1. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 1
ERICSSON
TECHNOLOGY
0 50 100 150 200 250 300 350 400 450
0.1
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100
Frequency (GHz)
Attenuation(dB/km)
N x 250MHz
channels
Frequency
bands
100mm/h
50mm/h
20mm/h
5mm/h
0mm/h
90
22 29 87 15 29 49 30
100 110 120 130 140
68GHz Spectrum not yet allocated
W band D band
150 160 170 180GHz
C H A R T I N G T H E F U T U R E O F I N N O V A T I O N | # 2 ∙ 2 0 1 7
MICROWAVEBACKHAUL
BEYOND100GHZ

2. ✱ THE NEW MICROWAVE BACKHAUL FRONTIER
2 ERICSSON TECHNOLOGY REVIEW ✱ FEBRUARY 21, 2017
JONAS EDSTAM,
JONAS HANSRYD,
SONA CARPENTER,
THOMAS
EMANUELSSON,
YINGGANG LI,
HERBERT ZIRATH
Microwave backhaul technology plays a significant role in providing
reliable mobile network performance and is well prepared to support
both the evolution of LTE and the introduction of 5G. Work has now
started on the longer-term use of frequencies beyond 100GHz, targeting
the support of 5G evolution toward 2030.
Constant pressure to improve performance
levels results in a need for more spectrum,
and the more efficient use of it – not just for
radio access, but for backhaul as well. By
continuously pushing technology limits, ever
higher frequencies have been brought into use
during the last few decades – a trend that will
continue in the future.
■ Asafinitenaturalresource,radiospectrumis
governedbynational,regionalandinternational
regulationstoensurethatsocialandeconomic
benefitsaremaximized.Spectrumisdividedinto
frequencybandsthatareallocatedtodifferent
typesofradioservices,suchascommunication,
broadcastingandradar,aswellasforscientificuse[1].
By2021,65percentoftheworld’scellsites
(excludingthoseinnortheastAsia)willbe
connectedusingmicrowavebackhaultechnology
[2].Therapidlygrowingcapacityrequirements
thatthisentailswillcreateaneedforsignificant
performanceimprovementsenabledbytechnology
evolutionandmoreefficientuseofexisting
spectrum[2,3,4].
Themicrowavebackhaulindustryhasstarted
preparingforthenextmajortechnologyand
performanceleaptoaccommodatethemarket’s
expectedvolumeneedsforthe2025to2030
backhaul
evolution– REACHING BEYOND 100GHZ
MICROWAVE

3. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 3
period.Makingsuchleapsrequiresmanyyearsof
researchanddevelopmentandagreatdealofwork
onspectrumregulation,aswellastheexperience
ofseveraltechnologyandproductgenerations
tomatureperformanceforlarge-scaleuse.The
aimistoopenupspectrumbeyond100GHz
frequenciesforuptoward100Gbpscapacity
tosupportdifferentapplicationsandusecases
withhopdistancesofuptoafewkilometers.In
thelongerterm,itisexpectedtoserveasahigh-
capacitycomplementtotheuseofotherfrequency
bands[2],especiallyinurbanandsuburbanareas,
asshowninFigure1.Thesmallerphysicalantenna
sizeatthesehigherfrequencieswillbeofparticular
advantageintheselocations.
Higherfrequenciesaremorelimitedinterms
ofreachandcoverage,buttheycangenerally
providewiderfrequencybands,andassuchhave
higherdata-carryingcapacities.Drivenbygrowing
communicationneeds,everhigherfrequencies
havebeentakenintousesincethemiddleofthe
lastcenturywhentheuseoffrequenciesofjusta
fewGHzwasthenormformicrowavetransmission
networks.Atpresent,the70/80GHzband –
71-76GHzpairedwith81-86GHz–israpidly
gainingpopularity,asitenablescapacitiesinthe
1-20Gbpsrangeoverafewkilometers[2,3].It
hastakenabout15yearsfromtheinitialeffortsin
thisbandforlarge-scaleusagetostarttakingoff.
Similareffortsarenowunderwaytoenabletheuse
offrequenciesbeyond100GHz[5,6]forcapacities
inthe5-100Gbpsrangeoverdistancescomparable
to70/80GHztoday.
