BSTJ 40: 4. July 1961: Project Echo: FM Demodulators with Negative Feedback. (Ruthroff, Clyde L.)

3.2 MB·English

PROJECT ECHO

FM Demodulators with
Negative Feedback

iy CLYDE L. RUTHROFF

he PAE eis dasiatre sued 9 the Hho experiment are de=
evi fu he yup. Thee rsors Die gato edbark opie the
Toon! aniatar to redo the PM wultin sda im the reece iner-
rotite frequency empire, This technague remite i a teaadl per
Fhomono bic ie anperior athat of concenanad PAE wee,

I the Paeiece Retin aumcunion:ione exper
te canst wo the rerever wan the caalite nce very lexge Kuen
‘si rensonubly buenos, high poster eu, al lowenive te
rivers thermic signal wa seal cadet teks oe
euite dot ade audit or sigal-tr-nnige ratio {8/3

Far thicexpevint, idebatl Feuer enaltion me aed, with
veering desualaon thawere PAE reecvurs with aogative feebuck

‘MIY, The sagative iellark result et nonoved FMT theese
sve siting xtput $0 Petes team in tex well Erne tebais
hte sine det,

Ie pas Is fon

A simpli! eck sagen of ee FMIFE denseilator is show i
Wig, Ae indiate i the igure, «pt of the busbar (aio utp
ie used to Fequemey muallaie te val votaxe-contralledoseilator
(VCO), The dione phased fn saa miapne tha the VCO dre
‘avec vad to fll the frauen Fatt of the TE inp ia
‘The rt isn alton of tho sno aor. sade ofthe LF signal wa

se areca ator Sek eames
M50. rm arta Sverre, BOLUS Sy BE

ee >a 5S

| eet

fo Nisin of che IE signal aon of aie, sganive foobar TE
te BP iex AF he LD inden ie MEP, whee #2 eek fae
Sinow the TF india eal, the TF noize boxdvidth ean be mule seller
thn the RE bandwith gd a hprovement ia threo ae be ex
eerie tletive to the thee ollsined asing conventional FNL in
{ie sun RE bandit,

“Phere are is limita the EF Ber By a wellenasn approx
mating i FM work, He hd sequived to eran Iaatbane
wrt stealing rn Oto eles pr sane ie

Bl an a
‘where AF = afifoinsbe EM fie laf is she pr requenty detain
jv eyeles per second, te elegr dal the msininsim required amt
i 2h nove the bandth of the TF Ete ina WM TR ever nist
Te at lat thi ier asi mization on the TF Glee bas to do
wth the sail 1 ella Lop,

or eotest veil augacvement the noe Bandwidth of the flor
could bs sal This eget seep aire. Bee's sti extern
“be other fu ins the seeprass of the sels I a wae exec:
{ng about 10 b per ostav ue practiva’ ravivn The caiterion ie 120
fry bul ot sfieient 20 aire Sabity when wodalavor 's pel

T venmplete theoretical ants of lw esol eet the recive
Thar oo buet made og yet Mower, thee iz ettong thewetiend and
fesperimental evidence! that de 740 a€ which the Uweboll area is &
Fooodna of the ele loo Faudwicth, the thresbold occurring when
the C/V othe intgole seo Esa ent a

"Wet referent to Fig. 1, 3" apetelood bona sa be eesure
by opening the lop been > a ad anesring ie gai guns
espn between any: The owsl-up bandit oa sand
ty miensurigg Lee win feaqueney reponee from the tranactte to tbe
osiven one ith shu was, For il a thee measurements,
lowclevel ial shonld be ned. Fi. inden he typeof rss toe
sspected. The haan sale ane eon ie atl LP ehanacevates
ing. symmetrieal abot the TF eure feueney,

he peak hv Uhe elea-pvespnse incre the noise bandwidth
and is therefre adeiabln. Tle light of the pak is depreet pon
the steepness af the gpenJoopeesponsn ad uj the pha bil Ws Hi
iret, Corrs the thresild of this PALF swore frat
‘ksigning the feboe: nelworie for minim closed loap nse band
swith

The peefarmnae of the FIER rossinee hove the threshold can be
esa ith the wid of Tig. 1 When she fedek op ie opened
X the reerver isan erdinary 3 receiver. Above the Tt the
output signalonoise power abo is

By%e = WEEN, iy
tvhowe A che meaduation index and 638 “the vere beaive newer
Fai a ne sto the Fegan eset, yc mses yer as
td ta Teeth of 25, The owed toe tie case he dl Ip
Tire
Wher che Toop % evse the FM aes the i rueed by the

i L Ngee tee

3

2
152 rane ag eve eH IPA TOURS, sO

feedback ‘ator 8. This eer fr Hath sgn cx oie, wo chat Sie
remains uncanged. ‘he inde f he transmit nw be nerense
by Pa resre voigingL ML inde the Pisces he pat
Sv Mo by ta eet?

‘Weis evident thea thet at operation above the Uhneduld tbe ouput
|syNotsgiven by (2), whore Afi the FM nex a the (ranemisee "Tis
isn fr both EAL nd MIF.

