BSTJ 50: 7. September 1971: TH-3 Microwave Radio System: The Traveling-Wave Tube Amplifier . (Bradford, C.E.; Waldron, C.J.)

5.6 MB·English

ome ran ag a me

TH} Microwave Radio System:

The Traveling-Wave Tube Amplifier

By C.F. BRADHORD ant C, J. WALDRON
(Mori sev Buch 2,18)

The TH-3 radio mje eons a aid aate eempanenee woth ave
exception, Becnse the vee! for wat power not siaknbie preoo
From slid lets deve, tao govepton ts the trang weave tbe power
fier. Thie anpier Suenos 40.8 Bw anit pars of 33.5 aD
fin ene avy eh! of the 3885-0 6.425-CHe onnewn carr ba
‘Thiele employs angtt made ead of elcome nickel.”
Also tive higher_peser att thaw fmlingwse I evioualy
‘esinat! jor Bell Sourn in clay seems, Pea wer bande
fprwanes! oagnel sire wer jail en a toga wot, TE dee nat
Fonarsfusing or ta staal ont pete dr Bae of We me

“Traveling-wave (ues are us asthe ennszaiting amplifiers for che
‘THB vedio system, The 161A lveliogerave tae, sanulectared by
ie Wastarn Bectie Cem for this apabeaton 2 ceed ta
vide power autout 0: 17 wfcts with 835 AB oF gain in Ue linear

‘Ae fe usual for wich devise, the tae i apersted at 2 Lo UB below
the suuimum gover aatpue sipabilty of 20 mats ip onler to herp
Tntertaotiliion eee Low. Nu, ik has bran designed ae «com
peter pact desea zo seve tas wiser af fete cl acjasbsele

fr age seine atthe iaetauetio ste. THe package is desmmee
fo tha the mgmt strulase can be zcelnitoed ne the nf the db
|e or beequet ree,

‘Phe apie, show" in Fig 1, mieamuge O48 20.1 0.11 meter

lcs ule fiom siteniritoe nike mess wn te el
ae ie ET
BRA uy ulti avORDN LEQAAONL JOURNAL, SEONIBNOEE en.

ig 2 he SA toot mene tbe power ame

sd weighs 2 ke, The evacuated cube is not visible ater kas been
packogo:, Input and output 1 connections ane retuoadebeiht (2.64
fam * 40.¢ ems} waveguie, Power lo run cb tube is nzovided
fold etete related bigs-vnkagr sippy

‘Table T sumaaviscs the system reayiemests un dhe 481A tube
‘nt egpiealdevier perormant

‘iner the passer ena For whic this deview. espn is higher
than wool previously for Bell Sysem radio wig tranerision, the
ince structure as een ci ‘of previous traveing-
ware tubes,

Taman] A614 TWT Ocueenoy asp Peavomuases

PRS ag eae Sets
‘Dpecatag bees acre ma
‘own ananarie 2225

2 kleotade Voinges oat Bran Carrot

CColeuntions showed that in oer to obtain » rurale pnmer aut
put of 43 dB it nou be weceaary te use o beams current! 58
hullismpenes, asnoming syuelronoue beliz veltaze of 3780 Ve. The
Aexinal poner enn alsp bo ablaived ving a semewbst higher Helix
voltage and lower heam exzres, However, this woud reat im longer
lic ad sure «ill he ix intenespepreblens.

"Tha collacorefiieacy of she deviee ss 19 pero spiel for tes
of this type. Tae uee of ruliple clletars asc! tapered hel sections
thud bern ncbenel te farther ivesar the fleieney, bus it ms eam
tleded twtr lfisiney mproverion: aod cals which were out
Of proportion to che rani be guince

Ths tlw earrant and voltae were whew a bra goed! compromise,
shies wlawe for eemomy a: anuexot design, wile will obtsiing
Foliefetory gain ad power output with n sesso Leng of li

2 Giker Parameters
‘With the beara valtsae stl ruck eetabliaed, some of the other
paramos of iene ae
‘Catade cums demily = 20 we
Bears tote dismetee rain —1.5,
Clie lengrsttze = T5020 fe)

Helis
se amtar foe 0.54 wwe lin
ive eng
ilptsn leans fetor = arse

fein per oontnseer = 3s an
il poqagaty naan 148,

4 order ly lian ‘igher operat porter, the Mesa current
Ten inesestl as dicueset iy he puovious srlion, Tha eet a
Fipter earnest bushy nthe bel aio boeouse he bel diameter
inteonsreized by eonsMcrier= ote design of the magnate visu
fu il shine reguiemante, Tie eo bse che advan HG, withont
rush sarge sit bean sonsryy ms, cho eethode reat dene x
ew ae the sense valve woe yervione tao the 4624, reall
jn in the long cathode lige egonb Thy cemanstrates by choo other

se sea to allow evs oh tn overcame hs wt the sh
22250 rom BOTT, RYSTEAT-TROMNTOAT ona, SNETENERR 171

eviews. The beron-so-belis diameter ria is u conservative value of
105; this is in eompurzen to higir rtivs such ns U8 oF O8 ih
evil in higher pun por wath Fis, bul es giee probes
in Lecping the beam in focus aed eould result fa eve sell
ment of the tne during operating fe. ac eathede teuperature of
HO°C ia alse oonservacive eioe; while goexer exchode fe aught
Ie achinves! at cempensturs ele ta che edge of the tempenatune-
limited emission regun, 680°C U9 TIC, se eae The nf 254,000
houns sssecnte® with the einen operating terpenes ie wore
thar adequate to mzeb the dosige intul, soe in prectioe ether
neers list the opeensing hie below ths He,

