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Stopping Cars With Microwave Radiation
Ponca City, We Love You writes "Researchers have created an electromagnetic system that can quickly bring a vehicle to a stop by sending out pulses of microwave radiation to disable the microprocessors that control the central engine functions in a car. A 200-pound unit attached to the roof of a police car can be used to stop fleeing and noncooperative vehicles. The average power emitted in a single shot is about 10 kilowatts at 100 hertz and since each radiated pulse lasts about 50 nanoseconds, the total energy output is 100 joules at a distance of 15 meters. One concern with the device is that it could cause an accident if a car is disabled and a driver loses steering control. The device could also disable other vehicles in the area so the most practical application may be for perimeter protection at remote areas. Criminals have a work-around too. Since electronic control modules were not built into most cars until 1972, the system will not work on automobiles made before that year."
With that said, if the steering somehow could not be controlled with the PCM disabled, I smell lawsuit. This computer killer thing would also disable any other computerized device... like airbags.
The game.
I've run diesel engines with NO electric power (dead/frozen battery, broken alternator belt). As long as the fuel is gravity-fed, it'll run.
Fat chance stopping someone who decided to take a front-end loader to make an "ATM withdrawal".
First a comment: "The average power emitted in a single shot is about 10 kilowatts at 100 hertz". What's that, a microwave at 100 Hz?? Microwaves have frequencies at the GHz range... Second: probably a trivial amount of shielding (likely already in place in the car, *if* the ECM is inside the engine compartment) would suffice to stop this since the penetration depth of a GHz signal is very very small in metals (microns of metal would block it). Seems like a nice toy, probably not very useful, possibly dangerous to people around (e.g. with a pacemaker). Just a ploy to get a government grant...
No. Each wire entering into the ECM is another vector, thus inputs into the ECM would have to be protected.
Coaxial feed thru capacitors through a RF gasketed cover followed by a small RF choke and ferrite bead should do the trick.
The truth shall set you free!
However, steer-by-wire systems are quickly coming into play in America, especially on some of the lower-end GM products. Now I'm no GM engineer yet, but from what I gather the steering system is either on the GMLAN high speed bus or it has its own bus but still gets data off GMLAN.
Now suppose the ECM stops giving out speed information on the GMLAN bus. Hopefully there is a contingency plan in the steering logic so that you can still have some steering I/O even without the vehicle speed information, but if the output isnt on its own bus, I cant say I'd want to be in that car.
I'd like to try to explain why their microwave design might work, and why the "faraday cage" argument isn't enough: Differential vs. Common-Mode Signals. It's because of all the devices connected to the car's central engine controller.
Lots of old school communications protocols are based on single-ended signaling, where one voltage represents a 0 or 1. This includes RS232, Parallel, and even ISA and PCI slots on your motherboard. However, almost everything new that's outside the computer is based on differential signaling -- reading the differential voltage between two wires. This includes 10/100/1000BaseT ethernet over twisted pair, USB, Firewire, etc.
Here's the key difference: when you get noise coupling onto your signal, whether it's a pulse from the engine ignition coil firing or from this car-stopping microwave device, it tends to be the case that the voltage of *both* of the differential wires is increased by the same amount -- so that when the voltages are subtracted, the effect of the noise cancels out.
However, this exploits the fact that no devices have an infinitely large common-mode range. That is, the average voltage of the differential pair must be within some predefined limit, or your circuit won't work. By putting in a big enough pulse, this microwave device might be able to move charges around on the outside of the car body (which happens to be the ground that most devices hook to) enough to move the voltages significantly. This would cause any devices (think an oxygen sensor or a tachometer) to act as though they were momentarily dead.
Thus, even with differential signaling (which cars already use), it's possible to break things by putting too much common-mode noise on top. See Wikipedia article.
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I'm pretty sure the technology has been available to crafty criminals for some time now. This is an old story, as I remember reading about a homebrew project HERF gun, complete with a video of the guy stopping a car in its tracks, right here on Slashdot eight years ago. Although, the car-stopping video could be a misplaced memory that actually goes with this later story. This is the commercialization of that tech, but (and my memory may be fuzzy here) the one I remember was built with a bank of capacitors from the flash circuits of discarded one-time-use cameras.
BTW, I totally lucked out on this one, since "HERF" is such a rare term. Slashdot search tends to be abysmal for more common words.