Th tuuuery, the sigan! ieee pertormas in EEE is loo hy
{2} above the thrall, and the threshold eerurs at 2 C/4" whieh d
tend pon he elven haat

“Sword of enti i ead hm The fnegoing elements have been
made on the essunption that dhe feedback i= large. For very small
mounts of feck, she tersbold hehavior appronches tht of ronven=
tional FM

‘A somlete bork ingra of dae eoriver i shown in Fig. . The man

eG tetas sw ey Le lc premier, ae,
ae atact op tes fe RF spin, sake
nt pwn an 8 eect aie
ee
bw oe,
“The purpose ofthe AGC i tw fold. Tke anion af FA Salar
Gc Joop gain) ponpertional to thn carer vel tbe inp of he
Uevasnaien, he AGC muaiatsiae hs level constant end tailines
"he Ino gain, Prastest miss anon god omengh fv Sv iy dh
fae’ iit pint annie sh he rnd for Lest Ting

"he second prapnee ofthe ACC ir provide « menaune ofthe noeived
carer strength, The ACC voltage is calfrated interme af kwh geal
levels ut the exteura anput

"Mabaso Mie foram af ty resins we: ae lh

tbe Kaaateny stdin the Fold, Fg ss ancronn of sale SM
ee apa CN aad adams oe eal, Ve C8 dy selene 1m
‘vk no's handwidrh As Image seeetinn filter pero the aie, wd

The RF CPN fs esi a of i le
"The ences CON ul wake the since secure sriewhalacbiearyy
singe “ie Kae of the atv at sap. Tevet I aie ae

He (28 hove Wie etd the itil very ies, Ab ie pin
reared “thveehol in Ig. eesing o pop aca beg, Cite

fect set eich wove ors-Koliy hike the popping of oom,
Th thie work, the verbo snes wv wen the poppe arts
This effet tthe ogee sh mee deat tha fy lene ay che
tiesto ts Sy Ts gna sty Hata Ul ek [as thot
"ne sis are wise way, be jal tne tel
Ue onelty accom. A menanenent Af Sy/My stats C2 Ta the

tae wee the eheek ewe ep pen i eid hr Fig 4 Ts Ue

‘CN 00 REFEREED To OME NOSE QANDWMI
Gt a wee SORA TRPMAGEAL LENA, JUL 6

ENG

Giguen ce actually 1/2. tha plotted ed seferred to the ri ontpn
Sh abeained aluve he Vavsold, ‘Tae ereekold nprvvernn of thie
feesver, come ig a ranvvationeh EBL reversing tie eae
andi, ie flo 9.

“The mula fr enoneyvepense cf th recive ingen i Ff, and
femined pry iy the lie athe uo ape

‘Dacine th wotationa* tha mein pseme see sted y inserting
ogi sgl ata th aateacas arc pol ing te omtpnt SNe wens
Tq canton poet. Hg, tan example of such = eabration trade at
Galdetona, For tas arto steel cece 129 Tl,
tl he fed appeal 23

When the woke wwwiving estens ia Svylon, he anor of the
tHhoslyid weusnvinene ina baucdon of the wvsrey of te RE input
fieuel TstT wo’ tle gain ene ses ceapenstary eben tye RE ae
feiver, The — 120 ln ssahold quoted alee, waste observed ane
Sf pte ls worn oni 2,

{Tee minimom fandidth nepnl foe a trequeney-vedlaled sigue
5s tovoe Fuel of he tdlaing sual, The TP fie i he
IMET raciver thenfave fa this baad, dy 2%. Ae diese
Drevions'sy the oxi WneeboalSmproweren else when the
Covalteop horalyidl ie tnimuge Sor given Tolbiek bane. Any
fxees phae nit il nese thn eleddu avddth ond tare
frees

Fes earesirents woe comnetin wll Noon Avoeutie and Space
dual Caos MAST
ro” pean
ai |
? ee ee =

Int Koko rersiven, all evita were mule wxnely oad to ie
sige exreas phase, cl the aheping wae dane in Cae TP ier. There ere
fevered important fuses whieh eran diesen

UF Feopunsy

‘The output cf she Enos diseiinator largely atvien poe
‘This eunsor be allowed to reach the VCO #9 4 lle ie vequized ta aeduoe
hs eur ol te Izmonios so lle the baasband throagh ith the
levst powible phase shift. Therefore the LF frequency should be as high
1s posable, be upper limit i defermine’ by the eet @ obtainable
fur the 1 filter, Cu Qs in tho magseyelo region are Limited to 400 t3
500, an TT freqoeney of 1.2 mo wus chosen sequing Imad Q's uf
approximately 12M) ke, ke — al, The eerespascng basen Site a
devi wit a exalt af

2, item

‘This fee akan win it 4 ing: kel natal, Nav ltorng bs
edn theca sce he noe he Tt Us srl te, The
tial ileringg wih ewpcitone wold senate the outta would
lntzoduce ext nae shite The bulumoed prety provides some
Smisng in the abou of sao
ims nm aresiae mmnnoat eRsan, SOLE 18H

aa Eiter

iitere contain reuelive cleats ane therefore add to the exeoss
phase For this msn snisage intone sore avoided and angle
tage liner yas ne Hie best ries thin iar reqites «eat
inpat level ees AUC operas ee feel tthe he inp

‘The anti 9 indebted Wy WT. Bdtmane, Je Zar muck of the
coaipmet design, Testing nl poretin of the ntcvers. Noceworl
(tosribicone were alse uate 1. P-Sbaer, HB, Rll Fs Da
dt be I, Elo,

1 Cgc, 3. Appleton of Noise Fale Hope Modo

Nef! Ro Fast idlaion —Tawory of the Pedhask Bowing

Fe te Heth fa ae Wave th Hd Noi, B04 20 188,

2 ots FG Hering tot, ies 3