‘ho hele paramos Tnced above 14 onmslte the deseription of
tho tube reel fro ‘he velluge al curnot devin poevioesy
dhacused,

2a Moguete Boeusieg

Yo obcain sreistuecory faoutng (ith Alnito-® mugoot u-evnl)
tha sangue: verod aust be somewhere lew thaa 16.3 mm. A valve
of 1539 mm was chosen for “hie dosign. Calealaticrs ot cho Beld
required showed that mummubc Hild douse prewar thu OTD
veel) ate tsquines, do 4.96 9f OID THe talon we the design
fignme* Exzesinertal vice of Sox invereeption corre lave been
Feu! tn i ln O pevser: of t= eathede cuent. Beenis> of t=
ih enor of le leutone whi are ilercepted and becaese the heli
tsructare dpa on lengttira’ conduction for coe, important
{hat this fice Tow, pavers bly Telow 0.5 mA. Hoot testing of Ue
fox structure ab helix currents yeealer ars 08 1mA begins (0 real
an aublition of li atria those ax ong

24 Operation

‘Tho BLA bas hen designed for qserstion aaove the eyasbroaous
nei yellag, The advanregee nf this mede 6° cpetction ene two
rst, thes valle Beeoen gan conte, ls ina!ing Ue ae! for
fhe ageter Uo necommlate spore aes gai. rend, she sari
vevtoise zitio ie greater by 3 to T AB, This evtrieroanie ead
sacvantege ia gained even though the noise Qaue ab the welval pera
ing point sua’ bo ove iv minivan ee, The sini noise gue
fours at ¢ nels voleage which wales seat fom tube to tobe,

Gigs seine a previous aie! Live bem aol Ma a wel:
ooh Chae
‘owt snmiarim pd

ad ne a bolic vellage wreter than sbat for evashronces operation,
‘The tule i raw with the helix voltage inreased atove synelronous
soltage uni the oulout omer decrees to a0. dln wich w eonetemt
ingot of 47 dim.

"The manner in whieh the power output vats with helix vatenge
uusler conditions af diffrent inpus power isnot very diferent for this
fleviee them for eeurable ties, 22 shosr in Pig 2 Higur dt bore
Ue satetion pone eats, when caeuleed inden the cendition
‘nat she tae ie ran wih Cie hells vllage inerese lo give 38.5
iptin, Figuce 4 shows the biga-level gain, ot mibaad,euleultod from
Fig. 2

a The Halts

Corumie ros syppest a molybdenum wire Delis whieh je glared
to tao rods ot cach poi of enact between tod ena wns, When RE
borer is sppliet ta the itpur of a medium. or high-power ceuvaling-
‘rave tube, the poser ouput gradually deereeces irom the initial
Yalu over a pesiod @f frum lwo Uo five minute, Thie “fade” oceure

¢e

ig, 2-Bovee i be vee ree for she AA end
§ De ge on oemee re ve
: Be See
ied

A

ig St of os gate pti on pro ci

Ione the delete provesew uf UheTelix siopar! vals change aa
‘rom: of heeing of th rod,

‘Since the 4044.42 boa postr density 21/2 Lowe a gh as
precceesore, the demo of fede eould become inveizuble snder some
‘erating eovlitione. ‘Therefore, ating was recuoed by the iatrodue~
tion of & gap of 0.27 mm between the halix ware nd eeramie support
rods fora siee ef sen ‘urns sway from the extpat coupler. The
tpi proce hy pricing a ato each Tea. "Thie yervonteexecesive
bhtving 0° the evtansie rose and cavocited glaze at the paint were
the Geb hens fs arenes, At Menthe ante dace is only 02 eR
‘wich this provision,

"The applied les iso taxzalnm film applied by aputeeing* Since a
toss of abt A0-aR iseequired een he input an etn sete
to prevent elton, grealer Us M7 of lose x apple co prove

94 The Moats Fo
ae of Tigh und eampaot perio permanent magnetic (PPM)
iepai allows the tube ard magnet to be ship ac an intogel wit
"The che beara focus and electien!eharveterieie ean be optinaized
at the iaetorg. At the end ot the taeful feof the me, the enti
sucka ie eeu la Ube footory ‘ar eat of Lae magoolio eit
sre suru 29