Microwavebackhaulbeyond100GHz
Microwavebackhaulorfixedservicesystems
(astheyareknowninITU-Rterminology)are
commonlyusedinamultitudeoffrequencybands
rangingfrom6-86GHz.Therangeoffrequency
bandsisneededtoprovidebackhaulfordiverse
typesoflocations,fromsparseruralareasto
ultra-denseurbanenvironments,withhop
distancesrangingfromaslittleas100mto100km
ormore.Theuseoffrequencybandsisgoverned
byregulatoryrecommendationsonchannel
arrangements[7].Beyond100GHz,spectrum
hasbeenallocatedforfixedservicesystemsup
to275GHz[1],butnochannelarrangements
havebeenmade.However,regulatorystudies
onchannelarrangementsareongoinginEurope
[5],withthefocusonthe92-114.25GHzand130-
174.8GHzranges:commonlyreferredtoasthe
WandDbandrespectively.
THE AIM IS TO OPEN
UP SPECTRUM BEYOND
100GHZ FREQUENCIES FOR
UP TOWARD 100GBPS
CAPACITY
Terms and abbreviations
BER – bit error rate | BPSK – binary phase shift keying | CMOS – complementary metal-oxide-semiconductor
| DHBT – double heterojunction bipolar transistor | GaAs – gallium arsenide | GaN – gallium nitride | HBT –
heterojunction bipolar transistor | HEMT – high electron mobility transistor | InP – indium phosphide | ITU-R –
International Telecommunication Union Radiocommunication Sector | LOS – line-of-sight | mHEMT – metamorphic
high electron mobility transistor | MIMO – multiple-input, multiple-output | MMIC – monolithic microwave
integrated circuit | MOSFET – metal-oxide-semiconductor field-effect transistor | NFmin – minimum noise figure |
pHEMT – pseudomorphic high electron mobility transistor | QAM – quadrature amplitude modulation | SOI – silicon
on insulator | SiGe – silicon-germanium

4. ✱ THE NEW MICROWAVE BACKHAUL FRONTIER
4 ERICSSON TECHNOLOGY REVIEW ✱ FEBRUARY 21, 2017
Thespectrumabove100GHzconsistsofa
multitudeofsub-bandsofdifferentsizeswith
passiveserviceallocationsinbetween,asshown
inFigure2.Thereasonevenwidercontinuous
spectrumisnotmadeavailableistoprevent
interferencewithpassiveradiocommunication
servicessuchastheEarthExploration-Satellite
ServiceandtheRadioAstronomyService.
Thereissomeinterestintheuseoffrequencies
beyondtheDbandforfixedservicesystemsin
theevenlongerterm.Severalfrequencybandsin
the275-1000GHzrangehavebeenidentifiedfor
passiveservices,butthisdoesnotprecludetheiruse
foractiveservices[1].ITU-Rwillcarryoutstudies
untiltheWorldRadiocommunicationConference
2019ontheidentificationoffrequencybandsinthe
275-450GHzrangeforlandmobileradioandfixed
servicesapplications[1].Itshouldbenotedthatthe
252-275GHzfrequencyrangeisalreadyallocated
tofixedservices.If275-320GHzwasaddedto
this,itwouldformacontinuous68GHzwideband
withmoderateatmosphericabsorption,asshown
inFigure2.Thiscouldbeusefulforfixedservice
applicationsinthedistantfuture.
Attenuationduetoatmosphericgasesandrain
[8]increaseswithfrequencyandtherearealso
severalabsorptionpeaks,asillustratedinFigure
2.However,betweenthepeaks,theattenuation
increasesquiteslowlybeyond70GHz.Forexample,
itincreasesabout2dB/kmfrom70GHztotheD
bandandabout4dB/kmfrom70GHzto275GHz.
