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Патент USA US3041534

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.United .l States Patent O ” ICC
3,041,524
Patented June 26, 1962
1
2
3,041,524
Hd_„ to the ferrite 19 in a direction parallel to the
longitudinal axis of the cylindrical cavity 10. The means
` FREQUENCY-DOUBLING MICROWAVE CAVITY
for applying, yand the magnetizing lield are rrepesented by
Nick Karayianis, Washington, D.C., and Clyde A. Mor
rison, Hyattsville, Md., assignors to the United States
of America as represented by the Secretary of the
the symbol Hd_c and «the arrow 21 in FIGURE 1. The
ferrite element rod 19 may alternatively be a sphere, -an
ellipsoid, or any other suitable shape.
Filed Feb. 13, 1958, Ser. No. 715,158
3 Claims. (Cl. 321-69)
(Granted under Title 35, U.S. Code (1952), scc. 266)
magnetic field at the input frequency f is perpendicular to
the `direction of D.-C. magnetization Hd_c of the ferrite ele
Army
As con be seen from FIGURES 1 »and 2, the R.-F.
10 ment 19. A-s described previously, this will produce sec
The invention described herein may be manufactured
and used by or for the Government for governmental pur
poses without the payment to us of any royalty thereon.
This invention relates to microwave devices in general,
land more particularly to a microwave cavity device for
frequency doubling.
Itis the object of this invention to provide a frequency
doubling microwave cavity device.
`In a typical embodiment, the frequency-doubling cavity
ond order components of magnetic liux in the vicinity
of the ferrite element 19 at double the R.-F. input fre
quency, and in a «direction Ialong the longitudinal axis of
the cavity 10. These »second order double-frequency
components of magnetic linx are -advantageously used in
the present invention by choosing the dimensions of the
cavity 10, the position of the `ferrite element 19 along
the axis, and the strength of the D.-C. magnetizing field
Hd_c, so that the double-frequency magnetic linx excites
device comprises a ferrite loaded ycavity excited in the 20 -a resonant mode in the cavity 10. A series of such pos
sible modes in the cavity 10 are the TEUum modes where
resonant TMm mode by an input signal of frequency
“n” and “m” are any integers other than zero. These
j‘, with -a D.-C. magnetiz-ing lield Iapplied to the ferrite
TEOnm modes 'are suitable because they have -an R.-F.
within the cavity. The position of the ferrite, the strength
magnetic field which Ihas a component along the longi
and‘direction of the D.-C. magnetizing ñeld, and the
tudinal axis of the cavity 10. Since the TEOm11 modes
cavity dimensions are chosen so that «a double frequency
are tunable (that is, their resonant frequency Imay be
component is produced which excites the cavity in the
varied) by changing the length L of the cavity 10, the
resonant TEM mode, thereby permitting a double fre
cavity length L is `chosen so that the cavity 10 is resonant
quency signal to be obtained at a properly located output.
at 2f in some TEOmn mode. The position of the ferrite
The specific nature of the invention, »as well as other
objects, uses, and advantages thereof, will clearly appear 30 element 19 along the axis is then chosen to excite this
from the fol-lowing description -and from the accompany- '
TEODLm mode. In the device of the drawing, the length
ing drawing, in which:
'L 'of the cavity 10 is chosen to be resonant at the TEM
mode. The length L of the cavity 10 may beV conven
tionally varied by a threaded member I40. An illustrative
FIGURE 1 is a longitudinal pictorial view of a micro
wave frequency-doubling cavity device in -accordance with
the invention. A portion of the cavity wall is cnt-‘out to 35 portion of the R.-F. magnetic field in the TEM mode
is shown by the dashed lines 30 in FIGURE 1.
reveal the disposition of the ferrite within the cavity.
Double-frequency energy in the cavity 10 may be con
FIGURE 2 is a sectional view -along 2-2 in FIG
ventionally extracted by means of an iris 51 and wave
URE 1.
guide arm 57 by locating the iris 51 at a point of strong
It has been theoretically derived and experimentally
verified that, when »a microwave magnetic lield is incident 40 R.-F. magnetic iield in the TEM mode at the double
on a ferrite or other- insulating ferromagnetic material in
a manner such -that the R.-F. lield has a component per
frequency 2f. 'Ilo prevent input frequency energy from
-appearing in .the output, it is preferable to have the cut
olf frequency of the waveguide arm 57 above the input
pendicular to the direction of D.-C. magnetization of the
frequency j. Suitable poi-nts of strong R.-F. magnetic
ferrite, second order components of magnetic> linx at
double the R.-F. frequency will be produced in the fer 45 lield in the TEM mode are well known in the art.
