Pixel receiver with low frequency noise reduction for ultrasonic imaging apparatus

Abstract

Apparatus and method for generating a DC pixel voltage are disclosed. The apparatus includes an amplifier configured to amplify an input signal to generate a voltage signal, wherein the input signal is generated in response to an ultrasonic wave reflecting off an item-to-be-imaged and propagating via a piezoelectric layer; a noise reduction circuit configured to pass the voltage signal from an output of the amplifier to a node, while reducing a propagation of noise from the output of the amplifier to the node; and a circuit configured to generate a DC pixel voltage based on the reduced-noise voltage signal.

What is claimed is: 
     
         1 . A method, comprising:
 amplifying an input signal to generate a voltage signal, wherein the input signal is generated in response to an ultrasonic wave reflecting off an item-to-be-imaged and propagating via a piezoelectric layer;   reducing noise from the voltage signal; and   generating a DC pixel voltage based on the reduced-noise voltage signal.   
     
     
         2 . The method of  claim 1 , wherein reducing the noise from the voltage signal comprises passing the voltage signal through a capacitor. 
     
     
         3 . The method of  claim 1 , wherein the noise comprises low frequency noise generated by one or more devices involved in the amplification of the input signal. 
     
     
         4 . The method of  claim 1 , wherein the input signal comprises an input current signal, and wherein amplifying the input signal comprises performing transimpedance amplification of the input current signal to generate the voltage signal. 
     
     
         5 . The method of  claim 4 , wherein a gain associated with the transimpedance amplification is based on a sense capacitance of the piezoelectric layer. 
     
     
         6 . The method of  claim 4 , wherein a gain associated with the transimpedance amplification is based on a ratio of a capacitance of a feedback capacitor associated with the transimpedance amplification over a sense capacitance of the piezoelectric layer. 
     
     
         7 . The method of  claim 1 , wherein amplifying the input signal comprises amplifying the input signal using a source-follower amplifier. 
     
     
         8 . The method of  claim 1 , wherein generating the DC pixel voltage comprises detecting one or more peaks of the voltage signal to generate the DC pixel voltage. 
     
     
         9 . The method of  claim 1 , wherein generating the DC pixel voltage comprises sampling and holding a portion of the voltage signal to generate the DC pixel voltage. 
     
     
         10 . The method of  claim 1 , further comprising selectively outputting the DC pixel voltage. 
     
     
         11 . An apparatus, comprising:
 means for amplifying an input signal to generate a voltage signal, wherein the input signal is generated in response to an ultrasonic wave reflecting off an item-to-be-imaged and propagating via a piezoelectric layer;   means for reducing noise from the voltage signal; and   means for generating a DC pixel voltage based on the reduced-noise voltage signal.   
     
     
         12 . The apparatus of  claim 11 , wherein the means for reducing the noise from the voltage signal comprises means for passing the voltage signal through a capacitor. 
     
     
         13 . The apparatus of  claim 11 , wherein the noise comprises low frequency noise generated by the means for amplifying. 
     
     
         14 . The apparatus of  claim 11 , wherein the input signal comprises an input current signal, and wherein the means for amplifying the input signal comprises means for performing transimpedance amplification of the input current signal to generate the voltage signal. 
     
     
         15 . The apparatus of  claim 14 , wherein a gain associated with the transimpedance amplification is based on a sense capacitance of the piezoelectric layer. 
     
     
         16 . The apparatus of  claim 14 , wherein a gain associated with the transimpedance amplification is based on a ratio of a capacitance of a feedback capacitor coupled between an output and an input of the means for amplifying over a sense capacitance of the piezoelectric layer. 
     
     
         17 . The apparatus of  claim 11 , wherein the means for amplifying the input signal comprises a source-follower amplifier. 
     
     
         18 . The apparatus of  claim 11 , wherein the means for generating the DC pixel voltage comprises means for detecting one or more peaks of the voltage signal to generate the DC pixel voltage. 
     
     
         19 . The apparatus of  claim 11 , wherein the means for generating the DC pixel voltage comprises means for sampling and holding a portion of the voltage signal to generate the DC pixel voltage. 
     
     
         20 . The apparatus of  claim 11 , further comprising means for selectively outputting the DC pixel voltage.