Thefreespacepathloss[8]alsoincreaseswith
frequency:byabout6dBfrom70GHztotheD
bandandabout11dBfrom70GHzto275GHz,for
Figure 1
Future use of spectrum
for microwave backhaul,
including solutions
beyond 100GHz
70/80GHz and
beyond 100GHz
Multiband 70/80GHz,
15/18/23GHz and
beyond 100GHz
Multiband 15/18/23GHz
and 6/7/8/11/13GHz
70/80, 60, 15/18/23GHz,
6/7/8/11/13GHz and
beyond 100GHz
Future 5G bands, 60GHz and beyond 100GHz
Airport connectivity
Port communication Broadcast
network
Network for
authorites
Business access
Utility
communication
Fiber closure
Events
Macro cell backhaul Other uses for
microwave transport
Small cell backhaul

5. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 5
Figure 2
Frequency bands and
atmospheric attenuation
beyond 100 GHz
0 50 100 150 200 250 300 350 400 450
0.1
1
10
100
Frequency (GHz)
Attenuation(dB/km)
N x 250MHz
channels
Frequency
bands
100mm/h
50mm/h
20mm/h
5mm/h
0mm/h
90
22 29 87 15 29 49 30
100 110 120 130 140
68GHz Spectrum not yet allocated
W band D band
150 160 170 180GHz
IT IS IMPORTANT FOR
SPECTRUM REGULATIONS
BEYOND 100GHZ TO ENABLE
EMERGING AND FUTURE
INNOVATIONS
example.Thepropagationconditionsarethusonly
slightlyworsebeyond100GHz.
Itisimportantforspectrumregulations
beyond100GHztoenableemergingandfuture
innovationsthatcansupportcapacitiesontheroad
toward100Gbps.Theyshouldcovertraditional
linkconfigurations,suchasFDD,aswellas
complementaryfutureinnovationsthatmight
betterhandletheasymmetricandpartlyunpaired
sub-bands,asillustratedinFigure3.
Likefibertransportnetworks,microwave
backhaulhashistoricallybeendesignedtobe
symmetrical.Inmostcases,thefrequencybands
aredividedsymmetricallyintohighandlowsub-
bands,usedwithFDD.Usedtoboostcapacityand
spectralefficiency,line-of-sight(LOS)multiple-
input,multiple-output(MIMO)isaninnovation
thatinitiallygainedinterest[4,9],buthaswaned
latelyonaccountthemoreattractivemultiband
solutions.However,thesmallspatialantenna
separationrequiredforLOSMIMOintheDband
makesitinterestingontheroadtoward100Gbps
capacity.Multibandsolutions,whichenable
enhanceddataratesbycombiningresourcesin
multiplefrequencybands,constituteanessential
partofmodernradioaccess.Assuch,theyhave
recentlyalsobecomeatopicofgreatinterestin
microwavebackhaul[3]bymakingitfeasibletouse
higherfrequenciessuchas70/80GHzovermuch
longerdistances.Multibandisalsoaveryattractive
optionbeyond100GHz.
Today,thelimitedspectrumwithunpairedor
asymmetricsub-bandsisusedwithTDD.FDD
withasymmetricchannelshasbeenstudied,
butdeemedtoocomplexandoflimitedvalue
inexistingsymmetricbands[10].Asymmetric
multibandsolutionsmightbeofinterestin
unpairedspectrum,ratherlikesupplemental
downlinkforradioaccess.FlexibleFDD
configurationsuseseparatetransmitandreceive

6. ✱ THE NEW MICROWAVE BACKHAUL FRONTIER
6 ERICSSON TECHNOLOGY REVIEW ✱ FEBRUARY 21, 2017
MIMO
Multiband
TDD
Time
Asymmetric FDD
Frequency
Asymmetric
multiband
Flexible FDD
FrequencyMultiple antenna
elements
Lower frequency band
for high availability
High-capacity configurations
Traditional configuration
Unpaired and asymmetric
spectrum configurations
FDD
Frequency
Figure 3
Examples of potential
configurations beyond
100GHz, to support high
capacities and facilitate
use of unpaired and
asymmetric spectrum
antennasinsteadofdiplexfiltersforisolation[5,
6].Thisdoesnotaddanyspectrumefficiency,but
mightprovideforbetterperformancethanthat
enabledbyTDDinunpairedspectrum.
Theroadto100Gbpstransportsolutions
Microwavebackhaultechnologyhasevolved
tremendouslyinrecentdecades,repeatedly
exceedingcapacitylimitsandreaching
performancelevelsonlybelievedpossibleforfiber
solutions.Thecommercial70/80GHzequipment
thatiscurrentlybeingintroducedsupports
10Gbpsin2GHzchannels(8x250MHz)andit
isreasonabletoexpect20Gbpssolutionsinthe
future.Highercapacitiesarefacilitatedbywider
channels,butnationalspectrumadministrations
commonlylimitthemaximumallowedchannelsize
tosecureafairdivisionamongdifferentusers.The
maximumchannelsizeistypicallylimitedtoabout
10percentofthetotalband.Forhigherfrequency
spectrum,withagreaterpossibilityoffrequency
reuse,channelsofuptoabout20percentofthe
totalbandmaybeallowed.
