The radome protective the Multi-Band Check Terminal — a big antenna on an MIT Lincoln Laboratory construction rooftop — is proven illuminated at night time. Credit score: Glen Cooper

Reconfigurable antenna can transmit and obtain indicators over a couple of radio-frequency bands related to army and business packages.

A 38-foot-wide dome-shaped radio antenna enclosure, or radome, sits at the rooftop of an MIT Lincoln Laboratory building. Inside the climate-controlled environment, shielded from the New England weather, a steel structure supports a 20-foot diameter, 20,000-pound satellite communications (SATCOM) antenna. Called the Multi-Band Test Terminal (MBTT), the antenna can rotate 15 degrees per second, completing a single revolution in 24 seconds. At this speed, the MBTT can detect and track satellites in medium and low Earth orbit (medium and low refer to the altitude at which the satellites orbit the Earth).

Prior to the installation of the MBTT in 2017, the laboratory relied on a variety of smaller antennas for SATCOM testing, including OTAKaTT, the Over-the-Air Ka-band Test Terminal. The MBTT is seven times more sensitive compared to the nearly eight-foot diameter OTAKaTT antenna. And unlike its predecessor, the MBTT, as its name suggests, is designed to be easily reconfigured to support multiple radio frequency (RF) bands used for military and commercial satellite SATCOM systems.

“As a much larger, more powerful, and more flexible test asset than OTAKaTT, the MBTT is a game-changer for enabling the development of advanced SATCOM technology,” says Brian Wolf. He is a technical staff member in Lincoln Laboratory’s Advanced Satcom Systems and Operations Group.

Wolf used to be concerned within the set up and preliminary commissioning of the MBTT in 2017. He then led the MBTT thru a rigorous certification procedure with the U.S. Military Area and Missile Protection Command, finished in 2019, demonstrating that the transmit and obtain efficiency of the antenna used to be enough for it to perform at the Wideband International SATCOM (WGS) machine.

A constellation of 10 satellites owned and operated by means of the U.S. Division of Protection, WGS supplies high-data-rate connectivity between more than a few issues on Earth. Since 2019, Wolf has served as predominant investigator on a mission that owns the MBTT, supporting the improvement of the U.S. Area Pressure’s Secure Anti-Jam Tactical SATCOM (PATS) functions.

“PATS is creating the aptitude to ship safe tactical waveform, or PTW, products and services over WGS, in addition to over business transponder satellites and new DoD satellites with devoted onboard PTW processing,” says Wolf.

Multi-Band Test Terminal and Protected Anti-Jam Tactical Satellite Communications Development Team

The Multi-Band Check Terminal and Secure Anti-Jam Tactical satellite tv for pc communications building workforce gathers inside of a radome at MIT Lincoln Laboratory. Credit score: Glen Cooper

As Wolf explains, a waveform is the sign transmitted between two modems when they’re speaking, and PTW is a unique roughly waveform designed to supply extremely safe, jamming-resistant communications. Jamming refers to when communique indicators are interfered with — both by accident by means of pleasant forces (who, for instance, will have misconfigured their SATCOM apparatus and are transmitting on the flawed frequency) or deliberately by means of adversaries searching for to forestall communications. Lincoln Laboratory began creating PTW in 2011, contributing to the preliminary design and machine structure. Within the years since, the laboratory has participated in prototyping and trying out efforts to lend a hand business mature modems for processing the waveform.

“Our prototype PTW modems were fielded to business websites in every single place the rustic so distributors can take a look at towards them as they broaden PTW methods that might be deployed in the true global,” says Wolf. The preliminary running capacity for PTW products and services over WGS is predicted for 2024.

Team of workers firstly conceived the MBTT as a take a look at asset for PTW. Without delay beneath the MBTT is a PTW building lab, the place researchers can run connections without delay to the antenna to accomplish PTW trying out.

Installing New Antenna Feed MBTT

Lincoln Laboratory technician John Boughner (foreground) assists two Normal Dynamics engineers in putting in a brand new antenna feed throughout the preliminary MBTT set up. Credit score: Glen Cooper

Some of the design targets for PTW is the versatility to perform on a variety of RF bands related to satellite tv for pc communications. That implies researchers want a solution to take a look at PTW on those bands. The MBTT used to be designed to fortify 4 frequently used bands for SATCOM that span frequencies from 7 GHz to 46 GHz: X, Ku, Ka, and Q. Then again, the MBTT may also be tailored someday to fortify different bands during the design of extra antenna feeds, the apparatus connecting the antenna to the RF transmitter and receiver.

