Question

Consider a radar with a PRF of 5 kHz. What is the maximum unambiguous range Rua of this radar, in km? If a target is located at a range of 50 miles, how many pulses will the radar have transmitted before the first echo from the target arrives? What will be the apparent range of the target, in kilometers?

Answer 1

PRF(Pulse repetition frequency ) = 5 KHz

PRT = 1/PRF = 1/(5x10³) =2x10^-4 sec.

R_max(Maximum unambiguous range of radar) = C.(PRT-PW)/2

Since, pulse width isn't given, we can expect that the transmitted pulse is short and can be overlooked.

• R_max = C.PRT/2 =(3x10⁸x2x10^-4 )/2
• R_max = 30,000 m = 30 km.

Target is located at a range of 50 miles, R= 50 miles

or R= 50x1.609 = 80.45km.

Let the no. of pulse the radar transmits before the reverberate from the objective arrives be N.

N= R/R_max = (160.9/2)/30 =2.68

Therefore, N=3.

Presently, X MOD Y -> Frac(X/Y) x Y

Evident range of target, R_A = R MOD [(C x PRI)/2]

• R_A = 80.45 MOD [((3x108x2x10-4)/2) x 10-3]
• R_A = 80.45 MOD 30
• R_A = 20.45 Km