Introduction to Radar Basics - MATLAB Simulations for Radar Systems Design - page 63

and in this case, the true target range is

ct r 1
2

R = --------- (1A.9)

Finally, if , then the target is in the first ambiguity. It follows that

t 1 = t 2

t r 2 == t 1 t 2

(1A.10)

and

R t r 2 = ⁄ 2 (1A.11)

Since a pulse cannot be received while the following pulse is being transmit-
ted, these times correspond to blind ranges. This problem can be resolved by
using a third PRF. In this case, once an integer is selected, then in order to
guarantee that the three PRFs are relatively prime with respect to one another.
In this case, one may choose

N

, , and

f r 1 = NN ( + 1 ) f rd f r 2 = NN 2 ( + ) f rd

.

f r 3 = ( N + 1 ) N ( + 2 ) f rd

1A.4. Resolving Doppler Ambiguity

The Doppler ambiguity problem is analogous to that of range ambiguity.
Therefore, the same methodology can be used to resolve Doppler ambiguity. In
this case, we measure the Doppler frequencies and instead of and f d 1 f d 2 t 1

. t 2

If , then we have

f d 1 > f d 2

( f d 2 – f d 1 ) + f r 2

M = ------------------------------------- (1A.12)

f r 1 – f r 2

And if , f d 1 < f d 2

f d 2 – f d 1

M = -------------------

(1A.13)

f r 1 – f r 2

and the true Doppler is

f d = Mf r 1 + f d 1

(1A.14)

f d = Mf r 2 + f d 2

Finally, if , then

f d 1 = f d 2

f d == f d 1 f d 2 (1A.15)

Again, blind Doppler can occur, which can be resolved using a third PRF.