To modify between the other supported RF bands, the MBTT should be reconfigured with a brand new antenna feed, which emits indicators onto and collects indicators from the antenna dish, and RF processing elements. When now not in use, antenna feeds and different RF elements are saved within the MBTT command middle, situated beneath the primary platform of the antenna. The feeds are available in a spread of sizes, with the most important registering six ft in period and weighing just about 200 kilos.

To change out one feed for some other, a crane within the radome is used to boost up, unbolt, and take away the outdated feed; a 2d crane then lifts the brand new feed up into position. Now not handiest does the feed at the entrance of the antenna wish to get replaced, however the entire RF processing elements at the again of the antenna — such because the high-power amplifier for reinforcing satellite tv for pc indicators and the downconverter for changing RF indicators to a decrease frequency extra appropriate for virtual processing — additionally wish to get replaced. A workforce of professional technicians can whole this procedure in 4 to 6 hours. Ahead of scientists can run any exams, the technicians should calibrate the brand new feed to verify it’s running correctly. Generally, they level the antenna onto a satellite tv for pc identified to broadcast at a selected frequency and accumulate obtain measurements, and level the antenna directly up into loose house to assemble transmission measurements.

Since its set up, the MBTT has supported a variety of exams and experiments involving PTW. All through the Secure Tactical Carrier Box Demonstration, a PTW modem prototyping effort from 2015 to 2020, the laboratory carried out exams over a number of satellites, together with the EchoStar 9 business satellite tv for pc (which gives broadband SATCOM products and services, together with satellite tv for pc TV, around the nation) and DoD-operated WGS satellites.

In 2021, the laboratory used its PTW modem prototype because the terminal modem to habits an over-the-air take a look at of the Secure Tactical Undertaking Carrier — a ground-based PTW processing platform Boeing is creating underneath the PATS program — with the Inmarsat-5 satellite tv for pc. The laboratory once more used Inmarsat-5 to check a prototype undertaking control and keep an eye on machine for enabling resilient, uninterrupted SATCOM. In those exams, the PTW modem prototype, flying onboard a 737 airplane, communicated thru Inmarsat-5 again to the MBTT.

“Inmarsat-5 supplies an army Ka-band transponded provider appropriate for PTW, in addition to a business Ka-band provider known as International Xpress,” explains Wolf. “During the flight exams, we have been in a position to exhibit resilient end-to-end community connections throughout a couple of SATCOM paths, together with PTW on army Ka-band and a business SATCOM provider. This fashion, if one satellite tv for pc communications hyperlink isn’t running smartly — perhaps it’s congested with too many customers and bandwidth isn’t enough, or any person is attempting to intrude with it — you’ll transfer to the backup secondary hyperlink.” 

In some other 2021 demonstration, the laboratory hired the MBTT as a supply of modeled interference to check PTW over O3b, a medium-Earth-orbit satellite tv for pc constellation owned by means of the corporate SES. As Wolf explains, SES supplied a lot of their very own terminal antenna apparatus, so, on this case, the MBTT used to be useful as a take a look at tool to simulate more than a few varieties of interference. Those interferences ranged from misconfigured customers transmitting on the flawed frequencies to simulation of improved jamming methods that can be deployed by means of different realms.

The MBTT may be supporting world outreach efforts led by means of Area Methods Command, a part of the U.S. Area Pressure, to increase the PATS capacity to world companions. In 2020, the laboratory used the MBTT to exhibit PTW at X-band over SkyNet 5C, an army communications satellite tv for pc offering products and services to the British Armed Forces and coalition North Atlantic Treaty Group forces.

“Our position is available in when a global spouse says, ‘PTW is superb, however will it paintings on my satellite tv for pc or on my terminal antenna?’” explains Wolf. “The SkyNet take a look at used to be our first the usage of PTW over X-band.”

Hooked up by the use of fiber-optic hyperlinks to investigate amenities throughout Lincoln Laboratory, the MBTT has additionally supported non-PTW trying out. Team of workers have examined new sign processing generation to suppress or take away interference from jammers, new ways for sign detection and geolocation, and new tactics of connecting PTW customers to different Division of Protection methods.  

Within the years forward, the laboratory seems ahead to appearing extra trying out with extra consumer communities within the Division of Protection. As PTW reaches operational adulthood, the MBTT, as a reference terminal, may just fortify trying out of distributors’ methods. And as PTS satellites with onboard PTW processing achieve orbit, the MBTT may just give a contribution to early on-orbit checkout, dimension, and characterization.

“It’s a thrilling time to be concerned on this effort, as distributors are creating actual SATCOM methods in response to the ideas, prototypes, and architectures we’ve evolved,” says Wolf.

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