U.S. patent number 3,928,824 [Application Number 05/497,263] was granted by the patent office on 1975-12-23 for waveguide circulator.
This patent grant is currently assigned to Oki Electric Industry Company Ltd.. Invention is credited to Atsushi Fukasawa, Kazunori Takahashi.
United States Patent |
3,928,824 |
Takahashi , et al. |
December 23, 1975 |
Waveguide circulator
Abstract
A waveguide circular which includes at least three waveguide H
plane ports, said ports so arranged that at their junction a
ferrimagnetic post is provided, one or two matching conductor or
dielectric members which are provided in relation to said
ferrimagnetic post, and a magnetic device which magnetizes
statically said ferrimagnetic post. The characteristic features of
the present invention are that the cross section of said
ferrimagnetic post is inscribed with a circle the diameter of which
is nearly equal to the value calculated from the dielectric
resonator mode TM.sub.ml (m .gtoreq. 2), one end of said
ferrimagnetic post is directly or indirectly fixed to the center of
the matching members the total thickness of which is selected to be
nearly equal to the height of said ferrimagnetic post and an air
gap is provided between the other end of said ferrimagnetic post
and the H plane of said waveguide or another matching member, and
the electrical length of said air gap is adjusted so as to obtain
the wide band characteristics of said waveguide circulator.
Inventors: |
Takahashi; Kazunori (Tokyo,
JA), Fukasawa; Atsushi (Tokyo, JA) |
Assignee: |
Oki Electric Industry Company
Ltd. (Tokyo, JA)
|
Family
ID: |
14172483 |
Appl.
No.: |
05/497,263 |
Filed: |
August 14, 1974 |
Foreign Application Priority Data
|
|
|
|
|
Aug 30, 1973 [JA] |
|
|
48-96717 |
|
Current U.S.
Class: |
333/1.1;
333/248 |
Current CPC
Class: |
H01P
1/39 (20130101) |
Current International
Class: |
H01P
1/32 (20060101); H01P 1/39 (20060101); H01P
001/38 () |
Field of
Search: |
;333/1.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Gensler; Paul L.
Attorney, Agent or Firm: Merchant, Gould, Smith, Edell,
Welter & Schmidt
Claims
What is claimed is:
1. A waveguide circulator including at least three waveguide H
plane ports, said ports so arranged that a ferrimagnetic post is
provided at their junction, at least one matching conductor which
is provided in relation to said ferrimagnetic post, and a magnetic
device for statically magnetizing said ferrimagnetic post,
characterized in that the cross section of said ferrimagnetic post
is circumscribed within a circle having a diameter equal to the
value calculated from the equation ##EQU11## wherein the resonance
mode is TM.sub.mn (m.gtoreq.2, n=1), D is the diameter, l is the
length of the resonator, X.sub.mn is an eigen value corresponding
to mode TM.sub.mn (m.gtoreq.2, n=1), .epsilon. is the relative
dielectric constant of the ferrimagnetic post, .mu..sub.r is the
relative permeability of the ferrimagnetic post, .lambda..sub.o is
the wavelength of the center frequency in free space, and p is the
number of the standing waves appearing along the ferrimagnetic post
in its longitudinal direction.
2. A waveguide circulator according to claim 1, wherein a conductor
member is arranged on H planes at the center of the junction of
waveguide ports, the thickness of said member is selected to be
approximately equal to the height of said ferrimagnetic post, one
end of said ferrimagnetic post is fixed to the center of said
conductor member and an air gap is provided between the other end
of said ferrimagnetic post and said H plane, and the electrical
length of said air gap is adjusted so as to obtain the wide band
characteristics of said waveguide circulator.
3. A waveguide circulator according to claim 1, wherein a first and
second conductor member are arranged respectively on upper and
lower H planes at the center of the junction of waveguide ports,
the total thickness of said first and second conductor member is
selected to be approximately equal to the height of said
ferrimagnetic post, one end of said ferrimagnetic post is fixed to
the center of said first conductor member and an air gap is
provided between the other end of said ferrimagnetic post and said
second conductor member, and the electrical length of said air gap
is adjusted so as to obtain the wide band characteristics of said
waveguide circulator.
Description
The present invention relates to a circulator and especially,
relates to the circulator which provides wide band characteristics
without insertion loss characteristics.
