# Chirp pulse xy.m

Chirp pulse waveform with a sine bell or quarter sine amplitude envelope in Cartesian coordinates.

## Syntax

    [amps,frqs,durs]=chirp_pulse_af(npoints,duration,bandwidth,smfactor)


## Description

The pulse is normalised to achieve an inversion across the band. It can be used either as conventional unidirectional chirp pulse, (wurst or smoothed) or smoothed saltire which is superposition of two counter sweeping chirps, as used in PSYCHE decoupling.

## Arguments

    npoints     - number of discretization points in
the waveform

duration     - pulse duration, seconds

bandwidth     - chirp sweep bandwidth around
zero frequency, Hz

smfactor     - smoothing parameter, a real positive number
for sine bell smoothing (wurst): normally 1 - 80
for quarter sine smoothing (smoothed and saltire),
in percent: should be in the range 0 - 50

chirptype    - 'wurst', 'smoothed', or 'saltire'


## Returns

       Cx       - real part of the waveform, rad/s

Cy       - imaginary part of the waveform, rad/s
(zeros for saltire pulse)


## Examples

See shaped_pulse_5.m in examples/nmr_liquids for a common usage case.

## Notes

Note that pulse amplitudes are given in rad/s. This matches the syntax requirements of shaped_pulse_xy.m function.