alt Hacker NewsI read a lot about passive radars trying to leech off of opportunistic waves, and lots about actual troops preferring to play hide-and-seem with anti-radiation weapons just to use active machines.
A config that strikes me as obvious but doesn’t seem to be popular would be just bistatic where you fire your own transmitter far away from yourself?
There’s got to be a reason, but it seems like best of both worlds.
Replies
One reason is Low Probability of Intercept radars (and transmitters / datalinks) do exist, and are very difficult (but not impossible) to identify and locate.
We've already got a really extreme version of this.
Probably more complicated to setup in a hostile environment because you'd need multiple transmitters, which also need to remain stationary, or at least you need to accurately know when they move.
Much more covert, and civilian infrastructure also less likely to be blown up.
Multistatic radars (of which bistatic are just the case with N=2) are like the nuclear fusion of radar systems: everybody agrees it would be neat to have them, but they're always 20-30 years in the future. In practice it is extremely difficult to maintain the precise timing synchronization required for radar systems. Especially when used in moving vehicles or in sparsely populated areas the expected error goes WAY up to the point of unusability.
The survivability gains are also overhyped since 1. the enemy can just blow up the transmitters leaving you with a bunch of useless receivers and 2. most air defense doctrines already treat radars as something that should be distributed widely, so you can lose a few without the whole system collapsing.
The article goes into this only briefly, but modern radar systems don't just send out any random pulse but they very specifically tailor the waveform going out in order to do cool signal processing tricks like pulse compression. There is also the matter of frequency. The lower the frequency, the bigger the antenna you would need to get a proper direction reading out of it. Fire control radars typically operate in the X-band, around 10 GHz. Most civilian radio transmitters are around 100 MHz, so you'd need impractically large antennas and even then the bandwidth limitations would severely limit spatial resolution. One saving grace here is that stealth airplanes are typically most highly optimized against X-band radars from the direction they're going to bomb (forward), so you might have a better chance with a normal system, but then you still might not have a precise enough target to actually shoot at.
So while the multistatic system does offer some advantages, in practice it's just cheaper and (importantly for military use) requires less fiddly bits in the field to just use normal monostatic radars. Civilian use also doesn't benefit greatly from being multistatic. It's a bit like Tesla turbines or hyperloops: cool idea and it even "works" in a way, but the normal way of doing things is just way better when budgets and engineering realities come into play.
Source: I was a radar engineering officer in the Dutch navy about a decade back.