The conventional wide band waveguide circulator is composed of
waveguide H plane ports, a ferrimagnetic post which is provided at
the junction of said ports, one or two matching conductor or
dielectric members which are provided in relation to said ferrite
pillar, and a magnetic device which magnetizes statically said
ferrimagnetic post.
However, the design theory with respect to the waveguide circulator
does not develop like the strip line circulator. Therefore,
concerning the waveguide circulator, only the qualitative
explanation is given and the design of said waveguide circulator
has been carried out experimentally.
Further, it is very difficult to produce, with precision, the
ferrimagnetic post, and the dielectric and conductor members, and
to precisely position the abovementioned elements. Also, a suitable
adhesive material for assembling these elements cannot be obtained.
These factors cause incongruities of the characteristics of the
circulator and result in the high cost of the circulator. Further,
an inconvenience is created because the use of a casted waveguide
port having insufficient accuracy is difficult. Above all, one of
the main drawbacks of the conventional waveguide Y circulator is
the fact that the elements to be assembled are numerous.
An object of the present invention is to provide a waveguide
circulator which can overcome the above-mentioned drawbacks.
Another object of the present invention is to provide a waveguide
circulator which is simply constructed and is composed of a minimum
number of components.
A further object of the present invention is to provide a waveguide
circulator which is manufactured in less time and at lower cost
than the conventional waveguide circulator.
According to the present invention, a waveguide circulator includes
at least three waveguide H plane ports, said ports so arranged that
at their junction a ferrimagnetic post is provided one or two
matching conductor or dielectric members which are provided in
relation to said ferrimagnetic post, and a magnetic device which
magnetizes statically said ferrimagnetic post. Characteristic
features of the present invention are that (a) the cross section of
said ferrimagnetic post is inscribed with a circle the diameter of
which is nearly equal to the value calculated from the dielectric
resonator mode TM.sub.ml (m.gtoreq.2), (b) one end of said ferrite
pillar is directly or indirectly fixed to the center of the
matching member, an air gap is provided between the other end of
said ferrimagnetic post and the H plane of said waveguide or
another matching member, and the electrical length of said air gap
is adjusted so as to obtain the wide band characteristics of said
waveguide circulator.
Further features and advantages of the present invention will be
apparent from the ensuing description with reference to the
accompanying drawings to which, however, the scope of the invention
is in no way limited.
FIGS. 1A and 1B show one embodiment of a conventional waveguide
circulator; FIG. 1A is a perspective view of said circulator and
FIG. 1B is a cross section viewed from the direction 0 indicated by
the arrow in FIG. 1A;
FIGS. 2A through 2C are diagrams showing the distribution of the
microwave electromagnetic field in the ferrimagnetic post; FIG. 2A
concerns the TM.sub.11 mode, FIG. 2B concerns the TM.sub.21 mode
and FIG. 2C shows the coordinate system;
FIGS. 3A through 3C show embodiments of the waveguide circulator
according to the present invention; FIG. 3A is a side view of the
waveguide circulator, FIG. 3B is the plan view of the waveguide
circulator shown in FIG. 3A; FIG. 3C is another embodiment of the
present invention;
FIGS. 4A and 4B are graphs of the experimental data of the
embodiments according to the present invention; and
FIG. 5 is a graph of the experimental data of another embodiment of
the present invention.
One example of the construction of a conventional wide band
waveguide Y circulator is shown in FIGS. 1A and 1B. FIG. 1A shows a
perspective view of the conventional waveguide Y circulator and
FIG. 1B is a cross section viewed from the direction 0. Referring
to FIGS. 1A and 1B, 1 is a waveguide Y port, 1a, 1b, and 1c are
conductor screws for adjusting the attenuation in the reverse
direction of the waveguide circulator, 2 is a ferrimagnetic
material, 3-1 and 3-2 are permanent magnets, 4-1a and 4-2a are
triangular member conductors, which are used for impedance
matching, 5-1 and 5-2 are triangular dielectric plates for
impedance matching. In FIG. 1A, permanent magnets 3-1 and 3-2 are
not shown: 1A, 1B and 1C are the opening portions of the waveguide
Y junctions.
