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Патент USA US3044028

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July 10, 1962
K. M. POOLE ETAL
3,044,021
GYROMAGNETIC AMPLIFIER WITH PARALLEL PUMPING
Filed May 19, 1960
5 Sheets-Sheet 1
in
aw
M<
3\NQ
K. MVPOOLE
INVENTORS
B!’
of
I? If. TIE/V
J. A. WEISS
m
ATTORNEY
July 10, 1962
K. M. POOLE ETAL
3,044,021
GYROMAGNETIC AMPLIFIER WITH PARALLEL PUMPING
Filed May 19, 1960
3 Sheets-Sheet 2
/Nl/EN7'O/-?S
K. M. POOLE
R K. TIEN
J.A. WEISS
sy?yém/é
_'
I '
July 19, 1952
K. M. POOLE ETAL
3,044,021
GYROMAGNETIC AMPLIFIER WITH PARALLEL PUMPING
Filed May 19, 1960
3 Sheets-Sheet 3
F/G.4
FIG. 5
FIG. 6
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FIG. 7
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_ SIGNAL
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SIGNAL
SOURCE
.K. M. POOLE
lNl/ENTORS R K. TIEN
J. A. ‘WEISS
>
ATTORNEY
United States Patent O
_
1
2
This parallel pumping style of operation is contrasted
3,044,021
with the Suhl type electromagnetic operation or the
GYROMAGNETIC AMPLIFIER WITH PARALLEL
PUMPING
Kenneth M. Poole, New Providence, Ping K. Tien, Chat
ham Township, Morris County, and Jerald A. Weiss,
semistatic style of operation wherein the pumping ?eld
is directed perpendicular to the biasing ?eld and wherein
the amplitude of the biasing ?eld is adjusted to produce‘
Summit, N.J., assignors to Bell Telephone Laboratories,
Incorporated, New York, N.Y., a corporation of New
York
‘
Filed May 19, 1960, Ser. No. 31,248
6 Claims. (Cl. 330-—56)
3,044,021
Patented July 10, 1962
main resonance at the pumping frequency.
It is also
contrasted with the modi?ed semistatic style of operation
wherein the pumping ?eld is applied. perpendicular to the
direction of the biasing ?eld and wherein the biasing ?eld
10 is adjusted to produce main resonance. at the idler fre
This invention relates to electromagnetic wave systems
and more particularly to gyromaguetic ampli?ers and
The parallel pumping style of operation may be em
oscillators.
ployed using separate idler and signal frequencies where
This is a continuation-in-part of our copending appli
the pump frequency equals the sum of the idler fre
cation, Serial No. 821,189, ?led June 18, 1959, and now 15 quency and the signal frequency in the usual manner;
abandoned.
or the degenerate style of operation may be employed
'It has long been known that if a nonlinear reactance is
wherein the signal frequency is equal to one-half the
driven by a low frequency signal and a single higher
pump frequency.
.
.
frequency pumping source,‘the ?ow i'of power at the
These and other objects and advantages, the nature
quency.
_
>
_
'
difference frequency. will introduce a negative resistance 20 of the present invention, and its various features, will
into the signal circuit. This principle has been applied
appear more fully upon consideration of the various
by H. Suhl (Serial No. 640,464, ?led February 15, 1957)
illustrative embodiments now to be described in detail
‘and M. T. Weiss (Serial No. 660,280, ?led May 20', 1957,
in connection with the accompanying drawings, in which:
now Patent No. 2,978,649) to produce microwave oscilla
FIG. 1 is a perspective view of the ?rst embodiment
tors and ampli?ers, the nonlinear reactance being sup 25 of the invention;
‘plied by means of a body of gyromagnetic material dis
FIG._ 2' is an end view of the-embodiment of FIG. 1
posed in the region of the network common to the three
showing in greater detail the location of the gyromag
signals. Since this initial work, various modes of opera
netic element;
_
tion of gyromagnetic ampli?ers have been evolved in an
FIG. 3, given by way of illustration, vis a diagrammati
attempt to ?nd a design, or class of designs, for such 30 cal showing of the magnetic ?eld patterns in the embodi
devices which would lead to a practical ampli?er. By
.ment of FIG. 1;
“practical” is meant an ampli?er capable of CW opera
FIGS. 4 to 6, given by way of illustration,’ show the
tion, and which can be energized from currently avail
e?ect of the signal and pumping ?elds on the precession
able (low power) generators.
