How do passive radar systems detect stealth aircraft?

[EngTechno]

I want to know the basic concept of Passive Radar System that can detect Stealth Aircraft? Which country invented this technology ? Is there any website that has information of this technology?

 

[Cliff_J]

I'm have no clue about this but I've seen a documentary on Discovery where they showed the ability to detect stealth aircraft by simply looking from above for moving "holes" in the radar emitted from the ground. The idea is that if the aircraft is designed to diffract and absorb radar energy it will always do it so therefore it will crete this hole as an undesireable secondary effect.

Of course the high altitude aircraft needed or satellites needed to get that vantage point would limit the number of countries with this capability if this is even what you are talking about. Maybe even bounce the transmissions off the upper atmosphere and look for a "hole" in the returning energy? Given how carefully the military plans the route of the aircraft to minimize radar coverage I'd guess they're fully aware of the limitations in the technology or I'm wildly misinformed...

Cliff

 

[Gokul43201]

I'm have no clue about this but I've seen a documentary on Discovery where they showed the ability to detect stealth aircraft by simply looking from above for moving "holes" in the radar emitted from the ground. The idea is that if the aircraft is designed to diffract and absorb radar energy it will always do it so therefore it will crete this hole as an undesireable secondary effect.

Of course the high altitude aircraft needed or satellites needed to get that vantage point would limit the number of countries with this capability if this is even what you are talking about. Maybe even bounce the transmissions off the upper atmosphere and look for a "hole" in the returning energy? Given how carefully the military plans the route of the aircraft to minimize radar coverage I'd guess they're fully aware of the limitations in the technology or I'm wildly misinformed...

Cliff

I can't see this "hole searching" scheme as cost effective. You have to be in the right place at the right time, or you get zilch. The odds strike as bordering on futile...even with Ionospheric Reflection (which I'm not sure will maintain integrity of the shadows).

 

[Gokul43201]

Anyway, I don't believe this is what EngTechno has in mind, as he's looking for a passive detection system.

I guess this means that you detect the onboard radar from the craft. I haven't read anything about this yet, and I'm curious too, what kind of signal/noise levels you can currently recover meaningful signatures from.

 

[CharlesP]

Picking up someone else's radar is a lot easier than seeing reflections from your own. It is common for stereos to buzz at the PRF of nearby radars. More sensitive receivers are used to detect radars at a distance.

 

[russ_watters]

...which is why stealth aircraft don't have radar.

 

[pack_rat2]

"Passive radar" is based on detecting the way an object blocks ambient UHF signals as it travels through them. Those signals are usually from cellular phone transmitting towers, which today are almost everywhere.