Low Noise Binary-Coded Gain Amplifier And Method For Time-Gain Compensation In Medical Ultrasound Imaging

Abstract

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.

1 . A method for controlling the gain of an ultrasonic signal comprising the steps of:
 (a) transmitting an ultrasonic signal into an insonified object   (b) receiving echo ultrasonic signals of said transmitted ultrasonic energy signal from scattering of said transmitted ultrasonic energy signal within said object;   (c) compensating the attenuation of said echo ultrasonic signal from different depths by progressively increasing the gain during the reception of said echo ultrasonic signal.   
     
     
         2 . The method of  claim 1 , wherein (c) further comprises the steps of:
 (a) supplying a received voltage echo signal in a parallel to a plurality of N transconductor cells wherein each of said transconductor cell comprising a differential pair of MOS transistors;   (b) converting said voltage echo signal to a plurality of N binary-weighted current signals;   (c) accommodating each cell of said plurality of N transconductor cells for switching the above step of converting ON and OFF in response to a control signal;   (d) summing said current signals over all cells to form a summed current signal;   (e) converting the summed current signal to a voltage signal;   (f) supplying said control signals to each of the transconductor cells from a look-up-table (LUT).   
     
     
         3 . The method of  claim 2 , wherein the control signals from the LUT is an N-bit-wide binary control word representing a desired gain setting. 
     
     
         4 . The method of  claim 3 , wherein said control word from the LUT controls the ON/OFF switching each of the transconductor cells. 
     
     
         5 . The method of  claim 2 , wherein the step of voltage-to-current converting comprises implementing transconductor cells having their transconductance binary-weighted. 
     
     
         6 . The method of  claim 5 , wherein controlling the cells' transconductance comprises selecting certain aspect ratios for said MOS transistors. 
     
     
         7 - 14 . (canceled)