System generating sidereal frequency signals from signals of standard solar frequency without use of mixing operations or feedback loop

Granata, R. L.

Mccaul, P. F.

English

NASA Technical Reports Server

REPLY TO 
ATTN OF: Gp 
TO z 
SUBJECT : 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
April 5, 1971 
USI/Scientific & Technical Information Division 
Attention: innie M e  Morgan 
GP/Qffice of Assistant General 
Counsel for Patent Matters 
Announcement of NASA-Owned 
U,S, Patents in STAR 
In accordance with the procedures contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8, 1970, 
the attached NASA-owned U . S .  patent is being forwarded for 
abstracting and announcement in NASA STAR. 
The following information is provided: 
U,S, Patent No. 
Corporate Source : eoddard 
Supplementary 
Corporate Source 
ASA Patent Case No,: 
Gayle Parker 
Enclosure: 
Copy of Patent 
N 
0 
9 
3 
9 
t -
=! 2 (NASA CR 8 8  TMX OR AD NUMBER) 
lb 
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19710013698 2020-03-17T03:02:44+00:00Z
Filed Sept. 28, 1965 
SIDEREAL FREQUENCY GENERATOR 
F) I ,- 
2 SheetsSheet  1 
INVENTORS 
F i l e d  Sept.  28, 1965 
P. F. McCAUL E T A L  
SIDEREAL FREQUENCY GENERATOR 
2 Sheets-Sheet 2 
A 
O B  0 
BY 
V c .- 
W E N T O R S  
tent 
3,417,316 
S ~ ~ E ~ E A ~  R E Q E N C ~  ~ E N E ~ A T ~ ~  
Paid F. McCaul, Mount Rainier, and Raymond L. Granala, 
WyattsviIPe, Md., assignors to the United States of 
America as represented by the administrator of the 
Naticanal Aeronautics and Space Administration 
Filed Sept. 28,1965, Sea. No. 491,054 
2 Qaims. (el. 321-60) 
ACT OF THE BlSCEOSURE 
Apparatus for the generation of sidereal frequency sig- 
nals from signals of standard solar frequency utilizing 
only multiplying and dividing means arranged in a serial 
manner. 
The invention described herein may be manufactured 
by or for the Government of the United States of Amer- 
ica for governmental purposes without the pay.ment of 
any royalties thereon or therefor. 
This invention relates generally to frequency con- 
verters, and more particularly to a system that generates 
a signal of sidereal frequency from a signal of standard 
solar frequency. 
For many purposes, it is desirable to have a time scale 
that utilizes as its basic reference the relative position of 
the stars with respect to  the rotation of the earth. A 
signal frequency based on this time scale, better known as 
the sidereal time scale, it utilized to drive telescope sys- 
tems and for checking out optical tracking systems. Many 
astronomical studies require a clock to record sidereal 
time; this being done by driving the clock with a signal of 
sidereal frequency. 
Sidereal time is defined in terms of a sidereal day, 
which is the interval between two successive transits of 
the first point of the star, Aries, over the upper meridian 
of any point on the earth’s surface. A sidereal day con- 
tains 24 sidereal horns, each having 60 sidereal minutes 
of 60 sidereal seconds. In mean solar time, the sidereal 
day is 23 hours, 56 minufes, and 4.09 seconds. The time 
difference in the two days is due to the fact that, during 
the course of the day, the earth’s orbital motion about 
the sun causes the sun to appear to move a little east 
among the stars. Even if the earth did not rotate on its 
own axis, the sun would appear to move eastward com- 
pletely around the earth during one period of the earth’s 
orbit, i e., one more complete rotation or solar day is in- 
cluded in a solar year as compared to a sidereal year. In 
other words, sidereal time has as a reference the time it 
takes for the earth to complete a full rotational cycle 
with respect to an object an infinite distance away, such 
as a star, while solar time has as a reference not only the 
time necessary to complete a rotational cycle but also a 
time factor due to the orbital motion of the earth about 
the sun. It will be noted that the difference between a 
sidereal day and a solar day is about one part in 365 
which .means that a sidereal year will contain one more 
so!ar day than that contained in a solar year. 
It is seen, therefore, that a clock keeping time in side- 
real units must in the course of a tropical year indicate 
the passage of one day more than it would indicate in 
mean solar units. The ratio of sidereal units to the units 
of mean solar time is 366.2422 to 365.2422, so it follows 
that a clock designed to indicate mean solar time when 
driven at a 1-kc. rate will indicate sidereal time when 
