AEEC Ku/Ka Satcom Subcommittee - Sep 2019 Meeting Report

The SAE-ITC AEEC Ku/Ka Satcom Subcommittee met at the Boeing Integrated Aircraft Systems Lab (IASL) for three days of deliberations revolving around aeronautical satellite communications.

Topics discussed included:

• Smaller form-factor antenna
• Thermal management of solid-state antennas
• Replaceable/Multiple Modems
• Standard Ka/Ku-band Antenna
• Enhanced Terminal Security
• Enhanced Network Security
• IF/RF over Fiber (modem to antenna)
• Baseband over Fiber (modem to antenna)
• Additional radios under the radome

Companies in attendance included: 

• Delta, United
• Boeing, Airbus, Mitsubishi
• Global Eagle, Gogo, Inmarsat, OneWeb, Panasonic, Viasat
• Collins Aerospace, Comtech, Honeywell, Kymeta, SCI, ThinKom
• Astronics, Carlisle, Saint Gobain
• Satcom.Guru

With the recent release of supplement 3 to ARINC 791 part 1 which included a mechanically steerable tail-mount antenna, ARINC 792 is now open for supplement 1 to include a new smaller-form factor antenna. While ARINC 792 lug locations and cutouts were derived to reuse as much of the ARINC 791 structural definitions, a smaller form factor does not easily fit that mold. The suppliers were encouraged to propose a clean-sheet design without regard to ARINC 791 or 792 layouts. The smaller antenna is designed for non-GEO applications with limited scan angles that would be suitable for regional jet fuselage mount. The final layout will follow the proposed layout with any adjustments that can drive it closer to the other layout locations.

Recessed conformal antennas are being explored, but principally the interest level is highest in business jet community. Doors and windows are evident - a cavity can be created, but there are weight offsets in the structural reinforcements. Frame spacing creates smaller pockets. Larger pockets break the frames.

Boundary layer allows standing one to two inches above the fuselage without significant drag penalty, which offers some life to antennas mounted on top.

Accumulated heat and moisture can be a challenge if the mounting resembles a sealed bathtub.

The use of standard lugs as prescribed in ARINC 791/792 remains the preference for regional and air transport, for the foreseeable future.

Thermal management of solid-state flat panel antennas was a hot discussion. Concerns are raised around aircraft skin limitations and the need to constrain the cooling problem to the outside antenna equipment. 

The common-modem ad-hoc working group met as a plenary session. The objectives of easily replacing a modem and hosting two modems while constrained to the rack space set-aside for the 4 MCU modman is only met by making the manager a stand-alone 2 MCU enclosure and the allowing one or more 1 MCU modem enclosures. A 2+1+1 combination provides for two modems within a 4 MCU space. Cooling and available volume are not sufficient for all suppliers today, but there were suppliers that felt they could accommodate this architecture. A 1 MCU enclosure suffers under vibration.

A card-level modem standard has not been proposed by any supplier.

A loadable software modem is evident in the marketplace. The suppliers are asked to propose an API with some means to assess the suitability of a given software defined radio to meet the waveform or other performance requirements for a given modem design.  The co-location of the modem inside the antenna has already moved some modems to adapt to loadable software implementations.

A standard Ka-band and a standard Ku-band antenna subsystem definition is proposed. The objective is to ensure any antenna installed can be used with any available satellite network. This includes transmit and receive radio performance plus regulatory compliance, beam agility, and any other unique beam characteristics.  The form and fit of the antennas is already defined; the additional criterial will be captured in an appendix to 791 Part 2 supplement 2, which is open for revision.

A proposal to emphasize the use of cryptography to enhance authorization to access satcom maintenance terminal was received, with action planned to review and update the materials in ARINC 791 Part 2.

The Network Infrastructure and Security (NIS) subcommittee was meeting at the same time, but in Chicago, with Project Paper 848 under final review. The project paper network security architecture was reviewed, with suppliers asked to comment on the needed Quality of Service (QoS) levels for each domain of traffic. 

The modem to antenna signal interface is conducted using two IF coaxial cables that can run over 100 feet. With the desire to support phased array antennas and with more than one beam, the subcommittee is looking to replace the coaxial interface with a digital interface. While both copper and fiber may be suitable, fiber offers a number of attractive benefits, notably the ability to include many fibers in the space of one coax, the benefits of non-conductive media, weight, and higher bandwidth. 

While a digital interface is the future of modem interfaces, the subcommittee learned of means to use fiber to communicate analog IF or RF. This feature favors single-mode fiber, but that does not limit its use for digital communication.  The pressure bulkhead interface remains an area of interest, with one option to include a fiber-connector pass through, the other approach to just pass the fiber through a grommet with potted sealing. The IF power level can be adjusted to allow for linear power control. 

The use of other radios under the Ku/Ka satcom radome can leverage the protected outside location, power and data interfaces. The use of fiber allows easy support for additional radio interfaces. 5G cellular or AeroMACs on the ground or an L-band satcom radio are candidates.

More info about the subcommittee can be found here.

Stay tuned!

Peter Lemme

peter @ satcom.guru

Follow me on twitter: @Satcom_Guru

Copyright 2019 satcom.guru All Rights Reserved

Peter Lemme has been a leader in avionics engineering for 38 years. He offers independent consulting services largely focused on avionics and L, Ku, and Ka band satellite communications to aircraft. Peter chaired the SAE-ITC AEEC Ku/Ka-band satcom subcommittee for more than ten years, developing ARINC 791 and 792 characteristics, and continues as a member. He contributes to the Network Infrastructure and Interfaces (NIS) subcommittee developing Project Paper 848, standard for Media Independent Secure Offboard Network.

Peter was Boeing avionics supervisor for 767 and 747-400 data link recording, data link reporting, and satellite communications. He was an FAA designated engineering representative (DER) for ACARS, satellite communications, DFDAU, DFDR, ACMS and printers. Peter was lead engineer for Thrust Management System (757, 767, 747-400), also supervisor for satellite communications for 777, and was manager of terminal-area projects (GLS, MLS, enhanced vision).

An instrument-rated private pilot, single engine land and sea, Peter has enjoyed perspectives from both operating and designing airplanes. Hundreds of hours of flight test analysis and thousands of hours in simulators have given him an appreciation for the many aspects that drive aviation; whether tandem complexity, policy, human, or technical; and the difficulties and challenges to achieving success.