Fig (ghetto fst af halls weg, bas

‘Phe magnetic est consists ¢f 40 Alsion-8 rng mmgnele sacked
llomacehy ch sme ioa pole peor (Fig. $1. "The magnets and pole
Sicere ae olizte ning @ oieeson cde. Av spexy achesire ie
sed fo eneapeulale we eases wit on easing hesing, An BF
‘hoe is provided ner Ue inal te prevent leaege of Uhe RF through
he gas

"Te athiove long hf i sesirable thet the eallestor be wlemuntely
cowie on that etic eutpereateo° the tube sxe aa everkeated. The
Tuoniual hea ceeipuion nf the enectar ie 110 watts A unximstn
ful eclar rncensture uf 161°C wernt far nominal eeoling eowetions
fx hie divsipaton, ho ellsctar ile ink a hole inthe copper cooling

a Sh conssitiol wow of he 461A sal acne
ad) mmr nett avermo TeoMvTOAL OURNAL, HEOTEEE 971

block. The bole dn the cooling block is 0.08 mm: larger thas: the ele
leetar diamocer ce allow rctir of te ealleetr which im torn. per
‘liazmeni 0” Le eleeron isan wi the magnetic fled. "Pie pace in
‘lled with w theraally conductive silicone paste, The elector ie held
rial (in single transverse lane) byw referee arfnoe lowed
between the mamatic sick und the cooling bed Tro cooling f
‘re actavsed to the cooling bled Caring ine.alnien ofthe teuveing-
crave cube in the rio by

"The sabe ie package in & sheet tes! enclosure ‘or RW shielding,
teenth, al mista eal peleeinn

8, Patra te

‘The A648 sacs a eoavengent Powe typeelesteon gun. Te gun as 8
parents of 207 310 "arp/sale™

"Phe eashle base matorial ea higa-purity nkel with 0. pereane
singoniues edditive, The eifusion zete of the sreoniure in thi mskel
Jn lower than that of the ativacing agente in “melt” nickel. Maro-
over, the arrival re of aieonium at the nickel-eostng intertane i
sore nearly in balance with the rates of the other nretses essential
to cleron emaign, The ris nf suet the aren nike
foe “mek” nik! ie thus the ultiunte oathode wn waa eating He
jn incteared are eathore autlimatie: vitally eaninatod de © fail
meenaniam, Furhermore, the sfitence of getturing oa barium pro
"Wetion ie creased. Figure 6 shows the seonium dfusion rato and
‘maling depletion ealeulated for this cathode £8 a funtion of time

Field experience with early designs of traveling-wave tubes indi
lente shat one he fare reekasini bas Seer aevocated ch the
fuse aterint uo ie eurbrseson The ler Coma Unt he
tease fer to slertealyar curing Ie Iie of the tube, heroin ene
fdetive in high eerie ele nal Teading ohieraely to Tnates, The
mmecharieal design of the 4044 cua is euch that n0 plc material is
‘ee in ite coastrction, Ono eerami pltfonn is waté to spore parte
ft high voltage god thie ie cone 20 ae to permit the wen of ee and
svt fastening. "The basis us surelure ie town i Hie. 7

44 Gain and Power

‘With on input power of 7 dBi applied, the dested output power
(of AOS dBm ie achieved hy adasting the helix voltage to an appro
rine value shove the aynehrenous leit volaye, Te nocunal hh
mr ooune si
iT Paar
£
EY
bet
g nnd,
- pee

devel grit about A ab wher sh We vleage i et a the eyusbo-
we ale

"The broatband gain fetness charleteien are optimized dorng the
aeseily oF the package st the Fmory See the be i preset fox
Shevntio aer the entire frequency but, comple inyedancr mateh=
ing udjoanenls gd essuremens are ot required for oting up the
{be sn the radio. bay, Tung adjuements ane incorporates he
hhiesomve-mlsgete ciuite whieh wttaeh to the snp ar obtpat
ports uf Ue tnieliagewave tube, ‘ese ere adjnetod for suximtsa
Deput in he sactealar vaio ebranet 9 mich the transmitor ie
petals

sn Note
“Phe ke perfomance ofthe 4941 traveling-wave tube ie menue
in tor of «ruie-pain poeuct (9). This ie defined us

me
Tig A vin uf esac ge

rhe Ny je he tema seats the bveTingae tae i
olsen’ constant, Tis allay temperarice, ani B i the band
width

‘The noietguin procuet is measund using on PM detcetor since FM
noi ie the ipertant cempanent in an IM ayetom. The measurement
i made with the traveling ware tube driven to an output pewer of
$045 dBm. A earsce milling terhrique i used ca inctesse the sensitivity
Df Ue measuring agen

Tot ive perormanes of the divite i achieved by immersing Ge
tun ine nall raaguelin fed. Phi has the otek iting, ae
Frowils af a quircange wave a voien Tie eal ree ek by
fielded by ent sshie™ osrmads the gun, The noise prfarnenis
'optinaed dating (he package noel hy adsting& sre eee
noe in the ool vine,

1a Live

‘Sinve the celiabilitio of otter eompocents inthe eystem are designed
far the long life sebievsble with sl state devices, this tbe has been
\esigned ts be se compatible ae posible