What exactly happens in a 'radar lock'?

[Mark R]

So, I've always had this impression of radar as being this thing that slowly sweeps round (or is phase array steered) gradually building up a picture of the surroundings.

So what exactly happens when a guided munition gets a lock? Does the guiding radar suddenly switch to a very narrow sweep angle, high pulse rep mode?

How much of the hollywood stuff should I believe? (Can't believe I just asked that)

 

[BrownTown]

I believe it simply means that the radar on the missile itself has the object in its view. So, a plane or SAM site might have a very powerfull radar sweeping the sky for targets, but then the missile itself has its own much less powerfull but more focused rader which has to acquire the target before it can home in. Of course the same would go for heat seeking or anti-radiation missiles, you have to wait till the onbaord detection system has acquired the target before you can fire. Obviously a lock is not a sure thing, and with the correct dodging technique you can casue the missile to lose its lock and miss.

 

[dkozloski]

A search radar does the sweeping around on a PPI scope like a round TV screen. A tracking radar has a narrow focused beam like a search light that has the ability to keep itself pointed at the target by developing error signals from the reflected signal that steer the beam to keep it pointed at the target. The search radar is used by the fire control system to designate and acquire the target otherwise it's like trying to find a mosquito in the bedroom with a pencil flashlight. The narrow focused beam can be steered either by mechanical means like a searchlight or electronically with a phased array antenna. When the target is detected in the focused beam the system picks up the signals that automatically keep the target in the beam, tracking begins, and the system is said to be "locked". The position of the tracked target can be located within thousanths or a degree and transmitted to whatever you are using to engage it.

 

[Witling]

I don't know what criteria are actually used but the power and signal characteristics (frequency and pulse rate) are distinctively different for fire control and search radars. I would presume there's some consideration of how long the signal paints the target.

 

[dkozloski]

Fire control tracking radars use a very narrow pulse width and a tightly focused beam for tracking accuracy and are of a higher frequency than search radars. A 3 microsecond pulse width is typical. Search/surveilance radars use lower frequencies, high power, and longer pulse widths to get more power into the return pulse to aid in painting obscure targets under adverse conditions. A 40+ microsecond pulse width is not out of the ordinary. A fire control target designation 3D radar has an azimuth sweep like a search radar but also has an elevation scan to enable the fire control designation system to get the tracking radar onto and pointing at the target. It also has narrow pulse widths for accuracy. Typically 6 microseconds.

 

[soydios]

Summary: search radar uses a different signal than a fire control tracking/guidance radar. A threat receiver can tell the difference between the two.

For search radar, the threat receiver can tell you if...
...it's detecting the search radar is on a certain bearing, but that the signal from the search radar isn't strong enough to generate a return (akin to you seeing someone with a flashlight, but they can't see you, even if they point the flashlight at you).
...the search radar is strong enough to generate a return that exceeds the detection threshold (akin to someone seeing you with their flashlight, at which point they can do whatever they want, like shoot at you).

For targetting radar, the the threat receiver can...
...tell you that you are in the missile system's sights (by detecting the new, different, and dangerous radar signal).
...jam the targetting radar.

 

[wwswimming]

how narrow the sweep is depends a little on the physics of the radar vs. its target.

most of my experience is with radar for trailers (carry behind a jeep) and airplanes. but a guided munition, a missile, jeez, i hesitate to speculate.

 

[sao123]

achieving a radar lock involves a white circle with a plus sign in it (called a cursor), following a enemy target on a digital display tv. Lock on is achieved when the cursor occupies the same space as the target and turns red.

/last night I stayed in a holiday-inn express knowledge.