III-Vs are Propelling Cable TV Services to a New Level

An Angel Business Communications publication June 2010 Volume 16 Number 4

Future researchIII-Vs to provide the key

to high speed mobility

Happy anniversary25 years anniversary for two leading GaAs chipmakers

MarketplaceStocks soar forcompoundsemiconductorcompanies

From lab to fabNitride LEDs ready totake their place in themarket place

Larger lampsGreater surface arealamps could be the key to DUV LEDs

Phase separationElectroluminescenceexposes AllnGaN phaseseparation

Plane for green lasersSemi polar planediscovered to helpproduction

Square lasersBenefit for PICs

Front Cover CS vFinalJC 1/6/10 16:33 Page 1

microelectronics ! technology

III-Vs start propelling cableservices to a new levelGaAs and GaN technologies can spur high-quality delivery of advanced video, dataand telephony services to the home, says TriQuint’s Chris Day.

L ike all consumer-driven services, the cableindustry always needs to find new ways to

generate cash. Higher sales can come from existingservices, but long-term success hinges on investment inthe new technologies that are starting to appear, such ashigh-definition channels, new services, “3-D TV”, andvideo on demand.

Each of these adds a layer of complexity, and demandsbetter performance from distribution resources alongsidegreater bandwidth and superior use of the bandwidth thatexists today.

At TriQuint we believe that compound semiconductortechnologies, principally those utilizing GaAs and GaN,will be essential ingredients in products that can meetthese challenges. These III-Vs combine higher efficiencywith greater linearity and a broader bandwidth, attributesthat cable system designers crave, and deployment ofthese superior technologies will have a positive impactthroughout cable systems, from headends to customerpremises.

One way to understand where technology stands today isto see where we’ve come from. There’s no doubt that the

Semiconductor technologies like GaAs and GaN are enablingCATV system operators to offer competitive ‘triple play’ services

like high-definition TV (HDTV), Video on Demand (VOD) as wellas voice and broadband data communications

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early days of television were wondrous for some, but formany the experience was marred by poor reception. Areasthat were not in a line-of-sight path to the transmittingantenna had to make do with weak, snowy pictures.Viewers resorted to erecting tall towers and addingpreamplifiers, which usually helped, but often not all thatmuch.

To address this weakness television pioneers, whosenames have been lost to all but fervent followers ofbroadcast technology, created the first communityantenna television (CATV) systems. The acronym CATVwas apt as these systems allowed a community to achievereliable reception of local stations on at least a fewchannels. Often these included major network channelsand perhaps a public broadcast station.

CATV was enabled by finding the highest point in oraround the community, erecting high-gain directionalantennas, and pointing them at broadcast towers manymiles away. Channels were aggregated at this “head-end”, and distributed via coaxial cable to the community’sresidents. Although results varied, they were invariablybetter than those achieved by individual viewers. Tomaintain an adequate signal throughout the system,distribution amplifiers were periodically spaced along thepath of the cable “plant”. They initially employed vacuumtubes that degraded the signal with high levels of second-order distortion, but this was remedied with the bipolartransistors introduced in the 1960s.

The tremendous benefits provided by CATV systemsresulted in explosive growth, and the “community” antenna

television concept expanded to cover entire metropolitanareas, states, regions, and ultimately into today’s MultipleSystem Operators (MSOs) that provide standard- andhigh-definition television services throughout NorthAmerica. Similar models were followed across the globe,although there was a notable difference. Residents ofEurope and many other countries were initially restrictedto broadcasts by state-operated monopolies thatinaugurated television service, and these viewers had towait to embrace the competitive service offerings thatthey enjoy today.

Growth of the cable TV service was achieved throughexponential advances in every key technology, from RFdevices through to the introduction of delivery via fiberoptic cables, which now form the latest generation ofhybrid fiber coax (HFC) networks. Significant additionalcontributions include signal-processing technology andimproved devices, better software, advanced modulationschemes, and linearization techniques. Today, cablesystems are flexible enough to provide over 80 channelsof legacy analog television programming alongside digitaland high-definition services, video-on-demand services,high-speed data service, and packetized telephony…andmore is on the way.