'
of the magnetization vector; and
The ability of a gyromagnetic ampli?er to operate CW 35 _ FIG. 7 is a view of a second embodiment of the
is intimately related to the ability‘ of the gyromagnetic
specimen to dissipate heat. Obviously, unless the speci
, invention.
Referring more particularly to FIG. 1, a perspective
.view of an illustrative embodiment of the present inven
tion is shown connected and utilized to produce ampli
fulness as ‘an ampli?er is severely limited. Conversely, 40 ?cation at microwave frequencies. Such an ampli?er
given a maximum rate of heat dissipation, some method
comprises two intersecting resonators, proportioned to
of operation must be devised whereby the heat generated
be resonant at different, though related, frequencies, and
within the specimen is maintained below this maximum.
oriented so that their respective magnetic ?elds are mu
It is therefore an object of this invention to reduce
.tually' perpendicular to each other in a common region
the power absorbed in gyromagnetic oscillators and ampli 45 . shared by both of said resonators. In the particular‘ em
?ers.
bodiment of the invention illustrated in FIG. 1, the ?rst
The second limitation upon the ability of gyromagnetic
of said resonators is of the waveguide type, comprising the
ampli?ers and oscillators to operate CW relates to the
portion of the reduced rectangular waveguide 10 having
magnitude of the pumping power needed to produce
a wide dimension of greater than one-half wavelength
useful gain. In the lower microwave frequency range, 50 and less than one wavelength at thesignal frequency f5.
available CW sources can provide ample energizing
The input end of guide'lt) is connected to guide 14 and
power. At the higher frequencies, however, the availhence to a signal source, through the tapered section 13
able power is substantially reduced.
and iris 11. The other end of guide 10 is ‘terminated in
‘It is therefore a further object of this inventionrto -, a conductive shorting member 12 whose longitudinal posi
reduce the pumping power requirements of gyromag‘netic
tion relative to iris .11 may be adjusted for-tuning pur
ampli?ers and oscillators.
'
poses by means of a plunger 16. The electrical dis
In accordance with the invention the above-mentioned?
tance between’iris 11 and the'shorting member 12 ‘is ad
objectives are realized by the particular arrangement
_1 justedi to be a multiple of one-half wavelength to pro
of pumping and biasing ?elds. In particular, the biasing
fduce resonance at the signal frequency ;f,,, as will be
men can dissipate heat at a reasonable rate and thereby
.maintain itself at some reasonable temperature, its use
, ?eld is applied in a direction parallel to the direction of 60
the magnetic ?eld lines of the pumping signal in the
region of the gyromagnetic element. The amplitude of
the biasing ?eld is adjusted'in accordance withthe re
discussed hereinafter.
_
'
Extending above the signal path and forming the upper
boundary thereof is the ‘second resonator, comprising
. the rectangular cavity 17 and the conductive block 18.
vCavity 17 and block 18 are proportioned to resonate at
. For example, the amplitude of the biasing ?eld may be 65 - the pumping frequencytfp. Block 18 is suitably supported
adjusted to produce gyromagnetic resonance at either the
7 within cavity 17 by means of thin dielectric spacers (not
signal frequency, the idler frequency, or at some fre
shown), and is vertically adjustable by means of the
quirements of the particular style of operation selected.
quency between the signal and idler frequencies. Alter
nately, the biasing ?eld may be adjusted to induce one or
t more of the higher order magnetostatic modes (the so
called Walker modes) in the gyromagnetic element. .
, threaded rod 2t)‘v which extends from the top surface of
70
block 18.
.
Energy at the pumping frequency is magnetically cou
pled into cavity 17 _by means of loop 21 which is con,
3,044,021
a
q
V
‘
>
o
.
illustrated by the closed loops 31 and 32 comprising the
nected to a source of pumping signal by way of coaxial
cable 22.