True science means that when you re-evaluate the evidence, you re-evaluate your faith.
What's to stop it from killing the engine to the police car?
Directional antennas are not exactly new technology. They work just fine for high-power microwave transmitters.
From TFA it looks like the 100 Hz number comes from the fact that it generates 100 pulses per second. The radio frequency that it operates is "tunable in the 350-1350 MHz range".
I have a vehicle built in 1981 and I know the electronics on it pretty well. The idle controller is the only part with ICs besides the modern stereo and car PC, and I believe it will simply idle rough without that controller functioning. My steering is rack and pinion, my auto transmission computer has nothing more advanced than a transistor; same for the door lock controller. Everything else is vaccum, steel cable, etc... So the date value for vehicles that are impervious to this attack can be set a little further forward.
That is why AMC is no longer making cars..... and no one but you is still driving them
RF on a wire can be shorted directly to the case with no way past due to lead inductance when coaxial feed through capacitors are used. They work well and are used on every microwave oven made. They are on the bottom of the magnitron. The fillimant leads come from the bottom inside a box. They then go through feed through capacitors to keep microwave energy from radiating out the wire.
http://www.freepatentsonline.com/7184256.html
photos here at the bottom of the page..
http://www.samwha.co.th/capacitor.htm
RFI suppression on motors..
http://www.freepatentsonline.com/6307344.html
RFI protection for pacemakers.. PDF alert..
http://www.interferencetechnology.com/ArchivedArticles/medical/Article08web.pdf?regid=
A full filter often includes an inductor. Here is an example. PDF alert..
http://www.dearbornelectronics.com/pdf/EMIFilters.pdf
This shows performance curves of various filters. A 3 DB change is the half power point. To have the same effect on a device 3 DB less sensitive would require double the power. Many of these devices have more than 80 DB attenuation at 10 MHZ and above. This would provide a high degree of immunity as the RFI source would need to be very close and very powerful to overcome the attenuation compared to an unprotected device.
Info on ferrite beads is here...
http://www.google.com/search?hl=en&q=ferrite+bead+RFI
Unlike a capacitor or inductor, a ferrite bead doesn't re-direct the RF current. It converts it to heat, and in the process, attenuates it. A capacitor on a wire, may make a tuned antenna at some frequencies. The ferrite bead is to prevent these tuned peaks by eating the power. Used in combination with a feed-through will prevent a tuned standing wave building on the wire.
A capacitor and inductor simply make a tuned circuit with a venurable frequency. Diodes, discharge tubes, resistors, and ferrite beads prevent a high Q tuned circuit.
http://en.wikipedia.org/wiki/Q_factor
The truth shall set you free!
*sigh* If enough ignorant people misuse a phrase then that misuse becomes 'common usage'. It doesn't make it correct, whatever thefreedictionary.com says. I didn't get my knowledge of grammar from Wikipedia, it was simply the most expedient site to link.
Rampant carbon sequestration destroyed the Dinosaurs' tropical paradise. I'm here to help repair the damage.
Those conditions are within specification for components rated for automotive application. That is why they cost more than the equivalent part for standard consumer applications.
Military spec is even more extreme.
USB doesn't use differential pairs. There are 4 lines - power, ground, transmit, receive. It was designed to replace RS232 and parallel ports - they weren't going for great speeds. I'm actually quite impressed that USB 2.0 works as well as it does as it is a bad design.
But 1394 does use differential pairs. There are either 4 or (more commonly) 6 lines. Power, ground, transmit+, transmit-, receive+, receive-. It is possible to omit the power and ground and thereby only use 4 lines - Sony likes to do this.
It is possible that I'm wrong as I have not done hardware design since the standards were introduced - but I believe I am correct on this one.
I'm fairly certain that any system put into place would likely be focused. The inverse square of the distance works great for a source that is radiated in every direction, but when you focus it, it changes the decay rate. If not, than a flashlight or satellite dish would not any better than an open antenna. Like the difference between a candela and a lumen.
With that in mind it would not be difficult to imagine the beam missing or passing through. Think of how nasty it would be if you lock up cars in front of somebody evading police, or even in front of a persuing cop.
Your car still has electronic ignition. An EMP blast will disable your distributor.
Only cars with point-type distributors are immune.