Microwave power receiving antenna solving heat dissipation problems by construction of elements as heat pipe device

Dailey, C. C.

English

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ATTN OF: Gp 
TO: 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
usI/scientif i c  & Technical Information Division 
Attentions Miss Winnie M. Morgan 
FROM: ~ ~ / 0 f f i c e  of Assiqtapt General Counsel for  
Patent Matters 
SUBJECTS ~nnouicement of NASA-Owned U. S. Patents i n  STAR , 
In accordance with the procedures agreed upon by Code GP 
and Code U S I ,  the attached NASA-owned U. S. Patent is being 
forwarded for  abstracting and announcement i n  NASA STAR. 
The following information is provided: 
U. S. Patent No. 
Government or 
Corporate Employee 
Supplementary Corporate 
Source (if  applicable) t #p . c.' 
NASA Patent Case No. 
NOTE - If  t h i s  patent covers an invention made by a corporate 
employee of a NASA Contractor, the following is applicable8 
yes NO O 
Pursuant t o  Section 305(a) of the National Aeronautics and 
Space Act, the name of the Administrator of NASA appears on 
the f i r s t  page of the patent; however, the name of the actual 
inventor (author) appears a t  the heading of Column No. 1 of 
-- the Specification, following the words *. . . with respect - -  to - -- 7?72&+/ CI( O N71- 1 3 4 8 6  
d -L/ -IL', + 5 f l  
Elizabeth - --  A. - -  Carter 5 
Enclosure 9 (PAGES) 
https://ntrs.nasa.gov/search.jsp?R=19710004011 2020-03-17T02:32:43+00:00Z
MTCROWAVE POWER RECEIVING ANTENNA 
Fi led  May 1, 1969 3 Sheets-Sheet I 
FIG. I 
INVENTOR 
CARROLL C DAiLEY 
Oct. 20, 1970 
Filed May 1, 1969 
C. C .  DAILEY 3,535,543 
MICROWAVE POWER RECEIVING ANTENNA 
3 Sheets-Sheet 2 
30jt l  28). k---cl---$6 --- --- 
M l CRO ------- 
POWER WAVE d- __)- -- - - - 
SUPPLY GENERATOR  - - - -  
- - - -  
POWER LOAD CONDITIONER 
----- 
F I G .  2 
F I G .  5 
INVENTOR 
CARROLL C. DAILEY 
Oet, 28, 1970 6. C ,  DAILEY 3,535,543 
M I C R O W A V E  P O W E R  R E C E I V I N G  A N T E N N A  
F i led  May 1, 1969 3 Sheets-Sheet 3 
IPJVEM TOR 
CARW0L.L C. DAILEY 
Udted States Patatem Bfi 3,535,543 ce Patented Oct. 20, 1970 
- "- -- - 
1 2 
face determine how miich heat can be radiated at a spccific 
3,535,543 temperature. In the case of antenna dipoles the radiating 
MICROWAVE POWER RECEBVING ANTENNA area is small, since the conductors are narrow and the 
Carroll C. Dailey, MtmtsvE1He, Ma., assignor to the United dipoles are also very 
States of America as represented by the Administrator 
of the National Aeronautics and Space Administration 5 SUMMARY OF THE INVENTION 
Filed May 1,1969, Ser. No. 820,965 
In$. C1. H02j 1/00 Accordingly, it is an object of this invention to provide 
U.S. Cl, 307-149 an improved microwave receiving antenna. 
Still another object of this invention is to provide a 
10 microwave receiving antenna having the capability of ef- 
ABSTRACT OF THE DISCLOSURE ficient dissipation of heat from its rectifier circuits. 