driven at a 1.00273792-kc. rate. 
It is desirable to derive this sidereal frequency from a 
highly accurate and readily available standard solar fre- 
quency signal, such as a 1 mc. signal. The problem is how 
to most efficiently convert from a standard solar fre- 
5 
10 
15 
20 
25 
30 
35 
40 
45 
60 
55 
60 
65 
70 
quency signal to a sidereal frequency signal with accu- 
racy up to nine places. It has been the general practice in 
this field to produce sidereal frequency signals by meth- 
ods which employ complicated and potentially unreliable 
signal mixing operations. The use of feedback loops also 
presents certain problems, for example, if a malfunction 
should occur the feedback loops would continue to oper- 
ate while generating signals of incorrect frequencies. Fur- 
thermore, check-out and repair of the feedback system is 
extremely complicated due to the interdependence of the 
individual signals generated by each individual feedback 
system. In addition, frequency drift has long been a prob- 
lem in the mixer circuitry needed in the prior art fre- 
quency converters. 
The present invention overcomes these afmementioned 
disadvantages by producing a signal of sidereal frequency 
from a signal of standard solar frquency without the use 
of mixing operations or feedback loops. This is accom- 
plished by utilizing only multiplication and division oper- 
ations and then only in a seriatim, or serial, manner. 
The foregoing advantages are attained by first recog- 
nizing what the needed conversion factor is between a 
standard solar frequency of 1 mc. and a sidereal fre- 
quency of 1.00273792 kc. The ratio of solar units to 
sidereal units is .997269580 and if this number, multi- 
plied by 1000, is divided into 1 mc. the desired 1.00273792 
kc. frequency will result. The conversion factor 
997.2695680 was broken down into its factors of 
4 1 ~ 8 3 ~ 1 9 X 2 4 0 x . 2 6 ,  or 4 1 ~ 8 3 ~ 1 9 ~ 2 4 1 / 5 6  for ease 
of division. The particular sequence of m(ultip1ication and 
division operations is then chosen so that readily available 
components can be used in the circuit arrangement. 
An object of the present invention is to produce a sig- 
nal of sidereal frequency from a signal of standard solar 
frequency employing only division and multiplication op- 
erations arranged in a seriati.m manner. 
Another object is to provide a signal of sidereal fre- 
quency from a signal of standard solar frequency which 
will possess the feature of fail-safe operation, so that a 
malfunction or failure at any point along the seriatim 
chain will cause the output to  fail. 
A further object is to reduce the difficulty of checkout 
and repair of the hardware involved in producing the 
desired sidereal frequency. 
Other objects and attendant advantages of the present 
invention will be more readily apparent as the same be- 
comes better understood by reference to the following 
detailed description when considered in conjunction with 
the accompanying drawing wherein: 
FIGURE 1 is a functional block diagram of the division 
and multiplication chain of the instant invention; and 
FIGURE 2 is a block diagram of a binary divider con- 
nected in a divide-by-82 configuration; and 
FIGURE 3 is a series of waveforms helpful in under- 
standing the operation of bhe binary divider of FIG- 
URE 2. 
The actual ratio of mean solar units to sidereal units 
is 0.997269566, but the number 0.9972695680 was chosen 
because of its ability to  be factored in a suitable fashion; 
this ratio resulting in a sidereal rate accurate to two digits 
in the eighth place. Now if the standard solar frequency of 
1 mc. is divided by 997.2695680 ( 1 0 0 ~  the above-men- 
tioned ratio), or multiplied by 
1 
997.2695680 
the desired 1.00273792 kc. rate will be produced. The 
number 
1 ~ 
997.2695680 
3,417,3 16 
can be broken &own into its Binary stages 2 and 5 h e a gated complement input 
which means that when either of the inputs are at “one” 
(-6 v.) the gate is enabled and a positive transition at 
the other input will cause the binary to change its state. 
for ease of division. 5 However, when any of the inputs are at “zero” (ground 
FIGURE 1, there is shown a functional block dia- potential) the gate is inhibited and a positive transition 
gram of the divider chain wherein the series of division at the other input has no effect on the binary. Binary stages 
and multip1ication operations, in conformity with the 7 and 8 have gated AC reset inputs SO that a positive transi- 