It is important «to note that the operation of the novel
rite in the direction of the D.-C. magnetization. (See (1)
cavity device of the drawing is based on the fact that
Journal of Applied Physics, vol. 27, February 1956, pp.
the resonant frequency of the cavity 10 in the TMm
18S-189, and (2) Proc. IRE, vol. 44, August 1956, p.
mode is dependent only on the diameter and is totally in
1054.) This second order frequency-doubling effect has
heretofore merely been a laboratory curiosity and it was 50 dependent of the length L. It is thus possible to adjust
the dimensions of the cavity 10 so that the double fre
not believed that the effect could practically be employed
quency magnetic linx will excite a resonant TEOmn mode
for frequency doubling. In the present invention, this
at the double frequency. The frequency at which a cylin
effect is employed in a novel and practical frequency
drical cavity resonates in a TEOnm mode is dependent upon
doubling cavity device as illustrated in the drawing.
In FIGURE 1, »a cylindrical cavity 10 is excited in the 55 both the diameter and the length L. Once the diameter
TMm niode by a microwave inp'ut at frequency ;f coupled
has been’chosen so that the cavity 10 resonates in a
to the cavity 10 by means of a waveguide arm 14 and an
iris 17 in a conventional manner. As is well known in
the art, the resonant frequency of a cavity excited in the
TMm mode at the input frequency f, the length L is then
chosen so that the cavity 10 also resonates in a TE()um
mode at the frequency 2f.
TMm mode is dependent only upon its diameter D and 60 I-t is also important to note that even though a cavity
is independent of its length L. This feature is very ad
has the proper `dimensions to resonate in a particular
vantageously used in the present invention as will be
mode, it will not resonate in that mode unless the mode
brought out later. The field pattern 25 of a cross section
is excited. In the present invention, excitation in the
in the TMm mode is shown by the dashed lines ‘in FIG
TEm,m mode is accomplished because it has an R.-F. mag
65 netic field component along the axis of the cylindrical
URE 2.
A ferrite rod element 19, preferably having a diameter
cavity. Thus, the ferrite element 19 can be positioned
which is considerably smaller than the diameter of the
along the axis so that the double-frequency magnetic flux
cavity 10, is disposed along the longitudinal `axis of the
which
is produced excites this TEDnm mode.
cavity 10. Supporting members 22 and 24 of insulating
material such as Teflon may be used to support the ferrite 70 It has been found that the double-frequency magnetic
linx obtained is maximum when the magnitude of the
element 19. Means are provided, which are also well
D.-C. magnetizing field Hd_c is at either of the half-power
known in the art, for applying a D.-C. magnetizing lield
3,041,524
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4.
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points'of the' ferromagnetic resonance curve. However,
tracting Ithe double~frequency TEOnm energy from said’
fields slightly further from ferromagnetic resonance should
cantv..
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f
be chosen because as is well known,‘the V»ferrite element
2. A frequency-doubling microwave cavity device com
19 absorbs a considerable amount of the input energy
' prising in combination: a microwave cavity having a longi
the vicinity of'resonancesthereby lowering the elîec
tive Q'ofitheiactivity V10.1 The_choice ofthe D.-'C. niag
Vti'zing íìeld Hd-_cg therefore, will be; some Vcompromise
value.deper'nient'uponV the magnitude of input’rpower,
>the Q of the cavity 10, andV Ymatching considerations.
tudinal axis, said cavity having dimensions such that the
cavity is resonant in the TMmjmode at the frequency f
«and ina” 'I‘EmmA mode at theA frequency 2f, means'for
exciting said' cavity in' `said TMl'm rnode at frequency f,
va D.-C. magnetizing field’ applied to said cavity parallel
The important requirement is that the percentage of the l0 to` said longitudinal axis, a ferrite element disposed within
input energyconvertedgto .double-frequency energy be
said cavity along said ¿longitudinal axis, the strength of
g Those skilled in`the artrwill readily` be able
said D.-C. ñeld- and' the position' of said‘ferrite element
to provide theaproper adjustments for satisfactory opera
along said axis being such :thatY TM'm Inode energy pro
-tions
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dudes double-frequency magnetic linx which excites said
Y.