A microwave power receiving antenna array having a Yet another object of this invention is to provide a 
solid-state rectifier circuit at the center of each of a plu- more efficient microwave receiving antenna by modifying 
rality of dipole antennas for conversion of the high-fre- conventional elements of antenna structure so as to better 
quency energy to direct current. The device effectively 15 radiate the heat from the antenna's rectifier circuit. 
and efficiently solves the problem of heat dissipation from These and other objects are accomplished in the pres- 
the diode rectifier enclosure by construction of the dipole ent invention which provides at least one pair of dipole 
supporting posts, the antenna reflecter and the dipole ele- antenna elements supported by an enclosure containing a 
ments as heat pipe devices. Each supporting post and the rectifying circuit comprising a plurality of diodes. Each 
antenna reflector may either communicate for greater ef- 20 enclosure and its corresponding pair of dipoles is mounted 
ficiency in dissipating heat or be physically separated to on a heat conducting support post, which in turn is mount- 
simplify fabrication. ed on a large antenna reflector. 
BRIEF DESCRIPTION O F  THE DRAWINGS 
ORIGIN OF THE INVENTION 25 The invention will be more fully understood by the 
The invention described herein was made by an em- following detailed description when taken together with 
ployee of the United States Government and may be the accompanying drawings in which: 
manufactured or used by or for the Government for FIG. 1 is an isometric view of an orbiting space labora- 
governmental purposes without the payment of any royal- 30 tory transmitting electrical po\ver to a subsatellite. 
ties thereon or therefor. FIG. 2 is a block diagram of a microwave power sys- 
BACKGROUND OF THE INVENTION 
tem capable of utilizing the present invention. 
FIG. 3 is a plan view of a dipole having a bridge recti- 
Field of the invention fier at its center, illustrating part of one embodiment of 
This invention relates to power receiving antennas and :IS 
more particularly to a rectifying dipole antenna array 
having a highly efficient structure for dissipation of heat 
from the rectifying circuit. 
Description of the prior art 40 
One of the comparatively recent modes of electrical 
power transmissioil is power transfer by microwaves using 
frequencies as high as about 30 gigahertz. One attractive 
use of this type of power transmission is for powering 
helicopters or other types of aircraft from a remote loca- 43 
tion. Another use which appears attractive is transmission 
of power from a central manner space station, which 
can service a number of small independent subsatellites 
or experiment modules located distances as much as sev- 
eral kilometers away. Batteries in a subsatellite can be 50 
recharged with energy generated in the main space station, 
thus precluding the need for solar arrays or extra batteries 
on the subsatellite, increasing its versatility, and prolong- 
ing its u s e f ~ ~ l  life. 
In the power receiving antenna for a microwave power 53  
transmission system, a rectifying circuit niay be used to 
convert the high frequency energy to direct current. The 
diodes which transform the high frequency energy to 
DC are iisuaily quite eficicnt   approximate!^ 70 to 90 
percent). However, tlrere is sonle loss of energy which ap- 
pears as heat. ?-;->is heat raises the ternperattire of the GO 
diodes. Also, thz diodes and the antenna or antenna array 
are subjcct LO the iieaiing of ihe srrn's ra..jis. -i-bese heating 
effects have the inherent disadvantage of limiting the 
amount of electrical power that can be handled by the o;, 
array bccause of the temperature limits of the diodes. For 
diodes of interest in space applications, this limit typicafiy 
occurs at about 120" centigrade, although specific applica- 
tions may show limits somewhat higher or lower. 
In order to keep the diode temperature down, it is 
necessary to radiate heat lo space. The area of the radiat- ''O 
ing surface available and the coatings applied to the sur- 
the present invention. 
FIG. 4 is a side view of part of a microwave receiving 
antenna, which illustrates one embodiment of the present 
invention. 
FIG. 5 is a horizontal sectional view of the support post 
taken along line 5-5 of FIG. 4 and showing the inner 
construction of the heat pipe support post. 
FIG. 6 is a side view of the n~icrowave power receiving 
antenna array showing one row of dipoles. 
FIG. 7 is a plan view of one embodiment of the micro- 
wave power receiving antenna array, showing two rows 
of three dipoles mounted on a reflector. 
