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which might result from synchronous detection of pulses of the form sin rrB( t-t i) gi(t) = A i rrB(t-ti) cos 2 rrVot (14) The spectrum of a single detected pulse is constant from 0 to B/2 Hz while that of a single pulse prior to detection is fiat from Vo - (B/2) to v0 + (B/2) Hz. Both spectra are zero outside these limits. The matched filter is either a predetection ideal bandpass filter of width B centered at uo or a postdetection ideal low pass filter of cutoff frequency B/2. (In this case, because the two in tandem are idempotent, both may be used,) Since in this case the matched filter does not affect the signal spectrum the signal shape is unchanged. If ti = i/B in equations (13) and (14) the peak pulse amplitudes will be independent. Thus independently detectable pulses may be sent at a separation of r = 1/tt sec, and we may consider r to be the effective pulse duration. We thus have Br = 1 (15) a relation that is approximately true for any matched filter where B is the RF bandwidth and r is the pulse duration, both appropriately defined. With white noise, the signal to noise ratio from equation (11) or (12) is S 2E i 2,4i2r A i2 N _o _o _o(B/2) If a long train of such pulses is sent with a constant (16) Ai=A, the transmitted signal amplitude will be constant at the value A representing a signal power A 2 and the received signal will show fluctuations about this amplitude of mean square value ¢/o (B/2) representing the noise power of spectral density 4o in the band B/2. We see that the combination of synchronous detection and matched filtering gives an output signal-to-noise ratio that is twice the received signal-to-noise ratio if the latter is defined as the ratio of the signal power to the total noise power in the RF band. and optical frequencies the radiation may be allowed to fall directly onto a photon counter. A photocell, like a square-law detector, gives a response (current) proportional to the incident instantaneous power. In principle, the limiting noise performance of both types of detector is the same; however, at radio frequencies most of the output noise is produced by fluctuation in the random noise input and shot noise is usually negligible, whereas at optical frequencies the reverse may be true. If a steady coherent signal of power Pr and an incoherent (black-body radiation or thermal noise) background of power Po are both applied to a square law detector or photocell the output signal-to-noise power ratio is shown in Appendix D to be where S rPr2 N (hvln)(Pr + Po) ÷ (eolB)[(2/m)Pr ÷ eo I r = integration time B = predetection bandwidth m = 1,2 = number of orthogonal polarizations reaching detector r/ = quantum efficiency of detector (17) The ratio of Po]B to hv]ri determines the relative importance of the ratio of fluctuation noise to shot in the detector output. If we let _brepresent this ratio, then Po/B _ spectral density of fluctuation noise hv/'O spectral density of shot noise (_/'o )/B hv In the last form we 'see that _ is the expected number (18) of background photons counted in the time 1lB. If _ >> 1 fluctuation noise predominates; if ¢
In this expression (Br) is the number n of independent samples that are averaged; Pr/Po is the input signal-to-noise ratio and SIN is the output signal-to-noise ratio. If (Pr/Po) >> 1 we see that (S/N) "_ (n/2) (er/eo). At high signal levels the square-law detector gives one fourth the signal-to-noise ratio of the synchronous detector, for which (S/N) = 2n(Pr/Po). If (Pr/Po)
Page 1 and 2: (NASA-CR- 11_5) PROJECT CYCLOPS: A
Page 3 and 4: CR 114445 Available to the public A
Page 6 and 7: At this very minute, with almost ab
Page 8 and 9: ACKNOWLEDGMENTS The Cyclops study w
Page 10 and 11: COMMUNICATION BY ELECTROMAGNETIC WA
Page 12 and 13: APPENDIX A - Astronomical Data ....
Page 14 and 15: t _ 2
Page 16 and 17: of the living beings evolved by the
Page 18 and 19: Figure2-1. M3I,the great galaxy in
Page 20 and 21: self.Thus,wecaninterpretFigure2-2as
Page 22 and 23: magnitude (low brightness) end, the
Page 24 and 25: Red Giant. The transition from main
Page 26 and 27: tion, as the central part of the cl
Page 28 and 29: TABLE 2-4 SELECTED NEARBY STARS WIT
Page 30 and 31: tideraisingforcesasr--_ where ,v =
Page 32 and 33: 3. Is it possible that living syste
Page 34 and 35: lawsof natural selection, more like
Page 36 and 37: starsthroughout the Galaxyhave also
Page 38 and 39: if the longevity of that life is ty
Page 40 and 41: The imaginative reader will have no
Page 42 and 43: Lookingfar ahead,supposewe aresucce
Page 44 and 45: usuallyterritorial expansion by the
Page 46 and 47: IOO IO 1 [ [ J [ J I J i [ i I i I
Page 48 and 49: order with what Morrison has descri
Page 50 and 51: The quantity gtPt is often called t
Page 54 and 55: 1. Wewillnothavenough resolving pow
Page 56 and 57: normalwith the meanat o x/--2. When
Page 58 and 59: Chapter11 in analyzingthe dataproce
Page 60 and 61: Therangelimitisthenfoundbyequating_
Page 62 and 63: TABLE 5-3 PARAMETER Wavelength Tran
Page 64 and 65: angeanddirectlyasthesquareof antenn
Page 66 and 67: "_ i i i i i p = STELLAR DENSITY AT
Page 68 and 69: I-- g u. O >- I--- .d tit (]O 0 0.
