Design of folded traveling wave maser structur

Buchmiller, L. D.

Degrasse, R. W.

Jones, W. P.

Peterson, W. A.

English

NASA Technical Reports Server

REPLY TO 
A m  OF: GP 
FROM : 
NATIONAL AERONAUTICS AND SPACE ADMlNlSTRATlON 
WASHINGTON, D.C. 20546 
October 15, 1970 
~~~/~cientific & Technical Information Division 
Attention: Miss Winnie M. Morgan 
~~/0ffice of Assistant General 
Counsel for Patent Matters 
SUBJECT: 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 : Microwave Electronics Corp. 
Supplementary 
Corporate source 
NASA Patent Case NO.: XNP-05219 
t b B 6  
Gayle Parker 
Enclosure: 
Copy of Patent -- - 
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19710006075 2020-03-17T02:38:31+00:00Z
,' 
L. D. BUCHMILLER ET AL 
WAVE MASER STRUCTURE 
, Filed Jan. 3, 1964 , 2 Sheets-Sheet I 
Jm. 17, 1967 L. D. BUCHMILLER AL 3,299,364 
POLEED TRAVELING WAVE MASER STRUCTURE 
Filed Jan. 3, 1964 2 Sheets-Sheet 2 
Lyle D . Buchmiltesr 
Robert W ,  Osgrasse 
William Plnkney Jones 
William A .  Pstsrson 
IN\'ENTOG 
United States paent Office Pakewted Jan, 3,299,364 17, 1967
$. 2 
3,299,364 output cowling for the amplified signal wave are dis-mscd 
FOLDED ~ A ~ E I N G  WAVE MASER S ~ U C T ~ E  adjacent one another for convenience of installation of 
Lyle D. Buchmiller, Menlo Park, Robed W. De G r a s s  the maser. Also, since the maser must be cooled to a 
and William Pickney Jones, Los Altos, and William A. low temperature such as, for example, the temperature 
Peterson, Palo Alto, Calif., assignors, by mesne assign- 5 of liquid helium, the traveling wave maser according to 
meats, to the United States of America as represented the present invention permits conduction cooling of the 
by the Administrator of the National Aeronautics and maser elements from one end and the heat conduction Space Administration 
Filed Jan. 3, 1964, Ser. No. 336,103 path is only half of what it would be if the maser were 
1 Claim. (C1.330--4) in a continuous straight line. Furthermore, by utilizing 10 a single common wall between the side by side wave- 
The invention described herein was made in the per- guides a good heat conduction path is provided to both 
formance of work under a NASA contract and is subject waveguides eliminating temperature gradients between the 
to the provisions of Section 305 of the National Aeronau- waveguides, and the size of the surrounding magnet as- 
tics and Space Act of 1958, Public Law 85-568 (72 Stat. sembly which provides a unidirectional field to the maser 
435; USC 4257). 15 is reduced to a minimum. 
This invention relates in general to  electromagnetic The corrugated resilient members not only provide a 
wave transmission devices and more particularly to de- good heat conduction path from the common separating 
vices in which amplification takes place by the stimulated wall to the elements of active material but also force 
emission of radiation from solid state media in propagat- these elements against the slow wave structure while per- 
ing structures. Such devices are now generally termed 20 mitting differential expansion and contraction of the slow' 
"traveling wave masers." wave structure and the active elements over the tem- 
The three-level, solid state maser, now well known in perature range from ambient temperature to  the operat- 
the art, employs a microwave pump signal to alter the ing temperature level. The corrugations in the resilient 
thermo-equilibrium of a paramagnetic salt or active mate- member are in a direction substantially normal to the di- 
rial in such a manner that an otherwise absorptive medi- 25 rection in which the periodic variations in the slow wave 
um becomes emissive when stimulated by radiation at a structure occur and therefore do not serve to disrupt the 
signal frequency. Microwave amplification can be ob- passband of the traveling wave maser propagating struc- 
tained in the propagating structure of a traveling wave ture. 
maser by stimulated emission radiation from an element Additicnally, in accordance with the present invention 
of active material. Efficient coupling of the microwave 30 the magnetic field strength is varied along the length of 
energy to the active material is obtained by slowing the the plurality of side by side waveguides thereby to pro- 
velocity of propagation of the signal wave over an in- vide an effective stagger tuning of the propagating struc- 
terval coextensive with the active material. The active ture. 
material produces an equivalent negative resistance in the Other objects of the present invention will become ap- 
slow-wave structure and a propagating wave having an 36 parent upon reading the following specification and re- 
exponentially increasing amplitude is obtained. Travel- ferring to the accompanying drawings in which similar 
