PULSAR COMMUNICATIONS SYSTEMS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-00120R000100020004-1
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 3
• Document Creation Date: December 20, 2016
• Document Release Date: December 4, 2003
• Sequence Number: 4
• Content Type: CONT

i'.325--053.
Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020004-1
XR 3550012 EX
Dec. 22, 1970 A. A. SHOSTAK ET AL
PULSAR COMMUNICATION' SYSTEMS
Filed Feb. 25. 19#9
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 Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020004-1
United States Patent
3,550,002
flice
Patented Dec. 22, 1970
1 2
3.5; 0.002
PULSAR COMMUNICATION SYSTEMS
Arnold A. Shostak, Al lint:VUi, V a., and Ronald H. Trout-
Iran, Essex Junction, t., a -i nor, to the t oiled States
of America as represented by the Secretary of the
Filed Feb. 25. 1969, Ser. No. 802,084
Int. Cl. 1104k 1/02
U.S. Cl. 325--32
milting detection and precision tracking of remote radiat-
ing sources such as satellites.
Other objects, advantages and novel features of the
invention will become apparent from the following iUe=
tailed description of the invention when considered in
conjunction with the accompanying drawings wherein:
FIG. 1 schematically illustrates one arrangement for
utilizing pulsar signals in an antenna interferometer hav-
ing a large base line; and h
FIG. 2 illustrates a communication system where t e
pulsar signal is utilized to achieve secure communication
between a pair of stations.
Referring now to FIG. I of the drawings, a pair of
steerable antennas I and 2 of a long base-line microwave
interferometer are oriented at one time during their opera-
tion to receive electromagnetic signals originating from a
predetermined remote pulsar. This pulsar may be C.P.
1919, for example, whose period is 1.3373008 secs.
The signals simultaneously detected by these antennas
ABSTRACT OF THE DISCLOSURE
There are disclosed arrangements which utilize the
signal energy from pulsars to accomplish, for example, the 15
synchronous operation of widely spaced electronic coax
portents or the secure transmission of signal information.
The invention described herein may be manufactured 20 are coupled to receivers 14 and 15 at the two sites, and
and used by or for the Government of the United States the outputs of these receivers are suitably amplified in
appropriate circuits 16 and 17. These amplifiers are ar-
of America for governmental purposes without the pay- ranged to control local free-running oscillators 20 and 21
meet of any royalties thereon or therefor. whose instantaneous phase is precisely regulated thereby.
ates The present invention r more ga Beall t, to appara- 25 Any drift, for example, in the oscillator signals at each
control and methods and, more synchronizing electronic devices, ovice site is recognized by an appropriate detecting system, and
suc for and methods en as, which o aed a or the magnitude and direction of the resulting error signal h more s receiving antennas, which are located at two or is used to return the oscillator back to its proper condition.
morwidely eparated, geogCircuits and techniques for achieving this control are well
There are a a wide variety of geographical electronic control systems,
o30 known in the art..
such as time display, pulse navigation, long base line in- It will be appreciated that the pulses appearing in the
fur-
terferometers, and radar countermeasure circuits, which s of amplifiers s 16 and 17 at each site, without the
require synchronizing signals for their proper operation. ohenutputsi signal processing, may be used as synchronizing
In the Loran, e lion system, for example, the various signals for any appropriate purpose. In this respect, the
transmitters itters of f the network must radiate their identifying 35 period of these pulses is, of course, invariably fixed by
opera-
pulse trains at extremely precise times during their open- the characteristics of the particular pulsar 12 then under
fed to multi-
tional cycles. Any deviation in the time of transmission observation. If a desired, these pulses may pulsar
of an appreciable error in the system. One way nincrease or desreasy their to ion etit of accomplishing this synchronization is by an ultra-stable rateplying If such u a conversion is desired as utilized, the new
master oscillator which must be brought to each location. 40 repetition rate of these pulses will, of course, be as stable
This transportation, of course, is expensive and oftentimes as the pulsar from which they are originally derived. This
i impractical. Also, since the local timing standard of the s be in the order of one part 107.
