US military boffins are preparing highly sophisticated technical defences against the dreaded electromagnetic pulse bomb, a weapon which has long been anticipated but never successfully built.

We know about the counter-electropulse defence technology because the company which will develop it - HRL Labs of Malibu, California - announced their contract win yesterday. The programme is referred to by the Pentagon as Electromagnetic Pulse-tolerant Microwave Receiver Front-end, or EMPiRe*.

The idea of the attacking e-weapon is that it would release a hugely powerful radio-frequency or microwave pulse. In the same way that a normal, very weak emission is picked up by a radio or radar antenna to produce a measurable current, the weapons-grade pulse would induce a vicious surge in exposed electronic equipment - potentially frying it for good, or at least shutting it down for a bit.

Such weapons, it's often thought, might be driven by explosions or other rapid processes rather than normal batteries or generators, because of the need to release large amounts of power very fast: hence pulse bomb rather than pulse raygun etc.

Normally, the defence against this sort of thing is simple. You merely enclose your electronics in a conductive metallic Faraday cage, perhaps fashioned of trusty tinfoil if nothing better comes to hand. The problems of generating and focusing powerful electropulses are already enormous - so enormous, in fact, that decades of secretive US effort have failed to produce any working EMP weapons**. Producing an EMP which has range, focus and power sufficient to sizzle its way through a decent Faraday cage is just not on.

But there are problems here. Some kinds of electronics are no use if you wrap them up in a radio-proof box. In particular, a microwave receiver in a communications or radar set needs to pick up RF radiation - but if you let it, an EMP bomb or whatever might fry the electronics of the connected system.

HRL's proposed solution is to isolate the "front end" of the receiver, which will "sense incoming electrical fields through a high-performance microwave photonic link". The new HRL front end will pass information to the signal processors optically, meaning that no electric surge through into the protected back end is possible.

"The thermal effects of a high-energy attack will be insignificant because our sensor head absorbs negligible radio-frequency power," says HRL Senior Scientist Dr James Schaffner.

HRL's research is funded by DARPA, the Pentagon's elite group of paradigm-punishing, technonoclastic nerd-wranglers. DARPA's goal often appears to the outsider to be that of rendering America's latest military tech obsolete well before it actually comes into service. In this case the Pentagon brainboxes may well excel themselves, as even the more ambitious ongoing US pulse-bomb efforts only see themselves starting a useful weapons programme from 2012. (To be fair, DARPA might be more worried about EMPs from nukes.)

Needless to say, some who already prefer to be on the safe side regarding Faraday Cage protective headgear will see this instead as solid evidence that the dreaded, functional pulse bomb - or even EMP ray-cannon - is already out there. ®

Bootnotes

*This breaks every rule of Acronym Club. We suggest Barrier Interposed Terawatt Countermeasures against High-powered Specialist Lightning Attack Pulses.

**Other than nuclear bombs, which produce a substantial EMP as a side effect when they go off. It has been suggested that if you wanted to EMP an enemy city - so knocking out all its comms and electronics, as opposed to leaving it a glowing glassy crater - you might touch off a suitable nuke above it in the extreme upper reaches of the atmosphere. Evil Sean Bean was fixing to do this to London in the Bond flick Goldeneye, using an eponymous Russkie space nuke pulse device hacked by Bean's henchmen from their thinly-disguised shopping centre base, apparently situated beneath the Arecibo radar telescope.