Patent ID: 8142360

Claim:
For implantation into a biological structure having a fluid flow of an average velocity with surfaces traveling with substantially the average velocity in the fluid flow through the biological structure, a system comprising: an oscillator configured to generate a first electrical signal having a first frequency; a transmit transducer electrically coupled to the oscillator to transmit an acoustic beam based upon the first electrical signal, the transmit transducer configured within the system to be positioned to transmit the acoustic beam into the fluid flow when the system is implanted into the biological structure; a receive transducer configured within the system to receive a reflected portion of the acoustic beam reflected off of a portion of the surfaces traveling in the fluid flow and to produce a second electrical signal based upon the portion of the acoustic beam received by the receive transducer; a mixer electrically coupled to the receive transducer to receive a third electrical signal based upon the second electrical signal, the mixer electrically coupled to the oscillator to receive a fourth electrical signal based upon the first electrical signal, the mixer configured to output a fifth electrical signal based upon the third electrical signal and the fourth electrical signal received by the mixer; an RF tank circuit electrically coupled to the mixer to receive triggering events based upon the fifth signal outputted from the mixer, the RF tank circuit generating bursts of RF oscillation based upon the received triggering events, and further including a low pass filter electrically coupled between the mixer and the RF tank circuit, the low pass filter configured to attenuate sum-frequency components from the fifth electrical signal outputted from the mixer, and further including a zero cross detector and an edge detector, the zero cross detector electrically coupled between the low pass filter and the edge detector, the edge detector electrically coupled between the zero cross detector and the RF tank circuit to output edge events to trigger the bursts of RF oscillation from the RF tank circuit; and a transmitter unit including an antenna, the transmitter unit electrically coupled to the RF tank circuit to transmit an electromagnetic signal containing pulses based upon the bursts of RF oscillation generated by the RF tank circuit.