,
,
standing wave pattern set up in cavity 10. Ideally, these
loops lie in planes which are parallel to the wide dimension
'
A signal to'be ampli?ed, es, at a frequency is is ap
of cavity 19. In accordance with the invention, cavity 10
is a multiple of half wavelengths of frequency is, and
plied to cavity 10 from waveguide 14. Simultaneously,
pumping energy 8p at a frequency f,, is applied to cavity
17 by way of coaxial cable 22. ‘The ampli?ed output E5
is taken ‘from cavity 10 by way of waveguide 14. The
ampli?ed signal and the input signal may be separated from'each other in any of the. usual ways well known in
; the art; as, for example, a directional coupler-or three 10
port circulator may be used to isolate the input circuit
more speci?cally extends an even number of quarter wave
lengths on either side of the region including the gyro
magnetic element 23 so that the magnetic ?eld in this
region is maximum and exists substantially in a transverse
direction with respect to cavity 10.
The magnetic ?eld loops of the pump frequency fp are
illustrated by the closed loops 33 encircling the conductive
from the output circuit.
‘
— Nonlinear coupling'between the energy supported in
block 18 and lie in planes perpendicular to the wide di
mension of-cavity 10. In accordance with the invention,
cavity 10 and cavityl'l is provided by an element of gyro
cavity
17 is tuned to the pump frequency where the tuning
magnetic material 23. The term “gyromagnetic ma 15
is a function of the dimensions of the cavity 17 and the
terial” is employed here in its accepted sense as desig
dimensions of the conductive block 18 and, in particular,
mating the class of magnetically polarizable materials hav
‘ing'runpai‘red. spin systems involving portions lOf the " of the space between the two.
7 It'will be noted that in the region occupied in common
atoms thereof that'are capable of being aligned by an
by the two cavities the magnetic ?elds of the pump and
' signal intersect at right angles toeach other. Consequent
external magnetic polarizing ?eld and which exhibit a
‘ signi?cant precessional motion at a frequency Within the
ly, there is no direct coupling, or tendency for any energy
range contemplated by the invention under the combined
in?uence ofrsaid polarizing ?eld and an orthogonally" transfer therebetween. It will also be noted that by virtue
of the presence of block 18 and the reduced height of
‘directed varying magnetic ?eld component. This pre
cessional motion is characterized 'as having an angular 25 guide 10, the magnetic ?elds are highly concentrated at
their points of intersection in the common region of the
momentum and, a magnetic moment. Typical of such
materials are ionized gases, paramagnetic materials and '
ampli?er.
such as'magnesiumaluminum ferrite,_aluminum zinc fer
structure of ‘the ‘formula A3B5O13 where O is oxygen, A'
is ‘at least __one element’ selected from the group consisting
between 62 and .7 1, inclusive, and B is iron optionally con
taining at least one element selected fromthe group con
sisting of gallium, aluminum, , scandium, indium and
.
,
r
_
'
'
,
7
,
Thisparticular orientation of magnetic ?elds has a
number of advantages. Since the, pumping ?eld is paral
lel to the biasing ?eld, vthe gyromagnetic material cannot
.
' ‘Element 23 may bemade of any low-loss gyrornagnetic
A
,
and in particular ‘to the direction of the steady'biasing
?eld with respect to the radio frequency magnetic ?elds.
As shown in FIG. '3, the steady biasing ?eld H0 is directed
parallel to the pump ?eld and perpendicular to the signal
of yttrium and ‘the rare earths having an atomic, number
,
v
magnetic material 23. The crux of this invention, how
ever, is in the means ‘whereby this coupling is e?ected,
rite and the rare earth iron oxidesrhaving a garnet-like
vchromium.
'
V The exclusive coupling bet-ween the ?elds is provided,
as in the prior art ampli?ers, by an element of gyro
V ferromagnetic materials, the latter including the spinels
material chosen from the above-mentioned groups.‘ Pref
made to resonate at the pump frequency. Conse
erably, however, it is a single crystal material having a 40 be
quently," the pumping power requirements for such an
narrow resonance line in order ,to conserve power. . For
‘ampli?er are substantially reduced. In fact, theoretically,
this use single crystals of manganese ferrite :or yttrium
iron garnet have been found satisfactory.
