Technology Update — Amplifiers Keeping Pace with Industry Changes

The satellite industry’s rapid rollout of high-bandwidth constellations is creating new performance demands on the amplifier market. That reality, along with recent and expected launches of a number of Low and Medium Earth Orbit (LEO and MEO) constellations, has put pressure on manufacturers to find ways to best serve the High-Throughput Satellite (HTS) sector. Ka-band will continue to dominate amplifier requirements, whether it’s the GEO HTS systems such as Jupiter and WildBlue/ViaSat, or the new brand of LEO and MEO HTS systems, which need a cost-efficient way to connect the multitude of gateways from their Non-Geosynchronous (NGSO) constellations. Ultimately, satellites today continue to deploy at higher frequencies, which is pushing the industry to find new ways to keep up, with an eye toward reliability and efficiency.

“The main technology challenges have been for many years and continue to be in making our amplifiers smaller, lighter and more cost effective, without sacrificing reliability, quality, interfaces or interoperability,” notes Gerard Charpentier, VP of business development for CPI International, a major manufacturer of both Gallium Nitride (GaN) amplifiers as well as traveling wave tube and klystron amplifiers.

The Game Changer: GaN

Emerging in the early 2000s before becoming a commercial technology around 2010, GaN has emerged as a dominant solid-state technology, often replacing its predecessor, Gallium Arsenide (GaAs). “Everyone at this point recognizes that any product from C-band and up will be GaN-based,” says Jim Rosenberg, CTO and co-founder of Wavestream, a pioneer in power-combining technology and GaN at Ka-band. “We have reached the point where there is no choice because the semiconductor manufacturers are discontinuing GaAs product at a really amazing clip.”

GaN amplifiers handle much higher temperatures and voltages than GaAs transistors. The technology originated through government-funded R&D, and found its first commercial validation in the lighting industry through the replacement of electrical bulbs with LEDs, recalls Cristi Damian, VP of business development for Advantech Wireless, one of the first manufacturers to develop GaN amplifiers. Damian says Advantech was looking to get more power from its amplifiers after the dramatic jump in broadband requirements that came with the broadcast television market moving from standard definition to high-definition video broadcasting.

“Every time you double the bandwidth requirement you need to double the power,” says Damian. “We knew we had to come up with something much more energy efficient with more linearity, which led us to do deep research into gallium nitride.”

Today, through significant effort by satellite amplifier pioneers, solid-state GaN amplifiers are fast becoming a commercial mainstay.

“GaN is going to be the future workhorse of the industry — it is high-power, more efficient and can tolerate higher temperatures,” notes Joe Przygoda, director of business development at Paradise Datacom, the satcom division of Teledyne Microwave Solutions.

High Power Still the Domain of Tubes

While no one in satellites today can deny GaN’s appeal in delivering high output in smaller packages, no technology is perfect. Each has technical limits that providers have to weigh when advising clients on the best amplifier option.

Heidi Thelander, senior director of business development for Comtech Xicom Technology, says that while all of her company’s newer solid state products are built with gallium nitride because of the higher power and greater efficiency gains, ”the one thing you have to be careful with GaN is linearity — it’s quite different from GaAs. It’s very important that operators carefully specify the linearity of their requirements, not just choose a saturated output power.”

Thelander and other experts say that Traveling-Wave-Tube Amplifiers (TWTAs) still are the power option of choice for ultra-high broadband applications using Ka-band in GEO orbit, where a user needs both very high power and wide bandwidth between 3 and 5 GHz. “For 1-2GHz and tens of watts, you use solid-state. In between is a gray area where there is a power level tradeoff between TWTA and SSPA,” Thelander explains.

“In space, tubes are still the right answer because their reliability is so high. On the ground they are a nice answer when efficiency is important and you don’t care about weight and size,” notes Theresa Brunasso, president of D&S Microwave Consulting, a firm focused on the antenna and subsystem satcom sector. Brunasso began her RF career working on a research fellowship for the U.S. Air Force focused on augmenting tube technology for electronic warfare and radar applications. “At the time, tubes were considered an old technology, yet here I am nearing retirement age and companies are still selling tubes like crazy — so the news of their demise, as Mark Twain would say, ‘was greatly exaggerated,’” she says.

Wavestream’s Rosenberg agrees, noting that “The place where tubes do better is at very high power levels and very high bandwidths … though the solid state technology will continue to chew away at the bottom end of the tube market.”

But, when pressed to look further out into the future, several in the amplifier market seemed to place their bet on solid-state as the winner long term. “Eventually solid state technologies will catch up,” predicts Charpentier.

Price Pressure from LEO/MEO

“Solid state is a fairly likely winner just because of the scale in it. Also, in terms of price, solid state has a much steeper price curve when you change power compared with TWTAs, where the price curve is flatter,” Thelander says. “If you need more power with a TWT, usually you pay a little more. But if you need less, you don’t save all that much. For SSPAs, if you need a lot more power, you will pay a lot more. But if you need a lot less, it can cost a lot less.”

Solid state is easier to scale because as a semiconductor, it can be replicated hundreds or thousands of times on wafers much more easily (and cost effectively) than doing the same thing with a tube.

