video Signal Conditioning
Digital sync-tip clamping allows an ac-coupled analog-to-digital converter to digitize analog video without restoring the horizontal timing. This technique can be implemented  in a stand-alone clamping ADC or with a complete front-end, including sync detection and AGC.
Ultrasound Tissue Characterization of Breast Biopsy Specimens: Expanded Study
The article describes  tissue classification method and techniques by examining sets of ultrasound parameters including sound speed, attenuation, and backscattering coefficient in the range 3 to 8 MHz.
Unbiased Estimation of Attenuation of Soft Biological Tissue Using the Mean Power Difference between Two Adjacent Envelope Samples
This paper presents a new time-domain method for estimating the slope of ultrasonic attenuation  in reflection.  The statistical analysis of the estimation is based on a multiplicative model of B-scan echoes.  The obtained results are used to define the relationship between the echo frequency downshift and its normalized mean power.
PATENT APPLICATIONS

Apparatus and Method for Class AB Ultrasound LNA Connected to a Transducer via Coaxial Cable
The invention discloses a wide-linear-range LNA comprising a Class AB CMOS transconductor and an I-to-V converter connected in series. The transconductor receives voltage echo signals from a transducer and converters them into RF current. Inherently exhibiting low input impedance, the proposed transconductor circuit provides active termination of a transducer cable. Moreover, the LNA input impedance can be operatively modified for matching cable impedance. A traditional transimpedance amplifier converts the above mentioned RF current signals into the form of voltage.
U.S. PATENTS

8,147,409: Method and Apparatus for Transducer Excitation in Medical Ultrasound Imaging
The invention provides a novel method of transducer excitation in medical ultrasound imaging. Basing on a stepped approximation of Gaussian modulated cosines, the proposed transmit waveform provides bandlimited spectrum and low level of second order harmonics while retaining the duration of the transmitting within two carrier cycles. Since the pulser architecture is suitable for IC implementation, its development will reduce the manufacturing cost of medical ultrasound systems. At the same time, the proposed solution makes the benefits of harmonic imaging available to midrange and entry-level machines
7,948,315: Low Noise Binary-Codded Gain Amplifier and Method for Time-Gain Compensation in Medical Ultrasound Imaging
A low noise variable gain amplifier and method for processing received signals in an ultrasound medical imaging system is disclosed.  Unlike solutions known from the prior art, the signals are amplified by a binary-coded gain amplifier having its amplification factor progressively increased during the penetration of the transmitted pulse into a patient’s body. This allows enhancing both the system dynamic range and Signal to Noise Ratio. 
7,889,787: Ultrasound Transmit Beamformer Integrated Circuit and Method
The invention provides a novel method of transmit  beam- forming , which allows compact analog implementation of complex digital algorithms without compromising their features. It is aimed to support envelope shaping, apodization, and phase rotation per channel and per firing. Each of three embodiments represents a complete transmit channel driven by pulse-width modulated (PWM) waveforms. stored in a conventional sequence memory. PWM signals control the transmit pulse envelope (shape) by changing the duty cycle of the carrier.  Beamformation data are loaded prior to a firing via serial interface. Under direction of a controller, the circuitry allows high precision (beyond sampling rate) phase rotation of the carrier. It is also provides transmit apodization (aperture weighting), which maintains an optimal trade-off among low sidelobe level and widening of the mainlobe. Implementing such an IC, the manufacturing cost of a high-end ultrasound system can be reduced. Equally, the proposed solution makes the benefits of digital transmit beamformers  available to midrange and entry-level machines since it merely requires a modified programming of the sequence memory.
7,513,873: Low-Noise Ultrasound Method and Beamformer System for Doppler Processing
An ultrasonic low-noise analog beamformer for Doppler acquisition achieves high sensitivity by translating the frequency of the ultrasound echoes to an intermediate frequency, which is well above of the 1/f corner. This is accomplished by beamforming the downconverted RF signals instead of using their baseband representation. The baseband conversion, succeeding the beamformation, also incorporates the steps of clutter filtering and anti-aliasing. The invention is particularly suitable for low-voltage process technologies that support broadband applications.
6,808,494:  Transmit Circuit for Imaging with Ultrasound
A DAC with differential outputs is connected to two difference amplifiers through current splitters. The current splitters isolate the compliance voltage of the DAC so that larger loads may be used with the difference amplifiers. This  allows to improve the circuit's SNR. The difference amplifiers provide current signals to a push-pull output amplifier through their supply nodes. A single scaling resistor connects between the conventional outputs of two differential amplifiers to reduce mismatching between the positive and negative waveform paths.
6,621,341: Diagnostic Medical Ultrasound System Having a  Method and Circuitry for Front-End Gain Control
A system and method of processing received signals in an ultrasound imaging system are disclosed. Ultrasound echoes are amplified by means of a gain controlled charge-sensitive preamplifier, and the gain of this amplifier is varied, by adjusting the load capacitance, as a function of time to compensate for the attenuation of ultrasonic energy at different depths within a patient's body.
6,572,546: Two Level Power Supply and Method for Ultrasound Transmission
A two level power supply and method are provided for ultrasound transmission.  A clamping circuit arranged between a high voltage power source and a low voltage power source provides direct current restoration for a two level power supply selector connected with an ultrasound transmit array.  A voltage rail of the transmit array connects with the clamp circuit and receives a low voltage for CW Doppler and a high voltage for B-mode imaging.
A DAC, which outputs positive and negative portions of the desired bi-polar waveform as a representative unipolar waveform, is connected to a switch. The switch selects between current driver paths as a function of the positive or negative polarity of the desired bi-polar waveform. The current drivers feed a push-pull output amplifier to generate the bi-polar ultrasound waveform.
6,432,055: Medical Ultrasonic Imaging System with Three-State Ultrasonic Pulse and Improved Pulse Generator
A three-state, pulse width modulated, bipolar waveform is constructed by summing a first component with an inverted, time-shifted version of the first component. By properly selecting the time interval for the time shift of the second component, frequency filtering benefits can be obtained. The three-state waveform is generated by a switched voltage source that provides a low, constant source impedance for all three voltage states.

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