there can be no absorption of energy at the pumping
'
frequency bythe gyromagnetic material unless the mag
The nonlinear element is located between?the bottom of . netization is made to precess with a component at half
45
block 18 and the wide'wall of guide 10 in, the common
the‘pump‘frequency' This fact is of the utmost im
region of the ampli?er shared by, both resonators. It is
portance in CW operation where heating of the gyro—
supported by dielectric spacer, 24 in a manner as shown in ’
magnetic sample may be a limiting factor. ‘It should
FIG. _2. The dielectric support, in addition to holding the '
gyromagnetic elementin position, maintains a minimum
spacing- between the, elementand the conductivegwall’of'
also be noted that in the absence of any signal no power
is dissipated in the gyromagnetic element. That such an
50
arrangement of ?elds is capable ofproviding ampli?ca
tion can be readily shown ‘by considering FIGS. 4, 5 and. 6.
‘guide 10. A second dielectric spacer may be placed be;
tween thegyromagnetic material and block 18 to maintain
. In operation as a microwave ampli?er, the frequency
a givenminimum spacing therebetween where this is
in of the pumping source in the embodiment of the’in
55 vention shown in FIG. 1 is adjusted to be twice the signal
3 Element23is biased by a steady polarizing magnetic
frequency is,‘ andvto have a magnitude below the threshold
7, ?eld of a strength anddirection to be described in greater
of self-oscillation.‘ The strength of the biasing magnetic
detail hereinafter.v As-illustrated ‘in FIG. l',._.the ?eld is _- ’ ‘?eld isladjuste'd to produce gyromagnetic resonance in
applied along the axis of waveguide 10 and is supplied
element 23 at the frequency of the signal. In FIG. 4
by the two solenoids 28 and 29 wound in a series-aiding
there is shown the‘motion of a magnetization vector
deemed
desirable.
,
V
V
,
t
vrelationship. The two windings are energized from .a 60
‘source of constant potential 30 through a potentiometer V
31.
Thebiasing ?eld, however, may be supplied by any ' ~. .
, other suitable means or element23~ may be permanently
of constant magnitude‘ precessing under the in?uence of
a constant biasing- ?eld
magnetized if desired. 7 .
.
_
The signi?cance of the direction of the steadybiasing» 65
Ho
?eld and other factors mentioned ,hereinbefore may be
and the orthogonally directed signal ?eld
moree'asily understood in connection with an examination
of the magnetic ?eld patternsrof wave energy supported
by the two resonant circuits 10 and 17. Referring, there 70
-' fore, to FIG. 3, the outline of the boundaries ofrthe am
hs
In a ‘uniform medium biasedto gyromagnetic reso
pli?er are shown along with the oscillatory magnetic ?elds 7 . nance, the path described by the precessing magnetization
,associated with’ the standing wave patterns supported in
-
. the respective cavities.
.
-
The magnetic ?eld loops of the'signal frequency is are
However, by suitably shaping and
orienting the gyromagnetic specimen, the path thus de—
scribed can be made to be elliptical (as‘shown in FIGS.
, vector is a circle.
r 3,044,021
5
6
4-6) due to the presence in the material of unequal
demagnetizing forces. FIG. 5 shows the position of the
transverse component
due solely to its interaction with the pumping ?eld and
where
‘
hp
.,
MT
is the amplitude of the pumping ?eld. For optimum
performance, the phase of the pumping ?eld is adjusted
of the magnetization vector
so that the amplitude of this ?eld is zero when
_,
p
-—>
MT
at various parts'of the cycle, and the corresponding di
rection of that component of the time rate of change of 10 is aligned with the principal i axes of the ellipse. . As
shown in FIG. 6, this corresponds to points E, F, G and
H.
due solely to its interaction with the steady biasing ?eld
->
Since
'
.
-—)
hp
15 is zero at these points,
Ho.
i
mT
MT’
is also zero. In the shaded regions 61 and 62,
the vector representing this component of the time rate
of change, is given as
20
->
-'>
-—>
x
.
_>
hp
->
is directed in the same direction as the biasing ?eld
M'r—,_~M'rXH0
—)
and is perpendicular to
.
_,
Ho
25 whereas in the unshaded regions 63 and 64,
MT.
.
