# Re: Hilbert transform

**URL:** <https://www.ruby-forum.com/t/re-hilbert-transform/231589>\
**Category:** GNU Radio\
**Created:** [August 17, 2014, 7:47pm UTC](https://www.ruby-forum.com/t/re-hilbert-transform/231589 "2014-08-17T19:47:27Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [August 17, 2014, 7:47pm UTC](https://www.ruby-forum.com/t/re-hilbert-transform/231589/1 "2014-08-17T19:47:27Z")

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Thanx Marcus and Tom fr ur explanations. I will read further and ask any  
questions if i have.

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**Author:** ![ali](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/8c91f0/32.png) [@ali](https://www.ruby-forum.com/u/ali)\
**Post date:** [August 18, 2014, 5:24pm UTC](https://www.ruby-forum.com/t/re-hilbert-transform/231589/2 "2014-08-18T17:24:04Z")

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Hi Tom,  
As hilbert transform is a high-pass filter which only allows the  
positive frequency components.And we know that only a complex signal  
can have a single sided spectrum,not a real signal.So, i am still  
confused that why the signal isn’t showing any imaginary part??May b i  
am not understanding fully…

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**Author:** ![ali](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/8c91f0/32.png) [@ali](https://www.ruby-forum.com/u/ali)\
**Post date:** [August 18, 2014, 6:03pm UTC](https://www.ruby-forum.com/t/re-hilbert-transform/231589/3 "2014-08-18T18:03:37Z")

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On Mon, Aug 18, 2014 at 11:22 AM, jason sam [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Hi Tom,  
> As hilbert transform is a high-pass filter which only allows the  
> positive frequency components.And we know that only a complex signal  
> can have a single sided spectrum,not a real signal.So, i am still  
> confused that why the signal isn’t showing any imaginary part??May b i  
> am not understanding fully..

Not sure. I think you definitely understand the concept. By removing the  
negative frequencies, you /must/ add an imaginary part to the complex  
signal. Basically, the Hilbert, as you understand, essentially just adds  
the appropriate imaginary part.

I just tried your example, and things looked fine for me:

[http://imgur.com/z305wlS](http://imgur.com/z305wlS)

Tom