Once you have gone through the
introduction,
try the exercises below to investigate K-Space:
Launch the Field_II_GUI in matlab. Set the number of elements to 1 (keeping
all of the other default parameters). Calculate the TX/RX Pressure
Field, and generate its plot. Notice that the sound field is
approaching a plane wave. Can you visualize what the K-Space representation
of this field will be? Return to the Calculate menu and calculate/plot
the K-Space TX/RX Field for this configuration. Is this what you
expected to see?
While the rules of thumb you have learned for K-Space computation in class
can be applied to pulsed wave systems, they are derived assuming continuous
wave (CW) excitation of the transducer. Modify the excitation pulse
to be a sine wave using the same center frequency as the elements (7.5
MHz), but with many cycles (i.e. 40) - in order to approximate CW excitation.
Using only a single element, calculate the TX/RX Field and the K-Space
representation. What differences do you notice from above?
Now we'll add a second element. Set the kerf (spacing between the
elements) to 20 mm, and change the number of elements to 2. Repeat
the above calculations/plots for this system, and note the differences.
Repeat the above for 3 elements.
Were you able to visualize the K-Space representations prior to looking
at them?