DESCRIPTION OF THE PREFERRED 
EMBODIMENT 
With continued reference to the accompanying figures 
wherein like numerals designate similar parts throughout 
the various views and with initial attention directed to 
FIG. 1 there is illustrated an orbital space laboratory, 
designated generally by numeral 10, transmitting elec- 
trical power by microwaves to a subsatellite, designated 
generally by numeral 12. Laboratory 10 includes a spent 
rocket stage 14 having solar panels 16, docking adapter 
$8 and command modules 20 and 22. Solar panels 14 
may be replaced by a nuclear power source in other ver- 
sions of laboratory 20. 
Referring now to FIG, 2, a microwave power system 
which incltldes the present invention is shown in block 
diapranr form. Electrical power in the form of micro- 
waves is furnished by microwave power generator 28 hav- 
ing power supply 30. Power transmitting antenna 24 is 
aimed at power receiving antenna 26 and transmits electri- 
cai power in the form of n~icrowave beam 3% to receiving 
antenna 26. Subsatellite 12 uses this power received from 
beam 32 to charge its batteries or fuel cells or for power- 
ing electric thrusters. The energy in beam 32 is converted 
from high-frequency energy (approximately 2 megahertz 
to 30 gigahertz) to a direct current which is fed into power 
3,535,543 
3 4 
conditioning equipment 34 to transform it to the actual able to effectively dissipate this heat by ~ad~al ioi i  rnlo 
voltages required for the load 36. space. 
FIG. 3 shows a self-supporting, single, half-wave, Hertz In an alternative arrangement of the ,nv,nlron the en- 
antenna, designated generally by numeral 38, having a terior cavity of each support post 50 docs :jot ~o:nmerr^.r- 
pair of dipole antenna elements 40. The conversion from cate with the interior cavity of the antenna ~ePzctor 52. 
high-frequency energy to direct current is accomplished " Instead, the upper sidewall 54 has no ope?~n$s Iri t h ~ s  
by a plurality of diodes 42 which are connected in a bridge embodiment, each support post 50 as well as the antemn~a 
rectifier circuit 44 (shown in diagrammatic form). Recti- reflector 52 contains its own supply of hcat transfer fltiad 
fier circuit 44 is contained in dipole center enclosure 46 60, which cycles within the cavity available. 7 IIL,~, heat 
and is connected between the dipole elements 40 and a is transferred down the support post SO and pa?scF: b ? ~  can- 
pair of output terminals 48. Dipole elements 40 are se- duction through wall 54 of the antenna reflcctor 52 T ~ E  
curely fastened to opposite sides of enclosure 46. heat is then transferred evenly to the wail5 of the znlennd 
FIG. 4 shows a single, half-wave dipole antenna 38 reflector 52 where it is dissipated in the rnanxr already 
mounted on enclosure 46. Enclosure 46 is shown in verti- described above. 
cal section so that diodes 42 may be seen, contained in 15 In another alternative arrangement, the ~~~ver?l~c.ii  * r c b ) i  
potting compound 49. Enclosure 46 is mounted on sup- be made with a conventional flat or concaw antenna re- 
port post 50 which is in turn mounted on an antenna re- flector 52, with a corresponding sacrifice in Ihc hest dls- 
flector 52. Support post 50 is a hollow pipe which is closed sipation capability of the antenna array. 
at its upper end where it is fastened to enclosure 46 and Any of the above-described arrangement? of the mvcn- 
open at  its lower end where it is fastened to antenna 20 tion may be made with still anothcr varlalron In its 
reflector 52. Reflector 52 comprises a pair of metal walls construction. Each of the antenna dipole elements 40 1s 
54 and 55, a pair of ends 56, and a pair of sides 57 (see made in the form of a heat pipe having 11s interlor wall3 
FIG. 7 )  all of which make reflector 52 a closed con- and ends lined with a wicking material 58. Also, each 
tainer. However, the cavity of reflector 52 communicates dipole element 40 is completely enclosed and contains 
with the lower end of support post 50, as described above. 25 its own supply of heat transfer fluid 60 Fluid 60 cycles 
Both support post 50 and antenna reflector 52 utilize within the cavity of each dipole element 40 in n manner 
known principles of operation of a heat pipe. As may be already described above for support post 50. taking on 
seen in both FIG. 4 and the horizontal sectional view of heat from enclosure 46 and removing it to the otatsrc'e end 
the support post shown in FIG. 5,  a11 the interior surfaces of each dipole 40, where it is radiated to space 
of both support post 50 and reflector 52 are covered with 30 Froln the foregoing it may be lprt 2pp!i.. 