LEO constellations also require a much larger volume of antennas and gateways compared with a GEO satellite, and amplifier providers have to find a way to offer lower priced equipment to make it affordable to these customers.

Thelander says no matter what happens with the LEO/MEO market, “there is massive infrastructure using GEO that is not going to go away.” One thing is clear: as industry pricing is cut to serve new markets in the LEO/MEO sector, it may put pricing pressure on the GEO business.

“The GEO folks will have to be more cost effective than they have been in the past to compete. And it might affect their investment levels. For the most part, companies that do satcom are going to use both,” Thelander predicts.

Growth Markets Eyed

Amplifier industry leaders shared where they see the biggest market opportunities for their business with virtually all universally pointing to the growth potential for the Ka-band market. Montreal-based Advantech Wireless says demand for their amplifier products remains high to the point that they need to build a new facility that will double their production capacity when it is completed sometime later this year. Another Canadian satellite hardware player, Norsat, which specializes in providing portable terminals, amplifiers, and Low Noise Block downconverters (LNBs), says its amplifier portfolio was recently enhanced through an acquisition, and last December, they launched a Ka-band dual-band solid-state amplifier, the latest in its Atom product family.

“Our Atom product line is one of the most compact, power-efficient, and light weight product in the industry. Norsat’s traditional strength in providing customizations such as custom frequencies, custom form factors, and military certifications are also supported in the product line,” says Amiee Chan, Norsat’s CEO.

She indicates that Norsat plans to continue to grow its amplifier capabilities through a combination of internal R&D and strategic acquisitions. “We are very strong financially and hope to leverage this into multiple acquisitions over the next few years to complement our existing development efforts, “ Chan says.

Innovations on the Horizon

Many providers are looking to their own engineering R&D and system design capabilities to bring greater capability to their amplifiers.

“One thing that Xicom has as an advantage over some of the other companies in our space is that we have our own internal chip and wire capability for our solid state. That has enabled us to do a little bit better when it comes to size, weight, efficiency and power draw, and we can use the best bare die available, enabling us to be first to market with new technology when others must wait for packaged parts,” says Thelander.

Advantech sees major gains through tighter integration between the amplifier and other components. “We are looking at designing fully integrated terminals with the modem built into the amplifier and everything closely integrated with the antenna, so you should be able to plug your laptop with an IP port and then directly into that power amplifier modem antenna system and run the satellite link without actually a need to have all this expertise,” says Damian. “We also are working on the second generation of GaN, which will improve linearity and power efficiency by around 50 to 60 percent. This is our focus — on one side, trying to integrate as much as possible into the amplifier, making the amplifier the base of a complete subsystem, and increasing the power and the linearity because in the end, power is what matters.”

CPI’s Charpentier says in addition to focusing on new bands — especially Ka-band — his company has introduced a number of patented technologies to increase the life of travelling wave tube technology.

“That’s one of the challenges that traveling wave tube technology has — it’s a limited life product that is consumable. We are introducing technologies that help increase the life and the reliability of that product, and provide our overall platform of technology with much more solid footing going forward,” he says.

CPI, echoing comments from other firms, is looking at the potential of the V-band market, balancing “what the market will respond to and what is viable from a technical and economic standpoint,” Charpentier adds. “We are looking at airborne applications even higher than V-band in our R&D scope at this point of time.” (See sidebar for more about the V-band opportunity.)

Paradise Datacom’s major R&D focus is on high-power Ka-band. “We’re looking to give power levels in solid state that are traditionally tube markets right now to give people an alternative for high-power Ka-band and solid state amplifiers,” says Przygoda, explaining that his group currently has a 100-watt solid state unit available. “We’ll have 200 watts later this year followed quickly by 400 watts,” he says.

The Coming of V-band

As Ka-band continues to dominate the next wave of satellite rollouts, operators and amplifier players are looking for how to address the bandwidth needs and coverage holes caused by HTS spot beam architecture.

Dave Rehbehn, VP of the international division at Hughes Network Systems, which has well over one million subscribers in North America, virtually all on Ka capacity, says that the attraction of V-band and even Q-band frequencies lies in the potential for more spectrum that can be used to increase the capacity of high throughput satellites.

“We like V-band and Q-band because spectrum, and more spectrum than we have today, is important as we increase the capacity of our HTS designs. Higher capacity will generally translate into better cost efficiencies and thus the ability to provide more effective services. However, using Q and V bands does present a number of challenges including the fact that the RF electronics for these bands have not yet been commercialized, but we are confident that this will be achieved over time. The satellite industry needs more spectrum and Q and V bands are good candidates for this additional spectrum.”

Rehbehn admits that one downside to these bands is the higher rain fade. “We’ll have to deal with that through a series of techniques including RF diversity, adaptive links and other rain fade mitigation techniques,” he says.

Transitioning to V-band would enable companies like Hughes to overlay Ka-band and V-band capacity, thereby enabling more flexibility for laying out the coverage for a given satellite design.

According to Thelander, there’s been a big V-band development push at Comtech Xicom Technology. “There are definitely space V-band amplifiers being developed currently and the technology for the ground side is getting close. I think within the next year you’ll see more about V-band for the uplink,” she says. VS