It is conventionally well known that, when the ferrimagnetic
material is in the form of a cylinder as shown in FIG. 1A, it is
difficult for the waveguide to provide wide band characteristics,
but when the ferrimagnetic material is formed as a triangular
member, adequate wide band characteristics can be obtained.
However, in the conventional construction as shown in FIG. 1A, (a)
it is very difficult to produce, with precision, the ferrimagnetic
post, the triangular dielectric plates 5-1, 5-2, and the triangular
member conductors, (b) it is very difficult to assemble with
precise positioning the above-mentioned elements and (c) suitable
adhesive material for assembling these elements cannot be
obtained.
Now, we will explain the waveguide circulator according to the
present invention, with respect to the most simple embodiment,
shown in FIGS. 3A through 3C.
The present invention is composed of the following three
conditions.
1. The form of the ferrimagnetic post is selected to be cylindrical
and the value of the diameter of the ferrimagnetic cylinder is
selected on the basis of TM.sub.210, that is, one of the higher
order modes, or near said value.
2. Mode matching between the ferrite cylinder and the external
waveguide is carried out with the most simple construction. For
example, on one triangular member, the ferrimagnetic post is fixed
directly with the adhesive material.
3. Impedance matching between the ferrimagnetic cylinder and the
external waveguide is carried out by precisely selecting the
distance between a free end of the ferrimagnetic cylinder (that is,
the end which is not fixed to the triangular plate) and an inner
waveguide H plane facing said free end or other triangular member
placed on said inner plane of the waveguide.
These three conditions will now be explained in more detail.
(Condition 1)
FIG. 2A shows the distribution of the microwave magnetic field
TM.sub.11 in the ferrimagnetic cylinder 2a when said distribution
is observed from the direction P indicated in FIG. 1B which shows
the conventional waveguide Y circulator. Referring to FIG. 2A, the
curved lines 9 in the ferrite cylinder 2a indicate vectors of the
magnetic fields and arrows viewed from the head or tail 10 indicate
the vectors of electrical fields. Arrows 1 , 2 and 3 on the
exterior of the ferrite pillar 2a show the direction of the opening
portions 1A, 1B and 1C of the waveguide Y junction.
When the direct magnetic field H.sub.DC is applied as represented
by the arrow viewed from the tail, in FIG. 2A, the input applied
from arrow 1 appears at the direction 2 but not at the direction 3
.
The distribution shown in FIG. 2A is a basic mode of the
circulator, that is, TM.sub.110. Herein, TM shows a magnetic
transverse wave and the numbers 110 represent the number of the
standing waves in coordinates .phi., r, z respectively,
corresponding to the coordinate system as shown in FIG. 2C.
Generally, the mode is expressed only with respect to the number of
standing waves in the direction of .phi. and r, and when we
calculate the electromagnetic energy or load Q; Q.sub.L, the number
of standing waves in the direction z must be expressed in
accordance with the resonance mode. However, the number of waves in
the direction z has no relation to the present invention, therefore
we have omitted it for purposes of simplifying the explanation.
According to C. E. FAY and R. L. COMSTOCK, Operation of the Ferrite
Junction Circulator, IEEE Transactions on Microwave Theory and
Techniques, January 1965, page 20, the following result is obtained
with respect to the TM.sub.110 mode. ##EQU1## wherein, Q.sub.L is a
load of the circulator, .omega. is an angular frequency, R and d
are respectively the radius and the height of the ferrite cylinder,
.epsilon. is the specific inductive capacity of the ferrimagnetic
cylinder, .epsilon..sub.o is the dielectric constant in vacuum
condition and G.sub.R is the conductance as viewed from the
exterior of the ferrimagnetic post.
On page 20 of the above-mentioned reference, it is described that
although the circulator can function with respect to mode TM.sub.21
or modes higher than TM.sub.21, the conclusion is that no advantage
exists with respect to mode TM.sub.21 or modes higher than
TM.sub.21. However, the present inventors are of the opinion that
this conclusion has room for doubt.
Therefore, the inventors calculated the Q.sub.L of the circulator
with respect to TM.sub.210.
FIG. 2B shows the distribution of the microwave electromagnetic
field of the TM.sub.210 mode. As is well known, the following
equation is obtained. ##EQU2## wherein U is an energy which is
stored in the ferrimagnetic cylinder and Pout is an electric power
which is radiated to the exterior from the ferrimagnetic cylinder.