Mixing old and newFrom a technical perspective, cable systems are incrediblydiverse. The plant of a typical system contains decades-old semiconductor technology sitting alongside itsleading-edge brethren. However, it is possible to combineanalog, digital, RF, microwave, and lightwavetechnologies, and make them all work together more orless seamlessly to provide today’s high quality of service.

This approach is employed in cable hybrid amplifiers, thelong-established staple of every cable distribution system.This device can be seen on utility poles everywhere,boosting signal levels throughout the system whilemaintaining high levels of linearity. While older siliconbipolar transistor amplifiers are still in service, the cablenetworks they support simultaneously employ fiber optictechnology, advanced digital modulation schemes, andassorted other technologies that are at or near the stateof the art. Not surprisingly, streamlining this technologicalalphabet soup is essential if the cable industry is toaddress three key objectives: meeting expectations setout by shareholders and investors; fending off competingnetwork technologies; and wooing legions of consumershankering after novelties such as 3-D TV.

In a larger context, the MSOs primary challenge is todeliver the greatest variety of entertainment choices withthe highest performance, at the lowest cost, to the

TAT6254C:FTTH / RFoGlow noiseamplifier forCATV receivers/ triplexers.AGC tomaintain +19dBmV/choutput (+23dBmV / highoutput mode).Ensures videoquality / ease ofdesign

Gallium Arsenide (GaAs) wafer processing in TriQuint’s Hillsboro, Oregon 150mm facility




greatest number of subscribers. The most effective way todo this is to reduce or eliminate components in thesystem. A classic example of implementing this advicewas the introduction of the so-called “power doubler” inthe mid 1980s. The power doubler reduced the need formany trunk and ‘bridger’ amplifiers and line extenderamplifiers.

The most pervasive mixed technology in the network isemployed in fiber optic distribution, which was introducedin the 1980s against a backdrop of a coax-only domain.The appeal of this lightwave technology is its far lowerdistribution losses compared to coaxial cables, coupledwith near immunity to interference. And as this technologyhas evolved, the number of amplifiers required to cover agiven area has diminished.

The upshot has been the removal of costly componentsfrom the distribution system, leading to improved signalquality and access to the immense bandwidth required by“triple-play” networks that offer voice, video, and data. Inshort, the end user is getting closer and closer to realizingthe benefits provided by fiber optic technology.

The holy grail for lightwave is Fiber-to-the-Home (FTTH).This high-cost approach eliminates coaxial cable and allcontent is delivered directly to the customer through fiberoptic cables.

In the US, this fiber-based approach has beenchampioned principally by Verizon, through its FiOSnetwork that competes directly with traditional cablesystems in terms of content. It has been very wellreceived, and its success has spurred an increase in thespeed of new service standards and deployments byentrenched cable MSOs. They responded with a thirdgeneration of the Data Over Cable Service Interfacespecification (DOCSIS), which has been developed byCable Labs. This not only provides support for IPv6 andIPTV – it also allows customers to tap into data at up to160 Mb/s in the downstream and 120 Mb/s in theupstream, making it competitive with VDSL and FTTH.

Although FTTH may be the ultimate data deliverytechnology, the edge that it has over the latest variant ofDOCSIS is not a big concern for today’s cable operators.

Verizon’s aggressive deployment of FiOS has created theonly real competitor to cable for state-of-the-artperformance. An intensive marketing war has ensuedbetween the two entities, with each side scrambling toexpose chinks in the armor of the other. While they battleit out, the differences between the two are increasinglynarrowing as the cable industry enhances its productofferings.

LinearizationRF linearization techniques at the circuit level have heldthe key to enabling optical transmitters to attain theiroptimum performance and arguably cement theirusefulness in cable distribution. Regardless of thetechnique employed to amplitude-modulate light,significant distortion arises that hampers the transmission

150mm Gallium Arsenide wafer with photo resist applied in the TriQuint Hillsboro, Oregon high-volume facility

The holy grail for lightwave is Fiber-to-the-Home (FTTH). This high-cost approacheliminates coaxial cable and all content is delivered directly to the customer through

fiber optic cables. In the US, this fiber-based approach has been championedprincipally by Verizon, through its FiOS network that competes directly with traditional

cable systems in terms of content. It has been very well received, and its limitedsuccess has spurred an increase in the speed of entrenched cable MSOs


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of information through the network. If this distortion werenot reduced, it would impair the effectiveness of lightwavesystems for cable applications. Even early systemsrequired extremely high linearity, and this demand becameeven more stringent over the years as bandwidth andchannel counts increased.