Realisticsolutionsonthecontinuedroad
towards100Gbpsindifferentfrequencybandsare
showninFigure4.Evenwiderchannelsuptoabout
5GHz(20x250MHz)mightbeobtainableinthe
Dband,enablingsolutionssupporting20Gbps,
40Gbpsandevenupto100Gbpsinthelonger
term,asindicatedbythediamondsinFigure4.
Buttherearemanytechnologychallengesonthis
road,suchastransmitternoise,signaldistortion
andotherimpairmentsthatmightlimitmaximum
modulationorderforextremelywidechannels.
Highercapacitiesandwiderchannelbandwidths
alsoplacemorerequirementsondigitaldata
converters.Moreadvancedsolutionsusingdual
polarization–andevenLOSMIMO–would
enhancecapacitybuttheyalsoaddcost.
TheuseofLOSMIMOsolutionsbeyond

7. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 7
100MHz
N x 250MHz 1 4 8 20 40
250MHz 1GHz 2GHz 5GHz 10GHz
100Gbps
40Gbps
20Gbps
10Gbps
1Gbps
Aggregated channel width
Capacity
20% of total spectrum per band 70/80GHz W D band
Dual polarization
Single
polarization
MIMO
potential
Figure 4
Realistic capacity versus
channel bandwidth with single
polarization, dual polarization
and MIMO
d_opt=
cD
fN
100GHzcarrierfrequenciesisattractivedueto
thereductioninrequiredspacingbetweenthe
antennaelementsasthefrequencyincreases.The
optimalantennaseparationd_opt,inaverticaland
horizontaldirection,maybewrittenas[11]:
Wherefisthefrequency,cisthespeedoflight,
Nisthenumberofantennaelementsinthevertical
orhorizontaldirectionandDisthehoplength.A
separationof70-80percentoftheoptimalvalue
ispossible,withonlyalimiteddecreaseinsystem
gain[9].Forexample,at155GHz,anantenna
separationof0.4mwouldbeneededfora300m
hopdistance,and0.8mfora1kmhop.Thereare
technologicalchallenges(suchassignalprocessing)
involvedindevelopingLOSMIMOintheDband,
butinthelongertermitisexpectedtoenablethe
finalstepto100Gbpscapacities,andevenbeyond,
asillustratedinFigure4.
Hoplengthsbeyond100GHz
Whenassessingtheabilityofmicrowavebackhaul
toprovidehigh-capacitytransportoverdistance,
threeparametersshouldbeconsidered:
〉〉 thetotalsystemgain–thetransmittedpowerplusthe
antennagainsminustherequiredreceivedsignalpower
〉〉 thetargetedavailability–theaccumulatedtimeaselected
capacityshouldbesustainedoverthehop,whichisusually
expressedinapercentageoftimeperyear,where
99.99-99.999percentarecommontelecomgradetargets
〉〉 thelocalclimate–thehopplanningisdonewith
propagationpredictionmethodsusinglong-termrainand
multipathstatisticaldataforthehoplocation
Themaximumhoplengthversustotalsystemgain
fordifferinglevelsofavailabilityandlocalclimate

8. ✱ THE NEW MICROWAVE BACKHAUL FRONTIER
8 ERICSSON TECHNOLOGY REVIEW ✱ FEBRUARY 21, 2017
SEMICONDUCTOR
TECHNOLOGIES FOR
BEYOND 100GHZ USE HAVE
UNDERGONE A TREMENDOUS
EVOLUTION IN THE PAST FEW
DECADES
conditionsat155GHzisshowninFigure 5.It
illustratesthetotalsystemgainfortwoequipment
examples:onewith50dBiantennas,whichisthe
generalrecommendedmaximumantennagainin
practicalmicrowavedeployments;andonewith
35dBi,whichistherecommendedmaximum
antennagainforsiteswithmastsway,suchas
smallcellbackhaulsitesmountedonlighting
poles.Eachoftheexamplesisforconfigurations
supportingthe10to100GbpsexamplesinFigure 4,
whichallhavesimilarsystemgains.AsDband
technologyismaturing,transmittedpowerand
receiversensitivityofthesameorderasfortoday’s
70/80GHzequipmentareexpected,evenifearly
implementationsmighthavemuchlowersystem
gain,asillustratedinFigure5.