It is known that U in equation (2) may be calculated as shown in
following equation. ##EQU3## wherein J.sub.2 (kr) is the first kind
and the second order of Bessel function, k is a constant, r and
.phi. are variables, and E.sub.m is the maximum electric field at
the periphery of the ferrite cylinder.
When we calculate the equation (3) using the value of the constant
k = 3.054 in the TM.sub.21 mode, the following equation can be
obtained.
when G.sub.R shows the admittance viewed from the interior to the
exterior of the ferrimagnetic post, the electrical power Pout is
calculated by the following equation.
From equations (2), (4) and (5), ##EQU4## therefore, the following
equation can be obtained. ##EQU5##
In the above calculations, we assume that G.sub.R is the admittance
viewed from the periphery of the ferrimagnetic cylinder to either
the exterior or interior of the ferrimagnetic cylinder. In the
strip-line circulator, G.sub.R is the characteristic admittance
corresponding to the TEM mode of strip-line which exists on the
outside of the ferrimagnetic post and is independent of the
frequency. Whereas, in the waveguide circulator, G.sub.R is the
admittance of the waveguide which exists outside of the
ferrimagnetic cylinder and has frequency characteristics. However,
the triangular member conductors 4-1a and 4-2a shown in FIG. 1B
have the function of converting the waveguide mode from the
TE.sub.11 mode into a quasi TEM mode for the reason given in
condition 2. Since, in the waveguide circulator, G.sub.R is a
characteristic admittance with respect to the TEM mode viewed from
the inferior to the exterior of the ferrimagnetic cylinder, and is
considered to be the same as in the strip-line circulator, the
above-mentioned equation (7) can be applied to the strip-line
circulator as well as the waveguide circulator.
Next, according to H. J. Butterweck, Der Y Zirkulator, AEU, Vol.
17, April 1963, pp 163 through 176 which is referred to in the
above-mentioned C. E. Fay and R. L. Comstock, if we assume that the
resonant frequencies of the resonators correspond to positive and
negative circular polarized waves in the TM.sub.110 mode circulator
that a center frequency of the circulator is represented by
.omega., and that .delta.' is expressed as ##EQU6## the following
equation (9) may be obtained because .omega..sup.+ and
.omega..sup.- have a phase difference of .+-.30.degree. with
respect to .omega.. ##EQU7## Now, the following equation can be
obtained with respect to the TM.sub.21 mode. ##EQU8##
Further, according to the reference H. Bosma, On Stripline Y
circulation at UHF; IEEE trans on MTT Jan. 1964, page 64, FIG. 4,
the values of splits 2.delta.' of the positive and negative
circular polarized waves with respect to the same value of K/.mu.
(wherein K and .mu. are Polder tensor components) are the same in
the TM.sub.11 mode and the TM.sub.21 mode. That is, when we assume
that the value of K/.mu. determined by a saturation magnetization
of the ferrite cylinder and that the internal direct field remain
constant, in equations (9) and (8), 2.delta.'.sub.1
.apprxeq.2.delta.'.sub.2, therefore, the following equation (11)
can be obtained. ##EQU9##
Equation (11) gives nearly the same result as equation (7). That
is, the circulator which uses the TM.sub.21 mode can obtain a wide
band twice as large as the circulator which uses the TM.sub.11
mode, and the value of the center frequency which is calculated
with the TM.sub.210 mode corresponds to the experimental
result.
The above explanation was given with respect to the TM.sub.21 mode
only of the ferrimagnetic post having a circular cross section.
However, in the waveguide circulators which are calculated with a
higher mode TM.sub.ml (m.gtoreq.2), the center frequency of the
circulator corresponds with the experimental results and it is
supposed that an optimum higher mode which has wide band
characteristics will exist.
Next, we will explain the relation between the diameter of the
ferrite cylinder and the mode TM.sub.mnp. As is well known, the
following equation exists only in approximate terms. ##EQU10##
wherein the resonance mode is TM.sub.mnp, l is the length of the
resonator, x.sub.mn is an eigen value corresponding to mode
TM.sub.mn, .epsilon. is the relative dielectric constant of the
ferrite body, .mu..sub.r is the relative permeability of the
ferrite body, .lambda..sub.o is the wavelength of the center
frequency in free space and f.sub.o = C/.mu..sub.o (wherein C is
the light velocity). And, p is the number of the standing waves
appearing along the ferrimagnetic post in its longitudinal
direction. The value of p is between 0 and 1, and in most cases
said value is near 0.