Linearization of RF and optical systems over wide CATVbandwidths is far from trivial. When performed usingexternal discrete circuits, this goal is complicated byparasitic effects that are difficult to compensate out of thelinearizer. However, if these circuits can be integrateddirectly on-chip, adjacent to the amplifying device, thenthe parasitic problem is largely eliminated. Thanks in partto the use of techniques developed by TriAccessTechnologies, a company that we acquired last year, wecan now linearize amplifiers for DOCSIS 3.0 and cableinfrastructure using on-chip techniques.

Substantial cost savings have already resulted fromlinearization, because it has enabled the construction offiber optic modulators with the necessary distortioncharacteristics for transmitting analog content. Lookingforward, linearization is poised once again to enable costsavings, this time to benefit RF amplification needs.Integrated linearization techniques are available to enablemature GaAs technologies to compete with moreexpensive semiconductor options without paying thepenalty of a substantial sacrifice in performance.Linearization can also enhance the already excellentperformance of newer device technologies, providing aneven higher level of power efficiency to the operator.

GaAs, GaN, and cableIt is safe to say that compound semiconductor technologyalong with advanced linearization techniques will be two

key enablers for allowing all types of future cable systemsto fulfill the cost, service quality and competitivechallenges lying around the corner. The RF, microwaveand lightwave portions of the system are already relyingextensively on compound semiconductor technologies,and will increasingly do so in the coming years.

On the RF side, the hybrid amplifier that has employedsilicon bipolar transistors for decades to deliver the highRF output power and linearity required for Class Aoperation is on its way out. The performance of silicon-based hybrids has reached its limit by failing to keep upwith increases in bandwidth made available to cableMSOs, which have grown from 300 MHz to 550, 870,and now 1000 MHz. In its place will be GaAs devicesdelivering greater performance in every key metric,combining greater bandwidth with much lower multi-carrier distortion, superior RF output power, lower noiseand greater efficiency. Spurring the switch to the superiortechnology is a shrinking price gap between GaAs-basedhybrids and their silicon rivals. The insurgent oftenbenefits from a single RFIC that leads to improved push-pull amplifier matching and fewer distortion-inducedproblems such as composite carrier noise ratio.

One of the big questions hanging over cable hybridamplifiers is this: how long will they be needed, as fibercontinues its march deeper into the network? Industryprophets have long predicted the demise of this class ofamplifier. However, to paraphrase Mark Twain, rumors oftheir death have been greatly exaggerated. The globalmarket for cable hybrid amplifiers, while very cyclical,shows only small signs of diminishing. What’s more, it israpidly being enhanced by widespread deployment ofGaAs devices. While some regions of the world aresignificantly built-out with cable service networks, othersare just beginning. In developing nations with growingeconomies citizens are just starting to enjoy the luxury ofdiscretional income, and there’s no doubt that some ofthis will be used for entertainment, including cable TV.

In addition, suppliers of GaN-based RF power amplifiershave recently introduced their first products. Although inmany respects GaN is still an emerging technology, it isstill a very attractive contender, offering tremendousperformance in several key figures of merit. Cost is amajor concern – it is three to eight times that of GaAsdevices – and this restricts GaN to use in situationsdemanding the highest possible performance. The higherprice of GaN devices is mitigated to some degree bygreater power output and other attributes, which canextend the reach from the fiber node to the customer(where the transition is made from fiber to coax) whilemaintaining low levels of distortion and powerconsumption. But it remains to be seen whether themarket embraces GaN, and is willing to shell out for thegreater performance that it offers.

TAT7467H:Edge QAM /DOCSIS 3.0amplifier forCATV headendapplications. Atrue differentialamplifier formedium powerapplicationswith excellent3rd orderdistortionperformance.350-380mApower usagethat is up to50% betterthan othersolutions

Quality check on a wafer being fabricated at TriQuint’s Hillsboro, Oregon facility




In the aggregate of systems throughout the world, costfactors rather than leading-edge specifications are ofparamount importance. This is particularly true in high-population, emerging economies such as China, India,and Eastern Europe. In these regions the monthlysubscription cost, and by extension the capital cost ofbuilding new networks, governs the decision over whetherto build out new networks. Silicon bipolar hybrids stilldominate those markets, but the GaAs performance valueis starting to take hold. The high cost of GaN-basedhybrids will likely restrict their success in these desirablehigh-growth markets.

