"J.Feldhaar" wrote:
>
> Hi all,
>
> another tack on the issue: what about the bandwidth required for good
> distance resolution, assuming a pulse or a chirp is used, considering the
> mandatory use of multi kilowatts of peak power needed for the 30 miles
> range earlier mentioned in this thread...??
>
> I personally have considered doing just this and I have not found an
> amateur frequency range where this would be permitted...even the 5 GHz
> band
>
> Comments?
>
> Greets,
> Jochen Feldhaar DH6FAZ

Ummm... What's "good resolution?"

From _Intoduction to Radar Systems_ by Merrill I. Skolnik- the error in
the time delay of a pulse (using rising and falling edges of the pulse)
can be written (Eq. 11.5):

Rise time error=(t/(4BE/No))^(1/2), where B is the bandwidth, E is the
signal energy, No is the noise power per unit bandwidth and t is the
pulse width.

The range error would be 1/2*time error*c) (1/2 since radar is 2-way,
but that also means that your power recieved goes down as a factor of
1/r^4)

A chirp would get you a greater effective power on the target-
increasing E.

As to peak power required and so forth, I direct the curious to chapter
2 of the same book, where the radar equation is discussed in some detail
(50+ pages).

That's your range resolution, but azimuth resolution is a factor of your
antenna and range.  I'm particularly fascinated by synthetic aperture
radar- while the range resolution is still a factor of system bandwidth,
azimuth resolution is *independent* of range with a focused SAR.
Depends on a moving radar (or target) and you can't make an image in
"real time" but it is fascinating anyway.

Matt Bennett

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