ing wave masers are described in U.S. Patent No. 3,004 - characters of reference represent corresponding parts in 
225 to R. W. De Grasse et al. and US Patent No. 3,076,- each of the ~everal views. 
148 to E. 0. Schulz-Du Bois. In the drawings: 
Broadly stated, the present invention, to be described FIG. 1 is a side elevational view, partially broken away, 
in greater detail below, is directed to a traveling wave of a traveling wave maser in accordance with the present 
maser which includes at least one pair of waveguides in invention; 
which a signal wave is amplified by stimulated emission FIG. 2 is a bottom view of the structure shown in 
of an active material contained therein. The waveguides 45 FIG. 1 taken along line 2-2 in the direction of the 
are arranged side by side with a common separating wall arrows; 
and are coupled together for coupling the wave being *FIG. 3 is an enlarged cross-sectional view of the 
amplified from one waveguide into the other. Addition- structure shown in FIG. 2, taken along line 3-3 in the 
ally, in accordance with the present invention, a resilient direction of the arrows; 
member is provided in each of the waveguides adjacent go FIG. 4 is a longitudinal sectional view of the struc- 
the surface of the common dividing wall for holding the ture shown in FIG. 3 taken along line 4--4 in the direc- 
active material in each of the waveguides against the tion of the arrows; 
slow wave structures therein. These resilient members 'FIG. 5 is an end view of the structure shown in FIG. 
are thin metallic spring strips provided with a plurality of I taken along line 5---5 in the direction of the arrows; 
corrugations across the width thereof, each of the cor- 55 and 
rugations extending the entire length of the resilient mem- FIG. 6 is an exploded perspective view showing the 
oer. elements of one waveguide of the traveling wave stmc- In accordance with the Dresent invention. the traveling 
- Lure. 
wave maser is foreshortened to approximately half its nor- Referring now to the drawing, there is shown a iravel- 
ma1 length by providing a pair of traveling wave wave- in$. wave maser in  accordance with present guides side by side and separated by a common wall. 
~b~ signal lo be: is coup~d into one of the including a main body structure 110 made of high con- 
first of the wavemides and travels the length thereof. A& "3;u"tivity material such as, for exam~le ,  ccspWr. "Ahe 
llle end of Ehe first waveguide, the signal is con- body is a semi cylindrical rod cut longitudinally thereof 
pled into the adjacent end o f  the second waveguide ip^p f o  provide a Plat mounting surface 11. ~ d d i t i o n a l l ~ ,  a 
which it travels back towards the end of the second wave- @' pair of longitudinal slots 12 and 13  (see FIGS. 3 and 6 )  
guide adjacent the input end of the first waveguide. are milled in the body 10 to provide a pair of Iongitu- 
This fold& traveling wave maser can eaectively pro- dinally extending, side-by-side rectangular waveguides 12 
duce the same amount of ampticcation of the input sig- and 13 extending the length of the body 110 and separated 
nal in half the length required by one continuous in-line 70 by a thin common dividing wall 14. These waveguides 
maser structure. Additionally, by this structure the in- TZ and 13  each have a pair of narrow walls and a pair of 
put coupling for the signal wave to be amplified and the wide walls one of which is the dividing wall 14. 
3,985,864 
3 4 
One end of the main body I0 is provided with ;a wave- 22 bg resilient memkps 41 and 42 respclively of, ~ Q I '  
guide short 15 closing one end of the waveguides 1% example, 3 mil thick beryllium copper extending the 
and 13. length of the slow wave structure. Each of the resilient 
At (he opposite end of the main body 310 from the members 41 and $2 is provided with a plurality of corru- 
waveguide short 15 is provided a common pump signal 5 gations 43 spaced across the width thereof, and each of 
input waveguide 16 having a flange 18 at one end thereof these cormgations extends substantially entirely the length 
for attachment to the pump source (not shown) and com- of the member. 
municating with the waveguides 12 and 13 through a As shown in FIGS. 1, 2, 4 and 5 an input coaxial line 
transition 17 (see FIG. 4). A cover plate 19 covers the 44 and a n  output coaxial line 45 extend fiom the wave- 
top of the input waveguide 16 to enclose the waveguide. lo guide flange 18 to adjacent the closest end of the slow- 
The slow wave structure within each of the maser wave structures in waveguides 12 and 13 respectively. 
waveguides includes a comb-like structure 21 (see FIG. The ends of these coaxid lines 44 and 45 are provided 
6) which is provided with a coplanar array of equally with lead-in or lead-out coupling assemblies 46. 
