M-1126-(US-DOD)
Space-constrained platforms like armoured vehicles could benefit from the small antenna sizes offered by MMW radios, although several technological hurdles must be overcome before these communications systems enter widespread use with the military.

L3Harris has told Armada International that it is forging ahead with the development of Millimetre Wave communications technology.

MMW Frequencies

Millimetre Wave (MMW) frequencies, so called because of the short distance of their wavelengths, inhabit the radio portion of the electromagnetic spectrum from frequencies of 30 gigahertz/GHz up to 300GHz. Such short wavelengths measure between 9.9mm for 30GHz down to 0.9mm for 300GHz.

MMW frequencies boast several benefits compared to conventional Very High Frequency and Ultra High Frequency (V/UHF: 30 megahertz/MHz to three gigahertz) wavebands traditionally used for tactical communications.

Security

Richard Gallindez, a systems engineer with L3Harris, says that MMW frequencies provide “less congested bands with greater bandwidth allocations than currently available in lower bands.” As such MMW frequencies are far less cluttered that their V/UHF counterparts.

From a tactical communications perspective this provides more frequencies which transmissions can ‘hop’ over improving transmission security.

Antennas

Regarding the physical layer MMW radios can use very small antennas. Antennas are typically one quarter the size of the wavelength they carry, hence an MMW radio using frequencies of 30GHz could have an antenna as small as 2.5mm.

The attractions for space-constrained platforms and troops using MMW radios are obvious. As Mr. Gallindez notes, this results in “more integration opportunities in different platforms.

Trade-offs

Yet MMW has disadvantages. Transmissions can suffer attenuation by which particles in the atmosphere such as water droplets impede range by absorbing some of the transmission’s energy.

Secondly, MMW transmissions have very narrow beam widths requiring antennas to be very closely aligned if one is to receive transmissions from another. With such small-sized antennas one can get the measure of how difficult this becomes in practice.

Nonetheless advances in precise antenna alignment technology, as witnessed in the mobile satellite communications domain; could help in this regard as could active electronically scanned arrays which electronically ‘steer’ transmission to ensure they reach the receiving antenna.

Despite the limited range of MMW transmissions which can be as low as six kilometres (3.7 miles) they could provide a good mechanism to handle high volumes of data across line-of-sight ranges on the battlefield.

Future of MMW

The widescale uptake of MMW frequencies for communications is still someway off. Mr. Gallindez says that this results from the paucity of RF (Radio Frequency) products handling such wavebands. This increases design times and hence costs. This may well change in the future.

MMW frequencies are being mooted for fifth-generation cellular networks and the uptake of MMW technology in the civilian sector could have a direct downstream benefit for the military customer.

For the time being the military will continue its reliance on V/UHF for tactical communications: “Currently many communication requirements can be met without having to resort to MMW frequencies,” says Mr. Gallindez.

“Traditionally as frequency bands have become crowded the military has moved up in frequency,” adding that as congestion increases elsewhere in the radio spectrum, and as demands for data carriage show no signs of abating, both factors could become drivers for the increased uptake of MMW communications in the future.

by Dr. Thomas Withington