Frequency tuning and/or frequency tracking of a mechanical system with low sensitivity to electrical feedthrough

Abstract

An apparatus and method for frequency tuning/tracking between an electrical subsystem and a mechanical transducer subsystem is presented. An electromechanical transducer generates acoustic pulses as it is driven by a transmit signal from an electrical subsystem. As the transmit signal goes inactive, the settling behavior of the transducer is registered from which the difference in frequency between the resonance of the electromechanical transducer and the transmit signal frequency is determined and utilized for locking the electrical subsystem to the mechanical transducer subsystem by either tuning operating frequency of the electrical subsystem, or the mechanical transducer, to keep them matched (locked).

What is claimed is: 
     
         1 . An apparatus for locking an electrical system to a resonant mechanical system, the apparatus comprising:
 an electromechanical transducer, of a resonant mechanical subsystem, configured for operation in a transmission mode for generating acoustic pulses; and   an electrical subsystem having a transmitter circuit coupled to said electromechanical transducer, in which acoustic pulses are generated from said electromechanical transducer in response to receipt of an electrical signal at an electronic transmission frequency from said electrical subsystem;   wherein said electrical subsystem is configured to determine operating frequency of the resonant mechanical subsystem from a resonance settling response of the electromechanical transducer when not being driven in its transmission mode; and   wherein the electrical subsystem is configured to lock transmitting frequency of said electrical subsystem to that of said resonant mechanical subsystem by either (a) tuning operating frequency of said electrical subsystem to match that of said resonant mechanical subsystem or (b) tuning operating frequency of said resonant mechanical subsystem to match that of said electrical subsystem.   
     
     
         2 . The apparatus as recited in  claim 1 , wherein frequency difference between the electromechanical resonance settling response and electronic transmission frequency is used to determine required adjustment to said transmission frequency to make these two frequencies match. 
     
     
         3 . The apparatus as recited in  claim 1 , wherein said electromechanical transducer comprises at least one ultrasonic transducer. 
     
     
         4 . The apparatus as recited in  claim 1 , wherein said electromechanical transducer comprises at least one piezoelectric transducer. 
     
     
         5 . The apparatus as recited in  claim 1 , wherein said electromechanical transducer comprises at least one capacitive transducer. 
     
     
         6 . The apparatus as recited in  claim 1 , wherein a switching circuit selects between transmission mode or receiving mode for said electromechanical transducer. 
     
     
         7 . A method for locking an electrical system to a mechanical transducer system, comprising:
 generating acoustic pulses from an electromechanical transducer within a mechanical transducer subsystem in response to receiving a transmit signal from a transmitter in an electrical subsystem;   registering settling behavior of said mechanical transducer subsystem, when said transmit signal goes inactive and is thus no longer driving an output from said electromechanical transducer;   determining operating frequency of said mechanical transducer subsystem from the settling behavior of said electromechanical transducer; and   locking the electrical subsystem to the mechanical transducer subsystem by either (a) tuning operating frequency of said electrical subsystem to match that of said mechanical transducer subsystem or (b) tuning operating frequency of said mechanical transducer system to match that of said electrical subsystem.