how to detect envelop of signal ?

Forum|Forum|7 years ago
May 26, 2018
7 replies
8960 views

How to find upper and lower envelop of the signal ? please check my mathcad file !

Best answer by Werner_E

@Mathcad111 wrote:

ok got it! in your file('WE_20180526_mathcad_ques-1') you have used 't' (which is basically belongs to transmitter end) but in the receiver side i don't have any idea about the time, for example if i know the exact time than i could able to find the frequency and i can used to reconstruct the 'Tx' signal, but the problem is, i don't know the exact time. could you able to do without the 'Transmitter time 't' ' (like approximation of that time).

As long as your data is sampled in equidistant time steps it should not matter what the vector t is as long as its values are equidistant and ist the same size as your data vector. But I guess it could be difficult to find working guess values.

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-MFra-

21-Topaz II

Hi,

The noise's maximum amplitude is ten times higher than that of the signal. How to distinguish a signal from such noise? it's impossible!

L

LucMeekes

23-Emerald IV

It's not entirely impossible. A lock-in amplifier will allow to detect signals that are below the noise level. Problem is you have to know the frequency you want to detect.

The OP's problem is extremely simple as posed, but I guess he's got a more fundamental problem (doesn't know his signal and which part of it is noise).

Luc

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-MFra-

21-Topaz II

If the given signal is sampled, a digital notch filter tuned to the frequency of the signal should be used in such a way as to attenuate only the carrier while the noise is emitted at the output. To have the envelope a peak detector is added with a capacity ...........

T

terryhendicott

21-Topaz II

Hi,

You must break the signal into segments and find minimum and maximum of each segment.

1_mathcad_ques_v2.zip

T

terryhendicott

21-Topaz II

Hi,

Sorry a mistake in the lower envelope is corrected here.

1_mathcad_ques_v3.zip

L

LucMeekes

23-Emerald IV

That's extremely simple. For the problem as posed the lower enevlope is XT, the upper is XT+1.

But I guess that's not what you're after. What do you know about your signal, and what exactly are you after?

Note that Terry showed a way to estimate the envelopes, but do you need the envelopes, or are the envelopes just part of your way of what you really want to know about the signal?

Success!

Luc

W

Werner_E