The20,50and100mm/hrainrates,exceededfor
0.01percentoftimeperyear,arerepresentativefor
mild,moderateandseverelocalclimateconditions.
Theavailabilitiesof99.9percentand99.995
percentinFigure5correspondtoapropagation
lossthatexceedsthetotalsystemgainforabout
9hours/yearandof26minutes/year.Using
adaptivemodulation,alowermodulationlevel
inheavyrainincreasesthesystemgaintoavoid
transmissionerrors,butresultsinreducedcapacity.
Forexample,reducingmodulationfrom64QAM
toBPSKcorrespondto15dBincreaseofsystem
gain,butareductionto17percentofcapacity.As
Figure5illustrates,hoplengthsofafewhundred
metersareachievableforlowergainantennas.
Usinghighgainantennas,itispossibletoachieve
hoplengthsofabout1-2kmandevenupto2-4km
forloweravailabilitytargets,suchasmultiband
configurations.Thehoplengthsinthe
Dbandarethuswellsuitedforurbanand
suburbandeployments.
Semiconductortechnologiesaskeyenablers
Semiconductordevicesareessentialinallmodern
radiotechnology.Microwavebackhaulequipment
hashistoricallyreliedongalliumarsenide(GaAs)
circuits.Morerecently,galliumnitride(GaN)
hasbeenintroducedincommercialproductsdue
toitshighbreakdownvoltageenablinghigher
transmitpower.Thereisalsoconsiderableinterest
insiliconchipsets,basedonCMOSorSiGe-HBT,
duetotheirlowerproductioncostperchipinhigh
volumesandhighintegrationdensity.Theseare
particularlyrelevantforshortrangedeployments
wherehighoutputpowerislessimportant,suchas
inthe60GHzfrequencyband.
Drivenbythespace,defenseandimaging
industries,semiconductortechnologiesforbeyond
100GHzusehaveundergoneatremendous
evolutioninthepastfewdecades[12].Thereare
todayafewcommercialtechnologiesavailablefor
beyond100GHzapplicationsandseveralmoreare
beingresearchedforevenhigherperformance,
asshowninFigure6.Thethreemaintransistor
technologyclassesareHBT,HEMT,andMOSFET
[12],whereMOSFETistypicallyimplementedin
SOICMOSforhighfrequencyoperation.Akey
propertyisthefeaturesize,sinceatransistorwith
smallerfeaturesizesupportshigherfrequencies.
Asaruleofthumbcircuitsaredesignedtooperate
atbelowhalffMAX,wherefMAXisthefrequency
atwhichthetransistor’spowergainisequaltoone.
Itispossibletobringtheoperationfrequencymuch
closertofMAXbutdoingsoresultsinlowerenergy
efficiencyandhigherdesigncosts.Otherimportant
materialpropertiesaretheminimumnoisefigure
(NFmin)andthebreakdownvoltage(Vbr),which
determinereceiversensitivityandmaximum
transmittedpower,respectively.Therightcolumn
inFigure6indicatesthecommercialmaturityof
thetechnology,whereadditionalaspectsarethe
developmentandproductioncost.Flickernoise

9. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 9
*Ready to be commercialized in 1–2 years
**NFmin is proportional to the frequency.
Technology
Feature size
(nm) fMAX (GHz) Vbr (V)
NFmin (dB)
at 50GHz**
Production
or research?
GaAs pHEMT 100 185 7 0.5 P
GaAs mHEMT 70 450 3 0.5 R*
GaAs mHEMT 35 900 2 1 R
InP HEMT 130 380 1 <1 R
InP HEMT 30 1200 1 <1 R
GaN HEMT 60 250 20 1
1.2GaN HEMT 40 400 42 R
SOI CMOS 45 280 1 2–3 P
SiGe-HBT 130 400 1.4 2 P
InP DHBT 250 650 4 3 R*
R
InP DHBT 130 1100 3 R
Figure 5
Maximum hop length
versus total system
gain at 155GHz, for
different rain intensities
(exceeded 0.01 percent
of the year) and for
two different antenna
configurations
Figure 6
Overview of
semiconductor
technologies beyond
100GHz and their key
parameters
Total system gain [dB]
Maxhoplength[km]
110
0
1
2
3
4
5
120
Maturing technology
Adaptive modulation
130 140 150 160 170 180
35dBi antenna 50dBi antenna
0mm/h
20m
m/h99.9%
5
0m
m
/h
99.9%
100mm/h 99.9%
50mm/h 99.995%
100mm/h 99.995%
20mm/h 99.995%

10. ✱ THE NEW MICROWAVE BACKHAUL FRONTIER
10 ERICSSON TECHNOLOGY REVIEW ✱ FEBRUARY 21, 2017
generation,memoryeffectsandtemperature
behaviorarenotincludedinthetable,butshould
alsobeconsidered.
