Multiple level transmitter and method of transmitting

Abstract

Transmitters for generating multilevel transmit waveforms for medical diagnostic ultrasound are provided. Voltages from a plurality of sources are superposed or summed. Switches control the amplitude and polarity of the summed voltages so that a transmit waveform having four or more, such as nine, voltage levels is provided. A simple switching pulser without a power amplifier combines voltages applied to two or more flux paths in a third flux path. Superposition of magnetic flux in the third flux path provides for an output voltage responsive to the sum and difference of two different voltages. Alternatively or additionally, the secondary windings of multiple transformers are connected in series with a transducer element. By providing different input voltages to each of the transformers, the multilevel transmit waveform is generated.

1 - 21 . (canceled)  
   
   
       22 . An ultrasound transmitter for generating multiple level transmit waveforms, the transmitter comprising: 
 a transducer element; and    a transformer having a core with at least first, second and third flux paths, a secondary winding around the third flux path, first and second primary windings around the first and second flux paths, respectively, the secondary winding connected with the transducer element and responsive to transmit voltages from the first and second primary windings.    
   
   
       23 . The transmitter of  claim 22  wherein the transformer is operable to output a secondary voltage at the secondary winding, the secondary voltage a sum of first and second voltages at the first and second primary windings, respectively.  
   
   
       24 . The transmitter of  claim 22  wherein a receive amplifier is connected with the secondary winding.  
   
   
       25 . The transmitter of  claim 22  wherein the transformer further comprises fourth and fifth flux paths.  
   
   
       26 . The transmitter of  claim 22  further comprising: 
 first and second switches connected to opposite ends of the first primary winding; and    a first voltage source connected to the first primary winding.    
   
   
       27 . The transmitter of  claim 26  further comprising: 
 a zero voltage winding around the first flux path; and    third and fourth switches connected with opposite ends of the zero voltage winding, respectively, and ground.    
   
   
       28 . The transmitter of  claim 27  wherein the zero voltage winding is untapped and the third and fourth switches are operable to connect the zero voltage winding to ground when the first and second switches are open.  
   
   
       29 . The transmitter of  claim 26  further comprising: 
 third and fourth switches connected to opposite ends of the second primary winding; and    a second voltage source connected to the second primary winding.    
   
   
       30 . The transmitter of  claim 29  wherein the first voltage source is operable to output a different voltage than the second voltage source.  
   
   
       31 . The transmitter of  claim 29  wherein second primary winding is operable to output a negative voltage and the first primary winding is operable to output a positive voltage.  
   
   
       32 . An ultrasound transmitter for generating multiple level transmit waveforms, the transmitter comprising: 
 an ultrasound transducer element;    first and second transformers having first and second secondary windings, respectively, connected in series, the transducer element connected in series with the first and second secondary windings, the first and second transformers having first and second primary windings, respectively; and    first and second switches connected with the first and second primary windings;    wherein a transmit pulse at the ultrasound transducer element is responsive to the first and second switches.    
   
   
       33 . The transmitter of  claim 32  wherein the transmit pulse comprises an output voltage, the output voltage a sum of voltages on the first and second primary windings.  
   
   
       34 . The transmitter of  claim 32  further comprising: 
 third and fourth switches connectable between the first primary winding and ground;    wherein the first switch is connectable between the first primary winding and ground on a different side of a voltage source tap of the first primary winding than the third switch.    
   
   
       35 . The transmitter of  claim 32  wherein a first turns ratio of the first primary winding to the first secondary winding is different than a second turns ratio of the second primary winding to the second secondary winding.  
   
   
       36 . The transmitter of  claim 35  wherein a same voltage source taps the first primary winding and the second primary winding.  
   
   
       37 . The transmitter of  claim 35  wherein the transmit pulse has at least four levels, the at least four levels responsive to the different winding ratios.  
   
   
       38 . The transmitter of  claim 32  wherein the first secondary winding is operable to output a negative voltage and the second secondary winding is operable to output a positive voltage.  
   
   
       39 . The transmitter of  claim 32  wherein the first transformer has at least three separate flux paths, the first primary winding comprising separate windings around first and second of the three separate flux paths and the first secondary winding around a third of the three separate flux paths.