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Simulating Transducer Field Patterns Example

Overview

This example demonstrates the use of k-Wave to compute the field pattern generated by a curved single element transducer in two dimensions. It builds on the Monopole Point Source In A Homogeneous Propagation Medium Example.

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Defining the time varying pressure source

As in the previous examples, a time varying pressure source is defined by assigning a binary source mask source.p_mask (which defines the shape and position of the source) along with a time varying source input source.p. Here a single sinusoidal time series is used to drive a curved transducer element.

% define a curved transducer element
source.p_mask = makeCircle(Nx, Nz, 50, 50, 30, pi/2);

% define a time varying sinusoidal source
source_freq = 0.25e6;
source_mag = 0.5;
source.p = source_mag*sin(2*pi*source_freq*kgrid.t_array);

% smooth the source
source.p = filterTimeSeries(kgrid, medium, source.p);

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Running the simulation

The simulation is again invoked by calling kspaceFirstOrder2D. Because no sensor output is required, the sensor input structure is simply assigned as an empty array. To allow visualisation of the source elements within the grid, the source mask is assigned to the optional input 'DisplayMask'. This mask is overlayed onto the plot during the simulation. The PML is also set to be outside the computational grid defined by the user and then hidden from display by setting the optional inputs 'PlotPML' and 'PMLInside' to false.

% create a display mask to display the transducer
display_mask = source.p_mask;

% assign the input options
input_args = {'DisplayMask', display_mask, 'PMLInside', false, 'PlotPML', false};

% run the simulation
[sensor_data, p_final] = kspaceFirstOrder2D(kgrid, medium, source, [], input_args{:});

The final pressure field is plotted below. Both the transducer focus and the side lobes are clearly visible.

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© 2009, 2010, 2011 Bradley Treeby and Ben Cox.