Themaximumtransmittedpowerlimitsthe
systemgain.Researchhasbeenpublishedonpower
amplifiersinGaAs,InPandSiGetechnologies
deliveringmorethan10dBmofoutputpower
beyond100GHz[13-15].GaNisinthefuture
expectedtodemonstrateevenhigheroutputpower
duetothematerialshighbreakdownvoltage.GaAs
pHEMTprovideshighbreakdownvoltageand a
lownoisefigureand,inafewyears,isalsoexpected
tobeabletosupporttheDband.InPsupports
veryhighfrequencies,albeitatahighmaterial
cost.Becauseofitsgoodperformanceitcouldbe
usefulforresearchandpredevelopmentactivities
ofequipmentintheDband.Itmightalsobe
applicableforlongertermcommercialapplications
around275GHz.
SilicontechnologiessuchasSOICMOSand
SiGe-HBTaretodayfeasibleuptotheDband
althoughthemaximumoutputpowerislimited
duetothelowbreakdownvoltageofsiliconand
thenoisefigureisworsecomparedtoGaNand
GaAstechnologies.Duetotheexcellentproperties
forhighintegration,silicontechnologiesare
promisingforshort-range,low-costapplications
beyond100GHz.
Therearemanyadditionalobstaclestoovercome.
Packagingandinterconnectabove100GHzare
challengingduetotheshortwavelengths.Parasitic
effectsaremorepronouncedandthetolerance
requirementishighindesign,manufacturing
andassembly,especiallywhenconsideringwide
bandwidths.Crosstalkandunwantedresonances
areadditionalissuessincethetypicalmonolithic
microwaveintegratedcircuit(MMIC)sizeisofthe
orderofthewavelength.Thismakestraditional
interconnects,suchaswirebondingandflipchip,
difficulttousewithhighyield.
Researchonhigh-frequencytechnologiesis
gainingglobalinterest.Oneexampleisthenon-
galvanicchip-waveguideinterconnectscurrently
beinginvestigatedbytheEuropeanUnion
fundedHorizon2020projectM3TERA,where
low-losssiliconwaveguidesaremadeusinga
3Dmicromachiningtechniquethatprovidesa
siliconplatformwithembeddedcomponents
forindustrializedassembly.Anotherexampleis
theresearchprogramcommissionedbyJapan’s
MinistryofInternalAffairsandCommunications,
“R&DProgramonMulti-tensGigabitWireless
CommunicationTechnologyatSubterahertz
Frequencies,”whichinvestigatesradiosources
beyond275GHz.AthirdexampleistheHorizon
2020fundedresearchprogramTWEETHER,
whichfocusesonhigh-poweramplifiers
beyond100GHz.
Itisalongandwindingroadfromresearchtofull
fledgecommercialequipmentthatmeetstheright
performanceandcost.Ultimatelythiscanonlybe
achievedwithacompetitiveindustryeco-system
sharingacommonvision[6].
Puttingtheorytothetest
WorkingwithresearchersatChalmersUniversity
ofTechnologyinGothenburg,Sweden,Ericsson
ResearchhasdevelopedaDbandtransceiver
module,showninFigure7.Themodulecontains
anInPDHBTMMICandaseparatecircuitboard
forbiascontrolandconnectors.TheMMIC
coverstheentireD-band.Theredsquareinthe
photoshowsthelocationoftheMMIC,which
measures1.3mmx0.9mm.Theclose-uponthe
rightshowsthetransceiverMMICgluedtoa
siliconcarrierandconnectedtothemodulewith
wirebonds.