system is subject to continuous drift, this comparison must stability
After may oscillators 20 ord r o one been synchronized by 21
be made periodically. The same synchronization problem the pulsar, the antennas can then move off this source and
is also present in the operation of large base-line micro- 45 track any other extraterrestrial radiating source such as
wave interferometers where the receivers are located at satellite 13 to determine its precise location. In this case,
widely spaced geographical locations. antennas 10 and 11 serve as part of a microwave inter-
rec radio sources, or so-called "pulsars." have ferometer, and their output signals, after reception and
te been observed both in the UHF and S b haves amplification, pass to suitable phase detectors which have
thee spy spectrum. The signals from these pulsars have cx- 50 as their other input signals from the now stabilized local
tremely regular repetition periods. For example, pulsar oscillators 20 and 21. Each phase difference so deter-
of C.P.P. 1133, , 1.87911019; s3 1 3 81of C. P all P. mined may be sent or otherwise processed at 22 to obtain
737620; and period that of 1.3373008
C0834, 1.2 1 1.2 .2 1 has a
a position plot`
plus or minus 3 X 10-7 Since each pulsar can be observed throughout a
Since these pulsars are remote electromagnetic energy 5.' hemisphere of the earth surface because of their remote-
sources, they may be simultaneously observed at widely Hess, calibration signals may be generated according to
spaced receiving stations equipped with suitable le antecular the system of FIG. 1 at any number of points within
These antennas may be programmed to track a panicu this area. The antennas may be shipbome, airborne or
pulsar or shift from one pulsar to another to inure the he round-base.
continuous availability of a suitable signal from these ex- 80 g -base.
arrangement of FIG. 1 can provide a time stand-
traterseaciordingl es. and from the pulsar source which may be simultaneously
it is accordingly a primary
method for accompliofshitheng synchrcnous - observed at widely different geographical locations. The
o #a electronic to provide a method devices accomplishing signal available at the various amplifiers may be fed per radiation from pulsars. which makes use of the to pulse counters to obtain the clock pulses. Each pulse
Another object of the from present emanating ent invention is to provide t1O counter, in effect, would multiply the pulse rate of the
ect
a method of synchronizing electronic circuits which utilizes pulsar by a known period to produce the desired clock
electromagnetic signal information ori__inatina from one pul,cs.
The availability of the pulsar signal and its stability
or more extr obje t radio sources. make it particularly useful in security communica!ions still vide a an n A arrangement ect for of maither.tpresent invention conoherer.to.c be-
pro- a) sv,tems. Each pulse may be used as a means for masking
ainin phae
N7- or ctwlin, the message signal.
iweert elements of an antenna interfenome:cr, thui
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3, 550,002
3
In, FIG. 2 a transmitting station 30 equipped with a
tracking antenna 31 for observing a particular pulsar
utilizes the signal so d_tccted as one input to a mixer
35 which has as its other input a message signal 34.
The output from mixer 35 modulates or otherwise con-
trols transmitter 36 which radiates the encoded signal
via a suitable antenna 37 towards a remote receiving
station 40. This station, too, has a tracking antenna 41
which is simultaneously observing the same puhar. The
pulsar signal available at the output of the amplifier 43
at this station is fed to a correlation detector 44 which
has as its other input the encoded signal picked up by
receiving antenna 46.
If the pulsar signal received at station 30 is fr(t)
and the message signal is S(t), the signal received by
antenna 46 will be S(t)?ft(t). This signal is correlated
with fa(t), the pulsar signal detected by antenna 41 at
station 40. The results of this operation is
(S+fl) *f2=S* f2+ft*f2
where the asterisk represents correlation. If the auto-
correlation of the pulsar signal is substracted off or if
the statistics of S(t) are made such that the cross-
correlation term is much larger than the autocorrelation
term, only the first. term S*f2 is left. Since f2 is avail-
able and known at the receiving site, any conventional
signal processing can be used to extract the message sig-
nal S(t) therefrom.
If the wave form characteristics of the pulsar change
slightly, there is no degradation of the system since
f1(t) and f2(t) are changed simultaneously and in a
similar manner. It would be pointed out that the slight
delay brought about by the finite transmission time be-
tween stations 30 and 40 may be readily compensated
for by adding an appropriate signal delay means any-
"4
where between tracking antenna 41 and the correlation
detector 44.
What is claimed is:
.1. A communication system for achieving secure signal
transmission between a pair of locations, comprising:
means at said locations for simultaneously receiving
signals from a particular pulsar;
means at one of said locations for encoding an infor-
mation signal with said pulsar signals and for trans-
mitting the encoded signal;
means at the other'of said locations for receiving said
encoded signal; and
means for processing said encoded signal with said
pulsar signals to reproduce said information signal.
15 2. In a method for achieving secure signal transmission
between a first and second location, the steps of:
coding an information signal available at said first
location with particular pulsar signals from a pre-
selected pulsar;
20 transmitting said encoded signal to said second location;
receiving said encoded signal at said second location;
and
decoding the received signal by utilizing the same
particular pulsar signals from said preselected pulsar.
References Cited
UNITED STATES PATENTS
3,137,854
6/1964
Anderson.
3,171,126
2/1965
Wiley --------------- 343-100
3,263,230
7/1966
Greenberg ---------- 343-100
RODNEY D. BENNETT, Primary Examiner
R. E. BERGER, Assistant Examiner
35
325-T~8; 343-113
/S,bs
Approved For Release 2007/09/21 : CIA-RDP81-0012OR000100020004-1