k-Wave Toolbox

Defining A Gaussian Sensor Frequency Response Example

Overview

This example shows how to account for the frequency response of detectors when this response has a Gaussian shape (for example, piezoelectric ultrasound transducers). It builds on the Homogeneous Propagation Medium Example.

• open the file in the MATLAB Editor
• run the file in MATLAB

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Defining the sensor frequency response

The frequency response of the sensor is assigned using the frequency_response field of the sensor input structure. This accepts two parameters, one for the center frequency, and one for the bandwidth of the frequency response. The transducer bandwidth, defined as a percentage, controls the full-width at half-maximum (FWHM) of the filter, where the FWHM = % bandwidth * center frequency.

% define the frequency response of the sensor elements
center_freq = 3e6;      % [Hz]
bandwidth = 80;         % [%]
sensor.frequency_response = [center_freq, bandwidth];

When an input for sensor.frequency_response is defined, a Gaussian filter is applied within the simulation functions after the simulation is completed by multiplying the Fourier transformed signals by a zero-phase Gaussian window using gaussianFilter. Note, the same filter can also easily be applied by calling gaussianFilter explicitly when the sensor data is returned.

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Running the simulation

To illustrate the effect of the filter, the time series recorded at the first sensor position for a simulation with and without the sensor.frequency_response field defined are plotted below. The corresponding amplitude spectrums are also shown. The removal of the low frequency information has a significant effect on the signal amplitude.

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Recording The Particle Velocity

Comparison Of Modelling Functions

© 2009-2014 Bradley Treeby and Ben Cox.