BothtransmitterandreceiverMMICscontaina
Gilbertcellmixerforupordownconversionanda
frequencytriplerforlocaloscillatorgeneration.A
low-noiseamplifierisimplementedinthereceiver
RESEARCH ON HIGH-
FREQUENCY TECHNOLOGIES
IS GAINING GLOBAL
INTEREST

11. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 11
Figure 7
D band transceiver module
(left) with a red square
indicating the position of
the wire-bonded InP DHBT
transceiver MMIC (shown in
close-up on the right)
MMIChavingapproximately15dBofgain,while
amedium-poweramplifierisimplementedinthe
transmitterMMICsupportingasaturatedoutput
powerofmorethan10dBm[15].TheMMICs
areassembledinaslotinsidea50µmthicksoft
substratethatalsoextendsintoawaveguideasan
E-planeprobe.Thewaveguideconnectstoadiplex
filterthatinterfaceswithanantenna.
Thetransmitterandreceivermoduleswere
measuredback-to-backbeforebeingassembled
intotheradioprototype.Figure8showsthe
measuredbiterrorrate(BER)versusreceived
signalpowerfora125MHzchannelat143GHz.
Themodulessupportedupto5GHzchannelsand
theinsetinFigure8showsthemeasurederror-
freeconstellationforasymbolrateof4GBaud
using16QAMforintotal16Gbps[15].Anoisefigure
of9.5dBwasmeasuredforthereceiverMMIC,
whichisagoodresultforreceiverchipsetsbased
onbipolartechnologiesatthesefrequencies.
The10-6
BERthresholdof-63dBmfor4QAM(in
Figure8)indicatesthattheseearlytransmitterand
receivermodulesaddapenaltyofmorethan8dB
tothereceiversensitivity.Theseresultsemphasize
theneedforcarefulcontrolofhowthemoduleis
designedandbuilt.
ThephotoontheleftinFigure9showsthe
completeradioprototypemountedinanenclosure
togetherwiththemodemandantennaforoutdoor
over-the-airmeasurements.Theantennais
only7.5cmindiameter,butstillprovides40dBi
gain.Long-termtestsonfrequenciesbeyond
100GHzwillbeimportanttovalidatetheITU-R
propagationandavailabilitymodels,similartowhat
wasinitiallydoneinthe70/80GHzband[16].The
smallantennafootprintsatthesehighfrequencies
couldenablenewcompactradioconcepts,as
illustratedtotherightinFigure9.

12. ✱ THE NEW MICROWAVE BACKHAUL FRONTIER
12 ERICSSON TECHNOLOGY REVIEW ✱ FEBRUARY 21, 2017
Figure 9
D band radio prototype
(left) and visionary design
idea (right)
Received signal power, dBm
Biterrorrate
-70
10-12
10-10
10-8
10-6
10-4
0
0
-1
I (a.u.)
Q(a.u.)
-1
-2
-2
-3
-3
-4
-4
-5
-5
1
1
2
2
3
3
4
4
5
5
10-2
-65
4QAM
16QAM
32QAM
64QAM
128QAM
256QAM
-60 -55 -50 -45 -40 -35
125MHz channel
Figure 8
Measured bit error rate at
143GHz versus received
signal power. Inset shows
measured constellation
diagram at 4GBaud and
16QAM modulation for in
total 16Gbps

13. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 13
1. ITU,2016,RadioRegulations,part1chapterIIarticle5(Frequencyallocations)and
part3resolution767(Studiestowardsanidentificationforusebyadministrations
forland-mobileandfixedservicesapplicationsoperatinginthefrequencyrange
275-450GHz),availableat:https://www.itu.int/pub/R-REG-RR-2016
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https://www.ericsson.com/assets/local/microwave-outlook/documents/
ericsson-microwave-outlook-report-2016.pdf
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https://www.itu.int/rec/R-REC-P.530/en
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Fixed Service Links, available at:
http://www.erodocdb.dk/Docs/doc98/official/pdf/ECCREP258.PDF
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112-134GHz SiGe amplifier with peak output power of 120mW, available at:
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References:
Conclusion
Theceaselessquesttoprovidehigherdata-
carryingcapacitieshasledtotheuseofever
higherfrequencieswheremorespectrumis
generallyavailable.Thetremendousgrowth
intheuseofthe70/80GHzbandthatwecan
seetodaywasmadepossiblebyseveralyears
ofresearchanddevelopmentandagreatdeal
ofworkonspectrumregulation,aswellasthe
experiencegainedfromseveraltechnologyand
productgenerations.Similareffortsarenow
underwayontheroadtomicrowavebackhaul
beyond100GHz,supportedbytherapid
evolutionofhighfrequencysemiconductor
technologiesandpromisingnewdevices.In
lightofthis,weexpecttoseethelarge-scale
deploymentofbeyond100GHzsolutionsin2025
to2030.TheWandDbandswillundoubtedly
beabletosupportcapacitiesinthe5to100Gbps
range,overdistancesuptoafewkilometers.

