Re: Wanted: Hilbert Transform source code

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2 total messages Started by Jacob Hirbawi Wed, 05 Aug 1992 22:08

#85

Author: Jacob Hirbawi
Date: Wed, 05 Aug 1992 22:08

24 lines
1623 bytes

In comp.dsp <1992Aug5.132704.1@zodiac.dsto.oz.au>
Witold Waldman <st_waldman@zodiac.dsto.oz.au> writes

> I would like to obtain source code in Fortran, C or
> Pascal for computing the Hilbert transform of a band-pass
> filter response function. Note that only magnitude response
> data is available for the band-pass filter, and the Hilbert
> transform would be used to compute the corresponding
> phase response of the band-pass filter.

It seems to me that you are trying to generate complex data from
real only measurements. You have two options: you can implement the
Hilbert Transform with analog components ,(nothing more than a 90
degree phase shifter) or digitally perform the transform. Each has its
own advantages but since you asked for source code I assume you've already
decided on the digital approach. You can just use a generic FFT to do this
as follows: perform FFT on your data and then multiply the array by the
"signum" function ( -I for 0<i<N/2-1 , +I for N/2<i<N-1 ) and then do an
inverse FFT to get the "quadrature" or imaginary part of your signal.
This may not be the most efficient way of doing the transform and in fact
I would be interseted in better ways if anyone knows of any. Hope this helps.

Jacob Hirbawi
JcbHrb@CERF.net

Re: Wanted: Hilbert Transform source code

#110

Author: Hoyt A. Stearns jr.
Date: Mon, 10 Aug 1992 00:22

23 lines
1456 bytes

In article <2459@nic.cerf.net> jcbhrb@nic.cerf.net (Jacob Hirbawi) writes:

>I would be interseted in better ways if anyone knows of any. Hope this helps.
>

I know of two other methods:  Any FIR filter with inverse mirror image
tap weights will 90o phase split with respect to a delay half its length.

The IIR solution is quite simple and symmetric but I don't have the
diagram handy.  It looked somehing like a n "X"

		  _______
			\  /
			 \/
		  ___/_\___

I don't rember in which legs the delays were and which the summers were in.

-- 
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