http://www.k-wave.org/forum/topic/modify-the-steered-linear-transducer-example-to-get-a-symmetric-focus-in-middle Support for the k-Wave MATLAB toolbox en-US Wed, 13 May 2026 00:17:11 +0000 http://bbpress.org/?v=1.0.2 q http://www.k-wave.org/forum/search.php http://www.k-wave.org/forum/topic/modify-the-steered-linear-transducer-example-to-get-a-symmetric-focus-in-middle#post-5952 Thu, 25 May 2017 17:14:12 +0000 kcox 5952@http://www.k-wave.org/forum/ <p>I figure it out! Thank you! </p> http://www.k-wave.org/forum/topic/modify-the-steered-linear-transducer-example-to-get-a-symmetric-focus-in-middle#post-5947 Tue, 23 May 2017 22:51:04 +0000 kcox 5947@http://www.k-wave.org/forum/ <p>'% create the computational grid<br /> Nx = 128; % number of grid points in the x (row) direction<br /> Ny = Nx; % number of grid points in the y (column) direction<br /> dx = 50e-3/Nx; % grid point spacing in the x direction [m]<br /> dy = dx; % grid point spacing in the y direction [m]<br /> kgrid = makeGrid(Nx, dx, Ny, dy);</p> <p>% define the properties of the propagation medium<br /> medium.sound_speed = 1500; % [m/s]<br /> medium.alpha_power = 1.5; % [dB/(MHz^y cm)]<br /> medium.alpha_coeff = 0.75; % [dB/(MHz^y cm)]<br /> medium.density = 1;</p> <p>% create the time array<br /> [kgrid.t_array, dt] = makeTime(kgrid, medium.sound_speed);<br /> kgrid.t_array = 0:dt:1000*dt;</p> <p>% define source mask for a linear transducer with an odd number of elements<br /> num_elements = 21; % [grid points]<br /> x_offset = 25; % [grid points]<br /> source.p_mask = zeros(Nx, Ny);<br /> start_index = Ny/2 - round(num_elements/2) + 1;<br /> source.p_mask(x_offset, start_index:start_index + num_elements - 1) = 1;</p> <p>% define the properties of the tone burst used to drive the transducer<br /> sampling_freq = 1/dt; % [Hz]<br /> steering_angle = 0; % [deg]<br /> element_spacing = dx; % [m]<br /> tone_burst_freq = 1e6; % [Hz]<br /> tone_burst_cycles = 20;</p> <p>% create an element index relative to the centre element of the transducer<br /> element_index = -(num_elements - 1)/2:(num_elements - 1)/2;</p> <p>% use geometric beam forming to calculate the tone burst offsets for each<br /> % transducer element based on the element index<br /> tone_burst_offset = 40 + element_spacing*element_index*sin(steering_angle*pi/180)/(medium.sound_speed*dt);</p> <p>% create the tone burst signals<br /> source.p = toneBurstCopy(sampling_freq, tone_burst_freq, tone_burst_cycles, 'SignalOffset', tone_burst_offset);</p> <p>% assign the input options<br /> input_args = {'DisplayMask', source.p_mask};</p> <p>% run the simulation<br /> kspaceFirstOrder2D(kgrid, medium, source, [], input_args{:});</p> <p>% =========================================================================<br /> % VISUALISATION<br /> % =========================================================================</p> <p>% plot the input time series<br /> figure;<br /> num_source_time_points = length(source.p(1,:));<br /> [t_sc, scale, prefix] = scaleSI(kgrid.t_array(num_source_time_points));<br /> stackedPlot(kgrid.t_array(1:num_source_time_points)*scale, source.p);<br /> xlabel(['Time [' prefix 's]']);<br /> ylabel('Input Signals');'</p> <p>I want to simulate a linear transducer being focused towards the center, i.e. inner elements being delayed from the outer elements, resulting in a symmetric input signal plot. I am confused with the syntax of the tone_burst_offset variable. What exactly would be changing to get this desired effect? </p>