-It' will be noticed that at the principal axes of the
ellipse described by the magnetization vector, the com
ponent
—)
hp
, is directed oppositely to
_,
30
.
H0.
‘
At points I and K in the shaded regions 61 and. 62,
-is tangentto the path. There is, consequently, no net
force operating. at these points which tend to increase
or decrease the precession angle. At the intermediate
_‘)
mT
is seen to have an outward component as ‘was the case
points A, B, C and D, however,
at points A and C in FIG. 5. It will also be seen that
at points L and M in the unshaded regions 63 and 64,
_,
MT
being perpendicular to
mT
'40
_,
direction of
is not tangent to the. path due to its elliptical shape. At
these points
_
also has an outward component due to the reversal in
MT
,
i)
45 in these intervals.
.
MT
This, it will be noted, is contrary to
the situation at points B and D in FIG. 5. The result,
therefore, of the presence of the parallel pumping ?eld is
to produce an outward component of
may be resolved into two components, one tangent to the
path and the other normal thereto. At points A and
C, the normal component is directed outward, tending to
increase
,50
at points all around the precessional path of the mag
‘ and hence tending to increase the precession angle. How
ever, at points B and D the normal component is directed
netization vector. The net effect of these outward com- .
ponents is to increase the precessional angle until a new
equilibrium condition is ‘established consistent with the
inward, tending to decrease
—>
MT
losses in the system. If the power flowing from the
pumping source to the gyromagnetic elements is suf
?ciently large, the system will oscillate. At lower values
.
7
and hence to decrease the precession angle. Since the
magnitudes of these e?ects are equal, they tend to can
cel. The net e?‘ect, therefore, is to maintain a constant
of. the transferred ‘power, the system will amplify.
'
V
It should be noted that if the precession path, is circu-\
hr, the components of
average precession angle.
MT and mT
If, now, a parallel pumping ?eld at twice the preces
4 sion. (signal) frequency is superimposed upon the biasing“
will all be tangent to the precession path and there will
?eld, it too interacts with the transverse component of 65 be no tendency to increase or decrease the precession
angle. Consequently, there can be no ampli?cation in
I the magnetization vector in accordance with the relation
where
V is the component of the time rate of change of , '6
such a system. Hence, for the style of operation described
above the geometry of the gyromagnetic element should
be such as to produce elliptical precession of ‘the mag
70 netization vector. In particular, the specimen should not
have axial symmetry about an axis parallel to the steady
biasing ?eld. In the embodiment of FIG. 1, element 23
, is shown as a thin disk, magnetized in a direction parallel
to its broad surfaces.
A quantitative analysis of the parallel pump ampli?er
3,044,021
(starts ‘from the equation of motion of the magnetization,
Equating <4‘and 5 give _ i
a
which may be written as
‘
-
‘
e
V
.
V
2
_
1i(p—1 ——AH=41rIVIF,,QS<—————(U+P)
2
p
_ >
(6)
P
where F5 is de?ned as the signal ?lling factor and is equal
to
'
where
'
Fr w.
M is the sample magnetization,
.
10
H is the total internal ?eld,
'y is the magnitude of the gyromagnetic ratio, and
a is the loss parameter.
7
-
The magnetization and ?eld components may, in turn,
be expressed with reference to the’ x—y-z coordinate 15
fhzdv
Ce
-
In a practical design, the right~hand side of Equation 6
will be, in general, smaller than, or comparable to AH.
Assuming it torrbe equal to AH,‘ Equation 6 reduces to
4AH
‘ hn="'—1‘
system shown in FIG. 3 as
(7)
Mx=A cos cost
My=% Sill Lust
20
From the de?nition of p and m1?
1 47rM'y
p-—---:
P
wt
Choosing a geometry'for the gyromagnetic sample such
as a thin (disk, for which (Ny—Nx)~l, Equation 7 gives
Hz=H0——(41rNzM —|—hp Sin 2405!‘
we
i 25
where
The pump power required to maintain this ?eld in th
has is the signal frequency, equal to the Kittel, or main
resonance frequency or, where
V
'_
'
pump cavity with‘a Q of QD is
'
wr=rwllHu+‘MM(Nx——Nz)llH0+41rM(Ny—Ns)]
'
~
P
w”
30
,='H<>+41rM(Ny—Nz)
.