spaced apart conductive fingers 22 projecting from a A similar coaxial line lead+ut mupling assembly 46 
metallic base block 23. Typically, the array of fingers 15 (see FIGS. 2 and 4) is provided at the end of the first 
22 and the block 23 are machined from a common block waveguide 12 adjacent the waveguide short 15, and a sim- 
of metal such as, for example, copper. The base block ilar coaxial lead-in coupling assembly 46 is provided at 
23 is provided with a stepped cut-out 24 adapted to rest that same end of waveguide 13 for coupling an amplified 
against one of the corners of the free end of the common signal from the end of waveguide 12 adjacent the short 
dividing wall 14 and a stepped recess 25 is provided the 20 15 through a coaxial line 47 t o  the end of waveguide 13 
length of the slot forming the waveguides 12 and 13 in adjacent the short 15. A matching assembly is provided 
each of the outside walls to receive the base block 23. in  the coaxial 47 to adjust the coupling between the wave- 
The stepped cut-out 24 and the recess 25 are so dimen- guides 12 and 13. 
sioned as to properly position the fingers 22 of the comb- The active material and gyromagnetic material are 
like structure 21 within the waveguides 12 and 13 sub- 25 magnetically biased by means of a common uniform mag- 
stantially midway between the wide waveguide walls netic field Hdc (indicated by arrow 48) in FIG. 4 directed 
and orthogonally disposed with respect to the longitudinal parallel to  the fingers 22. The source of this field is not 
axes of the waveguides 12 and 13. shown but can be supplied in any convenient manner such 
Referring now particularly to FIG. 3 positioned ad- as, for example, by an electromagnet o r  a permanent jacent the outer side of the comb fingers 21 in the wave- 30 magnet. 
guides 12 and 13 are elements 26 and 27, respectively of According to another aspect of the present invention 
active or negative temperature material. Additionally, the strength of the magnetic field Hdc can be varied along 
tip loading material such as, for example, sintered alumina the length of the side by side waveguides effectively to 
rods 28 and 29 are positioned above the elements 26 and stagger tune the propagating structure. Thus, with a plu- 
27 against the tips of the comb fingers 22. Various para- 36 rality of side by side waveguides a variation in the mag- 
magnetic salts are suitable for use as the active or nega- netic field at one position along the length of the magnet 
tive temperature material of maser devices of the general structure produces a plurality of  such variations along the 
type described herein. A typical example of such a mate- effective length of the traveling wave structure. 
rial is aluminum oxide which has an impurity content of The traveling wave maser is conduction cooled to a 
approximately one-thirtieth of one percent of trivalent 40 temperature of approximately 4-30 K. or below by a 
chromium referred to as "mby" material. Any material refpigeration system in contact with the flange 18. It may 
capable of amplifying a signal wave by stimulated ernis- 3 j ~ ~  k bath cmtled in a dd~at - .  
sion of wave energy can be used, and such materials are Obviou6ly, wupliag arrangements other than the so- 
referred to herein as the active matei-ial or the maser axial line: 47 can & utiliEd to couple the signal from 
material. qg one waveguide to the other. 
The active elements 26 and 27 are compressed against The traveling wave maser described above is assembled 
the comb fingers 22 by a plurality of dielectric rods 31 by first securing the base block 23 to the main body 10 
which are mounted in bores 32 spaced along the length such as, for example, by solder. Next, with the wave- 
of the outward waveguide wall in a row. These rods 31 guide shorg 15 removed, the active elements 26 and 27 
are forced against the active elements 26 and 27 by One 50 a d  tip loading elements 28 and 29 are slid into the wave. 
end of leaf springs 3.3 the other end of which is secured to guides 12 and 13. A flat metallic strip is .attached to one 
the main body 10 by screws 34. end of each of the resilient members 41 and 42, and these 
Loading elements 28 and 29 of, for example, alumina strips are slid into the waveguides 12 and 13 through the 
are ~ositioned adjacent the tips of the fingers 22 on the pump power input waveguide 16 tto the position ultimately 
same sides thereof as the active elements 26 and 27. 65 owupied by the resilient members 41 and 42. ~h~~ the 
These loading elements are held against the fingers 22 by isolator spacers 35 and 36, the active elements 26' and 27', 
dielectric rods 31', leaf springs 33' and screws 34' in the the tip loading elements 28' 29' and the dielectric 
