Practice Problems#
A RADAR transmitting \(100\ \text{kW}\) of power at \(350\ \text{MHz}\) receives a return from a plane with an RCS of \(100\ \text{m}^2\) after \(250\ \mu s\).
How far away is the plane?
An F-15 has enough fuel to travel \(100\ \text{km}\). The F-15 is receiving a signal from a TACAN located on the airfield. It takes \(500\ \mu s\) for the TACAN signal to travel to the F-15.
Does the pilot need to hit a tanker, or does it have enough fuel to reach the runway?
A fighter has an RCS of \(20\ \text{m}^2\). Will a fire-control RADAR that operates at \(1\ \text{GHz}\), has a transmit power of \(50\ \text{kW}\), and a gain of \(50\) be able to lock onto the fighter if the range is \(50\ \text{km}\) (and LOS is established)?
To lock-on, the received power must be at least \(10\ \text{pW}\).
The RCS of a fighter is approximately \(20\ \text{m}^2\). The RCS of a missile is approximately \(0.2\ \text{m}^2\).
How many times farther away can the fighter be detected than the missile?
During an exercise, a UAS is used to gather information on red forces. The red team has deployed a mobile RADAR unit with the following parameters:
Mobile RADAR Unit |
UAS |
|---|---|
\(f = 450\ \text{MHz}\) |
\(\sigma = 0.4\ \text{m}^2\) |
\(P_T = 1.5\ \text{kW}\) |
\(G_R = 3\) |
\(G = 200\) |
\(P_{R,\min} = 1.25\ \mu\text{W}\) |
\(P_{R,\min} = 1\ \text{fW}\) |
Answer the following:
(a) If the RADAR signal takes \(133.3\ \mu s\) to return, how far away is the UAS?
(b) How much power is received by the RADAR if the UAS is \(30\ \text{km}\) from the RADAR?
(c) If the RADAR is located on a \(45'\) hill and the UAS is ingressing at \(200'\) AGL, who will see who first?