Fara c.
~
hzdp
(9)
where h is the total ?eld at any point in the cavity for
Ho+41rM(Nx_Nz)
which the z directed ?eld at the sample is hp. The integral
o‘ is the polarization of the signal ?eld given as the ratio
is taken over the pump cavity volume. Expressing the
of the amplitudes ‘of the y and x transverse components
pump-?lling factor ‘as '
35
of the signal ?eld, and 11K is its x component;
hp is the magnitude of the z directed pumping ?eld at fre- ‘
FD :lail is
(10)
quency 2%;
.
I
-
, I hZdU ,
Nx, Ny and NZ are the normalized ‘demagnetizing factors
(NX+NY+NZ=1);
‘
V
-
M is the saturation magnetization of the gyrom-agnetic
‘
material, and
'
'
,
40
_
-'
2
AH2V.
(11)
Equation 11 gives the threshold power for the parallel
pump style of operation, which may now be compared
'45 with the electromagnetic and modi?ed sernistatic cases.
‘
The solution of Equation 1 leads to the expression
'A[%(p—-f;)—AH]=Mh,o+p>
cn‘
w?TMzFn "Q. ~ “’”“’“
A the magnitude of the x component of the signal fre- I
quency magnetization. '
.
and substituting Equations 8 ‘and 10 in Equation 9, gives
<2).
‘In this comparison a is assumed equal to zero, and (2 equal
to unity.
'
a
For the electromagnetic style
where AH is the resonance line width, de?ned on a variable
frequency, ?xed ?eld basis and is given as
41rM AHV,
__w w 2
Penn: ____._
2"I3FsFiWm2 QsQi p B
where F1 and Q, are the ?lling factor and Q, respectively,
The power supplied to the signal frequency circuit by’
the sample under the in?uence of thepumping ?eld hp is
. of the idler circuit.
For the modi?ed semistatic style of operation
P __
7
_
AHVB
2
Clearly, P_e'm=1>,s if (rgggem equals (Fpgpm, and 1
~ where V5 is the sample volume; Substituting for M and
v ,H and dilferentiating gives
47PM ‘_
60'
' For the better available materials, AH~1 oersted and
41rM~2000 oersted. With a loaded circuit Q3 of 1000,‘
and a ?lling factor FS of 0.1, the threshold power for the
65 parallel pumping style of operation is seen to be, from
Equation 12, approximately an order of magnitude less
than for the other two modes of operation, that is,
At the oscillation threshold, this power must be equal '
7 to the power absorbed in the signal circuit and its load .
From the above analysis it will be noted that th
parallel pumping arrangement, in accordance with the in
vention, is capable of operating at much reduced power
levels as compared to the electromagnetic and modi?ed
where h is the total ?eld in the signal'cavity, andQs the
loaded Q of the signalcircuit. The integral is talcen over 1., semistatic styles of operation Furthermore, since the
75 pumping ?eld and biasing ?eld are parallel, substantially
the signal cavity volume.
:
ms
3,044,021
19
none of the pumping power is dissipated in the gyromag
netic material.
appropriate amplitude of biasing ?eld. For the de
generate mode of operation, this is a relatively simple
The parallel‘ pumping ampli?er may
consequently be operated CW since there are substantial
ly no losses in the material in the absence of the signal.
From Equation 6 it is also seen that a low signal
?lling factor F5 and a low signal cavity Qs are desirable
in order to keep the pumping ?eld, hp, low.
In a second embodiment of the invention shown in
FIG. 7, the pumping circuit comprises the conductive
cavity 70 and conductive block 71. Pumpinég energy 10
is coupled to cavity 70 by means of the loop 72 at the
end of the coaxial line 73.
,
matter since only one frequency and hence only one
mode must be induced. However, for the nondegenerate
type parametric ampli?er, it is necessary to select a
material and a biasing ?eld which will induce resonance
at two discrete frequencies which are so related that their
sum is equal to the pumping frequency. Each of the
Walker modes thus induced has its own particular pre
cessional pattern.
.
‘
.
