Re: Envelope Detector using Hilbert Transform

>w106pjs wrote:
>>>
>>>w106pjs wrote:
>
>
> ...
>
>>>Let's see, 300kHz/50MHz = 0.006.
>>>
>>>That's a serious amout of oversampling. 3" = 8 cm, the medium is
air...
>>>
>>>What kind of application is this? How much noise is present in the
>>>data? How stable is the temperature, humidity and wind in the air
>>>where you make your measurements?
>>>
>>>To take the "half-easy" part first, Rick Lyons mentioned a couple of
>>>months ago that somebody had submitted a Hilbert transformer to his
>>>"DSP Tricks" column in IEEE Signal Processing Magazine. The "new"
>>>stuff with this Hilbert transformer was that it was supposed to be
>>>reliable for seriously oversampled signals, like the ones you have.
>>>If you are lucky, Rick is lurking here and may perhaps let you know
>>>when the article is published.
>>>
>>>The second concern, is whether the very accurate timing information
>>>you get, is useful. Remember, the sound velocity in air depends
>>>on lots of factors (humidity, temperature, wind, atmospheric
>>>pressure). You ought to be a ware that any very-fine-scale variations
>>>you observe in your measurements *could* be due to such factors, and
>>>not necessarily the physical distance you try to measure.
>>>
>>>Rune
>>>
>>
>>
>> Rune , Al Clark
>>
>> I have been thnking about this problem with a different perspective..
>>
>> Say the target is at 3.000".
>> What if you intend to measure the a target movement of +/- 0.001" or
>> less..
>> i.e target displacement from 2.999" - 3.001" or so..
>> the time resolution you would need should be better than the change in
the
>> time of flight to the target..
>
>I think you -- to quote my President -- misunderestimate how much faster

>than sound light is.
>
>> I realise the effect of change in Temperature, RH, Pressure.. wind
>> turbulence...and other factors..
>> Let me.. know ... what you think about this..
>> I have been hearing about the article you mentioned in the previous
>> threads... does... someone.. has a copy of that article...
>>
>> Also please share some more thoughts on the hilbert transformer..
>> implementation in MATLAB...
>
>The square root of Re^2 + Im^2 (with Im possibly computed using a
>Hilbert transformer) gives the envelope even when few samples are taken
>near the peaks of the waveform. With a continuous waveform, a simple
>peak detector is enough. You are so heavily oversampling that a peak
>detector should work for you just fine. I doubt that the oversampling
>will do you much good aside from that, but you might as well benefit
>from it that way.
>
>Jerry
>--
>Engineering is the art of making what you want from things you can get.



>¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
>

Jerry

Sorry for getting everybody offtrack....I guess my concern for resolving
implementation of hilbert transformer still remains ...
How would the transofmer.be implemented in MATLAB ?
Please share some thoughts... and possibly recommend any good literature
as well..

Thanks
Paul




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