(Conditions 2 and 3)
Condition 1 is essential for the present invention, however,
condition 2 and 3 mentioned hereinafter are secondary
conditions.
When we connect the ferrite cylinder having wide band
characteristics to the external waveguide, the mode conversion and
the characteristic impedance matching must be considered. With
respect to the impedance matching, the reactance component can be
matched with the conductor screws 1a, 1b and 1c which is provided
on the waveguide H plane.
In the simplest embodiment of the present invention, as described
hereinafter, the object of the invention is achieved by fixing one
end of the ferrimagnetic cylinder with a diameter determined by the
mode TM.sub.m10 (m.gtoreq.2) of the dielectric resonator, directly
or indirectly to the center portion of one matching triangular
conductor member, and adjusting precisely the distance between the
other end of the ferrimagnetic cylinder and the inner surface of
the waveguide H plane.
FIG. 3A shows a side view of the portion of the embodiment
according to the present invention, FIG. 3B is a cross section
along A--A of FIG. 3A and FIG. 3C is another embodiment of the
present invention wherein the matching triangular conductor member
6 shown in FIG. 3A is divided into two portions, that is, 6-1b and
6-2b and these divided portions are fixed on upper and lower H
planes at the center of the junction of the waveguide ports.
Referring to FIGS. 3A through 3C, 1 is the waveguide port, and 3-1
and 3-2 are permanent magnets, similar to FIGS. 1A and 1B. And 5
and 5b indicate the ferrimagnetic cylinder, 6, 6-1b and 6-2b
represent matching triangular conductor members. The diameter of
the ferrimagnetic cylinders and the dimensions of the triangular
conductor members are determined in accordance with the
above-mentioned conditions 1, 2 and 3.
The experiments confirmed that when the sides of the matching
triangular conductor members 6, 6-1b and 6-2b are equal in length
and the thickness of the member 6 is equal to the sum of the
thicknesses of members 6-1b and 6-2b the wide band characteristics
of the embodiments shown in FIG. 3A and FIG. 3C are the same. The
total thickness of the matching member or members is selected to be
nearly equal to the height of the ferrimagnetic post.
Further, according to the experiment, it was confirmed that the gap
between one end of the ferrite cylinder and the H plane has an
optimum value and the thicknesses of the members 6, 6-1b and 6-2b
and the air gap are the same.
FIGS. 4A and 4B show experimental results of the characteristics of
the waveguide circulator according to the present invention. FIG.
4A is the characteristic data showing the relation between the
frequency GHz and the attenuation in the reverse direction dB of
the waveguide circulator which is adjusted to the Tschebysheff form
by using the conductor screws which are respectively provided on
the H planes of the opening portions 1A, 1B and 1C of the waveguide
Y junction and FIG. 4B represents the case of the waveguide
circulator being adjusted to the maximally flat form. In FIG. 4A
and 4B, the curves shown by o--o, x--x and .DELTA.--.DELTA. show
the characteristic of each portion of the three opening portions
1A, 1B and 1C.
This explanation was given with regard to the case where matching
triangular conductor members are used, however, when matching
circular conductor members are used, a result the same as shown in
FIG. 5 can be obtained the curves shown by o--o, x--x and
.DELTA.--.DELTA. are respectively the same as those shown in FIGS.
4A and 4B--.
As mentioned above, the waveguide circulator, which is composed of
the ferrimagnetic post calculated by the dielectric resonator mode
TM.sub.210 and one or a pair of matching members and conductor
screws, provides the same characteristics as the conventional
waveguide circulator having a complex construction. Therefore, the
waveguide circulator according to the present invention can be
manufactured inexpensively and with simple construction and the
time required to manufacture the waveguide circulator can be
considerably reduced.
Further, the above explanation was given with respect to the case
where the ferrimagnetic post is a cylinder, however, it should be
understood that the same effect can be obtained by triangular or
other forms of the ferrimagnetic post, the cross section of which
is inscribed with a circle the diameter of which is calculated
according to the abovementioned condition 1.
* * * * *