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Altera_Forum's avatar
Altera_Forum
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12 years ago

Sine wave manipulation

Hello everyone,

I have a project where i have to do the adc conversion of sine wave. From there I got a 16 bit output. now i want to detect the tip(peak or crest) of the sine wave, for this I wrote a program to generate a strobe pulse at the tip. But when there is a spike or noise anywhere in the signal, then I will get an unecessary or unwanted peak at this noise. Can anyone suggest how can I get right peak without using any filter to remove noise? I am doing it in VHDL

Help will be highly appreciated

5 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Hi, so you will make a peak detector

    what's difference between peak and crest ?:p

    ? without using a filter ? How does your board slect the good peak ? What are the conditions ?

    "to chose" is already an action of filter ! take the good :cool: and forget the bad :evil:.

    You cannot mask or attenuate without a filter, of course !:wacko:

    You can make a threshold filter, Schmitt-trigger filter, low-pass filter, band pass filter....

    Welcome to this unperfect noisy word !

    Regards

    EDIT : Grrr, in this forum, no more than 4 smileys are allowed !
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    hi thanks for reply.....in this process i made one bit squarewave from the noisy sine wave ....then i applied filter in this square wave... its works....it helps in the frequency measurement but problem with peak to amplitude measurement is same :(

  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    You applied a filter to a bit signal. I think it is a temporal filter like "wait for the signal to be stable for 100us before commuting".

    You want to measure amplitude of a signal without noisy peaks, you have to filter. You seem confused.

    Make a Low Pass (FIR, IIR, median....) on the digital signal from ADC.
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    --- Quote Start ---

    hi thanks for reply.....in this process i made one bit squarewave from the noisy sine wave ....then i applied filter in this square wave... its works....it helps in the frequency measurement but problem with peak to amplitude measurement is same :(

    --- Quote End ---

    If you want to avoid filtering and its hassle of cutoff and if you are serious then you can use fft. I assume you are interested in amplitude measurement rather than the time of peaks.

    fft will tell you the amplitude of your tone directly and any power of noise outside your tone will be separated. You wil need to do some scaling though.
  • Altera_Forum's avatar
    Altera_Forum
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    12 years ago

    Hey thanks alot for rply .....

    As I am using delta sigma digital modulation and sinc3 filter,, once filter is already used... then after we r using this so that we can find the zero level or zero crossing correctly......then now for amplitude, we r registering the value in min and max amplitude and then transfer it to the output at the coming rising and falling edge of sine wave respectively...............it works now.... but some ripple at the peak and bottom may make a problem.