calcRfBandwidth

Calculates the bandwidth of an RF pulse using a Fast Fourier Transform (FFT). It assumes a low-angle approximation. The function returns the bandwidth, center frequency, and optionally the spectrum and frequency axis of the RF pulse. It handles frequency offsets and resamples the pulse to a specified resolution before performing the FFT.

Syntax

function [bw,fc,spectrum,f,rfs,t]=calcRfBandwidth(rf, cutoff, df, dt)

Calling Pattern

mr.calcRfBandwidth(...)

Parameters

Required Parameters

Name	Type	Description	Example	Units
rf	struct	Structure containing the RF pulse information. This struct must include fields 't' (time vector), 'signal' (complex amplitude of the RF pulse), 'freqOffset' (frequency offset in Hz), 'freqPPM' (frequency offset in ppm), and 'phaseOffset' (phase offset in radians). It also needs 'center', which represents a central point of the RF pulse used in resampling.	{t=[0:1e-6:1e-3]; signal=exp(-(t-0.5e-3).^2/2e-6); freqOffset=0; freqPPM=0; phaseOffset=0; center=0.5e-3;}

Optional Parameters

Name	Type	Default	Description	Example
cutoff	double	0.5	Fraction of the maximum amplitude used to define the bandwidth. The bandwidth is determined by the points where the spectrum falls to this fraction of its maximum value. Valid values: [0, 1]	0.1
df	double	10	Frequency resolution of the FFT (spectral resolution). (Units: Hz)	1
dt	double	1e-6	Time resolution of the resampled RF pulse. (Units: seconds)	5e-7

Returns

Output	Type	Description
bw	double	Bandwidth of the RF pulse in Hz.
fc	double	Center frequency of the RF pulse in Hz.
spectrum	double	Complex spectrum of the RF pulse.
f	double	Frequency axis corresponding to the spectrum.
rfs	double	Resampled RF pulse signal.
t	double	Time axis corresponding to the resampled RF pulse.

Examples

  [bw, fc, spectrum, f, rfs, t] = mr.calcRfBandwidth(rf_pulse_struct, 0.2, 5, 1e-6);

See Also

mr.aux.findFlank