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From: night on 24 Jun 2008 06:43
Hi,

I'm supposed to analize a received signal on a Doppler continuous wave
radar for an university practice.

I only have a file with samples taken at 20KHz. The only information I
know about the radar is its center frequency (24GHz) and trasmitted signal
power. The recieved signal values that I have are the baseband outputs of
the front-end that have a DC offset of 2.6Volts and seem to be a sinusoidal
wave.

I'm new on radar comunications but not on signal proccesing and I'm
having problems...I'm trying to perform the FFT to get the doppler
frequency offset but I'm not sure about what I'm doing because I haven't
found it.


To obtaining such frequencial resolution I've taken 200 samples of the
received signal and I've perform the 2048-FFT.


Could someone help me?? I know I'm making a "very simple" mistake but
I'm not being able to find it....

Thanks!

From: Rune Allnor on 24 Jun 2008 06:51
On 24 Jun, 12:43, "night" <sandracorr...(a)gmail.com> wrote:

>  I'm new on radar comunications but not on signal proccesing and I'm
> having problems...I'm trying to perform the FFT to get the doppler
> frequency offset but I'm not sure about what I'm doing because I haven't
> found it.
>
>     To obtaining such frequencial resolution I've taken 200 samples of the
> received signal and I've perform the 2048-FFT.

How many samples do you have? As a concept check,
use all available data and compare the spectrum
with the spectrum of the baseband reference data.

Apart from that, I think the usual way to estimate
Doppler shift is to modulate the baseband reference
up or down in frequency, and use a correlator to
do the comparision in time domain. Use several
correlators, one for a Doppler interval, and
search for the correlator with highest output
magnitude to find the Doppler shift.

Rune
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