Possible future sharing of the band will limit technical parameters, at least for now.
The FCC has authorized radars for the detection of “foreign object debris” on runways – FOD, in airport-speak. Typical FOD includes parts that fell off prior aircraft, misplaced tools, equipment and supplies, rocks and pavement fragments, luggage, and wildlife. (So that’s what happened to our missing suitcase.)
The Commission proposed to open the 78-81 GHz band to FOD-detecting radar two years ago. This frequency band has long been allocated for radar, along with radio astronomy and a few other uses, but had not been listed in the FCC rules as being available for non-federal radiolocation operations (such as FOD detection technology). Now it is.
The impetus for this change was a proposal from a company called Trex Enterprises Corporation, which had developed FOD-detecting radar for the 78-81 GHz band. Three years ago Trex requested a rule change to permit use of its technology. The FCC asked for comments on whether the rules should be amended to expressly permit such use, and if so, whether on a licensed or unlicensed basis. It also asked whether radar use of the band should be limited to FOD detection. The FCC granted Trex a waiver to deploy its equipment pending the rulemaking.
The answers: the 78-81 GHz will be available for radiolocation, but for FOD only, and only on a licensed basis. (In a separate proceeding the FCC will continue to consider whether to authorize unlicensed radar operations for other applications in a number of bands, including this band.)
Historically, the FCC has avoided technical rules for most licensed radar systems, and instead has evaluated applications on an individual, case-by-case basis. It plans to continue that approach for FOD-detection radar. However, the FCC warns that – at least until it resolves other uses of the band – it will “consider” the technical limitations it imposed on the initial Trex waiver granted in 2011. Details of the Trex specs are at paragraph 18 of this link. Applications for certification that meet these standards, or are more conservative, should go through smoothly. Applications showing higher levels of interference potential will be evaluated on a case-by-case basis. The FCC suggests that manufacturers confer with the FCC lab; we agree, but recommend that you go through your test lab or TCB.
(Note, though, that a nearby band at 76-77 GHz is authorized for unlicensed FOD radar at respectable power levels. Systems that meet the unlicensed technical requirements will likely pass the equipment certification process more quickly, and with certification in hand, can then be placed in operation without licensing delays.)
To protect vehicle radars, licensed FOD radars are not permitted to illuminate public roadways. On the other hand, operators will not be required to prior-coordinate with radio astronomy facilities, as Trex had originally proposed. The FCC, however, will process license applications through a federal body that reviews them for compatibility with radio astronomy observations, among other federal spectrum interests.
The rules will take effect 30 days after publication in the Federal Register, which will probably happen in a month or so. Check back here for updates.
After that, we will all rest a little easier as the aircraft accelerates for take-off. Except for the crying baby right behind us.