Page 70 and 71: andwidth that will still give near
Page 72 and 73: acquisitionphasefor otherraces.Supp
Page 74 and 75: 1. They would transmit continuously
Page 76 and 77: and ¢-Ceti. No signals were detect
Page 79 and 80: vz .i g)mo PAGE NOr Ir[[,MZ 7. THE
Page 81 and 82: The price of incomplete sky coverag
Page 83 and 84: modest size.A largedatabaseontapeor
Page 85 and 86: THEAUXILIARYOPTICALSYSTEM Althoughn
Page 88 and 89: edetectedat 20,000light-years byCyc
Page 90 and 91: feeds must correct for spherical ab
Page 92 and 93: side of the dish and shade on the o
Page 94 and 95: TABLE 8-1 UNADJUSTED UNIT COST DATA
Page 96 and 97: 7. Using huge specially designed ji
Page 99 and 100: 9. THE RECEIVER SYSTEM The receiver
Page 101 and 102: whereP is the radiated power. Divid
Page 103 and 104:
SHADOWED AREA SHADOWED AREA // // /
Page 105 and 106:
Corrugatedhornssupportingbalancedhy
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o 50 ----- - _ T i 20 _,o 5 ,,,5 09
Page 109 and 110:
TABLk ?- I A COMPARISON OF VARIOUS
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CENTRAL POINT STATION LSB LINE FREQ
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A02 .... + No (25) (i C 1 where No
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COAXIAL LINE DIRECTIONALCOUPLER FRE
Page 117 and 118:
DeJager, J.T.:IEEETrans.onMicrowave
Page 119 and 120:
pR_ING PA6E BLANK HOT FILMF_ 10. TR
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o-------------o_ _ o o o o ing of t
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addedto theother IF channel. The tw
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INPUT MHZ _PF 500 MHZ i : 575 T1 92
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azimuth _) has a delay (2a/c)sin 0
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stripline. For 2 _< k _< 6, appropr
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mation are common to all antennas i
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A cable pair costs about 20 cents/m
Page 135 and 136:
11. SIGNAL PROCESSING The Cyclops s
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1.0 T t t I I r .9 -8 asynchronousl
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collimated coherent light. A simple
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power of the film and associated op
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samples simultaneously onto the sam
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outputs is assumed. COMPOSITE SIGNA
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SPECTRUM I n LINES M n LINES U SPEC
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signal andyet have a tolerable fals
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i --_- i i i i large values of n. T
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plottedin Figure11-15for various va
Page 155 and 156:
All the1Fsignalswillarrivein phasei
Page 157 and 158:
x:(1 +x) x 2 - _ -- (53) If we wish
Page 159 and 160:
3's = unitcostof signal planelectro
Page 161 and 162:
where0ma x is the maximum value of
Page 163 and 164:
Roughestimates of the costs of buil
Page 165 and 166:
12. CYCLOPS AS A BEACON Although th
Page 167 and 168:
13. SEARCH STRATEGY The high direct
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distantgalaxies (oraninertialrefere
Page 171 and 172:
wouldfollowtheuppermost linein Figu
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persquaredegreeof fieldwouldberequi
Page 175 and 176:
starsfrom/'18 to G5 could support a
Page 177 and 178:
14. CYCLOPS AS A RESEARCH TOOL Thro
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Only a few such galaxies have been
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15. CONCLUSIONS AND RECOMMENDATIONS
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perhapsdecadesand possiblycenturies
Page 185 and 186:
APPENDIX A ASTRONOMICAL DATA DISTAN
Page 187 and 188:
PLANETARY Planet ORBITS Semimajor S
Page 189 and 190:
APPENDIX B SUPERCIVILIZATIONS AND C
Page 191 and 192:
ABIOLOGICAL CIVILIZATIONS Many writ
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182
Page 195 and 196:
tqOT APPENDIX C OPTIMUM DETECTION A
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to rmsnoise.Wenotethatthematchedfil
Page 199 and 200:
APPENDIX D SQUARE LAW DETECTION THE
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If the output filter is very wide c
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if B/2 > T we can start instead wit
Page 205 and 206:
Let us now introduce the normalized
Page 207 and 208:
where h-- = expectation count of si
Page 209 and 210:
APPENDIXE RESPONSE OF A GAUSSIAN FI
Page 211 and 212:
APPENDIXF BASE STRUCTURES AZ-EL BAS
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ack,it shouldnotbenecessary to prov
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204
Page 217 and 218:
206 i
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PAGE BLANK NOT APPENDIX H POLARIZAT
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APPENDIX I CASSEGRAINIAN GEOMETRY C
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APPENDIXJ PHASINGOFTHE LOCALOSCILLA
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APPENDIXK EFFECTOF DISPERSION IN CO
Page 227 and 228:
APPENDIX L TUNNEL AND CABLE LENGTHS
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where r = "Ym/'rs- If we let o-_--o
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L-4 we see that the length of IF ca
Page 233 and 234:
APPENDIX M PHASING AND TIME DELAY A
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andobtain V = 2 (Ps [! + _(Ar)] +Pn
Page 237 and 238:
L" D 226
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APPENDIX N SYSTEM CALIBRATION The p
Page 241 and 242:
APPENDIXO THE OPTICAL SPECTRUM ANAL
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232
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APPENDIX P LUMPED CONSTANT DELAY LI
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Thevalueofthefinalcoilonthelineis =
Page 249 and 250:
APPENDIXQ CURVES OF DETECTION STATI
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I I I I LE :E oo
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APPENDIX R RADIO VISIBILITY OF NORM
Page 255:
io 3 - l rlrllll I I I ]l+,ll_ I _f
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