14. ✱ THE NEW MICROWAVE BACKHAUL FRONTIER
14 ERICSSON TECHNOLOGY REVIEW ✱ FEBRUARY 21, 2017
Jonas Edstam
◆ is wireless strategy
manager at Business
Unit Network Products,
Ericsson. He is an expert
in microwave backhaul
networks with more than 20
years of experience in the
area. Since joining Ericsson
in 1995, he has held various
roles, working on a wide
range of technology,
system, network and
strategy topics. His current
focus is on the strategic
network evolution to 5G
and the convergence of
access and backhaul. He
holds a Ph.D. in physics
from Chalmers University
of Technology in
Gothenburg, Sweden.
Jonas Hansryd
◆ leads Ericsson’s
research on microwave
and millimeter-wave radios
including antennas and
high-capacity frontends to
meet traffic demands on
future microwave backhaul
and 5G radio access. He
has more than 20 years
of R&D experience in
advanced communication
systems and joined
Ericsson Research in
2008. He holds a Ph.D. in
electrical engineering from
Chalmers University of
Technology in Gothenburg,
Sweden, and served as a
postdoctoral fellow at the
applied engineering physics
department at Cornell
University between 2003
and 2004.
Sona Carpenter
◆ received an M.E.
(Hons.) in electronics and
telecommunication from
the Shri G. S. Institute of
Technology and Science
in Indore, India, in 2008.
She is currently working
toward a Ph.D. at Chalmers
University of Technology in
Gothenburg, Sweden. Her
research interests include
the design of millimeter-
wave integrated circuits
and systems with a focus on
millimeter-wave high-speed
wireless communication. In
2013, she was a recipient of
the GaAs Association Ph.D.
Student Fellowship Award.
Thomas
Emanuelsson
◆ is an expert in microwave
technology at Ericsson
whose work focuses on
microwave point-to-point
communication for the
MINI-LINK system. This
role includes coordination
of future technology
development, system
and subsystem design
as well as interaction
with universities about
research on upcoming
technologies. He received
his M.Sc. in electronic
engineering from Chalmers
University of Technology
in Gothenburg, Sweden,
where he currently holds
the position of adjunct
professor at the Microwave
Electronics Laboratory
in the Department of
Microtechnology and
Nanoscience.
Yinggang Li
◆ is a senior specialist in
microwave and millimeter-
wave circuits, components
and subsystems at Ericsson
Research. He holds a Ph. D.
in theoretical physics from
Gothenburg University in
Gothenburg, Sweden. Since
joining Ericsson in 1996 he
has worked on a number
of product development
projects and research
programs. He is currently
involved in Ericsson’s
5G hardware research
program, focusing on the
development of millimeter-
wave technologies beyond
100GHz.
Herbert Zirath
◆ is a research fellow
leading the development
of a D-band (110–170GHz)
chipset for high-data-rate
wireless communication at
Ericsson. He holds a Ph.D.
in electrical engineering
from Chalmers University of
Technology in Gothenburg,
Sweden, where he has
served as a professor
in the Department of
Microtechnology and
Nanoscience since 1996.
His research interests
include MMIC designs for
wireless communication
and sensor applications
based on III-V, III-N,
graphene, and silicon
devices.
theauthors
The authors
would like to
acknowledge
the support and
inspiration they
received from
their colleagues
Mingquan Bao,
Björn Bäckemo,
Simon He, Johan
Jonsson, Magnus
Johnsson, Git
Sellin, Martin
Sjödin, Per-Arne
Thorsén and
Vessen Vassilev.

15. THE NEW MICROWAVE BACKHAUL FRONTIER ✱
FEBRUARY 21, 2017 ✱ ERICSSON TECHNOLOGY REVIEW 15
ISSN 0014-0171
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