Referring again to the structure of FIG.‘ 7, non
degenerate-operation' can be established in the ampli?er
Situated below block 71 is the thin disk 74 of gyro
there shown by suitably selecting the biasing ?eld prw
magnetic material sandwiched between, and supported
*duced by pole pieces 77 and 78.’ Under properly chosen
by, the dielectric members 75 and 76. Members 75 15 operating‘conditions, apair of Walker modes is prefer
and 76, in addition to supporting the gyromagnetlc ele
entially excited in element 74.
ment, act as spacers between the latter and the con
induced function as signal and idler resonances in the
usual sense. Since the resonant ?elds are substantially
The two modes thus
ductive wall surfaces of cavity 70 and block 71.
The gyromagnetic member 72 is magnetically biased
entirely contained with the body of the gyromagnetic
in a direction parallel to the pumping ?eld in accordance 20v element itself, no additional external circuit components
with the invention by any suitable means. As shown in
are required. As before, the signal is coupled into and
FIG. 7, a permanent magnet, whose pole ends 77 and
out of the ampli?er by means of the coupling loop com
78 are shown, is used.
prising the extension 79 of the center conductor of co
Signal energy is applied to the gyromagnetic material
axial cable 80, block 71, element 81'and cavity 70.
74 by means of the coupling loop comprising the exten
The magnetostatic mode of operation herein described
sion 79 of the center conductor of coaxial cable 80,“
in which the pumping power is directly coupled to the
which extends up to, and terminates on, block 71; the
magnetostatic modes is to be distinguished‘ from the
bottom surface of block 71 itself; the conductive ?lament
prior art magnetostatic mode of operation wherein the
81; and the bottom surface of cavity 70 between the ?la
pumping power is ?rst coupled to the uniform preces
ment 81 and the outer sheath of cable 80. In addition
sional mode which in turn couples to one or more mag
to forming part of the signal coupling loop, conductive
elements 79 and 81 support block 71 within cavity 70.
Situated along the coaxial cable 80 is the coaxial tun
ing stub 82 for tuning the signal circuit.
In operation, a signal as applied to branch 83 of the 35
three-port circulator ‘84, is directed by the circulator to
coaxial cable 80 and hence to the ampli?er. The ampli
?ed signal, E5, in turn, leaves the ampli?er along the
netostatic modes. By coupling directly to the desired
resonant modes, magnetostatic operation, in accordance
with the invention, avoids the possibility of coupling to
other spurious modes and thus affords a more ei?cient
style of operation.
While it was indicated above that the magnetostatic
.mode of operation may be obtained using a uniform
biasing ?eld and a symmetrically shaped sample, the
same cable 80, enters the three-port circulator 84 and
biasing ?eld or the sample may be modi?ed in any man
is directed by the latter to the load situated in branch 40 ner consistent with the particular mode to be induced so
85. In this manner, the input and output signal circuits
as to facilitate its establishment within the sample. This
are separated from each other.
is generally not essential but may be resorted to where,
While the above discussion was directed to embodi
for some reason, the desired mode is not otherwise
- ments of the ampli?er in which the signal frequency and
readily induced.
the idler frequency are equal (the degenerative form), 45 In all cases it is understood that the aboveedescribed
the parallel pumping style of operation, as taught by the
arrangements are illustrative of a small number of the
invention, can be practiced equally as Well using un
many possible speci?c embodiments which can represent
equal idler and signal frequencies subject to the usual
applications of the principles of the invention. Numerous
limitation that their sum be equal to the pumping fre
and varied other arrangements'can' readily be devised
quency, or such other frequency limitations common to 50 in accordance with these principles by those skilled in
the parametric ampli?er art.
the art without departing from the spirit and scope of
In addition, the above discussion was directed to em
the invention.