a wicking material 58, which may be screen wire or a cant has invented a novel type of n~icrowaiie uov :r 
similar material. The communicating space enclosed by receiving antenna capable of nlore cl%clznk diistp,?- 
poth the support post 50 and the mtenna reflector S2 tion of heat than antennas previoirsi:~ 1'1-onn 7111: 
gether contains a heat transfer fluid 60, which be outputs from the individual dipole anle17nzs rilay be 
water, lithium or a number of other substances which are .,> connected either in series, in parallel or SerPeS- 
easily vaporized. parallel, as desired. Also, diodes 42. n-ay be iilounteli 
FIGS. 6 and 7 are side and plan views, respectively, of directly in the cavity of po21 lm- 
a mi~mwave power receiving antenna 26 having a plu- prove heat transfer efficiency, provided lney ale propyIy 
rality of dip01e antennas 38- Each dipo1e 38 is insulated electrically and the appropriate ei;eclrrca, coa- 
supported a center 46 40 nections are made through the upper end of support post 
and support post 50. 38 are On One 50. This approach, although more dificult flonl the 
antenna reflector 52, as provide a combined broad- standpoint of fabrication, is desirable at high power i-veii. 
side and cO1linear antenna array' Each post Of the various described m dElall abolie, 
communicates with the antenna reflector 52 in a manner the embodiment which has support posts aihlch 
described for above' The 'On- cate with the antenna reflector and lwhicII ;Iso has heal 
struction of each support post 50 and the antenna reflector 45 
52, including wicking material 58 and the presence of heat pipe conducting dipole elements is, of course, tile most 
transfer fluid 60, is also as described for FIG. 4. efficient. The simpler embodiments, although ihcy sacii- 
One cycle of operation of the microwave power receiv- fice efficiency which is highly desirable m the invention, 
ing antenna 26 follows: Microwave power beam 32 is do have the advantage of being cheaper and easler to 
received on the dipole elements 40 of half-wave antenna 50 manufacture. 
38. Bridge rectifier circuit 44 comprising diodes 42 recti- What is 'lairned 
fies the incoming high-frequency energy to convert it to A power receiving antenna CQwrISW 
direct current. Power conditioner 34 changes the form of (a)  a t  least one pair of dipole antennz eiemerlt.;, 
the direct current as desired and transmits it to the load (b) at least one dipole center enclosure, tl?e ~nsrde end5 
36. Heat developed within enclosure 46 is by 55 each pair of said antenna elen~elris being r~rauntec! 
the top end of support post 50. Heat transfer fluid 60 ab- on one said enclosure, 
sorbs heat from the end of support post 50 and is vapor- (c) a rectifying circuit in each said eilclosare, sard 
ized. The vapor 62 then moves under vapor pressure rectifying circuit complising a plurality of daociey, 
down the support post 50 and passes into the inner por- (d) at least one support post, each sa~d  cndosuee being 
tion of antenna reflector 52. When the vapor 40 reache3 80 by one said support post. 
a comparatively "cool spot" on the surface of antenna (e) an antenna reflector, each said suppcrt post being 
reflector 52 (which would theoretically be midway be- mounted on said antenna reflector. 
tween the "hot spots" caused by the heat input from the 2. The microwave power receiving antenna of c l a ~ , ~ ~  
support post 50 or as far as possible from a support post 1 wherein each said support post comprises. 