same manner as the active elements 26 and 27. spacers 38 and 39 are slid into place in the waveguides 12 
On the opposite side of the fingers 22 from the eIe- and 13 through the shorted end of the waveguide. Then, 
menls 26 and 27 in waveguides 12 and 13 are positioned by holding these elemenls in place and the metal- 
active elements 26' and 27' reswctively. These elements lic strips attached to the resilient members 41 and 42 
26' and 27' are isolated from the base block 23 by ceramic through the waveguides 12 and $3 the resilient 
spacers 35 and 36 respectively, extending the entire length properly positioned so as to force the !active elements 
of the slow-wave structure. Mounted on the spacers ad- 26. and 27' and leading elements 28' and 29' against jacent the active elements are periodically spaced apart g)g fingers 22. The metallic strips are then cut from (Ire flat disks 37 of ~ ~ l ~ m a f i n e t i c  material sufh 3% for ex resilient members afnd the wavewide short *cured In  
ample, ytlrirrm-iron-garnet. - place such as, for exmple, by screws. Loading elements 28' and 29'ooT, for example, alumina In operation of the traveling wave maser in accord- 
are also position& adjacent the tips of the fingem 22 on an, with the present invention, a pump signal is directed 
the same sides thereof as the active elements 26"nd 27" ,o Into the waveguides I2  and 13 through the input wave- 
and these loading elements 28' and 29' are spaced from guide 16. A signal to be amplified is directed by means 
the commolr dividing wall by dielectric spacers 38 and 39. of ithe input coax 44 into the waveguide 12 in which the 
The active elements 26' and 29', isolator spacers 35 signal is amplified by stimulated emission of radiation as 
and 36 and loading elements 28' and 29' in the appro- it travels the kngth of the waveguide. At the end of the 
priate waveguides 12 and 1-3 are held apainst the fingers 75 waveguide 1% the amplified signal is coupled through 
3,2@9,384 
5 6 
coaxial line 47into waveguides $3 and is again amplified to thereby cool each of said waveguides and struc- 
as it travels the: length of the waveguide. The output ture therein; 
signal is brought out through the outward coaxial line id )  means adjacent said waveguide short for soupling 
49. Obviously, two, three, four or more waveguides may an amplified signal from said one wavepide to said 
be phced side by side and may be subjected to the same 6 other waveguide; 
or 5everal different fields. (e)  a tip loaded slow-wave comb strusturn dispoxd 
By way of example, an S-band traveling wave maser within each of said wave~ides ;  
built in accordance with 4he present invention has a center ( f )  active material on each side of said comb structure 
frequency of 2300 mc. plus or minus 5% and an instan- for amplifying a signal wave imposed on each comb 
taneous band width of 15 mc. minimum at 3 db power 10 structure; 
points. The maser at the input flange has a noise tern- (g) spring means for holding said active material 
perature of 12" K, and a gain stability of less than plus against said comb structure in each waveguide, 
o r  minus 0.1 db in 10 hours and utilizes a pump power (1) said spring means including a corrugated 
of 35-75 milliwatts at a frequency of about 12 kmc. The metallic resilient 'member substantially coexten- 
maser itself weights 3.5 pounds. 15 sive with each comb structure and being dis- 
Although the foregoing invention has been described posed adjacent to and in contacting engagement 
in some detail by w8ay of illustration and example for with the common wall to thereby provide a heat 
purposes of clarity of understanding, it is understood that conduction path between said waveguides; and 
certain changes and modifications may be practiced within (h)  means for sending a signal down said one wave- 
the spirit of the invention as limited only by the scope 20 guide and extracting an amplified signal returning via 
of the appended claim. said other waveguide. 
It is claimed: 
A traveling wave maser structure which comprises: References Cited by the Examiner 
(a)  0 body of conductive material having a pair of 
parallel waveguides therein; (1) said waveguides be- 25 UNITED STATES PATENTS 
ing separated by a common wall; 3,214,701 10/1965 Chen et al. ------------ 3 3 0 - 4  
(b) a waveguide short on one end of said body for FOREIGN PATENTS 
closing one end of said waveguide and contributing 
to reversing a signal traveling down one waveguide 1~2771321 France. 
and returning via the other waveguide; 30 
(c)  a common pump signal input waveguide at the LAKE!Primary Examiner. 
other end of said body which is cryogenically cooled D. R. HOSTETTER, Assistattt Examiner. 


Folded traveling wave maser structure Patent

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server