Undersampling a signal

[Milruwan]

Sir,
I tried to undersample a band limited signal which is 10.7MHz and it's
bandwidth is 200kHz. I undersample the signal and got the signal into
250kHz to 450KHz range.Then I tried to low pass filter the signal(0Hz to
450kHz). But the filtered signal was distorted.

My question is can I under sample a signal and L.P.F the signal in this
way?

Or is there a better way to do undersampling and recover the band
limited signal?

 

[vkansal12]

According to Nyquist theorem, if you undersample a signal, you cannot get back the information contained in it. To recover the signal, you have to sample it at a rate more than 10.7/2 MHz.

 

[Milruwan]

To recover the signal, you have to sample it at a rate more than 10.7/2 MHz.

vkansal12,
Thanks for your reply.According to my knowledge in order to recover the signal we need to undersample the signal more than twise of the bandwidth.

 

[vkansal12]

You are erring here. The statement you have heard is true only in case of amplitude modulated signals. You need to check what your information frequency is. If the bandwidth of your information signal is 200 kHz, then you can reconstruct it.

 

[andre_luis]

My question is can I under sample a signal and L.P.F the signal in this
way?

Or is there a better way to do undersampling and recover the band
limited signal?

You can oversample signal a from a limited acquired sample rate by using multiple samples, symmetrically shifted. However, it requires employ multiple acquiring systems ( in other words, A/D ), and also must certify if processing system are able to deal with that.


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[FvM]

Can you elaborate your question? What's the sampling frequency, which signal do you try to recover?