SO), the vapor 62 condenses back to fluid 60 and forms G5 (a)  a cylindrical section of pipe ha\~ing two closdd 
deposits on the inner sides of antenna reflector walls 54 ends, 
and 55, antenna reflector ends 56, and antenna reflector (b) a fluid contained inside said pipe, for absoibing 
sides 57. The fluid 60 (condensate) then moves by means heat at the end of said pipe attache01 1% sai$ centcr 
of capillary flow through the wicking material 58 back to enclosure, and discharging heat to said anrcnra re- 
the top of support post 50, where it absorbs more heat and flector at the end of said pipe atiacl~ed te s a ~ d  nn- 
starts the cycle over. In condensing, vapor 62 gives up tenna reflector, 
heat which is absorbed by walls 54 and 55, ends 56, and (c) a wick positioned along the inner sur'accs of sn-d 
sides 57. Thus, heat is distributed evenly to all parts of cylindrical section of said pipe and .;a13 pipe enr?s, for 
the surface of antenna reflector 52 so that reflector 52 is 75 returning said fluid from said end of saic+prpe aa- 
3,535,543 
5 6 
tached to said antenna reflector to said end o f  said jc j  said total encioseci area containing: 
pipe attached to said diode enciosure. ( I )  a fluid for absorbing heat from said center en- 
3. The microwave power receiving antenna of claim closure and discharging the absorbed heat to 
2 wherein said antenna reflector is a completely enclosed, points on the surface of said antenna reflector 
flat, double-wall enclosure, said cnclosare containing: remote from points of attachment of each said 
(a)  a fluid for absorbing heat at the poifit of attach- support post, so as to distribute the absorbed 
ment of each said support post to said antenna re- heat to the whole surface area of said antenna 
flector and discharging the absorbed heat to points on reflector, 
the surface of said antenna reflector remote from (2) a wick positioned on substantially all of the 
poinst of attachment of each said support post, so as lo inner surface areas of said antenna reflector and 
to distribute the absorbed heat to the whole surface each said support post, for returning said fluid 
area of said antenna reflector, from said remote points to said end of each 
(b)  a wick positioned on substantially all of the inner said support post attached to said center en- 
surface area of said antenna reflector, for returning closure. 
said fluid from said remote points to said point of 15 4. The microwave power receiving antenna of claim 5 
attachment of said support post. wherein each said dipole antenna element comprises: 
4. The microwave power receiving antenna of claim 3 (a)  a cylindrical section of tubing having two closed 
whsrein each said dipole antenna element comprises: ends, 
(a)  a cylindrical section of tubing having two closed (b) a fluid contained inside said tubing, for absorbing 
ends, 20 heat at the end of said tubing attached to said cen- 
(b) a fluid contained inside said tubing, for absorbing ter enclosure and discharging heat a t  the opposi:e 
heat at the end of said tubing attached to said center end of said closed section of tubing, 
enclosure and discharging heat at the opposite end of (c) a wick positioned along the inner surface of said 
said closed section of tubing, tubing for returning said fluid from said opposite end 
(c) a wick positioned along the inner surface of said 25 of said tubing to said end of said tubing mounted 
tubing for returning said fluid from said opposite end on said center enclosure. 
of said tubing to said end of said tubing mounted 
on said center enclosure. References Cited 
5. The microwave power receiving antenna of claim B 
30 UNITED STATES PATENTS wherein: 
(a)  each said support post com~rises an enclosed. 3,432,690 3/1969 Blume. 
cylindrical section of ROBERT I<. SCHAEFER, Primary Examiner (b) said antenna reflector comprises an enclosed, flat, 
double-wall enclosure. the enclosed area of each said H. J. HoHAUSER> Assistant Examiner 
support post communicating with the enclosed area 35 
of said antenna reflector, to form a total enclosed U.S. CI. X.R. 
area including the enclosed areas of each said sup- 174-15; 317-100; 313-105; 321-8; 3 1 0 4  
port post and said antenna reflector, 


Microwave power receiving antenna Patent

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