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bodiments of the invention wherein the gyromagnetic
What is claimed, is:
material is biased in such a manner as to induce with
1. A high frequency signal ampli?er comprising an
‘
in the material a resonant state of uniform precession, 55 electromagnetic resonator proportioned to support an
generally referred to as “gyromagnetic” or “Kittel”
oscillatory electromagnetic wave at a pumping frequency
resonance. However, as is well known in the art, other
fp, means for establishing within said resonator said os
nonuniform resonant modes are capable of being induced
cillatory wave with magnetic ?eld components extending
in an element of gyromagnetic material. Such nonuni
in a given direction within a region of said resonator, an _
form modes are referred to in numerous ways such as, 60 element of gyromagnetic material having a noncircular
for example, “higher order modes,” “magnetostatic
surface area in a plane perpendicular to said given direc
modes” or “Walker modes.” (See “Magnetostatic Modes
tlon disposed within said region, means for establishing
in Ferromagnetic Resonance” by L. R. Walker. The
.within said region a magnetic biasing ?eld in a direction
Physical Review, volume 105, pages 390-399, January
15, 1957; also, “Resonant Modes of Ferromagnetic
Spheroids” by L. R. Walker, Journal of Applied Physics,
volume 29, pages 318—323, March 1958.)
These resonant modes are characterized in that the di
rection of the magnetization vectors is different through
out the volume of the gyromagnetic sample and their
existence, in Igeneral, does not necessarily depend upon
any nonsymmetry in the geometry of material or non
solely parallel to said components, said biasing ?eld
65 having an intensity to produce gyromagnetic resonance
‘in said element at half said pumping frequency,vand‘
means for introducing into said region a signal at half
said pumping frequency having magnetic ?eld com~
ponents perpendicular to said given direction and ‘for
extracting from said region an ampli?ed signal at half
said pumping frequency.
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2. The combination according to claim 1 wherein said
uniformity in the biasing ?eld. Nonuniform resonant
element is a thin circular disk magnetically biased in a
modes are inherently capable of existing within most
direction parallel to the circular surface of said disk.
gyromagnetic materials and are induced by selecting the 75 3. A high frequency signal ampli?er comprising a plu
3,044,021
12
'11
quency magnetic ?eld having an intensity to produce
'gyromagnetic resonance in said element at said signal
rality" of’ intersecting electromagnetic field supporting
' structures,‘ 'a gyromagnetic element disposed within the
intersection of said'strjuctures, means-for establishingia
high frequency ‘magnetic ?eldpattern at said intersection
in a given direction, means for magnetically biasing said
element solely in a direction’pa‘rallel to said given direc
frequency.
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5.1The combination according'to claim 4 wherein said
element isfa thin circular disk magnetically biased. in ‘a
direction parallel to the circular surfaceof said disk.
6. A high frequency signal ampli?er comprising a plu
rality’ of electromagnctic‘?eld supporting structures sup
portive of mutually orthogonal magnetic ?eld components
at apurnping frequency fp andat a signal frequency is
tion,’ meansrfor introducing into one of said structures
a ‘signal at a frequency lower than said high frequency
“having magnetic ?eld components perpendicular-to said
given direction, and means ‘for, withdrawing ampli?ed
10 lower than said pumping frequency, an element of gyro
signal ‘energy from said ampli?er.
magnetic material electromagnetically coupled to ‘said
'‘ 1‘ 4. A‘ high frequency. signal ampli?er comprising ?rst
mutuallyrorthogonal ?eld'components in said structures,
and'se'cond'conductively bounded rwaveguide cavities sup
portive of two distinct oscillatory magnetic ?eld patterns " 'meansg'for magnetic-ally biasing said element ‘.solely in
a direction parallel to the magnetic ?eld» components of
a?eld components, the ?rst of said cavities being tuned to 15 said pumping frequency, meansfor introducing into one
of said structures a signal atsaid signal frequency, and
resonate at a signal frequency is, the second of said
meansfor Withdrawing ampli?ed wave' energy from said
cavities being tuned to resonate ‘at a pumping frequency
'thaving a region of orthogonally intersecting magnetic
xZfS, means for coupling between said orthogonally inter
secting magnetic ?eld components comprising an element
of gyromagnetic material disposed within said region 20
ampli?er.
whose surface area in a plane perpendicular to said pump- ~
‘
- ing??eld components‘ is noncircular, and meansfo'r cs
tabljshing' ‘a steady magneticubiasing’ ?eld within said
region in a- direction solely parallel to said pumping fre- ‘_
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25.
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References Cited in the ?le of this patent
Weiss“: v“Physical Review,” July 1, 1957, page 317. T
V Denton; “Proceedings of the_IRE,”pl960, pages 937
938.
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