Doppler Shift Detection

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Cihan Tunca

New Member

• Apr 23, 2014

• #1

Hi!
I'm working on a lidar system. I need your help to desing an important part of the system. It is the frequency shifting detection. I have to detect the Doppler shift to calculate the velocity of a moving target. At this point I couldn't find out a circuit to do this detection for me. I will be waiting for your advices to detect the Doppler shift and calculate the velocity of the target using different ways at the next a few weeks.
Thanks.

 

Last edited: Apr 24, 2014

ronsimpson

Well-Known Member

Most Helpful Member

• Apr 23, 2014

• #2

ADC8302 or AD8302?

 

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Cihan Tunca

New Member

• Apr 24, 2014

• #3

You are right. I wrote it down wrongly and It is AD8302

 

alec_t

Well-Known Member

Most Helpful Member

• Apr 24, 2014

• #4

What is the approximate target velocity?
The AD8302 has a 2.7GHz bandwidth. Will that be sufficient for detecting Doppler shifts of optical frequencies (~hundreds of THz)?

 

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Cihan Tunca

New Member

• Apr 25, 2014

• #5

I'm not trying to detect doppler shift at the optical frequencies. I'm going to modulate the light at aproximately 1 GHz such a sin wave or pulse train which has quite low duty cycle values,

 

ronsimpson

Well-Known Member

Most Helpful Member

• Apr 25, 2014

• #6

Do you have a good 1ghz amp?

 

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Cihan Tunca

New Member

• Apr 25, 2014

• #7

I think, I don't need amp. I'm planing to use APD photo detector to collect the reflected light and it's output current is enough to process using an PIC, I think.

 

ronsimpson

Well-Known Member

Most Helpful Member

• Apr 25, 2014

• #8

I just looked at some data sheets. "APD photo detector" Nice parts.

 

ccurtis

Well-Known Member

• Apr 26, 2014

• #9

Cihan Tunca said:

I'm not trying to detect doppler shift at the optical frequencies. I'm going to modulate the light at aproximately 1 GHz such a sin wave or pulse train which has quite low duty cycle values,

Click to expand...

So, you propose to compare the frequency of the modulating signal with the shifted frequency of the demodulated signal? If so, a simple mixer followed by a low pass filter should work to provide the difference frequency; perhaps something like the AD8343 with an R-C lowpass filter.