hilb — FIR approximation to a Hilbert transform filter
xh=hilb(n [,wtype [,par]])
odd integer : number of points in filter
string : window type ('re','tr','hn','hm','kr','ch') (default ='re')
window parameter for wtype='kr' or 'ch' default par=[0 0] see the function window for more help
Hilbert transform
Returns the first n points of an FIR approximation to a Hilbert transform filter centred around the origin.
The FIR filter is designed by appropraitely windowing the ideal impulse response
h(n)=(2/(n*pi))*(sin(n*pi/2))^2 for n not equal 0 and h(0)=0.
An approximation to an analytic signal generator can be built by designing an FIR (Finite Impulse Response) filter approximation to the Hilbert transform operator. The analytic signal can then be computed by adding the appropriately time-shifted real signal to the imaginary part generated by the Hilbert filter.
http://ieeexplore.ieee.org/iel4/78/7823/00330385.pdf?tp=&arnumber=330385&isnumber=7823
A. Reilly, G. Frazer, and B. Boashash, "Analytic signal generation Tips and traps", IEEE Trans. Signal Processing, vol. 42, pp.3241-3245, Nov. 1994.