BioSono provides a cyberspace (www.biosono.com) where researchers, engineers, and students can find useful reference and educational materials, conduct acoustic simulation, post questions on design and development, and get answers. The online KLM based transducer acoustic stack simulation, which is currently free, can help you choose piezoelectric, matching and backing material, and a tuning electrical network. The output from the model includes electrical transmit impedance, acoustic receive impedance, and the impulse or pulse-echo response. The ultrasound beam profile simulation provides the calculated transmitted ultrasound pressure field under certain excitation for a given transducer aperture in a number of different geometrical configurations, including circular elements (flat and concave piston), rectangular elements, linear arrays, convex arrays, and 2D arrays. The simulation is based on Field II, which is a free program that utilizes the spatial impulse response method, and has been validated by many researchers for accuracy. In addition to the web based acoustic simulation, we also provide pulse-echo system, transducers, and customized design and develop services.
Transducer KLM Model Simulation
Beam Profile Simulation
SonoLab Echo I
Time Gain Control
Ultrasound Bipolar Transmitter, Pulser
How it works:
This circuit transmits a bipolar burst and the number of cycles depends on the trigger signal. A single bipolar pulse is usually used in diagnostic applications. The circuit requires two high voltage (HV) supplies with one positive and one negative. The trigger signal has to be well controlled with one positive and one negative, having 180° phase difference. The negative trigger signal turns on MOSFET M1 sending a positive pulse on the load RL through D1. The followed positive trigger signal turns on M2 and sends a negative pulse on RL via D2.
Guideline for the Component Value Selection:
M1: Three parameters for M1 are important.
Vds: how much voltage it can handle. This parameter has to be at least 1.2 times higher than your pulse amplitude. For example, if you want to transmit a 100v peak-to-peak bipolar pulse on the transducer, the Vds for M1 & M2 should be 120 - 150 v.
Cgs, tr, tf: Switch speed. These parameters determine how fast M1 &M2 can turn on/off. Tr, tf, is determined by Cgs, and testing circuit. With a special designed driving circuit, a faster switch speed can be achieved. Normally, tr/tf should be less than a quarter of your center period. If you excite the circuit at 10MHz, the center period is 100ns, and tr+tf should be less than 50ns.
RDS(on): the on resistance. It should be less than five percent of the transducer impedance.
Diode: current rating, make sure it can handle the peak current.
Additional circuits are required to make above transmitter work properly including trigger signal coupling and MOSFET drivers. The complementary dual pulse signal can be generated from an edge signal (a single pulse with uncontrolled width).
With some modifications of the above circuit, only one positive HV is required and cost will be reduced. However, for each transmit, only one cycle bipolar pulse is transmitted and it satisfies most diagnostic applications. Transformer coupling is required to transmit a burst.
The following modules includes combinations of above functions.
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