Other important sub-markets within cable TV are those forheadend high-efficiency amplifiers and customer premisedistribution. While the RF output level of the headendapplication is 5 to 10 dB lower than that of line extendersin coaxial distribution networks, the high density ofequipment in headends makes high efficiency a sought-after premium.

Our DOCSIS 3.0 amplifiers address this issue, cuttingpower consumption by up to 50 percent and slashing thecircuit board “real estate” required to employ thesedevices by up to 80 percent. These GaAs-basedamplifiers are designed for use in customer premisesequipment to support multi-room deployment as well asadvanced in-home distribution architectures such asEthernet over coax, the Multimedia over Coax Alliance(MOCA) standard, and for FTTH receivers. When theseare used in cable hybrid amplifiers and line extenderamplifiers they provide lower distortion than ever before,plus very high efficiency and low power consumption.

Taken together, these attributes benefit cable MSOs interms of reduced operating cost and system complexity.They allow amplifiers to be smaller and more frugal withpower. The latter benefit must not be underestimated,given the large numbers of hybrid amplifiers usedthroughout a system, and the consequent opportunity forconsiderable annual savings associated with operatingcosts. The benefit of greater efficiency also makes adifference to amplifiers at the headend, where it translatesinto reduced cooling requirements.

In short, the hegemony of silicon bipolar devices in hybridamplifiers is drawing to a close. That’s because thisvenerable technology that has played an enormous role inthe growth of cable since the 1960s is no longer viable inthe higher-frequency, higher-performance cable systems

that will drive the industry into the future. In its place willbe GaAs devices that are already enjoying rapiddeployment, which combine low-cost with highperformance, making them well suited to both current andfuture cable systems.

GaN, which has inherent characteristics that are highlydesirable in cable hybrid amplifiers, is currently tooexpensive for use in most systems. Nevertheless, its rolewill continue to expand in years to come. It is destined tomake an impact, because the combination of processevolution and economies of scale will enable the pricereductions necessary for historically frugal-minded cablesystem manufacturers and operators to begin to adoptthis compelling technology.

What’s on tomorrow?There are many variables that will determine the exactpath of entertainment distribution to the home, includingthe possible entry of wireless technologies. However,there are some facets of the industry that will not change.First, the deployment of FTTH has altered the face of TV,data, and voice delivery to the home, giving traditionalcable MSOs a true competitor for the first time.Distribution via satellite remains a key player, but itstruggles to provide voice and data services, and itsfuture is uncertain in those areas where established cableproviders are highly competitive in terms of price andservice.

In a competitive environment, the cable industry has littlechoice but to do whatever is necessary to retain itspremier position. FTTH, from Verizon in the US and agrowing number of operators in world-wide markets, willcontinue to gain market share as it is deployed in newregions. Together these two fierce competitors will rely onGaAs and GaN to deliver the highest levels ofperformance at the lowest cost.

As a result, the market for GaAs- and GaN-based cablehybrid amplifiers will continue to grow. Finally, fiber willinch its way closer and closer to the customer location inHFC systems, driving the growth of optical receivers andother system elements that also rely on III-Vs.

For consumers all of this is great news, since competitiondrives innovation, and innovation tends to lead to better,more varied services. From any vantage point, the homeentertainment industry will be theater at its technologicalfinest — and compound semiconductor technologies are ashoe-in for the leading roles.

TGA2807-SM:Edge QAM /DOCSIS 3.0RF amplifier forCATV headendapplications.ACPR ~2 dBbetter thanpreviousgenerations.Standard5x5mm QFNoffers high-efficiencyperformance

The hegemony of silicon bipolar devices in hybrid amplifiers is drawing to a close, because this venerable technology that played anenormous role in the growth of cable since the 1960s is no longer viable


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III-Vs are Propelling Cable TV Services to a New Level