A specilic example of a device constructed in accordance 15 TEOIlm mode, and means` foruentracting the double-fre
with‘the; invention for frequency-doubling from about 9000
to 183000'megacy'clesl employsV a cylindrical cavity V1t)
having a' diameter of about 1.6 inches and a Ilength L
quency ÍIÍEomn mode energy from said cavity.
v V1i.1A.frequency-doubling microwave cavity device com
prising a cylindricalV microwave resonan-_t`_.cavity having a
of about 0:758 inch: Y, The ferrite element 19 comprises
longitudinal axis, said cavityhavinga p'iredeterr'ninedV diam
a" ferrite-rod abouti 0.2 inch longI with aj diameter of
about Olinch. The rod is disposed along the axis of
eter such that the cavity is resonant in the TMm mode at
the' cylindrical-cavity about 0.19 inch from oneend. The '
an Vinputfrequency f, means for adjiisting the length of
the cavity so that the cavity is simultaneonsly resonant
input/waveguideY ‘arm 134Y is- centrally locatedjbetween both
in a TEM@ mode atan output frequency 2f, input wave
ends of’ the cavity 10, and the outputvarm VS7 is located
guide` meansv coupled w»to said cavity for exciting said
about'0.l9 inch v’from the other end at Va point- of strong V25 cavity s_aid >TMm mode, means'- for applyingv a D.-C.
'R.-F.V magnetic ñeld in the excited '['Em ‘mode
magnetizing field to’saidfA cavity t'ßa‘l‘allelv ‘to said longi
tudinal axis,rferrite means responsive to said D.-C. ñeld
Y
Althoughy a Ycylindrical cavity has been used in Vthe
dravving'toA illusrhfatethe invention, it Ywill be understood
'by those skilled in the art «thatithis invention canreadily
»and to TMmym'ode energy for lprodìlcing-double-frequeney
magnetic
lI_neansîr lfor mounting
ferri-tc means
lwithin `said ¿cavity ¿along ¿said >longitudinal >axis so that
be extended to aY rectangular cavity.'
said `donble-frequency lmagnetic ñux excites said ."I'Ef,nm
mode,l andoutput waveguide means coupled to vsaid cavity
for extracting’the double-frequency rIY‘Eßnmumode energy
nlt'will-be `apparent that; the embodiments shown‘a're
only exemplary “and that various modifications can be
made inI construction and arrangement within lthe scope
' of the'invention as‘deíined in the appended claims, Y
We ola'imiíasïour invention: l
g
’
Y '
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„
» Y Y
l'. A'?requencydoubling microwavey cavity device comf
prising in‘combination: a microwave cavity haw'ng'di-A
35
from ¿said cavity, said output’means having a cut-oit fre
lque'ncy above the input frequency f.
Y ,Referençes cnedra menteur this patent
rme'nsionssuch that the cavity is resonant in the TMm
mode »at‘vrthe frequency f andr inV afI‘Eònm mode' at the `
» frequency'Zf, rn'eansffor exciting ’said cavity in said TMm, 40
-mode at the frequency f,»a ferrite element disposed within
said‘cavity, a D.-C;;magnetizing-iield applied trof` said fer
rite element,- the location'of Vsaid'rferrite element and the
Vstrength and-’direction ofi saidDfC. field being such Vthat
TMzimf modeV energy 'produces double-frequency magnetic
'ilux ví?hic/:liY excites said' TEd?m' mode; and`me`ans for ’ex~`
UNITED STATES PATENTS
‘ 26713841
ì 2,817,760"
Y
'zaiëskir_____g_- f____v___«__ Mar. 9,' 1954
Y Dobbërtin'.._j;.;.'__;__'_1_;._r- Dec. 24, 1957
OTHER' REFERENCES'
_
i
“Microwave Frequency DonblingfFrom 9 to 18v KMC
in Ferrite'sï’ ll-Sy I; I3. Melchor, W. PxAyres", and P; H.
45 Va'rtanianrin :Proceedings’tof' the I‘.R.'E. ` (May 1957) -, pages
643'f6‘4‘6'relied'on.
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