factored ratio set forth above, are performed in a se- tion applied to either input when the binary is in the set 
quential manner. The partitcular sequence of division ,and 10 (zero) state resets the binary to the “one” state. 
multiplication operations was carefully chosen so that the The binaries are connected in the following manner: 
frequency present a t  the input of each element is Su& The output from binary.1 is utilized as one of the gate 
that readily available components could be used in the inputs to both binary 2 and 8. The other gate input to 
circuit elements. Also with regard to the sequence em- binary 2 is the OWUt 31 of binary 8, while the output 
ployed in the instant invention, it was found that it would 15 32 of binary 8 is fed back as the other gate input to the 
be most efficient to  divide the signal by 41 initially. H ~ ~ -  Same binary. The Output 33 Of binary 4 is utilitzed as one 
ever, due to the propagation delay of the carry pulse of the gate inputs to both binary 5 and 7. The other gate 
through the binary divider circuit, it was impossibIe to input to binary 5 is the output 34 from binary 7 and the 
divide the high frequency 1 mc. signal by 41. This prob- output 35 from binary 7 is fed back to the same binary as 
lem was solved by employing an additional divide-by-2 20 the other gate input. 
circuit in the initial binary divider, thereby effectively re- n e  first 64 Pulses Cause the circuit to operate as a 
ducing the input frequency to 500 kc. This operation, of stmight binary counter. The 64th pulse, however, causes 
course, transformed the initial binary divider into a divide- binary 7 to change its state, SO that output 34 which was at 
by-82 element, 80 that it became necessary to add an addi- ‘‘One” ( - 6  V.) now becomes a “zero” (ov) inhibiting 
tional frequency doubler and tuned amplifier 19 to  com- 25 the to binary 5 .  The output 35 of binary 7, Which 
pensaie for the additional division by two. was at “zero,” now becomes a “one” enabling the gated 
The operation Of the system will now be described by input 10 binary 7. 
proceeding from the input standard solar frequency signal The 72nd input pulse will cause binary 4 to change its 
to the output sidereal frequency signal. The 1 mc. stand- state again, but the o W u t  33 of binary 4, which is a nega- 
ard solar frequency signal, which could be provided by a 30 tive transition, Will have no effect on the other binaries. 
number of signal Sources such as a crystal oscillator, The 80th input pulse will cause binary 4 to change its state 
cesium beam resonator, or hydrogen maser, is first applied again. Output 33 Of binary 4, which is a positive transi- 
to (a Schmitt trigger circuit (not shown) to  convert the tion, will have no effect on binary 5 because the input gate 
signal to a rectangular wave compatible with t,he binaries is inhibited, however, this positive transition will cause the 
used in the divider chain. This rectangular signal is then 3.5 sevmth binary to  change its state. Furthermore, the WSi- 
fed to the divide~by-82 circuit 11, the operation of which tive transition occurring at output 35 of binary 7 will cause 
will be explained more fully hereinafter, which produces 
a 12.195 kc. output signal. The 81st input pulse iwill cause the first binary to 
The 12.195 kc. signpal is then applied to tuned filter change its State again, but Since it iS a negative transition 
2, which is tuned to resonate at the fifth 40 it will have no effect on the other binaries. The 82nd input 
harmonic d the input frequency, SO that in effect the Wke, on the other hand, will cause a positive transition 
output frequency is multiplied by five. This 60.975 kc. at the output Of binary 1, which in turn will cause the 
i g a d  is then amplified to  produce a more stable output eighth binary to change its state again. Therefore, one 
and to reduce the signal ripple. The tuned filter portion output Pulse will be obtained for every 82 input pulses. 
of element 12 is composed basically of a conventional tank 45 The 0 t h  dividers operate in a similar manner but, of 
circuit while the tuned amplifier contains ,a tuned tank cir- course, prodL1Ce an OUtput signal after a different nu’inber 
cuit located (at the collector of the amplifying transistor. of input Pulses have been received. 
A tuned filter and amplifier, such as described in Chapter It is evident that the instant invention provides a novel 
16 of Electronic Designer Handbook by Landee, Davis system for Producing a &kreal frequency signal from a 
