This item is admittedly obscure, even by our standards. But we strive to meet the needs of even our most specialized readers.
Since 1996, the FCC has allowed vehicle-mounted radars in the 76-77 GHz band. This band is well up into the “nosebleed” region of the spectrum, approaching the highest frequencies ever authorized. If this band were a sound, only very small dogs would be able to hear it.
The radars up there help to guide the automatic braking systems offered in some high-end cars. They are allowed to emit considerable power – up to 68 watts –when the vehicle is in motion, to achieve adequate range and precision. Greatly reduced power limits apply when the vehicle is stopped, as at a traffic light, in order to protect passing pedestrians from excessive radio-frequency exposure.
A company called Era Systems has asked the FCC for a waiver to allow stationary (non-vehicle) use of radars in this band. Era hopes to install up to ten units on structures at the Atlanta airport. They will be used track the locations of aircraft and vehicles on the ground in ramp and gate areas for “airport management purposes,” possibly a euphemism for keeping things from running into each other.
The requested power is 55 dBm (316 watts), somewhat higher than the maximum for vehicle radars in motion, and much higher than the one-fifth watt limit for stationary vehicles. Era proposes to address the radio-frequency exposure problem by blocking radar emissions towards roads open to the public. Its system uses the same radar modulations as the vehicle units do, and so (according to Era) should not interfere with vehicle radars even if they could see its signals.
The FCC public notice is here; Era’s request is here. Comments are due on May 6, and reply comments on May 18, in docket ET Docket No. 09-55.