Simulating broadband ultrasound transducer in Matlab.

Hi there. I am attempting to simulate a broadband ultrasound transducer in matlab. I would like the centre frequency to be 5MHz with a bandwidth of 100%. I've attempted to apply a window to the FFT (<http://www.mathworks.co.uk/help/matlab/ref/fft.html>) of a single sinusoid of frequency 5MHz but have been unsuccessful. It strikes me that there should be a simple way of doing this?

[Image Analyst]

I dont' understand. Are you masking your spectrum with one hump of a sinusoid centered at 5 kHz? What does a bandwidth of 100% mean? Does that mean all frequencies pass? If so, then what does the 5 Khz and window have to do anything? Or do you mean that it passes the signal at 100% amplitude within some window around 5 Khz? A diagram and code would help.