and Albrecht, McGraw-Hill, 1957, could be employ& in 5o ptandard solar frequency signal without the need for mix- 
the present invention. ing circuits or feedback loops. Obviously, the particular 
The output signal from element 12 is sequentidly multi- sidereal frequency signal produced is only by way of ex- 
plied and divided by the appropriate prime factors SO as to ample, and other output frequency signals can be at- 
produce the desired 1.002737908 kc. standad solar fre- tained with only slight modifications. Similarly, varia- 
quency, or 1 kc. sidereal frequency. Binary dividers 14, 17 55 tions in the design of the frequency muftipliers and divid- 
and 22 operate in a similar manner as divider 11, while the ers could be accomplished within the scope of the inven- 
tuned filter and amplifier elements 13, 15, 16, 18 and 21 tion. 
are identical to element 12 exceot that they are, naturally, Obviously, numerous modifications and variations are 
tuned to different frequencies. Frequency doubler and possible in the light of the above teachings. It is there- 
amplifier 19, which is present to compensate for t k  addi- fore understood that within the scope of the appended 
tional division in divider 11, is tuned to resonate at the clai,ms, the invention may be practiced otherwise than 
second rather than the fifth harmonic. described herein. 
Referring now to FIGURE 2, there is shown a block What is claimed is: 
diagram of the divide-by-82 element 11 of FIGURE 1 1. A system for developing a signal of sidereal fre- 
with the eight binaries connected in ,a particular configura- 65 quency from a signal of standard solar frequency com- 
tion. In FIGURE 3, waveform (a)  is the input signal while prising: first dividing means having applied thereto a 
waveforms (b) through (i) are the DC potentials at the signal of standard solar frequency for dividing the fre- 
output from each binary 1 to 8, respectively. quency of said signal by 82, first multiplying means con- 
Reading from left to right, each up-going Iine is a nected to  said first dividing means for multiplying the 
positive going pulse (for example -6 v. to  ground) which frequency of the signal therefrom by 5, second multiply- 
causes a binary to change its state while each down-going ing means connected to said first multiplying means for 
line (from ground to -6 v.) has no effect on the binary. multiplying the frequency of the signal therefrom by 5, 
In the following discussion it is assumed that initially second dividing means connected to said s’econd multiply- 
all binaries are in the “Zero” state, Le., the true outputs ing means for dividing the frequency of the signal there- 
from each binary are at ground potential (zero volts). 75 fram by 19, third multiplying means connected to said 
56 
41X83X19X241 
8 to  chmge its state. 
3,417,316 
second dividintg means for mlultiplying the frequency of 
the signal therefrom by 5, fourth multiplying means con- 
nected to said third multiplying means for multiplying the 
frequency of the signal therefrom by 5, third dividing Chapman --------- 331-50 
means connected to said fourth multiplying means for 5 2j945~997 7/1960 Kennedy --------- 318-171 
dividing the frequency of the signal therefrom by 83, 
fifth multiplying ‘means connected to said third dividing 
from by 5, sixth multiplying means connected to said 
fifth multiplying means for  multiplying the frequency of 10 
the signal therefrom by 2, w e n t h  mltiPlYing rr~eanS 
connected to said sixth multiplying means for multiplying 
the frequency of the signal therefrom by 3, fourth divid- 
ing means connected to said seventh multiplying means 
for dividing the frequency of the signal therefrom by I 5  G. GOLDBERG, ~~~i~~~~~ ~ ~ ~ ~ j ~ ~ ~ .  
241. U.S. C1. X.R. 
References Cited 
UNITED STATES PATENTS 
27719 ,917  
OTHER REFERENCES 
“Frequency Division by Cascaded Binaries” by I. Got- 
llleans for multiplying the frequency of the signal there- tlieb., Tele-Tech & Electronic Industries March 1956, 
pp. 92, 93, 142, 144, 146 relied upon. Copy in 321-66. 
“A ~~~~l Method for Frequency M&iplication” by 
H. T. McAleer, Electronic Industries August 1959; pp. 
96-99 relied upon. COPY in 321-66. 
LEE T. H E ,  Primary Examiner. 
2. The system as described in claim 1 wherein the said 
signal of standard solar frequency is 1 mc. 328-28, 38, 39; 307-225, 260; 331-50 


Sidereal frequency generator Patent

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server