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FMCW Radar help required.

Started by charlesadi April 11, 2010
Hi All, 
For an FMCW Rdar I plan to provide a 100us ramp to sweep 300MHz . I get an
(IF) of 40Khz for a distance of 1meter . My Gunnplexer datasheet shows an
(IF) band width of no more than 5000Hz . Then how is it possible to capture
40Khz (IF) ? .


Charles 


charlesadi wrote:
> Hi All, > For an FMCW Rdar I plan to provide a 100us ramp to sweep 300MHz . I get an > (IF) of 40Khz for a distance of 1meter . My Gunnplexer datasheet shows an > (IF) band width of no more than 5000Hz . Then how is it possible to capture > 40Khz (IF) ? . > > > Charles > >
Dunno... maybe it tracks? That might well explain it. But, I didn't try to follow your numbers. 1 meter would have a round trip time of 2m/300,000,000m/sec, or 2m/300m/usec = 0.006666usec or 6.6666nsec 300MHz/100usec = 3MHz/usec So, 3MHz/usec X 0.006666usec = 0.02MHz or 20kHz frequency difference between transmit and receive for a ramp. So maybe we get the same numbers when one if it's a sawtooth instead of a ramp? AND it has to track the transmit frequency at that!! Now, if the range is relatively fixed at 1m then the return is going to be 20kHz and then -20kHz but outputting the same range. But then, only you have that datasheet..... Fred